| survey of q-fever agglutinins in birds and small rodents in northern california, 1975-76. | serum samples from 15 species of rodents and 33 species of birds were tested for agglutinins against coxiella burnetii by the microagglutination test. of 759 rodents tested, 21 (3%) were seropositive. antibody positive rodents included muskrats, ondatra zebethica, (11%), rattus spp. (10%), beechey ground squirrels, otospermophilus beecheyi, (6%), wood rats, neotoma fuscipes, (5%), and peromyscus spp. (2%). of 583 birds tested, 118 (20%) were seropositive. this included white crowned sparrows, zo ... | 1979 | 522220 |
| the effect of corticosterone on standard metabolic rates of small passerine birds. | resting metabolic rates of gambel's white-crowned sparrows (zonotrichia leucophrys gambelii) and pine siskins (carduelis pinus) were evaluated at thermoneutral temperatures before and after administration of corticosterone (b) at physiological doses. there was no effect of b on basal metabolic rate of either species, but nocturnal metabolic rate varied significantly less over the 3-h period of measurement in b-treated sparrows and siskins than in control birds. these results, coupled with observ ... | 1991 | 1939747 |
| ferromagnetic coupling to muscle receptors as a basis for geomagnetic field sensitivity in animals. | over the past decade several investigators have provided convincing evidence that the orientation of pigeons and other birds during homing and migrational activities is significantly affected by earth-strength (less than or equal to 0.5 g) magnetic fields. the presumed mediator of such effects would be a highly sensitive magnetoreceptor which the birds would normally use to extract navigational information from the geomagnetic field. the recently reported measurement of magnet remanence in honey ... | 1980 | 7374763 |
| season and migration alters the corticosterone response to capture and handling in an arctic migrant, the white-crowned sparrow (zonotrichia leucophrys gambelii). | the gambel's race of white-crowned sparrow (zonotrichia leucophrys gambelii) migrates each year from their wintering grounds in the southwestern united states to the arctic to breed. associated with this migration is a change in both the nonstressed and the stress-induced levels of circulating plasma corticosterone. birds were captured at two sites on their wintering grounds (new mexico and arizona). although stress-induced corticosterone levels were elevated at each site compared to nonstressed ... | 1997 | 9134701 |
| effects of spatial and host variables on hematozoa in white-crowned sparrows wintering in baja california. | a survey of blood parasites was conducted in february 1995 on white-crowned sparrows (zonotrichia leucophrys) wintering in two environmentally different localities of baja california sur (mexico). blood parasite prevalence was higher in la purísima (49%) than in san josé del cabo (8%), but there were no differences between ages or sexes within each locality. all haematozoa infections were by haemoproteus coatneyi, except one bird in each site that were positive for trypanosoma sp. we found no ev ... | 2001 | 11763742 |
| seasonal changes in androgen receptor immunoreactivity in the song nucleus hvc of a wild bird. | in seasonally breeding songbirds, song behavior and neural morphology change seasonally. song control nuclei are larger during the breeding season, as determined by multiple cytological labels. seasonal changes in song nuclei are regulated by testosterone (t), and several song nuclei contain intracellular androgen receptors (ar). changes in ar levels may interact with changes in plasma t levels to regulate song nuclei morphology. we measured seasonal changes in ar-immunoreactive cells in the tel ... | 1999 | 10379916 |
| effects of day length and temperature on gonadal development, body mass, and fat depots in white-crowned sparrows, zonotrichia leucophrys pugetensis. | we tested the effects of ambient temperature (5 degrees, 20 degrees, and 30 degrees) on photoperiodically induced reproductive functions in male and female white-crowned sparrows, zonotrichia leucophrys pugetensis. transfer from short days (9l 15d) to long days (16l 8d) resulted in rapid testicular growth and partial ovarian development in all three temperature treatments. there were no differences in sizes of testes and cloacal protuberance following 30 or 70 days of exposure to long days at th ... | 1997 | 9208305 |
| interrelationship of day length and temperature on the control of gonadal development, body mass, and fat score in white-crowned sparrows, zonotrichia leucophrys gambelii. | we tested the effects of naturally relevant environmental temperatures on long day-induced reproductive development in male and female white-crowned sparrows, zonotrichia leucophrys gambelii. transfer from short days (8l 16d) to long days (20l 4d) resulted in rapid testicular development and partial ovarian development as has been reported many times previously. exposure of experimental groups to low (5 degrees), moderate (20 degrees), and high (30 degrees) temperature during photostimulation ha ... | 1996 | 8729934 |
| effect of day length on luteinizing hormone beta-subunit mrna and subsequent gonadal growth in the white-crowned sparrow, zonotrichia leucophrys gambelii. | we have applied a cdna probe for chicken luteinizing hormone beta-subunit to adenohypophysial preparations collected from gambell's white-crowned sparrows. in situ hybridization showed luteinizing hormone (lh) beta-subunit mrna distributed throughout the adenohypophysis in a manner identical to that of lh visualized by immunocytochemistry. northern blot analysis showed a single band (0.8 kbp) identical to that from japanese quail. dot blot analysis was used to quantify changes in lh beta-subunit ... | 1994 | 7926654 |
| fluorescence microscopy of neurons containing primary catecholamines in the ventral hypothalamus of the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1973 | 4743253 |
| some endocrine correlates of renesting after loss of clutch or brood in the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1979 | 488683 |
| brain transcriptome sequencing and assembly of three songbird model systems for the study of social behavior. | emberizid sparrows (emberizidae) have played a prominent role in the study of avian vocal communication and social behavior. we present here brain transcriptomes for three emberizid model systems, song sparrow melospiza melodia, white-throated sparrow zonotrichia albicollis, and gambel's white-crowned sparrow zonotrichia leucophrys gambelii. each of the assemblies covered fully or in part, over 89% of the previously annotated protein coding genes in the zebra finch taeniopygia guttata, with 16,8 ... | 2014 | 24883256 |
| one meadow for two sparrows: resource partitioning in a high elevation habitat. | resource partitioning is the basis of the coexistence of sympatric species and has therefore received much attention in ecological studies. however, how variation in environmental conditions (and particularly natural variation in resource availability) can influence resource partitioning in free-ranging animals is not well understood. in the present study, we addressed the hypothesis that natural changes in the availability of food resources affect food partitioning between sympatric species. to ... | 2012 | 22526943 |
| extreme spring conditions in the arctic delay spring phenology of long-distance migratory songbirds. | arctic regions are warming rapidly, with extreme weather events increasing in frequency, duration, and intensity just as in other regions. many studies have focused on how shifting seasonality in environmental conditions affects vegetation phenology, while far fewer have examined how the breeding phenology of arctic fauna responds. we studied two species of long-distance migratory songbirds, lapland longspurs, calcarius lapponicus, and white-crowned sparrows, zonotrichia leucophrys gambelii, acr ... | 2017 | 28779226 |
| a species-specific acoustic cue for selective song learning in the white-crowned sparrow. | song learning in birds is paradoxical. without tutoring, songbirds do not develop normal songs. yet despite this inability, birds possess extensive foreknowledge, in a mechanistic sense, about the normal song of their species. when given a choice of tape recordings, young, näive songbirds select sounds of their own species for imitation. we tape-tutored white-crowned sparrows, zonotrichia leucophrys oriantha, with a set of manipulated songs to investigate whether the introductory whistle univers ... | 2000 | 11007638 |
| use of data on avian demographics and site persistence during overwintering to assess quality of restored riparian habitat. | monitoring responses by birds to restoration of riparian vegetation is relatively cost-effective, but in most assessments species-specific abundances, not demography, are monitored. data on birds collected during the nonbreeding season are particularly lacking. we captured birds in mist nets and resighted banded birds to estimate species richness and diversity, abundance, demographic indexes, and site-level persistence of permanent-resident and overwintering migrants in remnant and restored ripa ... | 2012 | 22443304 |
| selective mobilization of fatty acids from adipose tissue in migratory birds. | during times of high energy demand, stored fatty acids are mobilized from adipocytes. this mobilization has previously been shown to be a non-random process, with more hydrophilic fatty acids being mobilized most readily. the objectives of this study were to characterize the relative mobilization of fatty acids from adipocytes in two migratory bird species and to investigate possible changes in selective fatty acid mobilization associated with the migratory period. captive ruffs (philomachus pug ... | 2008 | 18083729 |
| greater shrub dominance alters breeding habitat and food resources for migratory songbirds in alaskan arctic tundra. | climate warming is affecting the arctic in multiple ways, including via increased dominance of deciduous shrubs. although many studies have focused on how this vegetation shift is altering nutrient cycling and energy balance, few have explicitly considered effects on tundra fauna, such as the millions of migratory songbirds that breed in northern regions every year. to understand how increasing deciduous shrub dominance may alter breeding songbird habitat, we quantified vegetation and arthropod ... | 2015 | 25294359 |
| the effects of acute restraint stress on plasma levels of prolactin and corticosterone across life-history stages in a short-lived bird: gambel's white-crowned sparrow (zonotrichia leucophrys gambelii). | the general reproductive effort model attempts to predict the resources that will be allocated to a current reproductive bout or to future survival by aborting the current reproductive attempt. life-history theory predicts that short-lived species should devote more resources toward a reproductive event because brood value is far greater compared with that of long-lived species that have multiple breeding opportunities. previous bird studies have used patterns of hormone secretion to understand ... | 2015 | 26658407 |
| the effect of extreme spring weather on body condition and stress physiology in lapland longspurs and white-crowned sparrows breeding in the arctic. | climate change is causing rapid shifts in temperature while also increasing the frequency, duration, and intensity of extreme weather. in the northern hemisphere, the spring of 2013 was characterized as extreme due to record high snow cover and low temperatures. studies that describe the effects of extreme weather on phenology across taxa are limited while morphological and physiological responses remain poorly understood. stress physiology, as measured through baseline and stress-induced concen ... | 2016 | 27449342 |
| factors influencing song development in the white-crowned sparrow (zonotrichia leucophrys). | nestling white-crowned sparrows (zonotrichia leucophrys nuttalli) were hand-reared in sound-isolation chambers under a variety of conditions. the songs of total isolates were compared with songs of birds tutored with song, and the number of inputs sufficient for a bird to produce a normal song was explored. the flexibility of the song learning system was investigated with a range of tape-recorded tutor songs: alien dialects, alien subspecies, alien species, alternating alien dialects, and an abe ... | 2013 | 3979027 |
| unsupervised bird song syllable classification using evolving neural networks. | evolution of bird vocalizations is subjected to selection pressure related to their functions. passerine bird songs are also under a neutral model of evolution because of the learning process supporting their transmission; thus they contain signals of individual, population, and species relationships. in order to retrieve this information, large amounts of data need to be processed. from vocalization recordings, songs are extracted and encoded as sequences of syllables before being compared. enc ... | 2008 | 18537387 |
| widespread and structured distributions of blood parasite haplotypes across a migratory divide of the swainson's thrush (catharus ustulatus). | we examined the phylogenetic distribution of cytochrome b haplotypes of the avian blood parasite genera haemoproteus and plasmodium across the migratory divide of the swainson's thrush (catharus ustulatus) in british columbia, canada. from 87 host individuals, we identified 8 parasite haplotypes; 4 of plasmodium and 4 of haemoproteus. six haplotypes were novel; 1 haemoproteus haplotype was identical to h. majoris found in the blue tit (parus caeruleus) in sweden, and another halotype was identic ... | 2007 | 18314697 |
| gonadotropin-inhibitory hormone in gambel's white-crowned sparrow (zonotrichia leucophrys gambelii): cdna identification, transcript localization and functional effects in laboratory and field experiments. | the neuropeptide control of gonadotropin secretion is primarily through the stimulatory action of the hypothalamic decapeptide, gnrh. we recently identified a novel hypothalamic dodecapeptide with a c-terminal leupro-leu-arg-phe-nh2 sequence in the domestic bird, japanese quail (coturnix japonica). this novel peptide inhibited gonadotropin release in vitro from the quail anterior pituitary; thus it was named gonadotropin-inhibitory hormone (gnih). gnih may be an important factor regulating repro ... | 2004 | 15225129 |
| evidence for a novel gonadotropin-releasing hormone in hypothalamic and forebrain areas in songbirds. | one or more of three distinct forms of gonadotropin-releasing hormones (gnrhs), has been found in all vertebrates studied. birds are known to contain two types of gnrh, chicken gnrh-i and -ii (cgnrh-i and -ii), but to date nobody has investigated the possibility of the presence of lamprey gnrh-iii in birds. thus, our objective was to investigate the presence and distribution of immunoreactive lamprey (ir-lamprey) gnrh-iii in hypothalamic and forebrain areas in house sparrows (passer domesticus) ... | 2004 | 14673197 |
| effects of temperature on photoperiodically induced reproductive development, circulating plasma luteinizing hormone and thyroid hormones, body mass, fat deposition and molt in mountain white-crowned sparrows, zonotrichia leucophrys oriantha. | the mountain white-crowned sparrow, zonotrichia leucophrys oriantha, breeds in subalpine meadows throughout many mountainous regions of western north america. mathematical analysis of 20 years of egg-laying dates at tioga pass, california (3030m elevation) indicated a highly predictable breeding season suggesting that precise environmental cues such as the annual change in day length were important for regulating reproductive function. additionally, it appeared that there was sufficient yearly v ... | 2003 | 12679091 |
| latitudinal variation in plasma testosterone levels in birds of the genus zonotrichia. | birds breeding in northern latitudes generally have elevated plasma testosterone levels throughout the breeding season with a peak at the onset of the breeding season. in contrast, tropical birds tend to have extremely low plasma testosterone levels year round with only a slight increase during breeding. while these patterns have been consistent in the species investigated, closely related species have not been investigated across a range of latitudes. birds of the genus zonotrichia present an i ... | 2002 | 12409091 |
| effects of vasoactive intestinal peptide on plasma prolactin in passerines. | vasoactive intestinal peptide (vip) is a potent releaser of prolactin (prl) in domestic fowl, turkey, and ring doves. however, few comparative studies have investigated this in wild species. we tested the effects of intravenously administered chicken vip on plasma prl concentrations in four passerine species: the white-crowned sparrow (zonotrichia leucophrys gambelii), the dark-eyed junco (junco hyemalis), the florida scrub-jay (aphelocoma coerulescens), and the western scrub-jay (a. californica ... | 1999 | 10068494 |
| central administration of chicken gonadotropin-releasing hormone-ii enhances courtship behavior in a female sparrow. | like most vertebrates, birds have two forms of gonadotropin-releasing hormone (gnrh). chicken gnrh-i (cgnrh-i) is released at the median eminence to elicit gonadotropin release; chicken gnrh-ii (cgnrh-ii) is thought to be non-hypophysiotropic and its function is unclear. both forms are hypothesized to act as neurotransmitters in the control of reproductive behavior. in the present study, we implanted chronic cannulae aimed at the third ventricle in female white-crowned sparrows (zonotrichia leuc ... | 1997 | 9344687 |
| effects of a social cue on reproductive development and pre-alternate molt in seasonally breeding migrant and resident female songbirds (zonotrichia leucophrys). | to time reproduction optimally, birds have evolved diverse mechanisms by which they respond to environmental changes that help them anticipate and prepare for the breeding season. while residents initiate reproductive preparation and breed in the same geographic location, migrant birds simultaneously prepare for breeding and migration far from their breeding grounds. as a result, it is hypothesized that migrant and resident birds use environmental cues differently to prepare to breed and that th ... | 2017 | 28814612 |
| delayed song maturation and territorial aggression in a songbird. | asymmetries in competitive ability can determine the outcome of social interactions in animals and are often expressed through differences in sexual traits. competitive ability (resource holding potential, rhp), trait expression and ultimately reproductive success may vary with an individual's age or experience. in some species, reproductively mature males delay acquisition of some adult traits and thereby signal their young age. theory on animal contests predicts that individuals assess the rhp ... | 2012 | 22319096 |
| white-crowned sparrow males show immediate flexibility in song amplitude but not in song minimum frequency in response to changes in noise levels in the field. | the soundscape acts as a selective agent on organisms that use acoustic signals to communicate. a number of studies document variation in structure, amplitude, or timing of signal production in correspondence with environmental noise levels thus supporting the hypothesis that organisms are changing their signaling behaviors to avoid masking. the time scale at which organisms respond is of particular interest. signal structure may evolve across generations through processes such as cultural or ge ... | 2017 | 28690825 |
| from song dialects to speciation in white-crowned sparrows. | the behavioural signals used in mate selection are a key component in the evolution of premating isolating barriers and, subsequently, the formation of new species. the importance of mating signals has a long tradition of study in songbirds, where many species differ in their song characteristics. in oscine songbirds, individual birds usually learn their songs from a tutor. mistakes during learning can help generate geographic dialects, akin to those within human language groups. in songbirds, d ... | 2017 | 28544663 |
| next-generation sequencing reveals phylogeographic structure and a species tree for recent bird divergences. | next generation sequencing (ngs) technologies are revolutionizing many biological disciplines but have been slow to take root in phylogeography. this is partly due to the difficulty of using ngs to sequence orthologous dna fragments for many individuals at low cost. we explore cases of recent divergence in four phylogenetically diverse avian systems using a method for quick and cost-effective generation of primary dna sequence data using pyrosequencing. ngs data were processed using an analytica ... | 2012 | 22063264 |
| male response to historical and geographical variation in bird song. | in many species, individuals discriminate among sexual signals of conspecific populations in the contexts of mate choice and male-male competition. differences in signals among populations (geographical variation) are in part the result of signal evolution within populations (temporal variation). understanding the relative effect of temporal and geographical signal variation on signal salience may therefore provide insight into the evolution of behavioural discrimination. however, no study, to m ... | 2011 | 20685696 |
| corticosterone inhibits feather growth: potential mechanism explaining seasonal down regulation of corticosterone during molt. | corticosterone (cort) is seasonally modulated in many passerines, with plasma cort concentrations lowest during the prebasic molt when all feathers are replaced. to explain why, we proposed that the birds downregulate natural cort release during molt in order to avoid cort's degradative effects on proteins and its inhibition of protein synthesis. if cort exerted these effects during molt, it could slow protein deposition during feather production and potentially result in a longer period of degr ... | 2005 | 16125989 |
| hippocampal neurogenesis is associated with migratory behaviour in adult but not juvenile sparrows (zonotrichia leucophrys ssp.). | it has been hypothesized that individuals who have higher demands for spatially based behaviours should show increases in hippocampal attributes. some avian species have been shown to use a spatially based representation of their environment during migration. further, differences in hippocampal attributes have been shown between migratory and non-migratory subspecies as well as between individuals with and without migratory experience (juveniles versus adults). we tested whether migratory behavi ... | 2011 | 20659933 |
| three-dimensional analysis of avian song control nuclei. | analysis of seasonal and developmental changes in the morphology of avian song control nuclei has traditionally been performed using two-dimensional (2-d) cross-sectional traces from brain sections. this method, although reliable, does not encompass the possibility that subdivisions of a nucleus might change in size to different degrees. three-dimensional (3-d) analysis of song nuclei under different conditions could provide insight on this issue. this approach could also be of value in guiding ... | 2002 | 12393163 |
| behavioural response to song and genetic divergence in two subspecies of white-crowned sparrows (zonotrichia leucophrys). | divergence in sexual signals may drive reproductive isolation between lineages, but behavioural barriers can weaken in contact zones. here, we investigate the role of song as a behavioural and genetic barrier in a contact zone between two subspecies of white-crowned sparrows (zonotrichia leucophrys). we employed a reduced genomic data set to assess population structure and infer the history underlying divergence, gene flow and hybridization. we also measured divergence in song and tested behavio ... | 2017 | 28036146 |
| altered expression of pectoral myosin heavy chain isoforms corresponds to migration status in the white-crowned sparrow (zonotrichia leucophrys gambelii). | birds undergo numerous changes as they progress through life-history stages, yet relatively few studies have examined how birds adapt to both the dynamic energetic and mechanical demands associated with such transitions. myosin heavy chain (myhc) expression, often linked with muscle fibre type, is strongly correlated with a muscle's mechanical power-generating capability, thus we examined several morphological properties, including myhc expression of the pectoralis, in a long-distance migrant, t ... | 2016 | 28018664 |
| adult neurogenesis leads to the functional reconstruction of a telencephalic neural circuit. | seasonally breeding songbirds exhibit pronounced annual changes in song behavior, and in the morphology and physiology of the telencephalic neural circuit underlying production of learned song. each breeding season, new adult-born neurons are added to the pallial nucleus hvc in response to seasonal changes in steroid hormone levels, and send long axonal projections to their target nucleus, the robust nucleus of the arcopallium (ra). we investigated the role that adult neurogenesis plays in the s ... | 2016 | 27559175 |
| twenty-one novel microsatellite dna loci isolated from the puget sound white-crowned sparrow, zonotrichia leucophrys pugetensis. | the white-crowned sparrow, zonotrichia leucophrys, has served as a model species for studies of song and reproductive physiology. here, we describe primers for 21 novel microsatellite loci isolated from the puget sound subspecies, zonotrichia leucophrys pugetensis, which will be useful for parentage and population genetic analyses. based on genotypes from seven to 22 adult birds from one population, the average number of alleles per locus was 10.9 (four to 21 alleles) and observed heterozygosity ... | 2009 | 21564746 |
| regulation of vernal migration in gambel's white-crowned sparrows: role of thyroxine and triiodothyronine. | appropriate timing of migratory behavior is critical for migrant species. for many temperate zone birds in the spring, lengthening photoperiod is the initial cue leading to morphological, physiological and behavior changes that are necessary for vernal migration and breeding. strong evidence has emerged in recent years linking thyroid hormone signaling to the photoinduction of breeding in birds while more limited information suggest a potential role in the regulation of vernal migration in photo ... | 2016 | 27234300 |
| patterns of song across natural and anthropogenic soundscapes suggest that white-crowned sparrows minimize acoustic masking and maximize signal content. | soundscapes pose both evolutionarily recent and long-standing sources of selection on acoustic communication. we currently know more about the impact of evolutionarily recent human-generated noise on communication than we do about how natural sounds such as pounding surf have shaped communication signals over evolutionary time. based on signal detection theory, we hypothesized that acoustic phenotypes will vary with both anthropogenic and natural background noise levels and that similar mechanis ... | 2016 | 27128443 |
| annual hematocrit profiles in two subspecies of white-crowned sparrow: a migrant and a resident comparison. | hematocrit is an easily measured parameter that can be used to assess changes in oxygen carrying capacity necessitated by fluctuations in metabolic demands. most hematocrit studies draw conclusions from changes in hematocrit that occur over a small sampling interval without an understanding of the variation that exists across the annual cycle. white-crowned sparrows provide an excellent model system due to the existence of a resident subspecies (zonotrichia leucophrys nuttalli) that serves as a ... | 2016 | 27082524 |
| network analysis of microrna and mrna seasonal dynamics in a highly plastic sensorimotor neural circuit. | adult neurogenesis and the incorporation of adult-born neurons into functional circuits requires precise spatiotemporal coordination across molecular networks regulating a wide array of processes, including cell proliferation, apoptosis, neurotrophin signaling, and electrical activity. micrornas (mirs) - short, non-coding rna sequences that alter gene expression by post-transcriptional inhibition or degradation of mrna sequences - may be involved in the global coordination of such diverse biolog ... | 2015 | 26545368 |
| breeding on the leading edge of a northward range expansion: differences in morphology and the stress response in the arctic gambel's white-crowned sparrow. | individuals at the forefront of a range shift are likely to exhibit phenotypic traits that distinguish them from the population breeding within the historic range. recent studies have examined morphological, physiological and behavioral phenotypes of individuals at the edge of their range. several studies have found differences in the hypothalamic-pituitary-adrenal (hpa) axis activity in response to acute restraint stress in individuals at the range limits. hpa axis activation leads to elevation ... | 2016 | 26423267 |
| haemoproteus infected birds have increased lifetime reproductive success. | the impact of haematozoan infection on host fitness has received substantial attention since hamilton and zuk posited that parasites are important drivers of sexual selection. however, short-term studies testing the assumption that these parasites consistently reduce host fitness in the wild have produced contradictory results. to address this complex issue, we conducted a long-term study examining the relationship between naturally occurring infection with haemoproteus and plasmodium, and lifet ... | 2015 | 25800822 |
| seasonal plasticity of precise spike timing in the avian auditory system. | vertebrate audition is a dynamic process, capable of exhibiting both short- and long-term adaptations to varying listening conditions. precise spike timing has long been known to play an important role in auditory encoding, but its role in sensory plasticity remains largely unexplored. we addressed this issue in gambel's white-crowned sparrow (zonotrichia leucophrys gambelii), a songbird that shows pronounced seasonal fluctuations in circulating levels of sex-steroid hormones, which are known to ... | 2015 | 25716843 |
| decreases in mineralocorticoid but not glucocorticoid receptor mrna expression during the short arctic breeding season in free-living gambel's white-crowned sparrow (zonotrichia leucophrys gambelii). | the acute stress response in vertebrates is a highly adaptive suite of physiological and behavioural mechanisms that promote survival in the face of deleterious stimuli from the environment. facultative changes of physiology and behaviour are mediated through changes in circulating levels of glucocorticoids (corticosterone, cortisol) and their subsequent binding to the high-affinity mineralocorticoid receptor (mr) or the low-affinity glucocorticoid receptor (gr). free-living male wild gambel's w ... | 2015 | 25411901 |
| reactive neurogenesis in response to naturally occurring apoptosis in an adult brain. | neuronal birth and death are tightly coordinated to establish and maintain properly functioning neural circuits. disruption of the equilibrium between neuronal birth and death following brain injury or pharmacological insult often induces reactive, and in some cases regenerative, neurogenesis. many neurodegenerative disorders are not injury-induced, however, so it is critical to determine if and how reactive neurogenesis occurs under noninjury-induced neurodegenerative conditions. here, we used ... | 2014 | 25253853 |
| changes in plasma concentrations of progesterone, dehydroepiandrosterone and corticosterone in response to acute stress of capture, handling and restraint in two subspecies of white-crowned sparrows. | the aim of this study was to determine circulating patterns of the three major adrenal steroids in blood in response to stress during acute restraint handling in two subspecies of white-crowned sparrow. gambel's white-crowned sparrows (zonotrichia leucophrys gambelii) are long distance migrants that breed at high latitudes and nuttall's white-crowned sparrows (zonotrichia leucophrys nuttalli) are residents of coastal california. column partition chromatography was developed to separate progester ... | 2014 | 25072921 |
| regulatory mechanisms for the development of the migratory phenotype: roles for photoperiod and the gonad. | this article is part of a special issue "energy balance". male white-crowned sparrows, zonotrichia leucophrys gambelii, were studied to investigate roles of natural day length and the testes in regulating development and expression of the vernal migration phenotype. previous work suggested that a pulse of androgen during winter months followed by the vernal increase in photoperiod promotes fueling (fat deposition) to support long distance flight; however, other traits required for successful mig ... | 2014 | 24780144 |
| environment, behavior and physiology: do birds use barometric pressure to predict storms? | severe storms can pose a grave challenge to the temperature and energy homeostasis of small endothermic vertebrates. storms are accompanied by lower temperatures and wind, increasing metabolic expenditure, and can inhibit foraging, thereby limiting energy intake. to avoid these potential problems, most endotherms have mechanisms for offsetting the energetic risks posed by storms. one possibility is to use cues to predict oncoming storms and to alter physiology and behavior in ways that make surv ... | 2013 | 23678098 |
| effects of experimentally elevated traffic noise on nestling white-crowned sparrow stress physiology, immune function and life history. | roads have been associated with behavioral and physiological changes in wildlife. in birds, roads decrease reproductive success and biodiversity and increase physiological stress. although the consequences of roads on individuals and communities have been well described, the mechanisms through which roads affect birds remain largely unexplored. here, we examine one mechanism through which roads could affect birds: traffic noise. we exposed nestling mountain white-crowned sparrows (zonotrichia le ... | 2013 | 23430998 |
| estradiol selectively enhances auditory function in avian forebrain neurons. | sex steroids modulate vertebrate sensory processing, but the impact of circulating hormone levels on forebrain function remains unclear. we tested the hypothesis that circulating sex steroids modulate single-unit responses in the avian telencephalic auditory nucleus, field l. we mimicked breeding or nonbreeding conditions by manipulating plasma 17β-estradiol levels in wild-caught female gambel's white-crowned sparrows (zonotrichia leucophrys gambelii). extracellular responses of single neurons t ... | 2012 | 23223283 |
| the relationship between migratory behaviour, memory and the hippocampus: an intraspecific comparison. | it has been hypothesized that memory-demanding ecological conditions might result in enhanced memory and an enlarged hippocampus, an area of the brain involved in memory processing, either via extensive memory experience or through evolutionary changes. avian migration appears to represent one of such memory-demanding ecological conditions. we compared two subspecies of the white-crowned sparrow: migratory zonotrichia leucophrys gambelii and non-migratory z. l. nuttalli. compared to non-migrator ... | 2006 | 17002950 |
| metabolism and distribution of p,p'-ddt during flight of the white-crowned sparrow, zonotrichia leucophrys. | this study evaluated the interactions of flight, fasting, and 1,1,1-trichloro-bis(4-chlorophenyl)ethane (p,p'-ddt) loading on residue metabolism and distribution in recently exposed white-crowned sparrows (zonotrichia leucophrys). female sparrows were dosed with 5 mg p,p'-ddt per kg body weight over 3 d. following 1 d of recovery, sparrows were flown in a wind tunnel for up to 140 min, in 15-min blocks. food was withheld from the start of the flight period until birds were euthanized. ddt, 1,1-d ... | 2012 | 22045600 |
| proximity to a high traffic road: glucocorticoid and life history consequences for nestling white-crowned sparrows. | roads have been associated with decreased reproductive success and biodiversity in avian communities and increased physiological stress in adult birds. alternatively, roads may also increase food availability and reduce predator pressure. previous studies have focused on adult birds, but nestlings may also be susceptible to the detrimental impacts of roads. we examined the effects of proximity to a road on nestling glucocorticoid activity and growth in the mountain white-crowned sparrow (zonotri ... | 2011 | 21712039 |
| effects of short-term fasting on stress physiology, body condition, and locomotor activity in wintering male white-crowned sparrows. | for wild free-living animals the availability of food resources can be greatly affected by environmental perturbations such as weather events. in response to environmental perturbations, animals activate the hypothalamic-pituitary-adrenal (hpa) axis to adjust physiology and behavior. the literature asserts that during weather events food intake declines leading to changes in hpa axis activity, as measured by both baseline and stress-induced glucocorticoid concentrations. here we investigated how ... | 2017 | 28472668 |
| dramatic orientation shift of white-crowned sparrows displaced across longitudes in the high arctic. | advanced spatial-learning adaptations have been shown for migratory songbirds, but it is not well known how the simple genetic program encoding migratory distance and direction in young birds translates to a navigation mechanism used by adults. a number of convenient cues are available to define latitude on the basis of geomagnetic and celestial information, but very few are useful to defining longitude. to investigate the effects of displacements across longitudes on orientation, we recorded or ... | 2005 | 16139216 |
| behavioral and physiological traits of migrant and resident white-crowned sparrows: a common garden approach. | to accommodate a migratory life history, migrants express a greater number of physiological and behavioral stages per annum than residents and are thus considered to have higher finite state diversity (fsd). to investigate the physiological mechanisms and constraints associated with migration, direct comparison of two subspecies of white-crowned sparrow - migrant, zonotrichia leucophrys gambelii, and resident, z. l. nuttalli - were made under common garden conditions of photoperiod and housing, ... | 2017 | 28183869 |
| seasonal influences on sleep and executive function in the migratory white-crowned sparrow (zonotrichia leucophrys gambelii). | we have previously shown that the white-crowned sparrow (wcs) decreases sleep by 60% during a period of migratory restlessness relative to a non-migratory period when housed in a 12 h light: 12 h dark cycle. despite this sleep reduction, accuracy of operant performance was not impaired, and in fact rates of responding were elevated during the migratory period, effects opposite to those routinely observed following enforced sleep deprivation. to determine whether the previously observed increases ... | 2010 | 20670404 |
| peripheral auditory processing changes seasonally in gambel's white-crowned sparrow. | song in oscine birds is a learned behavior that plays important roles in breeding. pronounced seasonal differences in song behavior and in the morphology and physiology of the neural circuit underlying song production are well documented in many songbird species. androgenic and estrogenic hormones largely mediate these seasonal changes. although much work has focused on the hormonal mechanisms underlying seasonal plasticity in songbird vocal production, relatively less work has investigated seas ... | 2010 | 20563817 |
| roles of syntax information in directing song development in white-crowned sparrows (zonotrichia leucophrys). | syntactical cues play an important role in song learning in songbirds. white-crowned sparrows (zonotrichia leucophrys), whose song typically consists of four to five different phrases, fail to construct normal songs if exposed to all phrase types presented singly (plamondon, goller, & rose, 2008; soha & marler 2001b). the specific role of acquired syntax information in guiding ontogenetic trajectories of syntax, however, and the respective contributions of instructive and selective processes to ... | 2010 | 20476811 |
| preparing for migration? the effects of photoperiod and exercise on muscle oxidative enzymes, lipid transporters, and phospholipids in white-crowned sparrows. | the extreme energetic demands of avian migration result in various physiological changes that can be observed during the migratory period. however, the degree to which birds alter muscle physiology in advance of migration has been poorly studied. we studied the effects of "migratory" photoperiod and exercise on metabolic enzymes, fatty acid transporter mrna expression, and muscle phospholipid fatty acid composition in captive white-crowned sparrows (zonotrichia leucophrys). ten sparrows were hel ... | 2013 | 20078207 |
| ecology shapes birdsong evolution: variation in morphology and habitat explains variation in white-crowned sparrow song. | ecological variation appears to underlie the evolution of mating signals in many taxa, yet understanding of how this process occurs over time is limited. here, i investigate whether changes over time in a well-studied mating signal-birdsong-are attributable to ecological factors that affect signal production and transmission. variation in the acoustic properties of songs is thought to be affected by the mechanics of sound production as well as by features of the habitat that affect sound transmi ... | 2009 | 19441960 |
| testosterone treatment diminishes sickness behavior in male songbirds. | males of many vertebrate species are typically more prone to disease and infection than female conspecifics, and this sexual difference is partially influenced by the immunosuppressive properties of testosterone (t) in males. t-induced immunosuppression has traditionally been viewed as a pleiotropic handicap, rather than an adaptation. recently, it has been hypothesized that suppression of sickness behavior, or the symptoms of infection, may have adaptive value if sickness interferes with the ex ... | 2009 | 19374904 |
| time course of changes in gambel's white-crowned sparrow song behavior following transitions in breeding condition. | seasonal changes in behavior and in its underlying neural substrate are common across animal taxa. these changes are often triggered by steroid sex hormones. song in seasonally breeding songbirds provides an excellent example of this phenomenon. in these species, dramatic seasonal changes mediated by testosterone and its metabolites occur in adult song behavior and in the neural circuitry controlling song. while song rate can quickly change in response to seasonal breeding cues, it is unknown ho ... | 2009 | 19013173 |
| impacts of frequent, acute pulses of corticosterone on condition and behavior of gambel's white-crowned sparrow (zonotrichia leucophrys gambelii). | little is known about how frequent, acute stressors affect wild animals. we present two experiments conducted on captive, gambel's white-crowned sparrow (zonotrichia leucophrys gambelii) that explore how frequent, acute doses of corticosterone (cort) affect condition and behavior. cort was administered either once or three times a day to birds in pre-breeding, early-breeding, or late-breeding life-history stages. two additional groups were included to control for the cort delivery vehicle, dmso, ... | 2008 | 18713634 |
| effects of repeated, short-term, corticosterone administration on the hypothalamo-pituitary-adrenal axis of the white-crowned sparrow (zonotrichia leucophrys gambelii). | our knowledge of glucocorticoid actions in vertebrates comes primarily from laboratory studies, which are often conducted with little consideration of how animals experience changes in glucocorticoid secretion in natural contexts. typically, free-living animals are exposed to acute perturbations of the environment, ranging from a few minutes to a few hours duration, with varying frequency. the cumulative effects of these perturbations and their resultant glucocorticoid surges are not well known. ... | 2008 | 18586038 |
| changes in brain gene expression during migration in the white-crowned sparrow. | long-term recordings of seasonal sleep patterns in captive white-crowned sparrows (zonotrichia leucophrys gambelii) have shown that these birds markedly reduce sleep time during the migratory period relative to the non-migratory period. it was also found that, despite this sleep reduction, sparrows showed no evidence of neurobehavioral deficits in a standard operant task used to assess the effects of sleep loss. in this study, we performed an extensive microarray analysis of gene expression in t ... | 2008 | 18534263 |
| homeostatic regulation of sleep in the white-crowned sparrow (zonotrichia leucophrys gambelii). | sleep is regulated by both a circadian and a homeostatic process. the homeostatic process reflects the duration of prior wakefulness: the longer one stays awake, the longer and/or more intense is subsequent sleep. in mammals, the best marker of the homeostatic sleep drive is slow wave activity (swa), the electroencephalographic (eeg) power spectrum in the 0.5-4 hz frequency range during non-rapid eye movement (nrem) sleep. in mammals, nrem sleep swa is high at sleep onset, when sleep pressure is ... | 2008 | 18505569 |
| seasonal-like growth and regression of the avian song control system: neural and behavioral plasticity in adult male gambel's white-crowned sparrows. | birdsong is regulated by a series of discrete brain nuclei known as the song control system. in seasonally-breeding male songbirds, seasonal changes in steroid sex hormones regulate the structure and electrophysiology of song control system neurons, resulting in dramatic changes in singing behavior. male songbirds can be brought into the laboratory, where circulating levels of steroid hormone and photoperiod can be abruptly manipulated, providing controlled conditions under which rapid "seasonal ... | 2008 | 18457836 |
| intracerebroventricular corticotropin-releasing factor decreases food intake in white-crowned sparrows. | neuropeptides such as corticotropin-releasing factor (crf) may play a role in regulating the pronounced seasonal changes in food intake shown by white-crowned sparrows (zonotrichia leucophrys gambelii). white-crowned sparrows held on short day length received injections into the third ventricle (icv) of saline or 5.0, 15.0, and 30 microg/kg. meal size over the subsequent 180 min was significantly depressed in a dose-dependent fashion. other non-specific behaviors such as preening, hopping, and i ... | 2007 | 11134705 |
| on the evolution of brain size in relation to migratory behaviour in birds. | migratory birds appear to have relatively smaller brain size compared to sedentary species. it has been hypothesized that initial differences in brain size underlying behavioural flexibility drove the evolution of migratory behaviour; birds with relatively large brains evolved sedentary habits and those with relatively small brains evolved migratory behaviour (migratory precursor hypothesis). alternative hypotheses suggest that changes in brain size might follow different behavioural strategies ... | 2007 | 18311316 |
| circadian and masking control of migratory restlessness in gambel's white-crowned sparrow (zonotrichia leucophrys gambelii). | avian migration is a seasonal activity that requires intricate timing on both an annual and daily basis. with increasing evidence for endogenous regulation of daily activities in migrant species, we tested whether a circadian oscillator may be involved with the expressions of daily locomotor activities and specific behaviors of the long-distance migrant, gambel's white-crowned sparrow (zonotrichia leucophrys gambelii). our previous studies have identified both daytime and nighttime behavioral pa ... | 2008 | 18258758 |
| latitudinal variation of immune defense and sickness behavior in the white-crowned sparrow (zonotrichia leucophrys). | there is a general trend that parasitism risk declines as latitude increases. host populations breeding at high latitudes should therefore invest less in costly immune defenses than populations breeding in temperate or tropical zones, although it is unknown if such an effect is mediated by environmental (photoperiodic) or genetic factors or both. acquired immune function (humoral, cell-mediated) and behavioral sickness responses to lipopolysaccharide (lps; mimics bacterial infection) were assess ... | 2008 | 18255257 |
| pre-migratory life history stages of juvenile arctic birds: costs, constraints, and trade-offs. | many young birds on the arctic tundra are confronted by a challenging task: they must molt their feathers and accumulate fat stores for the autumn migration before climatic conditions deteriorate. our understanding of the costs and constraints associated with these stages is extremely limited. we investigated post-juvenal molt and premigratory fattening in free-ranging juvenile white-crowned sparrows (zonotrichia leucophrys gambelii) on the arctic tundra. we found evidence for trade-offs between ... | 2007 | 18051640 |
| molecular correlates of sleep and wakefulness in the brain of the white-crowned sparrow. | in the mammalian brain, sleep and wakefulness are associated with widespread changes in gene expression. the extent to which the molecular correlates of vigilance state are conserved across phylogeny, however, is only beginning to be explored. the goal of this study was to determine whether sleep and wakefulness affect gene expression in the avian brain. to achieve this end we performed an extensive microarray analysis of gene expression during sleep, wakefulness, and short-term sleep deprivatio ... | 2008 | 18028333 |
| evolution of bird song affects signal efficacy: an experimental test using historical and current signals. | mating signals act as behavioral barriers to gene flow in many animal taxa, yet little is known about how signal evolution within populations contributes to the formation of these barriers. although variation in mating signals among populations is known to affect mating behavior, there is no direct evidence that the evolution of mating signals changes signal effectiveness within a natural population. making use of historical recordings of bird song, i found that both male and female white-crowne ... | 2007 | 17683435 |
| parasite-mediated heterozygote advantage in an outbred songbird population. | coevolution with parasites is thought to maintain genetic diversity in host populations. however, while there are sound theoretical reasons to expect heterozygosity and parasite resistance to be related, this pattern has generally been shown only in inbred laboratory and island populations. this leaves doubt as to whether parasite-mediated selection for genetic diversity is in fact a general process. here we show that haematozoan parasite load is linked to two complementary measures of microsate ... | 2005 | 17148140 |
| plasma metabolite profiles: effects of dietary phospholipids in a migratory passerine (zonotrichia leucophrys gambelii). | plasma metabolites, including triglycerides, beta -hydroxybutyrate, and glycerol, can be used to estimate mass change in birds. although dietary fatty acids can be ingested and absorbed as phospholipids, they have been largely overlooked as a potential indicator of mass change. the plasma ratio of triglyceride to phospholipid could also provide insight into diet quality because a high ratio in food items indicates high relative energy content. variability in dietary phospholipid content and trig ... | 2006 | 16826501 |
| the relationship between uric acid and its oxidative product allantoin: a potential indicator for the evaluation of oxidative stress in birds. | uric acid is the main nitrogenous waste product in birds but it is also known to be a potent antioxidant. hominoid primates and birds lack the enzyme urate oxidase, which oxidizes uric acid to allantoin. consequently, the presence of allantoin in their plasma results from non-enzymatic oxidation. in humans, the allantoin to uric acid ratio in plasma increases during oxidative stress, thus this ratio has been suggested to be an in vivo marker for oxidative stress in humans. we measured the concen ... | 2006 | 16705445 |
| hypothalamic pro-gnrh-gap, gnrh-i and gnrh-ii during the onset of photorefractoriness in the white-crowned sparrow (zonotrichia leucophrys gambelii). | gambel's white-crowned sparrow is a long distance migrant that undergoes spontaneous gonadal regression as a result of long day exposure. this termination of breeding is caused by the development of photorefractoriness and the birds become insensitive to long days, including continuous light. the present study investigated its possible mechanisms by examining the activity of the gonadotrophin-releasing hormone (gnrh) system under different photoperiodic regimes. we investigated the localisation ... | 2006 | 16454805 |
| neurally active stress peptide inhibits territorial defense in wild birds. | it is unclear whether the behavioral effects of peptides in laboratory studies always reflect natural conditions. here we test whether we can detect measurable behavioral changes after rapidly injecting peptides into the brains of wild birds. we used a modified stereotaxic-like technique to inject corticotrophin-releasing factor (crf) and arginine vasotocin (avt, the nonmammalian form of arginine vasopressin), two hormones important in the stress response, into the brains of wild, freely behavin ... | 1998 | 9878273 |
| variation in circulating corticosterone levels is associated with altitudinal range expansion in a passerine bird. | organisms frequently need to adjust physiological mechanisms to successfully breed in novel habitats. to explore how some populations physiologically acclimate to novel environmental conditions while others do not, we examine three subspecies of the white-crowned sparrow, zonotrichia leucophrys. of these subspecies, z. l. pugetensis has expanded its breeding range to high altitude over the last 60 years. we investigate physiological acclimation to high altitude conditions by comparing circulatin ... | 2011 | 21533815 |
| migratory sleeplessness in the white-crowned sparrow (zonotrichia leucophrys gambelii). | twice a year, normally diurnal songbirds engage in long-distance nocturnal migrations between their wintering and breeding grounds. if and how songbirds sleep during these periods of increased activity has remained a mystery. we used a combination of electrophysiological recording and neurobehavioral testing to characterize seasonal changes in sleep and cognition in captive white-crowned sparrows (zonotrichia leucophrys gambelii) across nonmigratory and migratory seasons. compared to sparrows in ... | 2004 | 15252455 |
| the effect of flight, fasting and p,p'-ddt on thyroid hormones and corticosterone in gambel's white-crowned sparrow, zonotrichia leucophrys gambelli. | this study examined the effects of p,p'-dichlorodiphenyltrichloroethane (p,p'-ddt), fasting and flight on thyroid hormones and corticosterone in gambel's white-crowned sparrows (zonotrichia leucophrys gambelli). female sparrows were dosed daily with either 5 mg p,p'-ddt per kg body mass or corn oil vehicle over 3 days. on the fifth day the sparrows were divided into 3 groups: (1) unstressed - non-stressed control sparrows; (2) fasted - sparrows fasted for intervals ranging from 20 min to 9 h; or ... | 2004 | 15050929 |
| the low-affinity glucocorticoid receptor regulates feeding and lipid breakdown in the migratory gambel's white-crowned sparrow zonotrichia leucophrys gambelii. | plasma corticosterone increases during spring migration in a variety of bird species, including the gambel's white-crowned sparrow zonotrichia leucophrys gambelii. corticosterone is elevated specifically in association with migratory flight, suggesting that corticosterone may promote processes such as energy mobilization and/or migratory activity. general effects of glucocorticoids support such a prediction. because glucocorticoids exert permissive effects on food intake, corticosterone may also ... | 2004 | 14638841 |
| immediate early gene response to hearing song correlates with receptive behavior and depends on dialect in a female songbird. | stimulus-induced expression of the immediate early gene zenk (egr-1) in the songbird's auditory forebrain presumably depends on the behavioral significance of the stimulus. few studies, however, have quantified both the zenk and behavioral responses to a stimulus in the same individuals. we played conspecific male song of either hatch (local) or foreign dialect to female white-crowned sparrows (zonotrichia leucophrys oriantha) and quantified both the auditory zenk response and their behavioral r ... | 2003 | 12879354 |
| differential mechanisms for regulation of the stress response across latitudinal gradients. | we examined plasticity of the stress response among three populations of the white-crowned sparrow (zonotrichia leucophrys). these populations breed at different elevations and latitudes and thus have breeding seasons that differ markedly in length. we hypothesize that in populations where birds raise only one or rarely two broods in a season, the fitness costs of abandoning a nest are substantially larger than in closely related populations that raise up to three broods per season. thus individ ... | 2003 | 12791587 |
| short-term fasting affects locomotor activity, corticosterone, and corticosterone binding globulin in a migratory songbird. | unpredictable events such as severe storms lead to an increase in circulating corticosterone (cort) in breeding birds. this increase is often accompanied by elevations in foraging and irruptive behavior. we were interested in determining if acute food restriction (such as might occur during inclement weather) is a sufficient cue to elicit an increase in locomotor activity, increase cort secretion, and/or decrease circulating levels of corticosterone binding globulin (cbg) in white-crowned sparro ... | 2003 | 12614645 |
| steroid hormone interrelationships with territorial aggression in an arctic-breeding songbird, gambel's white-crowned sparrow, zonotrichia leucophrys gambelii. | the breeding season is very brief for arctic-breeding passerines, and any interruptions of parental care by aggressive interactions over territory may reduce reproductive success. we tested both the "testosterone insensitivity" and "corticosterone insensitivity" hypotheses in the arctic-breeding gambel's white-crowned sparrow, zonotrichia leucophrys gambelii. additionally, we tested whether simulated territorial intrusions (stis), known to stimulate increases in luteinizing hormone (lh) and test ... | 2002 | 12367574 |
| altitudinal variation in parental energy expenditure by white-crowned sparrows. | we used the doubly labeled water technique to measure daily energy expenditure (dee) during the incubation and feeding nestling stages in two populations of white-crowned sparrows (zonotrichia leucophrys) - one montane and migratory, the other coastal and sedentary - that differ in thermal environment and clutch size. we assessed the birds' thermal environment by continuously monitoring (among other variables) operative temperature and wind speed both in the open and within bushes and willow thi ... | 2002 | 12177156 |
| cultural and genetic evolution in mountain white-crowned sparrows: song dialects are associated with population structure. | bird song often varies geographically within a species; when this geographic variation has distinct boundaries, the shared song types are referred to as song dialects. how dialects are produced and their adaptive significance are longstanding problems in biology, with implications for the role of culture in the evolution and ecology of diverse organisms, including humans. here we test the hypothesis that song dialect, a culturally transmitted trait, is related to the population genetic structure ... | 2001 | 11831670 |
| avian orientation at steep angles of inclination: experiments with migratory white-crowned sparrows at the magnetic north pole. | the earth's magnetic field and celestial cues provide animals with compass information during migration. inherited magnetic compass courses are selected based on the angle of inclination, making it difficult to orient in the near vertical fields found at high geomagnetic latitudes. orientation cage experiments were performed at different sites in high arctic canada with adult and young white-crowned sparrows (zonotrichia leucophrys gambelii) in order to investigate birds' ability to use the eart ... | 2001 | 11564346 |
| gender and seasonal differences in the adrenocortical response to acth challenge in an arctic passerine, zonotrichia leucophrys gambelii. | we evaluated the adrenocortical response to acute stress in free-living gambel's white-crowned sparrows (zonotrichia leucophrys gambelii) using a standardized capture stress protocol in which five serial blood samples (70 microliters) were taken for measurement of plasma corticosterone (b) over the course of an hour of captivity (at 1, 5, 10, 30, and 60 min). in field-captured birds, male plasma b levels rose two to four times higher than those of females under capture stress during the breeding ... | 1994 | 8045366 |
| vocal syntax development in the white-crowned sparrow (zonotrichia leucophrys). | birdsong development exemplifies the interplay between experience and predisposition that occurs during behavioral ontogeny. songbirds must hear song models to develop normal song, yet they preferentially learn conspecific song when given a choice in the laboratory. to the extent that features guiding this selective learning are pre-encoded in the brain, such features should also develop in the song of young birds not exposed to them in tutor models. to investigate whether song syntax-phrase num ... | 2001 | 11459164 |
| song overproduction, selective attrition and song dialects in the white-crowned sparrow. | male puget sound white-crowned sparrows, zonotrichia leucophrys pugetensis, form large vocal dialects along the pacific northwest coast of north america. most adult males sing a single song dialect throughout their lives. to determine how dialects are maintained in this species, i studied two populations at the columbia river mouth in a contact zone between two dialects. singers of each of the two dialects clustered together in space, forming local song 'neighbourhoods'. two hypotheses for the m ... | 2000 | 11124888 |