| 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 |
| fluorescence microscopy of neurons containing primary catecholamines in the ventral hypothalamus of the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1973 | 4743253 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| some endocrine correlates of renesting after loss of clutch or brood in the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1979 | 488683 |
| the acth-immunoreactive system in the brain of the white-crowned sparrow, zonotrichia leucophrys gambelii (passeriformes, emberizidae). | the acth-immunoreactive (ir) system of the avian brain is particularly conspicuous in the male white-crowned sparrow (zonotrichia leucophrys gambelii). the irperikaryal population is concentrated mainly within the tuberal region, projecting primarily in a dorsal direction: (i) into the striatum; (ii) into rostral diencephalic, septal, hyperstriatal, and thalamic areas; and (iii) into dorsal and ventral areas of the brain stem. ir-fibers seemingly contact local non-immunoreactive neurons mainly i ... | 1988 | 2835335 |
| absence of gonadal-hormone feedback on luteinizing hormone in both photorefractory and photosensitive white-crowned sparrows (zonotrichia leucophrys gambelii). | elimination of gonadal-hormone feedback by castration from photorefractory male white-crowned sparrows in mid-july or early october, and from photosensitive males in early december, had no significant effect on plasma levels of lh. photorefractory birds held on natural daylengths regained photosensitivity in the absence of gonadal-hormone feedback with no increase in plasma levels of lh. implants of testosterone propionate into castrated males during november and december had no effect on plasma ... | 1985 | 4076763 |
| 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 |
| 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 |
| plasma corticosterone increases during migratory restlessness in the captive white-crowned sparrow zonotrichia leucophrys gambelli. | plasma corticosterone increases during the period of spring migration in a variety of bird species. long-distance migrants show elevations in corticosterone specifically in association with the stage of flight, suggesting that corticosterone may support flight-related processes, for example, locomotor activity and/or energy mobilization. the pattern of corticosterone secretion as it relates to migratory flight has hitherto not been clearly described in migrants that frequently interrupt flight t ... | 2004 | 15555499 |
| 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 annual cycle of plasma irlh and steroid hormones in feral populations of the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1978 | 743540 |
| the sites of encephalic photoreception in phosoperiodic induction of the growth of the testes in the white-crowned sparrow, zonotrichia leucophrys gambelii. | in bilaterally enucleated white-crowned sparrows, zonotrichia leucophrys gambelii, testicular growth and development at rates similar to those of intact birds subjected to long days, can be induced by illumination of sites within and near the ventromedial hypothalamus from the tips of single, chronically implanted, light-conducting fibers. essentially identical results are obtained with the same mode of encephalic illumination of birds with intact eyes held on short days that are otherwise nonst ... | 1978 | 657255 |
| 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 |
| 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 |
| binding of follicle-stimulating hormone by homogenates of testes of photostimulated white-crowned sparrows, zonotrichia leucophrys gambelii. | | 1976 | 188717 |
| hypothalamic and hormonal control of the photoperiodically induced vernal functions in the white-crowned sparrow, zonotrichia leucophrys gambelii. 1. the effects of hypothalamic lesions and exogenous hormones. | to assess the role of the hypothalamo-hypophysial complex in the control of photoperiodically induced vernal premigratory responses in the white-crowned sparrow, the effects of hypothalamic lesions and systemic administration of several hormones on these responses were investigated. lesions that destroyed the posterior median eminence (pme) or the entire median eminence (me) inhibited photoperiodically induced testicular growth, premigratory fattening and zugunruhe. lesions in the basal infundib ... | 1976 | 1000582 |
| the annual cycle in luteinizing hormone in the plasma of intact and castrated white-crowned sparrows, zonotrichia leucophrys gambelii. | | 1976 | 992335 |
| 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 |
| 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 |
| 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 |
| rapid behavioral response to corticosterone varies with photoperiod and dose. | the magnitude of the adrenocortical response to stress can be modulated by a variety of environmental and physiological factors, such as daylength and body condition. to determine the consequences of this modulation for the organism, one also needs to investigate behavioral sensitivity to glucocorticoids. we examined the behavioral response of gambel's white-crowned sparrows (zonotrichia leucophrys gambelii) to elevated glucocorticoids. using a behavioral assay in which a rapid and transient dos ... | 2000 | 10712855 |
| effects of complex radiative and convective environments on the thermal biology of the white-crowned sparrow (zonotrichia leucophrys gambelii). | the energy budgets of small endotherms are profoundly affected by characteristics of the physical environment such as wind speed, air temperature and solar radiation. among these, solar radiation represents a potentially very large heat load to small animals and may have an important influence on their thermoregulatory metabolism and heat balance. in this investigation, we examined the interactive effects of wind speed and irradiance on body temperature, thermoregulatory metabolism and heat bala ... | 2000 | 10648222 |
| effects of n-methyl-d-aspartate on luteinizing hormone release and fos-like immunoreactivity in the male white-crowned sparrow (zonotrichia leucophrys gambelii). | seasonal breeding is terminated in the white-crowned sparrow by the onset of absolute photorefractoriness, a condition in which the reproductive system is switched off indefinitely until it is dissipated by short day lengths. absolute photorefractoriness is controlled by the central nervous system; however, the mechanisms underlying gnrh quiescence in photorefractory birds have yet to be elucidated. using the excitatory amino acid glutamate agonist n-methyl-d-aspartate (nmda), plasma lh levels i ... | 1999 | 10579359 |
| neurohistological studies of the hypothalamo-hypophysial system of zonotrichia leucophrys gambelii (aves, passeriformes). | | 1974 | 4139882 |
| seasonal changes in the reproductive system of the female white-crowned sparrow, zonotrichia leucophrys gambelii, in captivity and in the field. i. the ovary. | | 1972 | 5018536 |
| electron microscopic and experimental studies of the pineal organ in the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1972 | 4335080 |
| investigations of the butylcholinesterase-containing cells of the adenohypophysis of the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1971 | 4327632 |
| [the visual system of zonotrichia leucophrys gambelii. neurohistological studies on an experimental basis]. | | 1970 | 5499373 |
| ecological influences on vocal development in the white-crowned sparrow. | gambel's white-crowned sparrow, zonotrichia leucophrys gambelii, is a long-distance migrant that, in contrast to other subspecies of white-crowned sparrow, does not form vocal dialects. i studied the process of vocal development in the field and laboratory to determine how it differed from the process in three other subspecies previously studied. four common song types existed in a random spatial pattern in my 2.6-km(2)study area. of 106 males studied in 2 years, all arrived at the beginning of ... | 1999 | 10413537 |
| diel rhythms of basal and stress-induced corticosterone in a wild, seasonal vertebrate, gambel's white-crowned sparrow. | glucocorticoids have a wide array of actions in vertebrates. daily fluctuations in basal levels of glucocorticoids are thought to regulate homeostatic mechanisms. in contrast, elevated levels secreted in response to stress stimulate changes in physiology and behavior. these changes are thought to aid an animal in avoiding chronic stress or death. twenty-four-hour rhythms in basal and stress-induced glucocorticoids have been detected in laboratory mammals, but studies in wild, seasonal vertebrate ... | 1999 | 10404125 |
| [acetylcholinesterase in the distal part of zonotrichia leucophrys gambelii (aves)]. | | 1969 | 5369932 |
| the role of the median eminence in control of photoperiodically induced testicular growth in the white-crowned sparrow. zonotrichia leucophrys gambelii. | | 1969 | 4905355 |
| electron microscopic studies on the adenohypophysis of the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1969 | 4895251 |
| light-microscope studies of the cytology of the adenohypophysis of the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1969 | 4183639 |
| acetylcholinesterase in the hypothalamo-hypophyseal axis of the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1968 | 5674702 |
| [receptor types in the retina of zonotrichia leucophrys gambelii]. | | 1968 | 4894070 |
| effects of reserpine on the white-crowned sparrow (zonotrichia leucophrys gambelii). | | 1967 | 6036408 |
| the tubero-infundibular neuron system: a component of the photoperiodic control mechanism of the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1967 | 4881289 |
| the pancreatic islets of the white-crowned sparrow, zonotrichia leucophrys gambelii, during its annual cycle and under experimental conditions. | | 1967 | 4877296 |
| evidence of a negative feedback on photoperiodically induced gonadal development in the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1966 | 5963171 |
| the development of the hypophysial portal system in the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1966 | 5987098 |
| observations on the uptake of 35-sulfur by the hypothalamo-hypophysial system of the white-crowned sparrow (zonotrichia leucophrys gambelii) following intraventricular injection of 35-s dl-cysteine. | | 1966 | 5973091 |
| the distribution of monoamine oxidase and acetylcholinesterase in the hypothalamus and its relation to the hypothalamo-hypophysial neurosecretory system in the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1966 | 5968189 |
| a possible endocrine basis for migratory behaviour in the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1965 | 5882804 |
| arterial blood supply to the brain of the white-crowned sparrow zonotrichia leucophrys gambelii. | | 1965 | 5851811 |
| a possible endocrine basis for premigratory fattening in the white-crowned sparrow, zonotrichia leucophrys gambelii (nuttall). | | 1964 | 14252202 |
| vascularization of the hypothalamo-hypophysial-complex in the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1964 | 14334648 |
| cholinesterases in the hypothalamo-hypophysial neurosecretory system of the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1964 | 14315538 |
| ultrastructural aspects of the neurohypophysis of the white-crowned sparrow, zonotrichia leucophrys gambelii, with special reference to the relation to neurosecretory axons to ependyma in the pars nervosa. | | 1964 | 14184081 |
| an annual cycle in the interrenal tissue of the adrenal gland of the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1964 | 14184080 |
| the effect of dehydration on acid-phosphatase activity, catheptic-proteinase activity, and neurosecretion in the hypothalamo-hypophysial system of the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1964 | 14185423 |
| the effect of photoperiodic stimulation on proteinase activity in the hypothalamo-hypophysial system of the white-crowned sparrow, zonotrichia leucophrys gambelii. | | 1962 | 14457441 |
| hypothalamic neurosecretion in the refractory and post-refractory periods and its relationship to the rate of photoperiodically induced testicular growth in zonotrichia leucophrys gambelii. | | 1961 | 13759712 |
| alterations in hypothalamic-pituitary-adrenal function associated with captivity in gambel's white-crowned sparrows (zonotrichia leucophrys gambelii). | gambel's white-crowned sparrows were captured and brought into captivity in order to study seasonal changes in the function of the hypothalamic-pituitary-adrenal (hpa) axis in captive birds. 30 min of restraint elicited a rise in corticosterone titers that varied depending upon the season and physiological state of the birds. restraint elevated corticosterone titers significantly more during the fall (within 2 weeks of capture from the wild) than during either the winter or during a prealternate ... | 1999 | 10327590 |
| contributions of social cues and photoperiod to seasonal plasticity in the adult avian song control system. | in seasonally breeding birds, the vernal growth of the song system is thought to result primarily from increased daylength and the associated increase in circulating testosterone. other environmental factors such as social cues between mates influence the timing of reproduction, but less is known about how social cues might affect the song system and song behavior. we used white-crowned sparrows (zonotrichia leucophrys gambelii) to test the hypothesis that the presence of a female in breeding co ... | 1999 | 9870975 |
| the relative roles of diurnal periods of activity and diurnal photoperiods in gonadal activation in male zonotrichia leucophrys gambelii (nuttall). | | 1953 | 13137555 |
| noninvasive corticosterone treatment rapidly increases activity in gambel's white-crowned sparrows (zonotrichia leucophrys gambelii). | recent evidence supports the hypothesis that corticosteroids influence behavioral changes associated with stressful events. most investigations into this relationship focus on the long-term behavioral effects of corticosterone. because many behavioral responses to environmental perturbations occur within minutes, we determined what rapid effects corticosterone may have on behavior. with this goal in mind, we devised and evaluated a method of corticosterone delivery which allowed us to examine im ... | 1998 | 9707484 |
| central opioid control of feeding behavior in the white-crowned sparrow, zonotrichia leucophrys gambelii. | many behavioral responses to stress do not appear to be mediated by glucocorticoids, suggesting another mechanism. we tested the effects of intracerebroventricular administration of beta-endorphin, a neuropeptide implicated in the stress response, on feeding behavior in captive, wild-caught white-crowned sparrows (zonotrichia leucophrys gambelii). the amount of time spent feeding and the number of feeding bouts were higher after infusion with beta-endorphin than after saline infusion. beta-endor ... | 1998 | 9571009 |