| predators as stressors? physiological and reproductive consequences of predation risk in tropical stonechats (saxicola torquata axillaris). | tropical birds usually lay smaller clutches and are less likely to initiate a second brood than their temperate-zone relatives. this reduction in annual fecundity is generally explained as an adaptation either to higher rates of nest predation or to a more limited food supply concurrent with higher adult survival in the tropics. however, the physiological parameters associated with lower annual fecundity in tropical birds have not been well investigated. we compared the annual fecundity, behavio ... | 2001 | 11487404 |
| slow pace of life in tropical sedentary birds: a common-garden experiment on four stonechat populations from different latitudes. | it has been hypothesized that organisms living at different latitudes or in different environments adjust their metabolic activity to the prevailing conditions. however, do differences in energy turnover simply represent a phenotypic adaptation to the local environment, or are they genetically based? to test this, we obtained nestling stonechats (saxicola torquata) from equatorial kenya (0 degrees n), ireland (51.5 degrees n), austria (47.5 degrees n) and kazakhstan (51.5 degrees n). birds were ... | 2003 | 14667355 |
| testosterone and corticosterone during the breeding cycle of equatorial and european stonechats (saxicola torquata axillaris and s. t. rubicola). | northern-temperate male birds show seasonal changes in testosterone concentrations with a peak during the breeding season. many tropical birds express much lower concentrations of testosterone with slight elevations during breeding. here we describe testosterone and corticosterone concentrations of male stonechats from equatorial kenya during different substages of breeding and molt. this tropical species has a short breeding season of approximately 3 months. we compare their hormone concentrati ... | 2006 | 16934809 |
| migratory status is not related to the susceptibility to hpaiv h5n1 in an insectivorous passerine species. | migratory birds have evolved elaborate physiological adaptations to travelling, the implications for their susceptibility to avian influenza are however unknown. three groups of stonechats (saxicola torquata) from (i) strongly migrating, (ii) weakly migrating and (iii) non-migrating populations were experimentally infected with hpaiv h5n1. the different bird groups of this insectivorous passerine species were infected in autumn, when the migrating populations clearly exhibit migratory restlessne ... | 2008 | 19584935 |
| repeatability and individual correlates of microbicidal capacity of bird blood. | with the rapid development of the field of ecological and evolutionary immunology, a series of new techniques to measure different components of immune function is becoming commonplace. an important step for the interpretation of these new measures is to understand the kind of information about the animal that they convey. we showed that the microbicidal capacity of stonechat (saxicola torquata) blood, an integrative measure of constitutive immune function, is highly repeatable when tested again ... | 2010 | 20434581 |
| genetic and phenotypically flexible components of seasonal variation in immune function. | animals cope with seasonal variation in environmental factors by adjustments of physiology and life history. when seasonal variation is partly predictable, such adjustments can be based on a genetic component or be phenotypically flexible. animals have to allocate limited resources over different demands, including immune function. accordingly, immune traits could change seasonally, and such changes could have a genetic component that differs between environments. we tested this hypothesis in ge ... | 2014 | 24436383 |
| harmonizing outdoor recreation and bird conservation targets in protected areas: applying available monitoring data to facilitate collaborative management at the regional scale. | in protected areas managers have to achieve conservation targets while providing opportunities for outdoor recreation. this dual mandate causes conflicts in choosing between management options. furthermore, the persistence of a protected species within the management unit often depends on how conservation areas elsewhere in the region are managed. we present an assessment procedure to guide groups of managers in aligning outdoor recreation and bird conservation targets for a regional scale prote ... | 2017 | 28467949 |
| geographically distinct reproductive schedules in a changing world: costly implications in captive stonechats. | with progressively faster global change, shifts in phenology, and distributional ranges are reported for an increasing number of species. the success of organisms at coping with novel seasonal conditions depends on the mechanisms that determine their schedules. species that rely on fixed schedules and those that time their activities by predictive cues may be particularly constrained in their ability to accommodate changes. the present study examines rigid scheduling and its implications for bre ... | 2009 | 21665841 |
| taxonomic status and evolutionary history of the saxicola torquata complex. | we explored variation in mitochondrial nd2 gene sequences from 171 stonechats (saxicola torquata complex) collected from 27 eurasian and 3 african localities. we found that two widespread neighboring eurasian subspecies of siberian stonechat, saxicola maura maura and s. m. stejnegeri, although very similar in appearance, are not each other's closest relatives. eastern asian s. m. stejnegeri appears to have split from other palearctic, african, and island stonechats well before differentiation oc ... | 2009 | 19464380 |
| non-migratory stonechats show seasonal changes in the hormonal regulation of non-seasonal territorial aggression. | in many birds and mammals, male territorial aggression is modulated by elevated circulating concentrations of the steroid hormone testosterone (t) during the breeding season. however, many species are territorial also during the non-breeding season, when plasma t levels are basal. the endocrine control of non-breeding territorial aggression differs considerably between species, and previous studies on wintering birds suggest differences between migratory and resident species. we investigated the ... | 2011 | 21803045 |
| repeatability and individual correlates of basal metabolic rate and total evaporative water loss in birds: a case study in european stonechats. | basal metabolic rate (bmr) and total evaporative water loss (tewl) are thought to have evolved in conjunction with life history traits and are often assumed to be characteristic features of an animal. physiological traits can show large intraindividual variation at short and long timescales, yet natural selection can only act on a trait if it is a characteristic feature of an individual. the repeatability of a trait, a measure of the portion of variance that is caused by differences among indivi ... | 2008 | 18571446 |
| low ambient temperature increases food intake and dropping production, leading to incorrect estimates of hormone metabolite concentrations in european stonechats. | non-invasive methods to measure steroid hormone metabolites in bird droppings or mammalian feces have become very popular. however, the accuracy of these measurements may be affected by many factors. here, we use the stonechat (saxicola torquata) as a passerine bird model to test whether differences in ambient temperature affect food intake and dropping production and whether these changes lead to measurement artefacts in hormone metabolite concentrations. in addition, we tested for diurnal patt ... | 2006 | 16469318 |
| noninvasive monitoring of hormones in bird droppings: physiological validation, sampling, extraction, sex differences, and the influence of diet on hormone metabolite levels. | during the past several years, the noninvasive measurement of steroid metabolites from mammalian feces and bird droppings has become more and more popular. with an increasing acceptance of the method, investigators may become less aware of the need to validate their assays. it is shown why such validations are essential for each new species investigated and various ways to physiologically validate such noninvasive methods are described. using the european stonechat (saxicola torquata rubicola) a ... | 2005 | 16055842 |
| testosterone, reproductive stage, and territorial behavior of male and female european stonechats saxicola torquata. | we investigated territorial behavior and circulating testosterone (t) levels in a multiple-brooded population of the european stonechat, a socially monogamous passerine bird with biparental care. between arrival at and departure from the breeding territories, we (1) quantified behavior of both sexes in response to a simulated territorial intrusion (sti) of a male conspecific and (2) measured plasma t concentrations in males and females. male response scores to a sti and male t concentrations var ... | 2005 | 15811351 |
| non-invasive methods to measure androgen metabolites in excrements of european stonechats, saxicola torquata rubicola. | traditionally androgen concentrations are measured invasively in blood plasma. however, non-invasive methods to detect androgens are desirable, as this reduces interference with the natural behavior of the study species and multiple samples can be obtained relatively easy. the aim of this study was to validate a method to measure androgens non-invasively in excrements of male european stonechats (saxicola torquata rubicola). extracts of excrements of a male stonechat injected with [3h]testostero ... | 2002 | 12441117 |
| seasonal differences in the hormonal control of territorial aggression in free-living european stonechats. | in birds, territorial aggression during the breeding season is regulated by testosterone (t). however, many bird species also express aggressive behavior during the nonbreeding season, when plasma levels of t are low. it has been suggested that during this period estrogens might play a major role in regulating territorial aggression. in the present study we compared the effects of simultaneous blockage of androgenic and estrogenic actions on territorial aggression during the breeding and nonbree ... | 2002 | 11863378 |
| moult and basal metabolic costs in males of two subspecies of stonechats: the european saxicola torquata rubicula and the east african s. t. axillaris. | the circannual patterns in resting metabolic rate (rmr) of males of two subspecies of stonechats, the european saxicola torquata rubicula and the east african s. t. axillaris, are compared. as the birds from the two subspecies were raised and kept under comparable laboratory conditions, differences in metabolic rate between the two subspecies had to be genetically determined. rmr peaked during moult in both subspecies. during the rest of the year rmr was fairly constant in both subspecies and as ... | 1995 | 28307657 |
| postjuvenile molt in east african and central european stonechats (saxicola torquata axillaris, s.t. rubicula) and its modification by photoperiod. | twenty-eight stonechats of the european race (saxicola torquata rubicula) from austria and thirty-one stonechats of the central african race (s.t. axillaris) from equatorial kenya were handraised and subsequently investigated with regard to the temporal pattern of their postjuvenile molt. about one half of the birds of each race were held under their own native photoperiod and the other half under the photoperiodic conditions of the other race. the results demonstrated clear differences in the p ... | 1983 | 28310535 |
| behavioural response of a migratory songbird to geographic variation in song and morphology. | sexually selected traits contribute substantially to evolutionary diversification, for example by promoting assortative mating. the contributing traits and their relevance for reproductive isolation differ between species. in birds, sexually selected acoustic and visual signals often undergo geographic divergence. clines in these phenotypes may be used by both sexes in the context of sexual selection and territoriality. the ways conspecifics respond to geographic variation in phenotypes can give ... | 2014 | 25484906 |
| annual cycles of metabolic rate are genetically determined but can be shifted by phenotypic flexibility. | birds have adjusted their life history and physiological traits to the characteristics of the seasonally changing environments they inhabit. annual cycles in physiology can result from phenotypic flexibility or from variation in its genetic basis. a key physiological trait that shows seasonal variation is basal metabolic rate (bmr). we studied genetic and phenotypic variation in the annual cycles of body mass, bmr and mass-specific bmr in three stonechat subspecies (saxicola torquata) originatin ... | 2012 | 22771752 |
| a tropical bird can use the equatorial change in sunrise and sunset times to synchronize its circannual clock. | at higher latitudes, most organisms use the periodic changes in day length to time their annual life cycle. at the equator, changes in day length are minimal, and it is unknown which cues organisms use to synchronize their underlying circannual rhythms to environmental conditions. here, we demonstrate that the african stonechat (saxicola torquatus axillaris)-an equatorial songbird-can use subtle solar cues for the annual timing of postnuptial moult, a reliable marker of the circannual cycle. we ... | 2012 | 22648153 |
| wing pointedness associated with migratory distance in common-garden and comparative studies of stonechats (saxicola torquata). | migration promotes utilization of seasonal resources, and the distance flown is associated with specific morphologies, yet these relationships can be confounded by environmental factors and phylogeny. understanding adaptations associated with migration is important: although migration patterns change rapidly, it is unclear whether migratory traits track behavioural shifts. we studied morphometrics of four stonechat populations representing a migratory gradient and raised under common-garden cond ... | 2010 | 20345819 |
| genetic modulation of energy metabolism in birds through mitochondrial function. | despite their central importance for the evolution of physiological variation, the genetic mechanisms that determine energy expenditure in animals have largely remained unstudied. we used quantitative genetics to confirm that both mass-specific and whole-organism basal metabolic rate (bmr) were heritable in a captive-bred population of stonechats (saxicola torquata spp.) founded on birds from three wild populations (europe, africa and asia) that differed in bmr. this argues that bmr is at least ... | 2009 | 19324832 |
| daytime light intensity affects seasonal timing via changes in the nocturnal melatonin levels. | daytime light intensity can affect the photoperiodic regulation of the reproductive cycle in birds. the actual way by which light intensity information is transduced is, however, unknown. we postulate that transduction of the light intensity information is mediated by changes in the pattern of melatonin secretion. this study, therefore, investigated the effects of high and low daytime light intensities on the daily melatonin rhythm of afro-tropical stonechats (saxicola torquata axillaris) in whi ... | 2007 | 17406847 |
| excremental androgen metabolite concentrations and gonad sizes in temperate zone vs. tropical stonechats (saxicola torquata ssp.). | many songbirds in the temperate zones have comparatively short breeding seasons and are migratory. this often implies high breeding synchrony and competition for food, space, and mates. tropical birds, in contrast, tend to be resident and react more flexibly to a more variable onset of environmental conditions conducive for breeding. therefore, it can be expected that androgen metabolite concentrations in breeding males vary among birds from different latitudes. studies on tropical birds, howeve ... | 2004 | 15504389 |
| is food availability a circannual zeitgeber in tropical birds? a field experiment on stonechats in tropical africa. | equatorial stonechats (saxicola torquata axillaris) in africa are seasonal breeders like their temperate-zone conspecifics (s.t. rubicola). their annual cycle in gonadal size and function is controlled by an endogenous circannual rhythmicity that has been shown to run for up to 10 years in a constant equatorial photoperiod under laboratory conditions, with a period deviating from 12 months. in nature, however, this rhythm is synchronized with the actual year. because photoperiod is essentially c ... | 2002 | 12002164 |
| endogenous gonadal, lh and molt rhythms in tropical stonechats: effect of pair bond on period, amplitude, and pattern of circannual cycles. | to investigate the effects of reproduction and associated stimuli on the circannual cycles of african stonechats saxicola torquata axillaris birds were held for 29 months in aviaries under a constant equatorial (12.25 h) photoperiod, either singly (10 females and 10 males) or in 10 male/female pairs. the birds of all 3 groups went through circannual cycles in gonadal size, plasma lh and molt, but groups differed with regard to actual reproductive performance. during the second cycle, only one of ... | 1995 | 7623296 |
| [patterns of bird nocturnal migration at shenyang taoxian international airport, northeast china]. | the high frequency of bird strikes at night during the migration season is a remarkable characteristic of bird strikes at airports. understanding the nocturnal migration patterns of birds is important for improving the methods to prevent bird strikes at night. in this study, we combined the methods of mist-net capture and sound recording to examine the composition of bird species and the patterns of nocturnal migration at taoxian airport. we found that 56 species of birds (88.9% of the total) mi ... | 2019 | 30907552 |
| flexible habitat use in a migratory songbird expanding across a human-modified landscape: is it adaptive? | behavioural plasticity during habitat selection plays a key role in determining whether organisms may thrive under human-induced rapid environmental changes. as organisms rely on environmental cues to make decisions, these behavioural responses may be maladaptive. we studied the european stonechat saxicola torquatus as a model open-habitat bird species breeding in three structurally different land-use types generated by agriculture and forestry activities. in this mosaic landscape, we compared t ... | 2020 | 33025265 |