| 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 |
| territorial aggression does not feed back on testosterone in a multiple-brooded songbird species with breeding and non-breeding season territoriality, the european stonechat. | testosterone mediates reproductive behaviours in male vertebrates. for example, breeding season territoriality depends on testosterone in many species of birds and in some, territorial interactions feed back on testosterone concentrations. however, the degree to which territorial behaviour and testosterone are associated differs even between species with seemingly similar life histories, especially between species that also defend territories outside the breeding season. here, we investigate the ... | 2017 | 27838361 |
| 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 |
| seasonal and diel variation of hormone metabolites in european stonechats: on the importance of high signal-to-noise ratios in noninvasive hormone studies. | most vertebrates living in seasonal environments show seasonal reproductive cycles and diel rhythms. the rhythmicity in behavior and morphology is accompanied by diel and seasonal patterns of hormone secretions. in small animals, the investigation of diel patterns of hormones has been hampered because repeated blood sampling is difficult and may influence subsequent measurements. a possibility to avoid these caveats is to investigate excreted hormone metabolites instead. here, we describe the di ... | 2011 | 21252365 |
| 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 |
| the hormonal response of female european stonechats to a territorial intrusion: the role of the male partner. | in many bird species, the female participates in defending a pair's breeding territory, however, the endocrine control mechanism of female aggressive behavior is largely unknown. the general statement that androgens are involved in the regulation of aggressive behavior is based on studies conducted only in males. here, we tested whether paired female stonechats show a hormonal response to a simulated male territorial intruder. since in males of territorial bird species androgen levels usually in ... | 2005 | 15811358 |
| 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 |
| testosterone, territorial response, and song in seasonally breeding tropical and temperate stonechats. | testosterone facilitates physiological, morphological, and behavioral changes required for breeding in male vertebrates. however, testosterone concentrations and the link between its seasonal changes and those in reproductive behaviors vary greatly among species. to better understand the impact of tropical and temperate environments and life history factors on this variation, we have compared testosterone, territorial behavior and song performance across sequential stages of the breeding season ... | 2017 | 28412929 |
| circannual basis of geographically distinct bird schedules. | to anticipate seasonal change, organisms schedule their annual activities by using calendrical cues like photoperiod. the use of cues must be fitted to local conditions because schedules differ between species and habitats. in complete absence of temporal information, many species show persistent circannual cycles that are synchronised, but not driven, by photoperiod. the contribution of circannual rhythms to timing under natural photoperiodic conditions is still unclear. in a suite of experimen ... | 2009 | 19376946 |
| 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 |
| 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 |