DOMINANCE, SURVIVAL, AND ENZYME POLYMORPHISM IN DARK-EYED JUNCOS, JUNCO HYEMALIS
نویسندگان
چکیده
منابع مشابه
Steroid hormones and immune function: experimental studies in wild and captive dark-eyed juncos (Junco hyemalis).
Monogamous and polygynous male songbirds generally differ in their breeding season profiles of circulating testosterone. Testosterone level spikes early in the breeding season of monogamists and then declines, but it remains high in polygynists. Male dark-eyed juncos (Junco hyemalis) are socially monogamous and exhibit the usual pattern, but experimental maintenance of high testosterone through...
متن کاملSeasonal and individual variation in response to GnRH challenge in male dark-eyed juncos (Junco hyemalis).
Concentrations of gonadal steroids such as testosterone (T) often vary widely in natural populations, but the causes and particularly the consistency of this variation is relatively unexplored. In breeding males of a wild population of the dark-eyed junco (Junco hyemalis), we investigated seasonal and individual variation in circulating T during two breeding seasons by measuring the responsiven...
متن کاملDifferential migration and an endocrine response to stress in wintering dark-eyed juncos (Junco hyemalis).
The dark-eyed junco (junco hyemalis) exhibits differential migration in autumn that, in general, results in females overwintering south of males, and young within each sex overwintering north of older birds. Individuals overwintering at higher latitudes face less predictable and more challenging environmental conditions. Rapid increases in circulating levels of the energy-regulating glucocortic...
متن کاملSong types , song performance , and the use of repertoires in dark - eyed juncos ( Junco hyemalis )
Song performance encompasses the idea of how physiologically demanding different songs are to sing, and this is thought to reflect the singing ability of individual birds. In the dark-eyed junco (Junco hyemalis), each male has a repertoire of song types, some of which are shared with other males in the population. We used 4 measures of performance, based on trade-offs between song traits, to te...
متن کاملTestosterone increases activity but not daily energy expenditure in captive male dark-eyed juncos, Junco hyemalis.
Plasma testosterone (T) levels in male dark-eyed juncos peak early in the breeding season, then decline. If T enhances opportunities for reproductive success, as suggested by previous experiments, why does elevated T not occur naturally? To address this question, we prolonged the early peak level throughout the breeding season and explored potential energetic costs of maintaining elevated T. We...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Evolution
سال: 1978
ISSN: 0014-3820
DOI: 10.1111/j.1558-5646.1978.tb04623.x