Yolk androgens vary inversely to maternal androgens in Eastern Bluebirds: an experimental study
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Yolk androgens vary inversely to maternal androgens in Eastern Bluebirds: an experimental study
1. Female birds deposit variable amounts of androgens in the yolks of their eggs, and it has been suggested that yolk androgen deposition is an adaptive mechanism preparing offspring for a competitive environment. Breeding pairs of Eastern Bluebirds ( Sialia sialis ) Linnaeus were stimulated with an intruder presentation while ovarian follicles were developing. Yolk steroid concentrations in eg...
متن کاملYolk androgens reduce offspring survival.
Females may favour some offspring over others by differential deposition of yolk hormones. In American kestrels (Falco sparverius), we found that yolks of eggs laid late in the sequence of a clutch had more testosterone (T) and androstenedione (A4) than yolks of first-laid eggs. To investigate the effects of these yolk androgens on nestling 'fitness', we injected both T and A4 into the yolks of...
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Black-headed gulls, Larus ridibundus, produce clutches of three eggs, which contain high levels of maternal androgens in the yolk. These levels increase with laying order and the eggs hatch asynchronously. Experiments have supported the hypothesis that this within-clutch variation in maternal androgens mitigates the disadvantage of last-hatched chicks in sibling competition, by enhancing embryo...
متن کاملVariable effects of yolk androgens on growth, survival, and immunity in eastern bluebird nestlings.
Female birds allocate androgens differentially within and among clutches, and it has been suggested that this is a strategy to maximize reproductive success. Only a few studies, however, have examined the effects of yolk testosterone (T) on the growth and development of nestlings, and none have reported on the immunological effects of yolk T nor have they examined several different effects in t...
متن کاملMaternal yolk androgens stimulate territorial behaviour in black-headed gull chicks.
Avian eggs contain substantial amounts of maternal androgens. The concentrations of these yolk androgens are affected by the maternal environment, such as the level of social competition, parasite exposure or food conditions. Since yolk androgens have been shown to affect a wide array of offspring traits, they may adjust the chicks to the expected post-hatching environment, but experimental evi...
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ژورنال
عنوان ژورنال: Functional Ecology
سال: 2006
ISSN: 0269-8463,1365-2435
DOI: 10.1111/j.1365-2435.2006.01114.x