SUMMARYBurrow-nesting petrels use their well-developed sense of smell for foraging, homing to their nest, and mate recognition. The chicks of burrow-nesting petrels can apparently learn odours associated with prey while still in the nest, but the development of individual-specific odour recognition is less well understood. We used a simple two-choice test to determine whether 4-to 6-week-old chicks of a small, burrow-nesting species, the Leachʼs storm-petrel (Oceanodroma leucorhoa), prefer the scent of their own nest material to (1) the scent of similar organic material collected from the colony or (2) the scent of a conspecificʼs nest material. Results suggest that chicks clearly preferred the scent of their own nest material to that of similar organic material collected from the colony (96%; N=24; binomial test, P<0.001). Results further suggested that birds preferred the scent of their own nest material to that of a conspecific, though the preference was statistically less robust (67%; N=39; binomial test, P=0.05). Because Leachʼs storm-petrel chicks do not normally leave their burrow prior to fledging, an ability to recognise individual or nest-specific odours is not likely to be used for homing but instead may be linked to the development of individual recognition in different contexts.
Summary
1.The pituitary hormone prolactin is thought to play an important role in the promotion of parental care in birds and mammals. The level of care parents provide is, however, likely to be influenced by additional factors, such as their physiological condition at the time of breeding. 2. We examined relationships between parental body condition, plasma prolactin levels and reproductive performance in Gould's Petrels ( Pterodroma leucoptera ), a long-lived seabird. We predicted that parental body condition would correlate positively with both prolactin level and parenting intensity, as measured by the quality of the chick they produced. We also examined the effects of parenting intensity on parental body condition and reproductive success in the subsequent breeding season. 3. Body condition of male parents positively correlated with prolactin levels at the start of their second protracted incubation bout. The body condition of both parents correlated positively with the body condition of their chick at its peak mass. However, producing a good-quality chick did not negatively affect parental body condition or reproductive success the following year. 4. These results suggest that prolactin reinforces parental behaviour in parents in good body condition, which facilitates production of good-quality chicks. Moreover, good-quality parents consistently produce good-quality chicks with no apparent tradeoff to their physical condition.
The aerobic capacity model proposes that endothermy is a byproduct of selection favouring high maximal metabolic rates (MMR) and its mechanistic coupling with basal metabolic rate (BMR). Attempts to validate this model in birds are equivocal and restricted to phenotypic correlations (r P ), thus failing to distinguish among-and within-individual correlations (r ind and r e ). We examined 300 paired measurements of BMR and MMR from 60 house sparrows before and after two levels of experimental manipulation -testosterone implants and immune challenge. Overall, repeatability was significant in both BMR (R=0.25±0.06) and MMR (R=0.52±0.06). Only the testosterone treatment altered the r P between BMR and MMR, which resulted from contrasting effects on r ind and r e . While r ind was high and significant (0.62±0.22) in sham-implanted birds, r e was negative and marginally non-significant (−0.15±0.09) in testosterone-treated birds. Thus, the expected mechanistic link between BMR and MMR was apparent, but only in birds with low testosterone levels.
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