Energetic constraints on hatching asynchrony

• At least nine hypotheses have been advanced to account for why many passerine species hatch their clutches asynchronously: 1) The brood reduction hypothesis; 2) The peak load reduction hypothesis; 3) The sibling rivalry reduction hypothesis; 4) The hurry-up hypothesis; 5) The egg viability hypothesis; 6) The sexual conflict hypothesis; 7) The equal investment hypothesis; 8) The nest failure hypothesis; 9) The adult survival hypothesis; This study measured the effect of experimentally increased food availability on the incubation pattern during egg laying, predicting that the degree of hatching asynchrony (measured by onset of incubation, hatching spread, and variation in the size of nestlings) would increase with increased food levels, because of the costs of hatching asynchrony, irrepective of possible benefits, are alleviated by the extra food. However, the hypothesized benefits also may be influenced by extra food. Hypotheses 1-3 are adaptations to varying or low food resource levels during the nestling phase, thus in contrast to the experimental situation. According to these three hypotheses, both benefits and costs will decrease with an increase in food availability. The benefits predicted by hypotheses 4-8 are unrelated to food level. Thus, following experimental provisioning of food, costs will decrease whereas benefits will remain unaltered, which will lead to increased levels of hatching asynchrony. The last hypothesis, 9, predicts no influence of food, on either costs or benefits. -from Author

Ämnesord

NATURVETENSKAP  -- Biologi -- Zoologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Zoology (hsv//eng)

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