Laying order, hatching asynchrony and nestling body mass in TreeSwallows Tachycineta bicolor

Tree Swallow (Tachycineta bicolor) Science Article 6


We studied the reproductive biology of a box-nesting population of Tree SwallowsTachycineta bicolor in southeastern Wisconsin, USA. We were interested particularlyin the relationship between laying order and hatching order and the extent to whicheach was a predictor of nestling body mass. We found that laying order was asignificant predictor of hatching order. Laying and hatching order were related tonestling mass at 4 days of age and to a lesser extent at 12 days of age. In addition,we investigated the effects of natural variation in hatching asynchrony. Hatchingasynchrony was positively related to the range of nestling body masses within abrood at days 4 and 12. The probability that brood reduction occurred was alsopositively related to the degree of hatching asynchrony, though this effect wassignificant only at day 4. Our results suggest that laying order and hatching orderhave their greatest effects on nestling Tree Swallows early in the nestling period.

Ethan D. Clotfelter, Linda A. Whittingham and Peter O. Dunn, JOURNAL OF AVIAN BIOLOGY 31:3 (2000)

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