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Individual quality and food availability determine yolk and egg mass and egg composition in tree swallows Tachycineta bicolor
 

Summary: Individual quality and food availability determine yolk and egg mass
and egg composition in tree swallows Tachycineta bicolor
Daniel R. Ardia, Matthew F. Wasson and David W. Winkler
Ardia, D.R., Wasson, M.F. and Winkler, D.W. 2006. Individual quality and food
availability determine yolk and egg mass and egg composition in tree swallows
Tachycineta bicolor. / J. Avian Biol. 37: 252/259.
Variation in egg size and composition can have important consequences for the quality
of offspring. We investigated the factors influencing the yolk mass and egg mass of tree
swallows breeding in Ithaca, NY. Using a nondestructive technique to estimate yolk
mass via standardized digital-candler photographs, we compared yolk size and egg size
of tree swallows Tachycineta bicolor in response to variation in food availability and
individual quality. Insect availability one to three days prior to laying, but not four to
six days, predicted yolk mass, while insect availability two to three days prior to laying
predicted total egg mass. This suggests that, while eggs are formed over longer periods,
food availability closer to time of laying has the greatest influence on egg size. These
results were supported by collected eggs, as yolk rings revealed that tree swallow eggs
are formed over 5/6 days. There was an influence of female quality as well, with early
laying birds, independent of food availability, laying larger eggs. Eggs laid later in the
laying sequence had larger yolks and greater egg mass. Overall, variation in egg quality
appears to be due to a combination of environmental conditions, reflected in food

  

Source: Ardia, Dan - Department of Biology, Franklin and Marshall College

 

Collections: Biology and Medicine