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Marcella Biaz, Lisa Bol, and Liberty Hightower ACF Abstract FY10

Parental Anti-predator Responses during the Nestling Period in Tree Swallows

Conference Name: Michigan Academy of Science, Arts, and Letters (MASAL)

In female Tree Swallows, environmental factors and breeding phenology influence the mass of eggs laid by experienced breeders.  Egg mass is positively correlated with nestling weight at hatching and subsequent survival.  In 2008 and 2009 on the GVSU campus, we noted the laying sequence and measured masses of eggs laid by swallows in their first breeding season.  Weather data were recorded at a nearby weather station.  Egg mass was positively correlated with mean and high temperatures one day before laying and negatively correlated with the amount rainfall three days before laying.  Air temperature and rainfall affect the availability of aerial insects.  Eggs are produced one day before they are laid.  Laying order had a significant effect on egg mass; eggs 1-3 were significantly lighter than eggs 4-6.  When all eggs were considered, there was no significant relationship between egg mass and laying date.  However, egg mass significantly increased with laying date in both early (8-29 May) and late (2-25 June) nests.  These results suggest that first-time breeders, like more experienced swallows, vary their investment in egg production by responding to environmental factors, laying order, and laying date.

Lisa Bol (Lead presenter), Liberty Hightower, Brad Houdek,Marci Baiz, Angel Hayden, Matthew Romeyn