Graduation Year

2023

Document Type

Open Access Senior Thesis

Degree Name

Bachelor of Arts

Department

Biology

Reader 1

Marion Preest

Reader 2

Diane Thomson

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© 2022 Emily K Radner

Abstract

Boat-tailed grackles (Quiscalus major) typically lay clutches of three eggs and begin incubation before the clutch is complete, resulting in hatching asynchrony. To study the developmental consequences of hatching asynchrony on boat-tailed grackles, data loggers measured nest temperatures and were compared to ambient temperatures to see when incubation began, and it appeared to begin after the second egg is laid. The third laid egg had a significantly shorter lay to pip time and lay to hatch time than the first laid egg, highlighting the need to investigate the consequences of a shortened incubation time on development. To do this, egg morphology, hatching measurements, enzyme activity of citrate synthase and β-HOAD in three key muscles, and ossification measurements of leg and wing bones were measured for first, second, and third laid eggs. Permutational ANOVAs in RStudio were used to determine if there were any differences in the groups with respect to lay order.

Enzyme activities (CS and β-HOAD) were higher in second laid eggs, but these eggs had shorter ossified bone lengths. This suggests that resources might be allocated differentially in chicks depending on lay order. It is possible that the third laid chicks are accelerating development to hatch at a similar stage of development of their siblings. Using increased resources (likely the yolk sac) could mean that the chick has fewer food stores after hatching. Further studies are needed to understand the regulatory drivers of these differences (such as differential hormonal levels) and whether these differences confer a survival advantage.

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