Factors Associated with Egg Hatching in Tree Swallows

We tracked the hatching success of 3,839 eggs (n=998 nests) laid by tree swallows nesting on the GVSU campus from 1992-2011. The year an egg was laid, the age of the female who laid the egg, the date the egg was laid, and clutch size did not affect the likelihood of its hatching. When in the laying sequence an egg was laid affected the likelihood of its hatching; eggs laid between the first and last eggs were more likely to hatch. For E1-6, the hatching of a previous egg increased the likelihood of the subsequent egg hatching (e.g., E1 vs. E2); however, whether E7 hatched was independent of whether E6 hatched. For the most common clutch sizes (4-6) first and last eggs were equally likely to hatch. Comparing the most common clutch sizes, E1 was most likely to hatch in clutches of 6 eggs but last eggs were equally likely to hatch. These results suggest that whether an egg hatches was most influenced by when in the sequence it was laid and whether the egg that was laid before it hatched