Understanding how environmental variation affects fitness and population dynamics is a central goal in modern population biology. Using a multilevel path model, I simultaneously examined the effects of food and temperature on multiple stages of the breeding cycle, and their relative contribution to annual variation in reproductive success in two tree swallow (Tachycineta bicolor) populations over the same 35 year period. In one population where food abundance peaked during the laying and incubation portion of the breeding season, the primary driver of annual reproductive success was laying period food abundance, which directly influenced clutch size and the proportion of eggs hatched. In the second population, food was relatively low during the first half of the breeding season, and the primary driver of annual reproductive success was temperature during the nestling period, which directly influenced nestling survival. My results show that understanding the factors that influence reproductive performance requires linking environmental variables to reproductive events throughout the entire breeding period and clearly demonstrate how climate change can have opposite effects on two populations less than 35 km apart
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OGU.10214/4750 |
| Date | 05 December 2012 |
| Creators | LeClair, Dayna |
| Contributors | Norris, Ryan |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Book |
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