Long-term effects of habitat quality on juvenile fitness along contrasting environmental gradients

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The long term objective of my research program is to understand how anthropogenic stressors contribute to population declines of migratory songbirds. Dozens of North American species have been in steep decline for decades and many are now designated as Species at Risk in Canada. One of the biggest challenges in migratory songbird conservation has been determining the link between well-studied breeding populations and threats elsewhere in their life cycle. In 2009, my lab published a ground-breaking study in Science that used miniaturized tracking devices to map the start-to-finish migration of songbirds for the first time, and this triggered a revolution in our understanding of songbird migration ecology and conservation. However, a critical gap in knowledge remains because juvenile survival is poorly understood in migratory songbirds yet is expected to have a large impact on population dynamics. Offspring disperse away from their parent’s territory a month or so after hatching, become increasingly mobile and difficult to track, and after migration few return close enough to their natal site to be detected by researchers. Environmental stressors are expected to have a big impact on independent juveniles because their foraging efficiency is initially low yet they must build fat reserves to prepare for their inaugural fall migration that is thousands of kilometers across unfamiliar terrain. My research program is novel because I will track juveniles by deploying new long-lasting (>1 year) coded radio-transmitters within a new array of automated telemetry receivers that blankets southwestern Ontario. By combining manual and automated tracking, my students will test how habitat quality affects juvenile condition, survival, dispersal and onset of fall migration and we will re-locate recruits that return the next spring within the ~100,000 square kilometer array. This novel technology will allow us to test a series of hypotheses for how and why habitat quality impacts short-and long-term juvenile fitness in migratory songbirds. Poor habitat quality is expected to reduce nestling body condition and carry over to have long-lasting and negative effects on juvenile fitness. We will evaluate the nature and duration of these development effects along two contrasting environmental gradients (forest fragmentation, agricultural intensification) that differ in their underlying ecological stressors. Our results will directly inform habitat management decisions through population modelling scenarios that clearly identify the consequences of habitat loss and fragmentation on migratory songbirds.