Spatial ecology and habitat exploration of neotropical migrants during spring migratory stopover
David L. Slager, MS
Advisor: Paul Rodewald
Thesis: Movement ecology and stopover duration of Northern Waterthrush and Yellow-rumped Warbler during spring migration along the Upper Mississippi River
Long-distance migrant songbirds spend the majority of their migratory time and energy stopping over between flights to rest and refuel at locations not previously encountered. They must efficiently exploit these novel environments to deposit fat stores and arrive at the breeding grounds early enough to maximize the probability of successful reproduction. In spring 2009-2010, I examined fine-scale movement patterns and stopover duration of Northern Waterthrushes (Parkesia noveboracensis) and "Myrtle" Yellow-rumped Warblers (Dendroica coronata coronata) at Trempealeau National Wildlife Refuge in western Wisconsin. I used a translocation approach and radio-telemetry to investigate how migrants that encounter different habitats in unfamiliar environments adjust their exploratory movements and stopover duration. In both Northern Waterthrush and Yellow-rumped Warbler, birds with more energy stores at capture had shorter stopover durations. Over the first two days following release, Northern Waterthrush movements became less linear, consistent with a transition from exploring habitat to settling on a preferred microsite. Northern Waterthrushes released in less suitable habitats showed increased exploration and decreased stopover duration compared to individuals released in more suitable habitats. The fact that Northern Waterthrushes released in less suitable stopover habitats departed sooner suggests an upper limit to a migrant's ability to locate suitable stopover habitats via exploration, highlighting the need for land managers to identify, acquire, and conserve quality stopover habitats for migratory landbirds.