Postdoc Dave Toews recently published a paper in the Journal of Avian Biology on why some warblers might not nest further into the northwest; All About Birds has a write-up on the work here. Dave shows that there is likely suitable habitat for several wood warbler species at high latitudes in northwestern North America, but the possible costs of a long migration limit their possible expansion into these regions. The paper is part of a special issue of the Journal of Avian Biology focused on using niche models to better understand the distributions of birds:
http://onlinelibrary.wiley.com/doi/10.1111/jav.01157/full
