Spring starts and stops here; it can’t seem to really get going. As a result, leaves have been slow to develop and that makes it a little easier to spot the flighty little warblers as they migrate through. In fact, the cold weather seems to have slowed their normal migratory rush down a little.
Our strange spring weather and the numbers of new warbler species arriving daily means that we often get multiple species flitting around in the backyard on any given day. Watching the warblers go about their daily hunt for food is a great illustration of a classical ecological study I learned about many years ago — Robert MacArthur’s study of niche partitioning in warblers to reduce competition. He found that several warbler species could co-exist if they harvested the resource in different ways or from different areas of the tree.
A few examples to illustrate how one basic body type of small insectivore has specialized to divide up the food resource:
Yellow-rumped Warblers pretend to be flycatchers, “hawking” insects from the air or gleaning them from the terminal ends of branches of shrubs or trees, often flitting from the bottom to the top of one tree, or the top of one to the bottom of another.
Orange-crowned Warblers poke around in the leaf litter on the forest floor or into the newly emerging clumps of leaves on the branches of shrubs.
Black and White Warblers are nuthatch-“wannabes”, foraging upside down along the trunk and large branches of big trees. They are constantly on the move and really hard to get in focus.
Yellow Warblers prefer to forage among the branches of shrubs and trees along streams or other wetland areas. Their bright color really makes them stand out among the willow branches.
Ovenbirds and Waterthrushes are the largest warblers and prefer to forage in damp, swampy marshes or moist forest floor.
Those are just the ones I have seen in my backyard so far. There are still more species arriving to fatten up for the last push toward the breeding grounds in the Canadian coniferous forest. Hopefully, I will get some photos of them too.