I did some early-morning birding at Wooded Island last week. It was a very unpromising morning: there was an icy wind out of the northeast, overcast skies–a typical spring day in Chicago. A wind off the lake usually means terrible birding along the lakefront.
Jackson Park was at that time a natural landscape featuring three long sand ridges running parallel to the lakeshore. These low ridges were once shorelines of Lake Michigan and its immediate postglacial ancestor, Lake Chicago. Between the ridges were low, marshy swales.
Best of Chicago voting is live now. Vote for your favorites »
These are all nesting species at Wooded Island. So far, we hadn’t seen a single migrant. Once across the bridge, we saw another probable resident, a warbling vireo. We finally got our first migrants a few yards down the walk when our approach scattered a large flock of white-throated sparrows that were feeding on the grass.
The birds also have to wait for their food sources to emerge. Arboreal insect eaters like vireos and warblers follow the opening leaves north, because the insects come out to feed on the leaves. Weather can speed up or slow down leaf emergence slightly, but the lengthening days are the major control on that process, so weather, again, plays only a minor role.
The big question now for local birders is when we will finally get a break in this persistent weather pattern. It could be that zillions of birds are hanging out in Tennessee or some other place in that general neighborhood just waiting for a strong southern wind to carry them to their nesting grounds.
