Bird Migration Information from Brian

In the previous post, I wondered why so many Red-winged Blackbirds were flying southbound over the woods at Hoffmaster State Park yesterday morning.  Brian Johnson emailed the following reply which I've posted separately rather than as a comment to my Hoffmaster post.  - Ric Pedler

Ric

With the above-average temperatures, somewhat southerly winds, and dry conditions, it is not surprising that migration is proceeding at an accelerated pace. However, among most species thus far, first arrivals are appearing only a couple days before their long-term averages. On the other hand, some of those species are filling their habitats faster than normal (i.e. subsequent individuals are appearing shortly after the previous, thus compressing their seasonal arrival phenology). Recent firsts not otherwise reported include, female Red-winged Blackbird (2 at Muskegon State Game Area on March 26), Brewer's Blackbird (2 males on April 1 at Wastewater), Ruby-crowned Kinglet (1 at Muskegon State Park on April 2), Swamp Sparrow (9 at Lanes Landing on April 3), and Savannah Sparrow (3 at Wastewater on April 3). Also, I counted Painted Turtles basking in the Maple River by the DNR Headquarters and found 157 on April 1.

As far as your southbound migrants, you are seeing only a small fraction of the northbound movement from the past several days. Early arriving landbirds migrate during the day (we are only now starting to see passerines that migrate predominately at night). These birds proceed north along a broad front in response to favorable weather conditions (warm fronts really move them), but they concentrate over the dunes of Lake Michigan. In the case of open-country species (meadowlarks, larks, buntings, longspurs), best movements are actually over the lake and shoreline. Reasons include geographic funneling effects, navigational aiding, weather (e.g. wind forcing), and habitat issues (terrestrial ecosystems are invertebrate poor at this time of the year). Thousands of these blackbirds, starlings, robins, bluebirds, finches, flickers, etc. pass northward during the morning hours and again near sunset. Many are hard to detect because they fly so high (and fairly fast in good tailwinds) and often remain silent (except when encountering other flocks). However, a portion of these birds, as you have noted, are flying steadily in the "wrong" direction. This phenomenon, sometimes referred to as a "morning flight", is considered by some researchers working along the coasts to be a reorientation or correction to the preceding migratory flight. Here, along the lake for instance, it may not be safely assumed that all these southbound individuals are the same birds that moved north on this same path minutes, hours, or days previously. However, I suspect that the southbound movements represent birds searching for suitable habitat for foraging, safety from predators, and refuge from harsh weather, and in turn seeking either sufficient space or additional members of their own species or guilds.

Similar patterns occur over the lake. While some species, such as Red-breasted Mergansers, have been showing a consistent trend north (or northwest in the case of Tundra Swans), certain other waterfowl seem to be moving south in better numbers. One of my better counts for loons was 101 in 1.5 hours moving NORTH in the fall.

- Brian