Back in early June, Shauna and I traveled to rural western New York, to attend the Allegany Nature Pilgrimage. It's quite the event, with hundreds of attendees, scores of field trips and other activities, and lots of speakers. I was there in the latter capacity, speaking about - what else, this year - moths.
The Pilgrimage takes place in a beautiful region with lots of interesting places nearby, so we took the opportunity to tack on a few days and visit some new sites. We saw lots of flora and fauna, managed to eke out some decent imagery, and learned lots about various things. One of the more interesting avian experiences for me was stumbling into a large shrubland that was occupied by both Alder Flycatchers (Empidonax alnorum) and Willow Flycatchers (E. traillii), in about equal numbers.
%20copy.jpg)
This site is near the southern overlap of these species' ranges, and maybe shrublands full of both species isn't that unusual in this zone, but I had never seen it. Where I live, in central Ohio, Willow Flycatcher is the common species, and Alders only occur sparingly in northernmost Ohio, especially in the northeast corner which has the most boreal-ish habitat. But I've spent scads of time in the north country, such as the northern tip of Michigan's Lower Peninsula and the Upper Peninsula, where Alder Flycatcher is very common, and I know it well.
Alder and Willow flycatchers were considered conspecific until 1973, although the differences between the two were noticed long before, perhaps most notably by Roger Tory Peterson. Much of the differentiation is in vocalizations, and habitat. They are well-named birds, as Willows typically occupy areas with some willow (genus Salix). Alders prefer, duh, alders (genus Alnus) and thus are typically found in wetter sites as that's where alder thickets thrive. But good luck identifying a silent bird in migration. If it issues a few distinctive call notes, you might nail it, but otherwise it'll have to go down as "Empidonax sp. Even birds in the hand, with measurements possible, cannot always be separated (ever?).
%20copy.jpg)
%20copy.jpg)
A brief, greatly compressed video of one of the singing Alder Flycatchers. Sorry, my learning curve with video processing is not very advanced, but you should be able to hear its distinctive song well. It is a burry ascending Free-beer! or Fe-bee-oh!
There apparently is no concrete evidence of hybridization between these very similar species, even though they are extremely similar genetically, much more so than most avian species pairings. Our observations in this mixed meadow, the type of site one might think that hybridization might occur if it indeed does happen, indicated that the two species maintained well-defined territories and did not interact much.