phil jeffrey:: An Odd Flycatcher in Central Park, Sept 12th 2015

Andrew Rubenfeld alerted me to this very confusing flycatcher at the north end of Strawberry Fields hunting in the Dawn Redwoods on Sept 12th, I spent some time looking at it and left while still quite frustrated at the ID.

Spoiler Alert: thanks to vocalization (two different types of calls via two different observers) we know what this species is. Nevertheless it's a really instructive bird from the point of view of ID of fall flycatchers.

My immediate ID call when seeing this bird was Empidonax - no obvious vesting, a relatively long tail but narrow without a fork in it, not the overall dusky gray-brown coloration of most Eastern Wood-Pewees. The head was rather rounded and lacked the more wedge-shaped profile arising from the Pewee crest. The bottom two photographs really show these characteristics relatively well - in fact the bottom left photograph reminds me of some Willow Flycatcher photographs I've taken. I think we can agree that it's not an Eastern Phoebe - no dark mask and strong contrast on the face, no tail wagging (trust me), yellow on the bill (Phoebe=all black) and evident wing bars. Also about a week earlier than we started seeing Phoebes.

This nominal Empidonax flycatcher had a medium primary projection (primary projection past the tertials, and relative to the length of the terials). It obviously wasn't a Least (larger size, large bill, primary projection too long), wasn't a Yellow-bellied (white throat, way too gray, a little too large), which put me in the camp of Willow/Alder or perhaps a rather gray Acadian. Willow Flycatcher averages a shorter primary projection than the very similar Alder. Alder and Acadian show a primary projection similar to this bird. The very weak eye-ring on this bird is also somewhat consistent with this bird, although all three (Willow/Alder/Acadian) typically average stronger eye-rings. Acadian averages rather greener. Therefore the my initial ID hinged around trying to discern which of Willow/Alder/Acadian it actually was.

One of the major complications of the ID is that this bird is still in molt. There's a mixture of shapes in the tail feathers (retrices) although they are the same lengths, the coverts are of variable lengths, and appearance consistent with something that is still molting body feathers. The small flycatchers pretty much universally molt on breeding grounds before migration, but this one is an anomaly. I also suspect - but am not certain - that this is a first year bird given that the tail feathers are somewhat pointed and the primaries hint at that too. First fall Empidonax show broad buffy wing bars, which isn't shown here since they are somewhat narrow and whitish.

The bird was not silent - it was giving a short call that I think of as a softer and shorter version of the Common Yellowthroat contact call. I attempted to memorize it, but these sort of calls aren't in the recordings you get in online field guides and fall flycatcher calls (as opposed to spring flycatcher songs) remain somewhat unknown to me. But having settled on likely Willow/Alder some things about the bird didn't sit right. For one thing it persistently sat on an open branch and returned to the same perch after flycatching - this is classical Pewee behavior. Also in flight, when it flew past me over the lawn, it resembled the longer-winged structure of a Pewee quite strongly. There had been several in the park each day around this time. Although I still felt that it looked more like an Empidonax and didn't show classical Pewee features (strong vesting, smudging in the vent, cresting creating a more wedge-like head profile) some aspects of the bird did suggest Pewee, much as some aspects of the bird suggested Empidonax. The coloration was also grayer than you expect in fall Empis - not as gray as you'd see in most fall Eastern Wood-Pewees but a coloration that I'd seen in some summer Western Wood-Pewees. The other stumbling block is that the lower mandible shows an appreciable amount of dark coloration towards the its tip. This is uncommon to rare in the eastern Empidonax species but fairly typical for Wood-Pewee of both species.

Subsequently I found a couple of vocalizing Eastern Wood-Pewees giving the same call as this bird and Anders Peltomaa indicated that it gave a stock Pewee call after I'd left the scene. So this bird is an Eastern Wood-Pewee, in heavy molt, not showing many of the classical plumage features (vesting, crest, forked tail, etc). It's very interesting, however, to post-mortem the ID of this bird since it didn't present as a Pewee to multiple observers in the field. These observers are not neophytes. Much of the initial ID call was based on plumage characteristics and impacted by the molt state.

• The call and song fragment (definitive)
• Dark tip to lower mandible
• Body relatively slim and tail relatively long with respect to body
• Coloration on the gray end of gray-brown-green.
• Choice of perch, returning to same spot, appearance in flight
• There is a single dark streak on the vent (definitive for Pewee sp.) but it was not field visible - either obscured or in heavy shadow

• No strong vesting on chest
• No obvious crest on crown (Emidonax show some cresting)
• No field-observable smudging/streaking on vent (see above) - such is the problem with "negative" ID points
• No forked tail - retrices still growing ?
• Primary projection not as long as a typical Pewee - primaries still growing ?
• The lores constrasting show a pale area that while not unprecedented for Pewee is rarely-if-ever seen as this contrasting, but quite typically constrasting for an Empidonax

As far as bill coloration goes, Peter Pyle's "Identification Guide to North American Birds" describes Willow Flycatcher bill as mostly or entirely orange/yellow/pink. It's probably the case that many eastern Empidonax species can show a little darkening to the tip of the lower mandible but extensive dark on the lower mandible is the preserve of the Pewee. This feature in Pewees is certainly pretty variable in my experience.

Best to make your own impressions. The following links are for Google image searches for: Willow Flycatcher, Alder Flycatcher Eastern Wood-Pewee

Of note is a BirdFellow web page by Dave Irons on this sort of ID challenge although it's discussing the western form of Willow Flycatcher with Western Wood-Pewee.

Phil Jeffrey, Sept 2015.