[Birdnet] Empid question

[Tim Avery]

David, et all,

Hardly a laughable question.  Empidonax flycatchers (empids), are one of the toughest groups of birds to identify.  Yes, during the breeding season they they are singing, and usually in a habitat suggestive of their species.  But the vast majority of empids are seen during spring and fall migration, with all the species in any type of habitat where food is present.  This means Gray Flycatchers at Garr Ranch, Dusky Flycatcher in my backyard, Willow Flycatchers in spruce trees away from water... You get the point. There are days at Garr Ranch when all 5 of the common Utah empids (Cordilleran, Willow, Dusky, Hammond's, Gray) are feeding around the same pond, and on some occasion throw in the Least Flycatcher, which makes it even more challenging.  The are obvious ways to sort out the majority of empids into two separate groups:  Hammond's, Dusky or Least AND Cordilleran, Willow or Gray.  The latter being large billed empids, the prior being petite billed empids.  Even then there is variation in bill size... So even more fun.

But to your question at hand.  It is probably safe to assume that the majority of Hammond's and Dusky Flycatchers, look the same.  Plumage is such a highly variable thing, that simple patterns like a vest of darker feathers, can turn into confusing ID markers.  Both these species have a vest most of the time, its just a question of how dark it appears, so YES, Dusky do often have that vested look.  

When I try to separate Dusky and Hammond's Flycatchers in the field, I rarely look at the plumage traits or colors and simple feather patterns.  For the most part there is a great deal of overlap between the two species, so it is a tedious and maddening process.  Both birds are similar in size, have similar eye-rings, their head shapes are similar (and change based on posture constantly).  Dusky may or may not have more pink under the bill, but they are similar and again, quite variable.  

What I have really come down to using almost exclusively is tail length versus primary projection.  Hammond's usually has a shorter looking tail, with a longer looking primary projection. Where Dusky usually has a longer looking tail, with a shorter looking primary projection.  The distance that a bird's longest primaries extend beyond its longest secondaries (or tertials) when its wings are folded is referred to as the primary extension or primary projection.  So typically Hammond's have a longer primary projection than Dusky.

If you have a copy of the BIG Sibley Guide, open to page 328.  Take a look at the pictures of the Hammond's and Dusky side by side.  It is a very subtle difference but a difference that can usually be seen in the field.  It takes some time and looking at a lot of empids to get a feel for what a "long-tailed" versus "short-tailed" bird would be.  Some experts say that only 75-85% of empids can be identified correctly in the field.  The other 15-25% are often unidentifiable and best left that way without an audible distinction.

But, to make this even more confusing, sorry, that's what I like to do I guess.  Feathers wear.  Simple.  The tips of feathers wear down over time, and therefore some Dusky have shorter looking tails, and some Hammond's have shorter looking primaries... No joke.

In any event, I still find it enjoyable to go out to Garr Ranch in August or September and work my way through tidal wave of little gray buggers flucatching... oops, I mean flycathing, just kidding Kris ;) in the trees.

Good Birding

Tim
Salt Lake City, Utah
tanager at timaverybirding.com
http://www.timaverybirding.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://secureserver.securesites.net/pipermail/birdnet/attachments/20080516/b7278f30/attachment.htm