It’s almost a cliché. When we think of difficult identification problems, we very often conjure up the image of a small, drab, greenish thing with wing bars and maybe an eye ring, but little else that one would traditionally call a field mark. We conjure up an Empidonax flycatcher. Members of this genus which, in the Eastern United States, include Yellow-bellied, Acadian, Alder, Willow, and Least Flycatchers, have the reputation of being nearly impossible to identify in the field unless their vocalizations are heard. Although it’s not quite that bad, the reputation is well founded and some birds are indeed best left unidentified. On the other hand, many are identifiable, so don’t give up just yet!
As with other identification problems, it is always helpful to begin with an understanding of the local status of each possible species. But before discussing the Empidonax flycatchers (also knows as “Empids” for short), we first need to address another small flycatcher that is often mistaken for an Empid. The Eastern Wood-Pewee (in the genus Contopus, not Empidonax) is a common breeder in most large tracts of mature, open forest in New Jersey. In Cape May County, Belleplain State Forest is a particularly good place to see pewees during the breeding season. Spring migrants begin to arrive in early May but they are often scarce until mid-late May, with some breeding areas not occupied until early June. Migrants are particularly numerous in fall when they are found in a wide variety of habitats from forest interior to forest edge to open brushy fields. Fall migrants are present in Cape May from late August to late October with peak numbers in the second half of September. None of the Empids are nearly as common in South Jersey as Eastern Wood-Pewee, so when looking at a suspected Empid, one must always consider Eastern Wood-Pewee first.
Two Empidonax species breed in southern New Jersey. The Acadian Flycatcher is an uncommon but widespread breeder in large stands of mature woods along streams, particularly favoring areas with a dense canopy and relatively open understory. Migrants are seldom found away from such habitats, so they are quite rare in the more heavily visited migrant traps in Cape May. Spring migrants may be encountered from early May to early June and fall migrants mostly from mid-August to mid-September. Our other summer resident Empid is the Willow Flycatcher. Willows are very localized and uncommon breeders in South Jersey, occurring primarily in remnant bits of dune forest and brushy marsh edges. Spring migrants occur primarily in these habitats from mid-May to early June. Fall migrants are a bit more widespread but still very scarce, occurring in August and early September.
The other three Empids occur only as migrants in South Jersey, yet, oddly enough, are encountered much more frequently during migration than our two resident species. Yellow-bellied Flycatcher is rarely seen here in spring but is a regular migrant in fall, mostly from mid-August to late September. Migrants prefer areas of mature, shady forest but are also occasionally seen on the forest edge. Alder Flycatcher is exceptionally rare in South Jersey in spring but is a regular fall migrant, mostly from late August to mid-September. They prefer brushy field and forest edge habitats such as at Higbee Beach where they always outnumber Willow Flycatchers. By far our most numerous Empid is Least Flycatcher. Leasts are uncommon in May but fairly common in fall, occurring from early August to early October, with a peak in late August. They use the same brushy field and forest edge habitats favored by Alder Flycatcher.
When faced with one of these little flycatchers in the field, what should one do?
1) Decide if you are looking at a Pewee or an Empid. Pewees are a bit larger than Empids, but this can be difficult to judge without lots of experience. A more useful feature, and one that is helpful even at a distance, is foraging behavior. Pewees tend to use wide-open perches from which they sally out on relatively long flights, then return to the same or a nearby perch. Upon alighting on a branch, Pewees tend to shiver their wings and tail a bit, but then sit very still without wagging or flicking their tails. Empids, on the other hand, tend to perch closer to dense vegetation, often within a bush or tree. Foraging flights tend to take them to a new spot each time and they seldom return repeatedly to the same branch. While perched, most Empids (including all five Eastern species) tend to gently flick their tails upward though they may go through still periods as well.
As you get a little closer, some structural characters become useful. Pewees are longer-winged than any Empid. This feature is most easily judged by looking at “primary projection” or the degree to which the primaries (the longest wing feathers) project past the tertials and secondaries (the shorter feathers stacked above the primaries). Pewees also tend to be bulkiest through the shoulders and chest, creating a top-heavy look. Empids are comparatively daintier-bodied, usually with slimmer shoulders and chest but often with larger heads. Although not always easy to see clearly, pewees have much shorter legs than Empids so that little more than the toes are usually visible below the belly feathers. Most Empids, unless they are really fluffed up and relaxed, will show obvious legs from the appropriate angle. With practice, these structural features give pewees a distinctly different silhouette from Empids.
A few plumage features are also helpful. Pewees usually have a vested look with olive-washed flanks contrasting with a pale mid-line to the breast. None of the eastern Empids show such a strong pattern below. The head pattern, however, is comparatively plain on a pewee with little or no eye ring and often a darkish look to the face. The wing bars on a Pewee tend to be thinner and less contrasting or clean cut than on most Empids.
Voice is another very useful feature. A Pewee’s song, of course, is very distinctive. Fall migrants tend to be less vocal but still regularly give a variety of distinctive calls including a unique, but often very soft “tewp,” often likened to a very soft warbler chip. Another call is a soft, rising whistle, “puu-eee” with a relaxed, drawn-out quality. Yellow-bellied Flycatcher has a similar whistled call but it is a quicker, more emphatic “pu-EE.”
2) If you do have an Empid, not a pewee, get as close a view as possible, use your ears, and stay tuned for part two of this article!
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Photo 1 – Eastern Wood-Pewee, late May, Maryland. Note especially the long primary projection, which is the degree to which the all-dark primaries project past the white-edged tertials and secondaries. Also notice the very short legs and near lack of an eye ring. The wing bars, though prominent, are somewhat thinner and less contrasting than on an Empidonax. Photo by Bill Hubick. |
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Photo 2 – Eastern Wood-Pewee, late September, Maryland. Even from below, the long primaries are evident. Also notice the broad chest and shoulders, dark vest, and darkish face with virtually no eye ring. Photo by George Jett. |
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Photo 3 – Least Flycatcher, early October, New Jersey. This is the most commonly seen Empidonax in Cape May and a good species to learn. Compared to Eastern Wood-Pewee, notice a more petite, compact look overall with shorter primary projection, larger head, and longer tail. The eye ring is bolder than on any pewee and the wing bars are thicker and more contrasting. Photo by Kevin Karlson. |
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Photo 4 – Least Flycatcher, early December, Belize. Least Flycatcher’s petite look is evident from all angles. Compared to a pewee, notice the Least’s shorter wings, longer tail, and slimmer chest and shoulders. From this angle, the longer legs are also evident. The eye ring is fairly prominent and the breast has much less of a vested look than on a pewee. Photo by Michael O’Brien. |
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