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This month, we’ve got three birds to study in attempts to derive the correct answer. From the left two individuals, we can determine that they have fairly wide wings with rounded wingtips, suggesting that these birds are
1) inhabitants of dense vegetation,
2) fairly short-distance migrants (if migrants at all), or
This is because long, pointed wings do not provide the exquisite control over the sharp turns so necessary in tight spaces that short, rounded wings do. Additionally, short and rounded wings are less efficient for long flights typical of the longer-distance migrants. These two aspects of bird ecology are the primary driving forces in wing shape in most species, though they are in opposition in some, with those species coming to some compromise between the constraints of their ecologies.
In addition to shortish and rounded wings, all three birds show fairly long tails, relative to body length, and the left bird shows well a thin and short bill. The various shape features should send us to the passerines where, due to the immense number of possibilities involved in that single order, we’ll have to gauge at least some of the species’ color pattern. The right bird shows a distinct white outer edge to its long tail, and with that white not extending around the corner of the tail. That bird’s underparts appear whitish (or, at least, pale) and unmarked (though we can see that bird’s right foot forming a distinct dark patch on the belly). The head looks grayish, but the image is so small and the lighting difficult, that we should not be surprised if that estimation turns out to be incorrect.
Expounding on that lighting, we should note that the sun is above and to the right of the three birds, thus they are backlit: the top of the right bird’s head is the only part of any of the three birds that we can see that is directly lit; all the rest of the parts of that bird and the entirety of what we can see on the left two birds are in shadow. Thus, caution is necessary in determining tail pattern, something that might be important in the identification of these birds.
While beasts like larks and wagtails might be considered, those species are all long-winged, being open-country birds. Chickadees are also pale underneath with some having white edges to the tail, but they all show a distinct black throat lacking in our quiz birds. Some age-sex classes of Tennessee Warbler are white-underparted (is that a word?), but that species has a short tail lacking white edges. Bushtits have short, rounded wings and long tails, but, again, those tails lack white edges.
We really are left no option but the gnatcatchers. The caveat provided with the quiz photo – “This picture of three different individuals was taken east of the Mississippi River” – should rule out all but Blue-gray Gnatcatcher. But, that species’ tail is much more extensively white below than shown by even the right bird! Ah, but this is where that difficult lighting comes in. Because of the manner in which tails are folded – individual rectrices layered over the neighboring distal (toward the outside) feather resulting in the two central feathers being the ones visible from above and the two outer feathers from below – when looking at a tail from below, the only part of the that tail with no feather layered over it is the outer part of the outer tail feathers. In backlit situations – with the light coming through the tail, multiple layers of rectrices blocks the light while the single layer of tail feather at the edges of the tail do not. This produces a Black-tailed Gnatcatcher-like tail pattern on the right bird of the three Blue-gray Gnatcatchers that I photographed in migration at Cape May Point, Cape May Co., NJ, on 20 April 2011.
The following people (listed by submission date beginning with the earliest) submitted correct answers for the June Bird Photo Quiz—Blue-gray Gnatcatcher:
The following list shows the number of submissions for each species guessed.
The photo and answer for this quiz were supplied by Tony Leukering.