Friday, March 30, 2012

Answers to Identification Quiz

A few weeks ago I posted an identification quiz with some bad bird shots. If you did not already check out the quiz, you can see it here before reading the answers.

Here are the answers:

Pennsylvania - February
Upon looking at this photo, it is clear that there are several species present. Let's start with the grayish bird in the center-right, the only bird with a face visible in the shot. The fact that the bird is flying over water, has pointed wings, and a bill with that shape means that this is a gull. Small gulls, like Bonaparte's can be ruled out by the fact that the bird looks rather large and has a thick beak. Another possibility would be Ring-billed Gull. This bird appears to have a "thick build" a characteristic not usually associated with Ring-billed Gulls. The dark color and bill with a dark tip identify this bird as a young Herring Gull. Looking around the photo, we see other birds that are similar in size and structure to this Herring Gull. These too are Herring Gulls.

Next are the birds in the foreground that are flying low over the water. On the left there are two birds with a lot of white and on the left, two gray birds. All appear to have noticeable short tails and pointed wings. These characteristics nicely fit those of ducks. The birds on the left have white and black bodies and wings and orange/red feet. If you look on the lowest bird in the photograph, you can see the bird has dark coloration near the head. If you compare these field marks to ducks in a field guide, you will see that Common Merganser fits perfectly. The ducks over on the left are much darker and grayer than the male Common Mergansers. The wings are dark, with darker tips, and there appears to be a white patch on each wing. Considering these field marks and the association with the male Common Mergansers, these are female Common Mergansers.

What about the blurry birds floating in the water in the back? The shape and coloration of these birds match those of Common Mergansers, and that is exactly what they all are.

Pennsylvania - August
Here we have a small bird facing away from the camera. A few field marks are visible including dark wings with two strong wingbars and some yellow or orange near the face. Off all of the songbirds, strong double wing bars and yellow/orange head coloration are really only found on warblers. So now we've narrowed it down to one of about thirty species that regularly occurs in Pennsylvania. On top of that, the photo was taken in August, which suggests that this may be one of the dreaded "confusing fall warblers". Actually, this is NOT one of those tough IDs. The combination of dark wings with two very distinct white wing bars and yellow on the face narrows this bird down to Blackburnian Warbler with little trouble at all!

Pennsylvania - August
This bird may be the toughest one in the quiz. We can see a plain-looking bird, with dark brown or olive upperparts and yellowish underneath. We have no distinctive markings, and we can't see the face, a place where many birds have distinguishing markings. The lack of noticeable field marks (stripes, spots, patterns) brings several groups of birds to mind--kinglets, fall warblers, flycatchers, and vireos. We can also see the underside of the beak, which appears too wide for a warbler, too flat for a sparrow, and too long for a kinglet. This beak shape fits flycatchers and vireos. Of the small, yellow-green flycatchers that occur in this area, there are none with such yellow coloration and no wingbars or other markings on the wings. This leaves vireos. A few species can be quickly ruled out: White-eyed, Blue-headed, and Yellow-throated would show wing-bars and Red-eyed should have some distinct head markings that would be visible even though the branch is somewhat covering the face. This leaves two species, Warbling and Philadelphia.

These two dull vireos are well-known for being tricky to identify, especially in migration when both can occur together. Most Warbling Vireos start migrating and the beginning of August (they also breed in Pennsylvania), whereas Philadelphia Vireos start showing up around the end of the month. Since this photo was taken in August, and we don't know a specific date, migration timing is not a helpful identification tool. We also cannot see the facial markings which are often useful for separating these two. Warbling Vireos are generally whitish underneath and Philadelphia Vireos have more yellow. Since this bird is mostly yellow underneath, this must be a Philadelphia, right? Well, let's take another look. Notice how the yellow coloration on the chest appears the same as that on the throat. A Philadelphia Vireo usually shows a brighter yellow throat. Also take note of the white that is visible on the middle part of the underside--something that is uncommon on Philadelphia Vireos which would be solid yellow on a bright individual. From these distinctions, we can come to the conclusion that this is a Warbling Vireo. In the field, a view of the head and posture of this individual would aid the identification. As a final note, the coloration in this photo is very deceiving. Although the bird had more yellow that the "average" Warbling Vireo, the photo taken with sunlight shining through green leaves accentuated this characteristic. Always be careful when using colors to identify birds!

Quiz Responses:

Photo 1: Common Merganser and Herring Gull (100%)

Photo 2: Blackburnian Warbler (50%), Pine Warbler (16.7%), American Goldfinch (16.7%), Rusty Blackbird (16.7%)

Photo 3: Philadelphia Vireo (50%), Warbling Vireo (16.7%), Red-eyed Vireo (16.7%), Least Flycatcher (16.7%)

Congratulations to Ethan Kistler, who got them all correct.

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