FOAM LAKE BIRDING
No. 95
Fall frosts have arrived, and considering the year, somewhat too soon. With the shortening of days and dropping temperatures, fall migration is now proceeding in earnest. The first snow geese were seen two weeks ago and our backyard is literally teeming with small birds from the north heading south.
The last two weeks I dealt with birds that are difficult to positively identify. In keeping with that theme I decided to cover a family of birds that I have not written about before, the vireos. Vireos are inconspicuous small greenish birds often tinged with yellow that behave and look like warblers but are not related to them. There are two characteristics separating warblers from vireos that are significant to taxonomists. First, the male and female vireos are the same; warblers are not. Because vireos look so much like several warblers this field mark is not very useful to birders. Second, vireos are good songsters; warblers are not. This characteristic is useful only if one is familiar with birdsong in general. Vireos are very often mistaken for warblers with the result that many birders claim to never having seen a vireo.
A case in point is this week's featured bird, the Philadelphia Vireo, so named because of where it was first identified. In size, colour and behaviour it is very similar to several fall warblers especially the Orange Crowned and Tennessee. Colours are not very useful here as the variation within species alone can cause confusion let alone between different families (and species) altogether. To experienced birders, or those with sharp eyes, there are three subtle field marks that are useful in identifying Philadelphia Vireos. They are: first, the vireo has a stubbier and thicker or heavier beak; second, the vireo has dark flight feathers (remiges) lightly barred with white that can be seen only when the bird is perched and look like elongated dark wing tips; third, and probably the best field mark, is the white eyebrow line and a thin dark eye line starting from the beak and extending back to the ear. Some warblers and other vireos share some of these characteristics so it necessary to note all three and not just one or two.
Four species of vireos occur here, two of which nest locally and two in the Boreal Forest. Our two local breeders nest in larger tracts of woods in isolation from man, much like the Goldfinch. Interestingly, only our two northern breeders are regularly seen in town and then only in the fall and spring. To see the local nesters one has to go out to wooded rural areas. The Philadelphia Vireo is a northern breeder that is listed as being uncommon. When one takes into consideration that the bird nests where it is seldom observed, and then when it is seen it is misidentified as a warbler, its apparent scarcity is understandable. I had not identified a Philadelphia vireo until just six years ago at Point Pelee in Ontario. Since then I have seen them regularly every fall simply because I now know what I am looking for and how to identify them.
One morning this past week was an example of just that. There were a pair of Philadelphia Vireos feeding on insects in our chokecherries in our backyard and, until recently, I would have misidentified them as Tennessee Warblers and that would have been that. Not anymore.
Because vireos are not quite as active as warblers, I was able to get several good shots of the pair in our yard. The pictures did not turn out as sharp as I would have liked but they do show the aforementioned field marks. Again, to identify this bird binoculars are a must. Have fun.
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