Saturday, June 18, 2011

When is a Collared Dove not a Collared Dove?

When is a Collared Dove not a Collared Dove would appear to be a pretty basic question - answer: When it's another species! Yet in North America that doesn't seem to be such an easy question - or answer! I got dragged into the subject this morning when I went to Cape May Point hoping to see my first North American Eurasian Collared Dove. What I saw, left me scratching my head!

I was aware of potential problems with the identification of Eurasian Collared Doves as we sometimes have the same problem in the UK, the problem being the domesticated Barbary Dove (or Ring-necked Dove - unfortunately a name already used for another African species!). Barbary Doves have been in domestication so long that their origin is obscure, but it is believed that they were brought to the Mediterranean from Africa by traders in Roman times, or perhaps even back in ancient Egyptian times. This obscurity has left people uncertain of what to call it 'officially', but it is usually refered to as Streptopelia 'risoria', the specific epithet best put in inverted commas to indicate uncertainty as a true species. Certain plumage features and - especially - its call indicate that it is most likely decended from the African Collared Dove (Streptopelia roseogrisea) and thisd would fit in with the assumed irigin mentioned above.

The Eurasian Collared Dove is said to have been introduced into Bermuda in the 1970s, from there spreading to Florida where it was first detected in 1982. From Florida it has shown the same invasive tendencies that it has shown in Europe, in both cases - interestingly - spreading north-west. Incidentally, the Eurasian Collared Dove spread into Europe from Instanbul where some now believe it was introduced, perhaps from Iran or India by traders. Now the problem comes in the USA, for domesticated forms of Barbary Dove were already established in Florida and it seems quite likely that the vanguard of Eurasian Collared Doves may well have hybridized with Barbary Doves. Pigeon Fanciers (like dog breeders, cat breeders and many other specialist folks) take pleasure in oddities and variety and a high proportion of Barbary Doves show elements of leucism in their plumage (that's abnormally pale coloration to you or I!). This may well have continued into the new hybrid population and even into any pure Eurasian Collared Dove pairings that may have occurred subsequently.

So, how does this relate to the Cape May bird I hear you ask. Well, my immediate reaction upon seeing the bird was - this is not a Eurasian Collared Dove, it's far too pale. However, spend a little longer with a bird and you get lots of different views under different light conditions. Here's some pictures of the bird with comments.

First impressions are of a rather patchily-plumaged bird, typical of the irregular leucism shown by Barbary Doves. Note also the paleness of the primaries which don't contrast particularly strongly with the rest of the plumage.

Up on the roof in better light, some of the plumage patchiness is burned out and less obvious, but an overall lack of contrast between primaries and other feather tracts still seems to hold.

Again, a rather scruffy looking bird with primaries that seem to be the color of dark, milky coffee rather than showing any gray tones.

Now the big but... Continued watching throws a few spanners into the works! A clear view of the undertail coverts while preening reveals them to have a gray cast - a feature of Eurasian Collared Dove. This is wrong for Barbary Dove which should be white here. The very strong contrast between dark inner and pale outer halves to the tail feathers also suggests Eurasian Collared Dove.

For me, this picture - taken during a fortuitously-timed wing stretch - clinches the bird as Eurasian Collared Dove and lays the ghosts to rest. It also makes it easy to understand what's happening with this bird. The brownish primaries with their pale tips are easy to see here - at least the outer five are. Doves should have 10 primaries with the outer (No 10) long unlike songbirds which generally have a very small 10th primary. So we can number inward from 10 to 2, but find that number 5 is very short and we are one missing. In fact, I reckon that 5 is so short that we can't see it and 4 is the half-grown one. The point is, these inner primaries are new and are much grayer than the old, brown, outer primaries. Couple this with the pale pink (not reddish) legs (see other photos!), rather small black collar and small amount of pink wash on the chest and it is clear that this is a molting youngster.

Back on the ground under the trees again, the bird returns to looking patchy and unconvincing, but here it is possible to see the gray undertail feathers, while the dark gray inner primaries can also just be seen poking out from under the secondaries. One other feature apparent here too is the rather scaly appearance to the wing coverts, produced by typical juvenile feathers which are shorter than those of adults and produce a slightly different effect in the way that they overlap each other (this same effect can be used for ageing shorebirds).

I'm not sure how this zoomed in and cropped picture will appear on the blog, but hopefully it should be possible to see that the eye is chestnut brown and not ruby red. Again, this is a feature of immaturity.

Currently this bird appears to be favoring the residential part of Cape May Point not far from the entrance to Cape May Point State Park. I suggest trying the block centered on Lehigh/Whilldin Avenues and Lincoln/Yale Avenues or a block in either direction of there.

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