Monday, 30 March 2015

"calidus-type" Northern Peregrine, Lincolnshire

Large falcons are not much better than ducks when it comes to the question of hybrids and escapes muddying the waters of any sighting or identification. However,  raptor expert Dick Forsman has commented on the photos I took of the large falcons near Donna Nook in Lincolnshire on Friday. It turns out that the larger of the two birds is a calidus-type "northern" peregrine. This means that it belongs to either the subspecies calidus, which is an arctic tundra breeding species, or to the north eastern extreme of subspecies peregrinus. The latter can look very like calidus and in some cases may be inseperable in the field.

Since calidus reaches as far west as northern Scandinavia, and the north eastern extreme of peregrinus range is to the north east of China, it would seem logical to me that this bird is more likely to be a calidus rather than a peregrinus, but this is pure speculation on my part. There are intergrades between the two and both are long distance migrants. Dick's comments are below.

Notice how large, long necked and barrel chested the bird on the right seems.

I did wonder if the larger bird was a Saker, it certainly seems to have a pale head.

In this photo you can really see the pale head. However, the diagnostic features which confirm that this is a peregrine are "the broad crossbars on the flanks of this juvenile and very finely marked falcon, as well as its head-markings, which both comply nicely with a "northern" Peregrine (subspecies peregrinus/calidus)" and "....even the wing-formula can be judged from the same image, showing a typical Peregrine-group wing-tip, with outermost primary longer than the third, whereas the Gyr-group (incl. Lanner and Saker) show the opposite, with outermost shorter than third (more rounded wing-tip)".

"Northern" peregrines breed in the Arctic and are larger, longer winged and longer tailed than our resident birds, and do have pale heads and are apparently very aggressive. I don't think I've ever seen a northern peregrine before, so nice to have one confirmed by an expert.

Now to play the waiting game...... how long before this bird becomes an armchair tick for me???

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