Tuesday, 17 June 2014

Carrion Crow x Hooded Crow

Carrion Crow x Hooded Crow hybrid, Svedala (Sweden), March 2008 - copyright Carl Gunnar Gustavsson
(photo ID: 1056)


Carrion Crows and Hooded Crows have in the past been considered to be different races of the same species, although most authorities now treat them as distinct species.  Part of the reason for treating them as the same species was the extensive zone of hybridisation, at least in Scotland.  Some texts I have read seem to play down this overlap zone suggesting it is quite small in reality, but at least in my own experience I have commonly encountered hybrids across a large range within Scotland. Their ranges adjoin elsewhere in Europe too and we have examples of hybrids here from Sweden and Germany.

Some hybrids are superficially similar to Hooded Crows and are sometimes mistaken as such when they turn up in places where Hooded Crows are scarce visitors.  Others are much darker, and easier to overlook among Carrion Crows.  As hybrids are fertile they may backcross with either parent species leading to some individuals that can be very hard or even impossible to detect.  Presumably those hybrids that most closely resemble one or other parent species are backcrossed, but it would be interesting to establish the extent of variation within first generation hybrids - if you have images of birds where the circumstances (not merely the birds' appearance) lead you to believe they are the offspring of a pure Carrion Crow and a pure Hooded Crow, we'd like to hear from you.

This individual photographed by Carl Gunnar seems to be fairly typical of the type that more closely resemble Hooded Crow. In the picture above Carl Gunnar notes the relatively broad black streaks at the bottom of the breast.  In the photos below you can also see black centres to the undertail-covert feathers and also the mantle and scapulars - these feathers would be plain pale grey on a pure Hooded Crow.




Carrion Crow x Hooded Crow hybrid (same bird as in photo ID 1056), Svedala (Sweden), March 2008 - copyright Carl Gunnar Gustavsson
(photo IDs: 1052-1055)


The next one from Germany has a similar pattern but the dark centres of the feathers seem a bit broader making the bird appear darker.

Carrion Crow x Hooded Crow hybrid, Magdeburg, Saxony Anhalt (Germany), 1st May 2013 - copyright Joern Lehmhus
(photo ID: 0549)


Many hybrids are darker such as the one below that shows a dark belly, dark scapulars and a dark back, although the grey on the mantle, sides of the neck and breast is very obvious.


Carrion Crow x Hooded Crow hybrid, Magdeburg Zoo (Germany), 3rd March 2012 - copyright Joern Lehmhus
(photo IDs: 0614-0615)


Next up is another paler bird more closely resembling Hooded Crow, though it has a bit more black on the rear belly compared to Carl Gunnar's bird at the top of this page (photo IDs 1052-1056).



Carrion Crow x Hooded Crow hybrid, Magdeburg Zoo (Germany), 3rd March 2012 - copyright Joern Lehmhus
(photo IDs: 0616-0618)


On the next bird although the grey extends to the back and scapulars it is rather heavily marked dark across the whole area including the mantle.

Carrion Crow x Hooded Crow hybrid, Three Lochs Forest Trail (Stirlingshire, UK), 29th April 2007 - copyright Dave Appleton
(photo ID: 0538)


Next another one with extensive black on the belly but still obvious Hooded Crow influence.

Carrion Crow x Hooded Crow hybrid, Loch Ryan (Dumfries & Galloway, UK), 30th December 2003 - copyright Dave Appleton
(photo ID: 0539)


The next bird is much more like Hooded Crow, and perhaps a backcrossed bird, but it has too much dark at the bottom of the breast and under the tail.  Also when compared to the apparently pure Hooded Crow to its left the grey parts are a shade darker.

Carrion Crow x Hooded Crow hybrid (right, with Hooded Crow to left), near Tain (Highland, UK), 24th February 2012 - copyright Dave Appleton
(photo ID: 0540)


The next two are much darker, though still obviously hybrids.  Interestingly on the first of these the mantle feathers seem to be palest in the centre with darker fringes.  This is perhaps unexpected given that many hybrids show grey feathers with dark centres.


Carrion Crow x Hooded Crow hybrids, near Tain (Highland, UK), 24th February 2012 - copyright Dave Appleton
(photo IDs: 0541-0542)


The next bird is much closer to Carrion Crow than most, so is perhaps a backcrossed bird.  The mantle, scapulars, upper belly and (though you can't tell from this photo) lower breast feathers were distinctly greyish though, albeit far less obviously so than on most of the other birds shown here.  It's another bird where on the mantle and scapulars the feather fringes are dark and the centres are greyer.

Carrion Crow x Hooded Crow hybrid, Arderseier (Highland, UK), 16th March 2014 - copyright Dave Appleton
(photo ID: 1609)


The next few photos were taken from among a large flock of corvids consisting mostly of Hooded Crows but containing a small number of apparently pure Carrion Crows and quite a few hybrids.  In the first photo you have an obvious hybrid back left, a pure-looking Carrion Crow in the centre flanked by two pure-looking Hooded Crows.  I'm not sure the Carrion really was pure though as it seemed to have dark grey centres to the mantle feathers, only a shade paler than the black edges.  I suspect it was a second or even subsequent generation backcrossed hybrid.

Carrion Crow x Hooded Crow hybrid (back left), probable backcrossed (Carrion Crow x Hooded Crow) x Carrion Crow hybrid and two Hooded Crows, West Tarbet (Argyll & Bute, UK), 15th March 2014 - copyright Dave Appleton
(photo ID: 1610)


In the next three photos the second and third images certainly show the same individual.  I think the first image is also the same individual, but if not it is a very similar bird.



Carrion Crow x Hooded Crow hybrid, West Tarbet (Argyll & Bute, UK), 15th March 2014 - copyright Dave Appleton
(photo IDs: 1611-1613)


There are at least two hybrids in the next couple of shots.  The bird in the front is fairly obvious but the more Hooded Crow like bird at the back right is also a hybrid.  The other birds are possibly pure (Carrion on the left and two Hoodies on the right).


Carrion Crow x Hooded Crow hybrids (front and back right, with apparently pure Carrion Crow left and 2 Hooded Crows right), West Tarbet (Argyll & Bute, UK), 15th March 2014 - copyright Dave Appleton
(photo IDs: 1614-1615)






Carrion Crow x Hooded Crow hybrids, West Tarbet (Argyll & Bute, UK), 15th March 2014 - copyright Dave Appleton
(photo IDs: 1616-1620)


The next bird was in the same flock but seems rather unusual in having the palest area on the flanks and lower belly.  Often these parts can be dark on hybrids even when the mantle and upper belly are much paler.  This bird is leucistic, having a pale wing-bar (just visible at the bases of the primaries in these images) and a pale band across the base of the tail (also visible in the first photo).  I suppose the pale flanks could also be down to leucism, but corvids with pale bars in the wings and tail are quite frequent and most such birds don't also express the leucism elsewhere on the body.  Even if it is due to leucism I still think the bird is a hybrid as it shows a ghost of the Hooded Crow pattern, albeit very much darker.


leucistic Carrion Crow x Hooded Crow hybrid, West Tarbet (Argyll & Bute, UK), 15th March 2014 - copyright Dave Appleton
(photo IDs: 1621-1622)


The next photos from Germany all show the same bird which was paired with a Carrion Crow.



Carrion Crow x Hooded Crow hybrid, Braunschweig, Lower Saxony (Germany), 12th June 2014 - copyright Joern Lehmhus
(photo IDs: 1633-1635)


Another clearly intermediate bird from Germany:


Carrion Crow x Hooded Crow hybrid, Frankfurt, Hesse (Germany), 3rd March 2015 - copyright Joern Lehmhus
(photo IDs: 2322-2323)


The front bird here looks pretty good for pure Hooded Crow but the vent is too dark.  Presumably it is a backcrossed bird.

Carrion Crow x Hooded Crow hybrids, Berlin (Germany), 14th January 2016 - copyright Joern Lehmhus
(photo ID: 2624)


The next one is a bit more obvious with extensively dark underparts and back.


Carrion Crow x Hooded Crow hybrid (with Hooded Crows), Berlin (Germany), 14th January 2016 - copyright Joern Lehmhus
(photo IDs: 2621-2622)


The next one isn't so solidly dark where a pure Hooded Crow would be pale, but it does have fairly obvious dark feathering throughout much of the pale part of the plumage.

Carrion Crow x Hooded Crow hybrid, Berlin (Germany), 14th January 2016 - copyright Joern Lehmhus
(photo ID: 2623)


Joern reports that the majority of Carrion/Hooded Crows he saw during a short stay in Vienna were hybrids and backcrosses with birds showing a wide variety of appearances, some close to Carrion Crow and others close to Hooded Crow.  Below is a composite of some of them.  There were also phenotypically pure examples of both species present, not shown here.

Carrion Crow x Hooded Crow hybrid, Vienna (Austria), October 2016 - copyright Joern Lehmhus
(photo ID: 2887)



Carrion Crow Corvus corone
Hooded Crow Corvus cornix

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