Monday 2 June 2014

Neoptropic Cormorant x Double-crested Cormorant

Neoptropic Cormorant x Double-crested Cormorant hybrid, Wakodahatchee (Florida, USA), 27th April 2013 - copyright Dave Appleton
(photo ID: 0504)

Neoptropic Cormorant was an extremely rare vagrant to Florida but when one or two arrived at Wakodahatchee they began breeding with the local Double-crested Cormorants producing numerous hybrid young.  Ongoing hybridisation and backcrossing (probably each way - Kevin Karlson has reported seeing two adult Neoptropics breeding with what seemed to be hybrids*, whereas there is more opportunity for hybrids to breed with Double-crested) so we can expect it to become increasingly difficult to separate either species from hybrids in this part of the world.

* On the NHBC ID-Frontiers listserv, 22nd April 2014

I visited Wakodahatchee in April 2014 in the hope of seeing both pure Neoptropic Cormorant and hybrids.  My own experience of Double-crested is limited to three holidays in North America while my experience of Neotropic Cormorant is limited to a single pure-looking individual seen during this visit to Wakodahatchee.  So my commentary on the hybrids presented here may be flawed - please comment if you think so!

The first bird struck me as being interesting immediately.  It looked small and sleek with a long tail, and I'm not sure if there was any significance to this or not, but it was actively feeding in a small relatively well vegetated pool which did not seem to be visited by Double-crested Cormorants.  The shape of the bare skin below the eye seemed closest to Neotropic and the colour rather pale yellow, lacking strong orange tones.  It was clearly immature but the underparts seemed to be uniformly dark brown, so far as I could see them.  But wrong for Neoptropic Cormorant was the absence of any white feathering below the gular pouch.  Also the shape of the gular pouch, whilst looking better for Neoptropic than Double-crested, didn't seem quite right - I believe the feathering should come forwards in a point more beneath it on a pure Neoptropic.  There seemed to be just a hint of the Double-crested's supraloral stripe too.

Neoptropic Cormorant x Double-crested Cormorant hybrid (same bird as in photo ID 0504 above), Wakodahatchee (Florida, USA), 27th April 2013 - copyright Dave Appleton
(photo IDs: 0506-0509)

The next bird was seen only in flight and it was the apparent size and structure again that made me take note, especially the longer-looking tail and shorter neck compared to Double-crested Cormorant.  This one seemed to be an older bird (I'm not sure if it's fully adult), but the rationale for thinking it was a hybrid is much the same as for the immature bird above.  The shape of the bare skin was more Neotropic-like and it lacked any significant yellow supraloral stripe, but it also seemed to lack any white feathering beneath the gular pouch.

Neoptropic Cormorant x Double-crested Cormorant hybrid, Wakodahatchee (Florida, USA), 27th April 2013 - copyright Dave Appleton
(photo IDs: 0510-0512)

The next two were together in a nest, but I'm not clear what age they are or what they were doing.  They strike me as being too mature to be young hatched in the nest but with significant amounts of brown plumage on the breast (and head) I would think they can't be fully mature.  Whether they're old enough to be a breeding pair I'm not sure?  Anyway, I identified them as hybrids for much the same reasons as the previous birds, except for the structural points which were harder to assess in this position.

Neoptropic Cormorant x Double-crested Cormorant hybrids, Wakodahatchee (Florida, USA), 27th April 2013 - copyright Dave Appleton
(photo ID: 0513)

Apparently the issue of Neotropic x Double-crested Cormorant hybridisation isn't unique to Florida and other states have also witnessed recent arrival of Neotropic Cormorants leading to extensive hybridisation.  Steve tells us that they've arrived in the Baton Rouge area of Lousiana within the last decade and he tells us that Jim Arterburn has studied mixed pairs and apparent hybrids extensively in Oklahoma.  He quotes Jim's analyis of his photos from Lousiana:
"My first glance of the photos said Neotropic Cormorant also.  The bird does look small, slender necked and round headed and definitely long tailed.  It looks like there might be some molt going on in the tail but it is still a long tailed bird.  The bill looks shorter, but I think part of that is the perspective of the photo.  There is some orange in the loral area but just a little and doesn’t extend to the forehead.  The shape and color of the gular pouch is off for Neotropic Cormorant also.  I can’t make it into either species as the characteristics don’t match either, but they do match for a hybrid.  It is a very interesting bird."

Neoptropic Cormorant x Double-crested Cormorant hybrid, University Lakes, East Baton Rouge (Louisiana, USA), 17th November 2014 - copyright Steve Mlodinow
(photo IDs: 1688-1689)

Neoptropic Cormorant Phalacrocorax brasilianus
Double-crested Cormorant Phalacrocorax auritus

1 comment:

  1. How do I submit a photo to find out if I have a shot of a hybrid cormorant?