Friday, July 24, 2015

Identification of 1st and 2nd year Neotropic Cormorants: Case Study




Neotropic Cormorant at Point Pelee (Tip), 13 May 2014

The ID of the bird appearing in this blog post was recently questioned by some American birder, and I had very little to offer in terms of field marks supporting it... I called the beast in flight at the tip of Pelee in 2014 as it passed by at close range with two Double-crested Cormorants (DCCO). Concern was raised that the structure was off for Neotropic Cormorant (NECO) and better suited DCCO - especially the tail looking too short. There was whispers that a lack of field marks definitively supporting NECO sealed the deal and the record should be located, taken out back, and shot without hesitation. 

Now I may take my bird ID less seriously than many high-horse-birder types, but my self-found rarity finding/identifying lists are rather important to me, so I took up the charge (in the name of Science) and - for the first time - began to actually look at this bird in detail (rather than ignore & move on). 

First, some photos - then some thoughts:






The culmination of some rather extensive research undertaken by Mr. Pawlicki and I. It's a bit embarrassing to say that I never really gave this bird much of a second thought on fine/proper ID points, but in the end I had a blast as we worked through various/potential ID criteria. The blog post may be a bit biased towards my own thoughts, but I did write it after all:


Age: 

How long does it take NECO's to mature? New Jersey has only two records of NECO, and it's of the same bird (one can only assume) that returned to the same ponds in 2014 and again in 2015. 

Here it is in 2014: 


And on the same freakin branch in 2015:



Not that it does NOT look like a glossy/fancy black adult with a tidy white facial border. Therefore these things take three or more years to mature. This will be important later. 


Tail length:

NECOs have relatively longer tails than DCCOs. My warning is that photos - especially without context, can be misleading. The Pelee-14 bird is about as misleading as possible because it is not only FLYING AWAY, but it is also turning it's head back to look at me as I wildly swing my camera towards it. The body&tail are angled away, looking shorter - than the head/neck which is parallel (looking longer and heavier). Given that the ID of this bird was in question, the onus was on me to find clear NECO's showing shorter tails. I found them:











Probably one of the best examples:



Head Features:

Next, we move onto the head. I've chosen five features to discuss, but first wanted to discuss that the time of year is also important in using these marks. When young cormorants are still in the nest, or just recently fledged - the can look quite different. These young DCCO's have black lores and black marks down their bills and their facial skin is shaped differently than older birds:



The features i'm discussing will relate to birds that are at least several months old (think "May" - like the Pelee bird we've discussed): 


A - Bill Colour-

Young NECO's often have pinkish bills, rarely going yellow or otherwise. DCCO's often have yellow, especially on the lower mandible. This is a "general" mark and in no way diagnostic. There is a LOT of variation out there. 

Here is the "general" look in young NECO - 

General look for young DCCO:

Again, it's variable - but I think the Pelee bird is spot on for standard NECO (especially in May).


B - Throat Pouch Colouration:

Same thoughts on time of year. The standard look of NECO is to have a little patch of yellowish-peach skin, almost square in shape. Not extending much further (closer to the tip of the bill) than below the eye. DCCO typically has extensive yellow covering most of their throat/skin and bleeding onto the bill itself. 
Standard NECO fare with a yellow patch/square: 


Standard DCCO fare with yellow bleeding elsewhere:



No doubt you will find a LOT of variation out there on a bird-by-bird basis, so be careful with it - but overall the Pelee bird is very much in the NECO-camp and would be unusual for DCCO.


C - Pointed facial skin:

This is a common field mark to look out for, with NECO showing pointed and DCCO showing - not pointed ? - but it is highly variable. The Pelee bird matches NECO, but you will find a lot of young DCCO out there with a similar feature. 

D - Whiteish feather border to the facial Skin:
Another field-guide field-mark, this is shown readily by both species. Heck, just check out the photo I shared for the throat colour of DCCO - 
That bird has pointed skin and a paler feathered border too! It is another feather that matches NECO - even if it is also shown by DCCO, so for case study purposes I'll just move on... 

E - Lore colour 

NECO typically does not show yellow lores. DCCO almost always shows bright yellow skin in the lores. Especially in May. I've discussed how baby DCCO's can have black lores, and there is the potential that feathers/fuzz can seemingly grow overtop of the loral skin, but 99.9% of the time DCCO will show a bright orange/yellow patch of skin on the lores sometimes extensive. NECO can seemingly show yellowish skin here at times (often peachy), but not like DCCO.

NECO fare - 


DCCO fare - 


I chalk this up as a very strong feature for the Pelee bird as NECO 


F - Overall Impression

A copout field mark here. I've discussed how each of these field marks have varying amounts of overlap between the two species, but when all taken into account they can strongly point to one species or another. The odds of having a bird with: Pinkish bill, small yellow patch at the top of the throat and dull lores being anything but a NECO is extremely unlikely. 




Feather Shape:

We really looked hard at this feature, something I had never seen/noticed before. NECO has more pointed body feathers/coverts than DCCO. Sometimes obviously. Check out the differences in this photo:


I was shocked at how different the two species are. This photo of the Pelee bird showed rather rounded feathers, which had me worried. Yet this photo shows feathers that look more pointed... I did some digging and ended up using the New Jersey bird as a case study. In 2014 it had rather rounded feathers:


In 2015, it was decidedly more pointed:


This age difference was really interesting to me. If you had really good photos, it could potentially help separate these confusing 1st or 2nd year birds... It was also pointed out that the Pelee bird appears to be molting, so new feathers coming in should be more pointed - but perhaps they get more pointed as they age? This leads me to my next though:


Molt Timing:

I have no knowledge of Cormorant molt but I read the birds of north america online account to see if molt gave any hints. It looks like DCCO can be molting just about anytime, especially with populations from Florida to James Bay and beyond - BUT - young DCCOs really shouldn't be molting coverts in May according to the account:

""First Basic" or "Basic I" plumage of Humphrey and Parkes (1959) and later authors; see revision by Howell et al. (2003). Present primarily Dec-Jun. Similar to Juvenal Plumage but juvenal feathers of head, neck, and breast become increasingly bleached through winter and spring, to pale brown or whitish, variably mixed with scattered fresher, darker brown, glossier, and more-rounded formative feathers. Ornamental crest plumes not developed or rudimentary at best. Juvenal upperwing coverts, primaries, and rectrices retained, increasingly worn and bleaching to paler brown"

Neotropic didn't have a detailed account like DCCO, but it shows May as being a primary time for molt... I have no experience with this, but I like that it supports the ID of the Pelee bird as NECO. 

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After a LOT of looking at online photos, it is possible to find some very difficult birds out there. Very difficult indeed. There are even hybrids! Not to mention the baby DCCO's that look rather odd as they come out of the nest.

So what about the Pelee bird? I think the finer details are in support of the identification as Neotropic. The bare part colouration on the face/bill may be bordering on diagnostic when all considered together. Yes, the birds tail looks short in the photos. If you think it looks too short, you'll always think it looks too short. I think it's a bit of photo trickery due to the angle of the birds body, head, and the angle I was shooting at - and I'll always think that... We also noticed it looks to be molting the tail feathers which may screw with the impression as well...

Only one "field mark" remains that wasn't valid for our photo interp - I actually saw the bird in real life. In my recent years voting on the OBRC I've learned to try and understand and appreciate that factor when reviewing reports. The suggestion of non-NECO features come from four photos appearing on this page here: http://peregrineprints.com/UOB/zz14_NECO.htm (prior to this blog post adding more)... It was pretty freakin obvious to those of us who saw it fly past at 50ft with two DCCO's at close range...  Yet I know I was very guilty in never doing any additional looking/research and had no additional details to provide when asked. That shows the questions raised about the photos were 100% justified. Presumably it was accepted by the OBRC without a whole lot of research as well (I know I didn't do it). In the end it was a lot of fun as we dug into these features and tested them out. Maybe this mish-mash of thoughts will help someone else somewhere/someday as they too enjoy ugly non-adult Cormorants around the Great Lakes!




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