Occurrence and ID of Hybrid Gulls in Ontario: Herring X Great Black-backed Gull

Close study of gulls, throughout Ontario, has lead to an increase in the discovery of hybrids and abnormally plumaged individuals. Gull ID is often considered one of the most difficult areas for a bird watcher to learn, and hybridization is one aspect that can compound the problem when looking to identify them correctly.

Hybrids are problematic when trying to include in field guides, due to the massive amount of variation that can be shown when they start mixing their genetics. This makes them poorly understood and infrequently studied by the birding community as whole. The common belief is that since a hybrid does not count as a check on a list, many birders are potentially (if I dare say) un-interested in delving into this aspect of gull ID.  

This article will try to deal with some ID points of gull hybrids recorded in Ontario, and will make some comments on how often I tend to come across them. We’ll start off with some of the combos I encounter the most:

Herring X Great Black-backed Gull 

Hybrid Gulls are amazingly variable. Considering the massive amount of variation shown by some species of gull, mixing genes can create quite the mess of plumage features. When identifying hybrid gulls, a number of general features are often used to make the observer more confident in the ID.

When dealing with these hybrids, I'll start the breakdown with the obvious individuals. Unlike the last hybrid discussed (Nelson's Gull), this hybrid combo is often most noticeable when dealing with adult birds. 

Adult Great Black-backed Gull (top), adult hybrid (middle), adult Herring Gull (bottom). 

I've heard many a birder remark that hybrids are too confusing and not much fun to deal with... However I've found that they can (sometimes) be surprisingly easy to figure out. This is due to the fact that a large percentage show obvious intermediate uncharacteristic between the parent species. The darker mantle of the hybrid shown above alerts the observer to something interesting. However it is clearly much too pale to be a Great Black-backed Gull. The large size (and very large bill), just scream "GBBG" parentage, leaving little doubt to this birds identity. 

 

Hybrid (lowest bird) with the parent species... 

Same bird with Herring Gull 

Same bird again

Three looks at the same bird (different than the first bird shown) from Point Pelee in Sept 2006. Virtually all of the same identifying field marks apply to this bird as the last discussed. I find it interesting to note that many adult hybrids I see (of this combo) have "sickly" colours to their bill and legs. 

New bird... 

While most birds give the impression of being a "Great Black-backed" like gull with an intermediate mantle, it is also possible to find birds that are structurally more similar to Herring Gull (as shown above). However the bird is still rather large, and combined with pink legs - there are very few options for this bird  --- other than some extreme rarities --- that will be discussed later in this post. But first, we'll look at some sub-adult birds... 

3rd basic 

I almost feel like I'm beating a dead horse here... Note how once again this sub adult bird gives a strong impression of "Great Black-backed" but isn't quite as large... Not nearly dark enough either, indicating a hybrid.  Let's skip to another example: 

3rd basic/alternate (left-ish) 

This is a good bird to compare with the previous picture (showing variation in mantle tone). This bird is a lot paler than the former, but the exact same ID criteria apply! All fine and well, however things get extremley sticky when dealing with 1st year birds that do not show their "mantle shade" - below: 

Suspected first basic Herring X Great Black-backed Gull 

Given the massive range of variation in first winter Herring Gull (and large variation in Great Black-backed Gull), identification of this hybrid at this age is extremely difficult. Essentially to the point where I don't think we could ever be totally confident in the ID... This bird however, was one I thought looked pretty darn good! In the field it resembled a Herring Gull - yet had a heavy set bill and round head (with a small beady eye) recalling Great Black-backed Gull. The heavily checkered body/wing feathers also looks a bit extreme for Herring Gull, and potentially explained by the influence of Great Black-backed Gull genes. 

same bird in flight

In flight, the pattern continued to "fit"... The tail pattern could be considered intermediate between the two species, yet the strange white markings on the tips of the secondaries also seemed very odd for a "pure" Herring Gull - but is something I see on Great Black-backed Gulls. 

Overall I was pretty happy with claiming this bird as a hybrid, but virtually all of the features I've mentioned here can be shown by the huge range of variation seen in Herring Gulls... I could go on, but I think I'll leave "first year" hybrids here, and move onto some more of the fun stuff:

Abundance - I see this hybrid far too regularly here in Ontario... I once had 3 in view at the same time while birding at Niagara Falls in November, however a yearly total of 7-10 birds is probably normal for me (rarely more than 1 in a single day, when they are in fact seen). One thing going in their favour is they're present a bit longer throughout the year than some other hybrids (early Sept to mid/late May is the norm) . 

Similar Hybrids/Species -

Herring X Lesser Black-backed Hybrid's are generally similar, with intermediate mantle shades as adults. However they are smaller with pink/yellow mix to the leg colour. Lesser Black-backed Gulls often have odd black blotches on their bill (close to the base), which regularly appears in their hybrid offspring... I'll discuss this in more detail with the account for HEGU X LBBG, but it is very useful. 

One reason I really enjoy (and hate) this hybrid combo is its ability to look like SEVERAL mega-rare species of gull that could occur in Ontario. It is a MAJOR culprit in calls all around the Great Lakes of these species mentioned below:

SLATY-BACKED GULL - if you look in a field guide, SBGU is essentially a "dark-ish mantled gull, not as dark as a Great Black-backed Gull - with pink legs"... The same description as our beloved hybrid... 

 

Slaty-backed Gull on left, hybird on right...

If you dive a little deeper, you'll notice that the book talks about a "string of pearls" on the flight feathers, yet even this can be shown (poorly) by our hybrid. See below: 

hybrid wings.. 

The "pearls" are the white spots ABOVE the black in the wingtips (not the very tips of the feathers)... Here's a hybrid that shows that pattern pretty well! Suddenly we see how the ID of rare gulls can be so darn confusing... As well as showing us why field guides have a very difficult time in portraying the necessary suit of characters needed to confirm an ID of a vagrant! 

Some points that I look for:

- string of pearls need to be LARGE

- DEEP pink legs on Slaty-backed Gull are needed. Pinker than any nearby Herring or GBBG (or hybrid)

- streaking on the breast extending very far down... hybrids often show limited streaking and only on the head/neck. 

Anyways I think we get the point.. They can be superficially pretty darn similar!

VEGA GULL - 

"Vega Gull" at Point Pelee in 2012 

GBBGxHEGU Hybrid from Hamilton 

Vega Gull now has 2 records from Ontario (pending acceptance of the bird shown above). It is currently considered an Asian subspecies of the Herring Gull - however adults can also be surprisingly similar to our hybrid combo discussed here. Once again, the problem of depicting a bird like a "Vega Gull" in a field guide is probably the main source of our problems. In a typical guide, Vega Gull will essentially be described as a "Herring Gull with a darker mantle"... As mentioned earlier, and shown in the second photo - that is almost EXACTLY what our hybrids could look like (in a nut shell)!

So how would we ever find a Vega?? Well similar to Slaty-backed Gull, you need a whole host of features to really be confident. Some things I would look for: 

--- Molt timing ... both Ontario records of Vega were notable in that their molt patterns were much delayed compared to our birds. This is a great field mark for Vega. The October Vega at Pelee had barely started molting out of breeding plumage. Our locals were 70-90% done! 

--- deep pink leg colour... As with all of these features, none are 100% clinching, but you shouldn't expect to claim a Vega in Ontario with ugly/light pink legs

--- dark eye ! I've seen a hybrid with dusky eyes, but most are pale. Many a vega is dark! (although not all).. fun eh? 

Anyways... Any more potential mix-ups?! Why yes!

WESTERN GULL 

There are no records of Western Gull for the Great Lakes, yet a year probably doesn't go by where one isn't posted to a local listserv.. Why? Well same reasons of course! The field guide that shows a sketch of a Western Gull can look remarkably similar... Too similar in fact (I've seen photos of Western Gull from California and thought "dang, that looks just like a Herring X Great Black-back"" ... 

Ugly hybrid from Waterdown, ON

So how do we tell them apart?! Well I don't really know. I've never seen a Western Gull. I've seen Glaucous-winged, which are built the same as WEGU - and the structure is pretty unique... That's probably a main feature that I would look for. Or better yet, here's a link to some photos of what may be the only accepted Western Gull for eastern North America:

http://oceanwanderers.com/unidBBGull.html

Just don't look too closely into that field guide! As many state that "Western Gulls" have a single white mirror on the 10th primary only - which is (apparently) a great field mark.. Just don't tell that to our hybrids - which show it all the time!

GBBG x HEGU from the Niagara River, showing one white mirror on P10... 

Conclusion: this is a pretty regular hybrid for me around Ontario... And the fact that it is a "dark mantled gull with pink legs" - allows it to be a lot of fun when trying to find a rare gull in the province. If you're interested in checking our some more photos, here's my full collection: 

https://picasaweb.google.com/117329578255897846071/HerringXGreatBlackBackedGullHybrids#