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:
Nelson’s Gull (Herring Gull X Glaucous 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.
Starting with the Nelson’s Gull, we will break the “hybrid” down into two types. First up is “Type 1” – birds that largely resemble Glaucous Gulls in appearance:
This hybrid combo is most frequently identified when dealing with a bird that looks like a Glaucous Gull, but has dark pigmentation in the wingtips and tail. Pure Glaucous Gulls always have pure-white (or nearly so) wingtips, so dark pigmentation is an easy to see sign of hybridization. See below for examples:
Photo on the left is a “Nelson’s” Gull, showing dark wingtips (and tail in flight). Compare to nearly-white wing tips of the pure Glaucous Gull shown in the photo on the right. This is a good example of a Nelson’s Gull that looks very similar to a Glaucous. Birds of all ages can show this general trait -> Similar to a Glaucous Gull, but with dark pigmentation in the wings and tail. More examples below:
Left photo: Another case of a “Nelson’s Gull” (this time in 3rd ba plumage), where this large Glaucous-gull like bird is showing dark wingtips/tail, vs. the pure-white wingtips of the Glaucous gull shown in the right photo (of the same age).
Next up will be the opposite end of the spectrum (called “type 2” here for clarity), being more like a Herring Gull in plumage:
Nelson’s Gulls that look like more like Herring Gulls can be harder to detect and identify. They often appear very similar to Herring Gulls, however can have a “washed out” look to the overall plumage, even recalling Thayer’s Gull at times. See photos below:
“Nelson’s Gull” on left, appearing similar to a Thayer’s Gull but much larger than that species (noticeable in the field with good looks) compared to a Herring Gull of the same age on the right. Hybrids often have a pink bill base with a black tip, although not as clean cut as a “typical” Glaucous Gull would be at this age. Although uncommon, pure Herring Gulls can show the same bill pattern. Note the “washed out” look to the plumage. Especially in the wingtips, secondaries and tail.
(Same individual birds as above photos)
This "variety" of Nelson's Gull can be difficult to detect when standing, or at a distance. The identification of this (always presumed) hybrid bird was made with a host of sanding and flight views/field marks. See below for another example of a Herring-like Nelson’s Gull.
2nd winter "Nelson's" Gull on left, 2nd winter Herring Gull on right. These "type 2" Nelson's Gulls are much harder to detect when standing (as mentione dabove) but show a messier and more "washed out" look due to the influence of the pale Glaucous Gull genes...
Adult Nelson's Gulls:
"Nelson's" Gull on left, Herring Gulls on right.
Adult Glaucous Gull
My experience with adult "Nelson's Gulls" is roughly similar to the immature noted above (and most hybrids in general) in that you're looking for a bird with intermediate characteristics. Given that adult Glaucous Gulls have little to no variation (with their pure white wingtips), you as the observer will be trying to separate adult "Nelson's" Gulls from Herring Gulls in the field.
Adult Nelson's Gull (tallest bird) with Herring Gulls
Many adult "Nelson's Gulls" in my experience, are quite large when compared to Herring Gulls (as seen here). The head structure can recall the big head of a Glaucous Gull and can sometimes have limited streaking (also seen here). Another clue that is sometimes present is a mantle shade paler than nearby Herring Gulls. With all of these features present, I felt the clinching mark was the primary tip pattern of this bird. Note that the white primary tips "bleed" into the black wingtips - unlike the nearby Herrings. I can only assume this is the "white" of the Glaucous Gull genes battling with the "black" of the Herring genes in this hybrid!
Same bird as shown above
Different adult Nelson's Gull on left. "Extreme Variation" of Herring Gull shown on right.
Note in both of these Nelson's Gulls above how the white in the very wingtip "bleeds" into the black markings, washing it out. Many Herring Gulls have extensive black wingtips, however there are some extreme variations that sometimes show very little black in the wings as well. I photographed a bird like this (shown above) years ago in Hamilton - however note that the black borders are still sharply defined - unlike the "bleeding" look of the Nelson's.
With hybrid gulls - it is important to note that you're looking for general characteristics and nothing is a "set in stone" field mark. I'm sure there are adult Nelson's Gulls that do not have the "bleeding" look in the primaries etc, - however these are just field marks that I have found useful in trying to "figure these birds out" when in the field. It is also not certain that all of these hybirds ARE ACTUALLY Nelson's Gulls. How do we know for sure that some of the above birds aren't Herring X Glaucous-winged Gull hybrids? Well, we don't know 100% - but all signs point towards Nelson's, so I'm pretty comfortable with it.
For ongoing learning, here's just a few more different individuals; with brief comments on their unique genetic blend of Glaucous and Herring Genes.
A 2nd basic "Nelson's' Gull. Looks very much like a Glaucous on the head and upper body - but rather dark wingtips!
A 3rd basic Nelson's Gull. Again, looks like a Glaucous on the head/eye - however this bird also shows an exceptional amount of dark markings on the primaries. At this age, the bird doesn't have that "bleeding" look - but the dark is much paler than the black expected on Herring Gulls of this age.
Similar species or hybirds: Thankfully there aren't many rarities one can confuse Nelson's Gull with in the field... The species that would cause confusion are Thayers's and Kumlien's Iceland Gulls - which can look very similar to Type 1 (Kumlien's) or type 2 (Thayer's) Nelsons Gulls in the field. Best field marks to separate them would be size and structure, as both Kumlien's and Thayers would be much smaller overall.
Abundance - this is one of the more commonly encountered hybrids in Ontario, however I do not believe that I have ever seen more than 2 in a day. It is greatly outnumbered by pure Glaucous Gulls in the province. Even with my extensive gull watching, 1 to 3 personal sightings per year would probably be the norm (upwards to 5 or 6 at max).
When do you see this hybrid?? It seems to be the belief of many birders that you find this hybrid combination when you're also seeing Glaucous Gulls around. This is 100% correct in my field experience in Ontario! If there is any place where you get concentrations of 10-30+ Glaucous Gulls, you can expect a "Nelson's" to appear eventually. With this said, I have also noticed that Nelson's can often occur somewhat earlier in the fall than the average Glaucous, and also staying later in the spring than most Glaucous Gulls would.
(eg,/ I have seen Nelson's on the Niagara River in November prior to seeing any individual Glaucous Gull. However in mid winter I can easily see 50+ Glaucous without any Nelson's recorded).
(eg,/ #2 I have seen Nelson's on Pelee Island in late April, after almost all Glaucous Gulls have returned north)
Although the extreme early and late dates for Glaucous Gulls are similar, Nelson's occur in dramatically lower numbers overall, making this noteworthy in my opinion. I can only assume this slightly extended "relative" window of occurrence is due to the influence of the Herring Gull genes!
Conclusion: I hope you have as much fun in the field with these hybrid gulls as I do! Here's a link to all of my online Nelson's Gull photos for any future looking you may wish to do:
