North American Herring Gull
Populations

Juvenile plumaged Herring Gull, locally, in June-July-August? It's a Great Lakes bird... How do we know? Because it's June-July-August... 

First basic mantle feathers become visible by early Fall. They start getting more worn / patchy / pale. The bill may be turning pink. 

By mid-winter, the paler barred first basic mantle feathers have come in... They look variably patchy / messy overall... The bill often looks like this, more pink above than below, think black line down the middle... 

An "old world" looking tail band is present on a small but regular percentage of our local birds... Their advanced molt (into first basic) would suggest they are not northern-nesting/late-molting Vega Gulls... Or that they didn't migrate from Europe in a few months (esp. while molting).... 

Note the extensive fine / small fleck marks (both white and dark) in the tail, which is most common locally. 

Peak messy occurs late winter into early spring. It's not uncommon for the eye to get a bit paler by early spring. This bird is an extreme example however. 

Second winter birds have reasonably advanced plumage, with lots of adult-like gray feathers coming in. Great Lakes birds do not migrate very far, saving energy. As immature birds, they did not put energy into nesting or raising young. Therefore they put a lot of energy into their develpment and molt. Primary molt is usually complete late summer. 

Same comments as above - flight example. Second winter. Significant variation occurs; however, many birds fit this general pattern of plumage advancement and molt timing. 

Plumage advances in third winter, with adult like inner primaries and a P10 mirror. Much variation exists. Structural cues remain similar. 

Apical spots are usually visible on primaries for third winter "Great Lakes" birds. Very adult-like plumage has been obtained. Beware the "five year gull problem" discussed for the Northern birds further down this page. 

Adult showing the "expected" primary pattern, with high reaching black on P10-P8, a full black band on P5, and a small rounded mirror on P10. Apical spots on primary tips are fairly small. 

Local birds appear small overall compared to "Atlantic" or "Newfoundland" types. Head is often rounded. Head streaking often brown. 

Less common, but not uncommon, example of a bird with mirrors on P10 and P9. 

Most distinctive in late fall and early winter, when young birds arrive in fresh juvenile plumage (photo Nov 18, Ontario). Bill is usually darker than local "Great Lakes" birds at the same time. Overall they are darker-based and less contrasting overall. 

Apparent northern migrants usually arrive by late September (although see adult "Northern" as well as "Boreal" further down)... Waves will pass through during cold fronts thereafter, with a final movement during ice-up conditions. Many/most (?) may move south of our area to winter. 

Some are quite "spangled" and may cause confusion for those seeking out Vega or European Herring Gulls. 

Tail markings occur with less frequency than local "Great Lakes" birds. Many have mostly dark tail. 

By mid to late winter, some are molting in first basic mantle feathers. Knowing if they are true "northern" nesting, or closer "boreal" nesting bird is currently hard to determine. Spring northward migration of non-adults is also fairly unknown. 

Second winter "northern" migrants can usually be detected in fall by their delayed primary molt - such as this bird still growing P10 in November. This molt timing may be similar to local adults - which did not start molting until after their nesting duties were complete. 

They are also often "behind" our local birds in terms of development, with more brown "immature" feathers and less gray "adult-like" feathers. The bill and eye may also be variably behind our local birds, but there is much variation. 

Many appear to have a similar small or dainty structure to our local birds. This structure + delayed development may help identify exceptional birds later in winter which have finished their primary molt. 

Third winter "northern" birds are likely to have similar features to second winter. Delayed molt timing, delayed development; however, things are getting complicated with smaller sample sizes and variability in plumage development between populations. 

The large structure of this bird, plus the extensive black in the primaries, makes confident ID difficult when considering "Newfoundland" or "Atlantic" types. 

"Northern" birds may also be part of the "five year gull problem" - where birds with more adult-like inner primaries, or primary mirrors,  could actually be very delayed third year birds, rather than second year which might be initially assumed by overall plumage. 

Further support for "five year" Northern HERG comes from birds with distinct near-adult plumages. Given the potential for notably delayed second and third year plumages, it is not unreasonable to assume this bird is at least four years old. Note the primary pattern on the underside of P10 - with an open mirror - supporting "Northern" origin. 

Again, keen observers may notice migrant Northern adults by late September. Their molt is significantly delayed, compounded by long migrations and later nesting. What may (or may not) be visible of the primary pattern still usually shows hints of the expected "northern" pattern. 

Head streaking of northern adults may be finer and more detailed, and more gray-ish brown than the pure brown of local birds. 

The bill may be more uniform yellow, with less black and less markings on the upper mandible. 

The tertial crescent may be more wide, the underside of the primaries more white, and the apical spots much larger. 

Primary pattern can be quite variable. Difference from local birds usually include a larger and more irregularly shaped P10 mirror, regular presence of a P9 mirror, more strongly uneven black on each primary - extending much higher on the outer shaft than the inner part (i.e., fingered), and a more variable black markings on P5. 

Exceptional birds have extreme primary patterns. Note thin bill and smaller structure, unlike "Newfoundland" or "Atlantic" birds. 

Molt timing may again help spot northern migrants in early spring, when they retain some winter head streaking. Local nesters are generally all white headed by Mar-Apr. Detailed primary pattern assessment can help confirm. 

Local birders visiting the east coast may be surprised at how distinctive some plumage, and structural, aspects are of their local Herring Gulls. 

They're massive. First year birds can be very dark overall, with new first basic mantle feathers with large dark centers. This is very rare to see in the Great Lakes. 

While some birds are very distinctive, the range of variation in first year plumage would require more study to understand (i.e., perhaps not by birders from the Great Lakes). Locally, any very large, heavy-billed first year HERG with atypical plumage could be scrutinized as a possible "Atlantic" or "Newfoundland" bird. 

Lambton, ON - Jan 22

An absolute hog with heavy overall structure, including bill. 

Plumage dark brown with grayish undertones. 

Simcoe, ON - Apr 4

Plumage suggestive of "Atlantic" with deep, dark tones and dark centered mantle feathers; however, structure is not significantly large. Could be a female, or it may represent a less common variation of a different population.  

They often look like the kind of gull you wouldn't want to meet in a dark alley somewhere. Massive bill, flat topped head, and mean look. They would likely look quite large next to our local Great Lakes birds (but note much individual variation in size exists). 

White apical spots on primaries are often quite large. Head streaking may be more grayish, and/or may include more horizontal markings on neck and breast than Great Lakes or Northern birds. Legs may average more gray (with pink feet). 

There appears to be subtle yet regular differences in the primary pattern. Large apical spots as noted. Often with mirrors on both P10 and P9. Extent of black from P9-P6 intermediate between Great lakes birds and Northern birds. Shorter black bayonets than "Northern" on outer edge of primaries. One potentially notable difference is that P5 is rarely a complete black band -either interrupted or partial. 

A monster HERG, with a huge bill and big flat-topped head. Apical spots are massive. Legs look notably gray. 

Unclear how if/how "Newfoundland" is different, or could be separated... 

Same as above. P10 with extensive mirror, P9 mirror. Black pattern between P9-P6 intermediate between Great Lakes and Northern. P5 with partial black only. 

The bird shown is a known (i.e., banded) "Newfoundland" HERG from southwestern Ontario. 

They may be the pro-typical HERG we see in field guides. Large with a big head and strong bill, similar to Atlantic birds... With a more uniform brown plumage, without exceptional pale markings or tailbands. 

Molt timing is likely somewhat behind Great Lakes and Atlantic birds. 

Possible adult from Ontario - Jan 1...  Adults may show similarities to "Atlantic" adults - large size, big bill, etc. The primary pattern may have reduced black compared to Atlantic birds, with highly irregular primary mirror shapes and the most reduced black "bayonets" pointing up off the outer web of each feather. 

This first basic HERG has replaced most of its mantle feathers by mid January in southern Ontario. Yet it's fairly dark like most "northern" birds. Do we make a large umbrella for "northern" birds and include it there? Or are there boreal nesting populations to study?! 

Another ambiguous first year HERG from southern Ontario in mid January. It is reasonable to assume it presented as a "northern" HERG back in October before replacing its mantle feathers. And how much year-to-year variation is there in nesting/fledging time among northern

This bird doesn't present with a typical "northern" HERG pattern - but the black on P9-P7 doesn't reach as close to the feather base as many southern "Great Lakes" nesters. Is it variation within "Great Lakes"? Or from an intermediate "boreal" population? 

?????