Separation of 1st and 2nd cycle Glaucous Gull (Larus Hyperboreous)

This is just a short article in response to a recent discussion on the North American Gulls facebook group regarding ageing Glaucous Gulls and separating 1st and 2nd cycle birds in particular. During fall and early winter most individuals can be separated easily enough, but as birds begin to wear and bleach things can become a bit more tricky for people that aren't fortunate to have the daily access to Glaucous Gulls of all ages like we have in Newfoundland in winter.

In general 2nd cycle Glaucous Gulls in fall and winter are relatively unpatterned or blotchy looking birds, but are never as neatly pattered as some first cycle birds, particularly in wing coverts. Things get tricky when some first cycle birds are particularly pale or become faded and bleached later in the season. As as general rule if you see a pure white glaucous gull (Oct-February) it will most often be a 2nd cycle bird (at least, this holds true for birds I see in eastern Newfoundland). One should also be sure to check the eye color. All 1st cycle Glaucous Gulls in fall and winter have dark eyes, while 2nd cycle birds can be variably pale, some being, clear yellow or creamy yellow, as in adults.

Occasionally, 2nd cycle Glaucous Gulls can appear to have dark eyes from even close range. Very close inspection of these individuals reveals the eye to be honey brown and not as dark as in 1st cycle birds. These bird can be accurately aged by combination of pure white or blotchy plumage and bill pattern with slightly reduced black and small pale tip.  Beware of  2nd cycle Iceland Gulls (Kumliens) show a bi-colored bill and can match Glaucous Gull in plumage in their second cycle. However, these birds are often much smaller, smaller billed, with a more rounded head and longer wings than any Glaucous Gull. As well, on close inspection the bills of 2nd cycle Iceland Gulls are often have fleshy or greenish tones in the base of the bill and not the pinkish tones of Glaucous Gulls.

Below are a series of photos of both 1st and 2nd cycle Glaucous Gulls, highlighting the features discussed above.

1st cycle Glaucous Gull, St.John's, NL, Jan. Note finely patterned wing coverts, dark eye and bi-colored bill, with all black tip.

1st cycle Glaucous Gull, St.John's, NL, December. A particularly well patterned individual that should never be confused with a 2nd winter bird. Note also, dark eye and typical bi-colored bill with all dark tip.

1st cycle Glaucous Gull, St.John's, NL, Jan. Again note patterning on wing coverts and lack of blotchy appearance. Also, dark eye and bi-colored bill, with all dark tip.

1st cycle Glaucous Gull, St.John's, NL, Jan. A somewhat pale individual, though note consistent patterning throughout scapulars and wing coverts- dark eye, bi-coloured bill, with pink base and all dark tip.

2nd cycle Glaucous Gull, St.John's, NL, January. Note much plainer body plumage than 1st cycle birds. Overall much whiter, and lacking consistent pattering on scapulars and wing coverts. Differing from 1st cycle birds above is pale eye and bill, with slight pale indentation along the cutting edge and slightly pale tip.

2nd cycle Glaucous Gull, St.John's, NL, December. A fairly typical individual, note pale eye, pale area at very tip of bill and overall more blotchy plumage than 1st cycle birds.

2nd cycle above, 1st cycle below. Aside from the difference in eye color, not the subtle difference in the bill pattern. In the 2nd cycle bird above the black at the tip is slightly more diffuse and the very tip of the bill is pale. Note also the small pale triangle along the cutting edge of the bill in the 2nd cycle bird above, this is a fairly consistent feature in 2nd cycle Glaucous Gulls.

2nd cycle Glaucous Gull, January, St.John's, NL. Note the very pale, unpatterned plumage and bill with small pale area at tip and pale triangle along cutting edge as described above. This individual appears to have a dark eye, which does happen occasionally in 2nd cycle GLGU.

From left to right- 2nd cycle GLGU, 2nd cycle GLGU, 1st cycle GLGU. St.John's, N:, January

To finish things off here is a shot of two 2nd cycle Glaucous Gulls (one with a dark one, with a pale eye) and a pretty regular looking 1st cycle Glaucous Gull. Hopefully, this helps people who have been struggling with ageing Glaucous Gulls.

**Want to learn more about ageing Gulls?Consider joining a Gull ID workshop, or if you are really want to learn Gulls, inquire about the January 2020 Newfoundland Winter Birding and Gull Extravaganza trip! I can be reached through the blog, also my website at https://birdingnewfoundland.com

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