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Seen today at the Nimbus Fish Hatchery, Sacramento, California. I've been down looking at gulls for hours using the book that Tony Leukering recommended me (Thank you so much, it has been super useful) and was able to confidently identify most of the gulls I found, but there are a few that have given me a little trouble. Here they are.


Bird One,

I have been having a hard time deciding if this is an adult Thayer's Gull, or a Herring Gull. I believe it to be a Thayer's Gull, given the small slim bill without any dark distal marks, the pinkish orbital ring, The bright pink legs, and the head that is not streaked and is lightly mottled. the pale lemon eye is what has been causing me trouble, as most Thayer's gulls do not have pale eyes, especially this pale. This is more like a Herring gull would look like, however, the other features point to Thayer's, and as Thayer's can have pale eyes, I believe it is a Thayer's Gull. This gull did not move the whole time I was observing it, and it flew without me seeing it, or else it would be easy. 



Bird Two, 

I believe this to be a first cycle Thayer's Gull, It shows a small black bill, a steep, not sloping forehead, the primaries are showing white tongues-tips,  and the tail is showing a broad dark distal band. The outer primaries also showed a two tone contrast, although that is hard to see in the photos. 



Bird Three, 

I believe this gull to be a second-cycle Thayer's Gull. The outer primaries of the gull show a two tone contrast, the primaries show white tips,  the eye is dark, and the tail is greyish, not black. 



Bird Four, 

Thayer's Gull. Basically a copy of bird three with a slighter paler eye and more white on the tail tips. 


Bird Five,

A copy of bird three with a darker tail.



Bird Six, 

This bird is either a California Gull or a Ring-billed Gull, but I have had a really hard time deciding. My assumption is that it is a Ring-billed Gull. The tail projection is shorter than I think a California Gull would have, and the greater upperwing coverts look grey to me, but I am not to sure. The gull itself is a more grey than brown color. I never saw this gull leave the water, so I was never able to see it's legs or primary pattern. 


Is there anything else I should be looking for with these Gull IDs? And are they correct? 

I thank you all for the help you have given me over the past three and a half months, I really appreciate it.


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1 not sure, yellow eyes support herring but smaller bill supports thayer's.

2 Thayer's 

3 Thayer's

4 Thayer's

5 California

6 California, note the larger scapulars and how they are darker then they would be on a ring billed. You also can see a relatively large bill that would be shorter on a ring billed.

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1 - Herring: Yellow eyes, very black in wing tip, small apical spots on the outer primaries

2 - juv Thayer's

3 - Glaucous-winged Thing: huge bill, marbled tertials and wing coverts (marbling is a sure sign of GWGU genes)

4 - Herring x Glaucous-winged - gull outside first-cycle plumage with nearly or entirely black tails are Cals or Herrings or have genes of one of those; see previous comment about marbling; additionally, it's bigger than the adult Herrings with it

5 - Obvious Cal

6 - Cal; Ringers in winter in first-cycle plumage have adult-color mantles, as the species is a three-year gull; ALL but one species of larger gull (YFGU) are four-year gulls and lack adult-colored mantles

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