By Ben Zyla of Bird Las Vegas
I wanted to recap on our day out ( 13 Sep ) at Lake Mead. Specifically, go over the Gulls we saw and discuss them by species and age class. Jeanne amd Cathy took some fantastic photos that day and allowed me to use them in this email for all of us to enjoy. Thanks ladies!
I am going to break this up into 2 parts because of all the context. I am also going to include Alex in on this in case he wants to add to the content with his Larus wisdom.
Two sundays ago, we saw 4 different species of Gulls at Hemenway Harbor:
1. Ring-billed Gull. This is medium sized Gull and the most common species that is present at Lake Mead during the Winter. 75% of the Gulls you will see will be RBGU so it is good to become comfortable in identifying them as to help pick out more uncommon species.
2cy bird in January: When I was at the Lake, i kept calling these birds "first cycle". However, I forgot that all birds (ALL birds in the universe!) have a birthday on Jan 1st, and thus after this date they are technically in their second year of life. Does that make sense? Here is a picture of a 2cy RBGU from J.Andrew:
The three things to look at are the 1. eye color 2. bill color 3. leg color. This bird has dark eyes, a pink bill with black tip and pink legs. We can deduce it is an immature bird. If we search through are field guides, we can see these characteristics match up with a Ring-billed. Also notice the white (not muddy breast) and mostly grey back (or scapulars and mantle). These will also strengthen the case for RBGU.
We did not get a picture of a 3cy RBGU, but here is a link for some images: http://gull-research.org/delawarensis/03cyjan.html
And here is an image of an adult:
This should be straightforward: light eye, yellow bill with a RING towards the end, and yellow legs. These should match up for an easy i.d.
Here is a link for more RBGU pics and information: http://gull-research.org/delawarensis/05cydec.html
2. California Gull. This is a large species or a large sized medium species. This is the second most common species seen at the lake.
2 cy birds in January:
Now, these birds may look superficially like the 2cy RBGU picture above, right? Dark eye, pink bill with black tip, and bluish-green legs. However, in these pics, please notice the very muddy or brownish colored breast (as compared to the RBGU). Also, notice how the coverts in the folded wings have retained juvenile plumage and looks muddy. These birds would be bigger in size in the field and have a larger bill size. More images on the same aged species:
This is going to be a 3cy jan bird:
Bird is going to have a dark eye. yellow-green legs. and yellowish bill with black tip (but not a ring to it). In this bird it still has a lot of juvenile plumage in the head and breast and in coverts. But more adult feathers are on back and coverts. Many CAGU will retain alot of muddy juvenile plumage in the head and neck, also referred to as a "bonnet."
And an Adult:
Here is a great comparison photo that C.Kozmary took of ADULT RBGU vs. CAGU:
Are the differences between the 2 species evident to you? looks at the size, eye color, and bill color.
Here is a link for more CAGU pictures and information: http://www.gull-research.org/california/rings.html