To add to Nick's comments, it's also a hell of a lot of fun! Glenn and I had a blast yesterday sorting through the mess that is gulls in Colorado. Thanks, Nick, for getting the word out on these critters.
Steve Larson
Northglenn CO
Sent from my iPhone
COMMENTS ON WARREN LAKE GULLS (long):1. I couldn't visit Warren Lake today, but according to reports on eBird, the show continues. For anyone interested in practicing and improving gull ID skills, this is a great opportunity.2. Many of the gulls at Warren Lake are large brown immature, mostly first year gulls. These can be quite variable and plumage patterns vary across species, with some plumages overlapping, making species ID difficult. The situation is further complicated by hybridization.3. Herring Gull hybrids are particularly confusing. At least 5 different hybrid combinations of Herring with different Gull species have occurred in Larimer County. Right now at Warren, presumed Herring x Glaucous ("Nelson's Gull") and Herring x Glaucous-winged ("Cook Inlet Gull") hybrids are being reported. There may indeed be multiple Cook Inlet Gulls.4. One large pale uniformly pale brown gull resembles Glaucous-winged Gull. Some west coast experts have reviewed low quality photos and have suggested some genetic influence from Herring Gull. I suspect that it might be a genetic backcross, one or (likely) more generations removed from the hybridization event. Whether you count this bird on your list (or in eBird) as Glaucous-winged Gull or as Cook Inlet is a personal decision. My guess is that the eBird reviewer will leave this rarity as unconfirmed until the Colorado Bird Records Committee judges the submitted rare bird reports and accompanying photo and video documentation.5. Several of these confusing gulls resemble first year Slaty-backed Gull (SBGU) which has only been documented in Colorado a few times, as adults. One in particular presents all the classic traits of SBGU as depicted in "gulls of North America, Europe and Asia" by KM Olsen and H Larson. I posted photos to eBird on 1/29/20 after receiving input from an expert that "it looks promising" for SBGU. Another expert was less supportive and suggested Herring or Cook Inlet as possible ID. In the description on eBird I wrote "tentatively identified" pending further review. After posting it on North American Gulls Facebook page, I received luke warm support for SBGU (roughly 50% of informed opinions have supported SBGU). Part of the problem is that published gull identification textbooks (e.g. Gulls of the America's by Howell and Dunn) claim that some young Cook Inlet gulls can look like the classic SBGU. Therefore, technically according to these experts, this plumage of SBGU is unidentifiable with certainty. Thus, again, counting this bird on your list or in eBird is a personal decision. I chose to report it to eBird as a way of spreading the word of a possible SBGU (through the eBird alert system). I don't expect it to be confirmed in eBird. However it is a bird that merits further study and better documentation. Had I reported it as Larus sp or gull sp, it would have been largely ignored by the birding community.6. Today, Glenn Walbek obtained much better quality photos of what appears to be the same bird. His assessment was the same as mine. I encourage you to read his description and see his high quality photos in eBird.7. We may never know with 100% certainty what is this bird's true identity (unless we get a DNA sample, or we manage to track it for several years through its molts to adult plumage).8. Regarding the suggestion that I may have mistakenly identified this bird, I reiterate that I do not know with 100% confidence what it is. I can say (with 100% confidence) that it LOOKS LIKE Slaty-backed Gull.9. Regarding the suggestion that I have erroneously identified birds in past years, I don't recall ever making a mistake ;-). However everyone makes mistakes, even the experts.10. The gulls at Warren Lake may not all be identifiable, but they definitely offer a great learning opportunity for birders who want to learn more about gull identification.Nick KomarFort Collins CO--Steve hasn't chimed in for the gulls because he is in Baja Mexico.Sent from my iPhoneOn Feb 1, 2020, at 6:33 PM, John D <jxdrummo@aol.com> wrote:--Aaron :
I have not heard of any confirmation from outside of CO gull experts to confirm either , but the Glaucous-winged looks more likely to me , I am very uncertain about the Slaty-backed .Nick Komar has been wrong in previous years .
Any way I will be traveling up with Lynne Miller tomorrow to check the gulls out , not that I need either for my state list but Lynne needs Slaty-backed .I think we will arrive around 10:30 .Perhaps we will see you there .
Best
John
-----Original Message-----
From: 'Azz85' via Colorado Birds <cobirds@googlegroups.com>
To: quetzal65 <quetzal65@comcast.net>
Cc: Cobirds <Cobirds@googlegroups.com>
Sent: Sat, Feb 1, 2020 4:59 pm
Subject: Re: [cobirds] Warren Lake gulls (Larimer)
I am interested in chasing the gulls at Warren lake. It is a bit of a drive, so I am wondering if anyone is 100% confident with the slaty-backed and glaucous-winged identification?
I have noticed that some people are calling the bird good and some hybrids. Are these pure gulls?
I'll defer to the experts
Any help would be appreciated.
Thanks
Aaron Shipe
Jeffco
Sent from my iPhone
> On Jan 29, 2020, at 10:54 PM, Nicholas Komar <quetzal65@comcast.net> wrote:
>
> Warren Lake is currently a gull hotspot, due to large fish population with a large flock of common mergansers and common Goldeneye bringing fish to the surface. Furthermore, there seems to be many dead fish frozen in the ice sheet at the west end. The smorgasbord is attracting 500-600 gulls present throughout the day. The area is private. However birders are welcome at the lake. Just use common sense. Stay off residential properties.
>
> Gull numbers are as follows:
> Ring-billed Gull - 500 (99% adult)
> Herring Gull - 20 (40% adult)
> Iceland (Thayer's) Gull - 10-15 (10% adult)
> Lesser Black-backed Gull- 6-10 (40% adult)
> Glaucous Gull -1 immature
> Great Black-backed Gull-1 immature
> Mystery gulls-10 or so.
>
> The mystery gulls are mostly immature gulls that are
> somewhat atypical. Most of these are probably Herring Gull hybrids such as "Nelson's" Gull (with Glaucous) and "Cook Inlet" Gull (with Glaucous-winged). Today there were two first-Year large gulls that resembled Glaucous-winged and one that resembled Slaty-backed. Better photos are needed to confirm these.
>
> Nick Komar
> Fort Collins CO
>
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