As we near the end of gulling season here in Utah, it often becomes the best time of year to find rare and uncommon gull species. With water starting to open up and more food available, the large ocean-favoring gulls show up with more frequency, or at least become noticed more. In a short month from now, the vast majority of these birds will be gone, and we won't seem them again till November. There have been a few identification requests for gulls lately, so I thought I would take a second and give a crash course on the basics for helping narrow down the possibilities when you see a gull you don't recognize using a matrix.
This is only for Adult Gulls however, so I will be working on similar matrices for each other age as well. As a disclaimer this is NOT 100% accurate in all cases. Measurements, relative sizes, colors, eyes, bills, etc are all somewhat averages. If you think something is drastically off or could be improved please contact me to talk about it. I would like these to be as useful as possible. With that said I wanted to throw some numbers around.
The best way to recognize the not so common stuff is to really know the common stuff well. This means getting to know our State Bird--the California Gull, and its smaller relative the Ring-billed Gull very well. I went into eBird and did some quick data compilations to show how common these two are in relation to everything else.
Between November and February there have been 711,265 total reported gulls in the database (rough estimate).
This is not total number of actual birds, this is total number of birds reported--so multiple people may have submitted checklists for the same birds. Of those, 14,643 were hooded gull species (Sabine's, Franklin's, Bonaparte's, and Little) so I removed them from the total to end up at 696,622 total white headed gulls reported during the gulling season into eBird (all time).
California and Ring-billed account for about 680,000 of these individuals, or roughly 97.3% of all gulls reported in eBird in Utah between November and February.
That means the other 8 species that you might encounter make up just 2.7% of all the gulls reported--roughly 16,600 individuals--still a pretty hefty number, but at least you know the odds are in the favor for the 2 most common birds.
So let's break it down a little more--aside from those two species, the other 8 most likely species you can encounter in Utah in the winter from most common to least:
Herring Gull -- 15,000 reported
Thayer's Gull -- 780 reported
Lesser Black-backed Gull -- 299 reported
Glaucous Gull -- 183 reported
Western Gull -- 176 reported
Mew Gull -- 96 reported
Glaucous-winged Gull -- 56 reported
Iceland Gull -- 29 reported
Using the matrix above, with a little practice, you can learn to narrow down the possibility of the species you are seeing based on the included attributes. The colors in the matrix may not be exact but for most adult birds its a good starting point. click on the above image or link below to download a high resolution version to your smart phone or iPad.
Check back soon for the matrices for 1st, 2nd, and 3rd winter birds, as well as another for hybrids.
Labels: gulls, identification