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ID Challenge (for me!) – Glaucous vs. Iceland Gull

OK, I admit it. I often don’t have the patience to scan through large flocks of gulls to find the “oddball”, the one that ISN’T the seemingly ever-present Ring-billed Gull (here in South Dakota). Sometimes, however, you see something that’s clearly so different than you can’t help but notice. That was the case yesterday near Pierre, South Dakota, when I saw a large, nearly all white gull sitting on the ice.  My first thought when seeing the bird from a distance…Iceland Gull, since recent bird reports had frequently mentioned an Iceland Gull being seen in the area. At first glance, that seemed to “fit”.  However, as one who isn’t well-versed in the dark art (I’m think of you Ricky Olson!!) of multi-age gull discrimination…I wasn’t sure. It wasn’t until I got home, downloaded the photos, and did some sleuthing  where I think I can safely call this an immature (probably 2nd winter), quite pale Glaucous Gull. Why?

Immature Glaucous and Iceland Gulls both share some characteristics that were evident in this bird. 1) Pale overall, including pale wingtips without markings. 2) two-toned bill. 3) pink legs.  However, when looking at Sibley’s and online resources, it’s clear the bird has characteristics of a Glaucous Gull.  First…the bird’s size.  There were a handful of Ring-billed Gulls around, and this bird was clearly larger. Much larger. Iceland Gulls are larger than Ring-billeds, but Glaucous Gulls are MUCH larger. With the distance between the Ring-billed Gulls and this gull, it was a bit difficult to judge, but it really did look a much, much larger bird than the Ring-billed Gulls.

Secondly…the head. From this excellent site (South Dublin Birds), it’s noted Glaucous Gulls have a large, flat-topped head, while Iceland Gulls have a more delicate looking, rounded head. This bird clearly has the head shape of a Glaucous. Also…that site is the only one I found that notes a “tertial step”…a clear angle where the tertial feathers on wings meet the primaries when the wing is folded as in the first photo below. Here, you definitely see a clear “step” down where the tertials meet the primaries. Finally, the bill. Young Glaucous and Iceland Gulls both may share a two-toned bill such as this, but the Glaucous Gull has a heavy, longer bill, with parallel top and bottom edges. The Iceland Gull has a much more delicate and smaller looking bill.   The bill on this bird is quite large and shaped as a Glaucous.

So my final call…a first- or second-winter (probably second), very pale Glaucous Gull. Darker juveniles often have a lot of brownish speckling. This bird has a very small amount of that, primarily near the tail. Given that Glaucous Gulls gradually lose that speckling and it’s mostly gone by the third year, my guess is its a second-year bird that’s lost most of the speckling.  Third winter birds generally already have the pale gray mantle of an adult Glaucous Gull. This bird clearly doesn’t have that yet, so it can’t be a 3rd year or adult bird.

In short…the bird looks very similar to the Sibley drawing of a 2nd-winter Glaucous Gull (Page 220 of my Sibley’s guide!).

There…that wasn’t so painful! And it was kind of an interesting challenge to ID. Perhaps next time I come across a flock of gulls, I’ll pay a little more attention and do some similar sleuthing!

Glaucous Gull - Larus hyperboreus

A large, pale gull found near Pierre, South Dakota. Given that others had reported an Iceland Gull in the area, that was must first thought. But upon getting home and seeing the photos in detail, I’m pretty sure now this is a very pale, immature Glaucous Gull. Reasons…1) The heavy two-toned till, with top and bottom roughly parallel. Immature Iceland Gulls also can have a two-toned bill like this, but it’s smaller and more delicate. 2) Head shape…large, flat topped. Iceland Gulls heads are more rounded and smaller looking. 3) “Tertial Step” – an ID characteristic where there’s a distinct “step” where the tertial feathers meet the primaries (unlike Iceland).

Glaucous Gull - Larus hyperboreus

With wings spread, you can see the complete lack of markings on the wings. However, the pale wings, pink legs, and brownish mottling (VERY pale and not widespread on this bird) can be found on both Iceland and Glaucous Gull.

Glaucous Gull - Larus hyperboreus

Another photo of the bird taking flight, showing the unmarked wings (again, characteristic of both Iceland and Glaucous).

Telling the difference between hawks (Buteos)

Ferruginous Hawk - Buteo regalis

When this guy flew by and I took photos, what first came to mind was dark-phase of a Rough-legged Hawk. It’s actually a dark-phase Ferruginous Hawk. The vast majority of Ferruginous Hawks that you run across are light phase, so this guy is a perfect example of how confusing it can be sometimes to identify Buteo hawk species.

As I look through visitor stats for my main website, one of the sections that is visited the most is a “Difficult ID’s” section.  That actually surprised me a bit, given that it’s a fairly small part of the website, and not a section that I’ve revised for quite some time.  The section is devoted to helping birders differentiate between certain species that tend to be difficult to identify, with photos, identification tips, key plumage characteristics, and other information.  I only had 10 different classes of birds that it helped to differentiate…thus my surprise to see how many visitors those pages get.  For the first time in probably 7 or 8 years, I updated several of those pages, providing more detailed identification keys, new photos, and range maps to help people see where and when certain species are likely to be present. I also started to think about other species that birders may have trouble identifying.

As I was going through my photos from my day-long trip to central South Dakota to look for winter raptors, one bird had me stumped.  It was a dark-plumaged bird that I originally was sure was a dark-morph Rough-legged Hawk.  After processing the photos, however, it became clear that it was actually a dark-morph Ferruginous Hawk, a color morph I just haven’t run across very often.  Given the variability between the different “Buteo” Hawk species, and given the variability WITHIN a single species in terms of plumage differences between different color morphs, and between adult and juvenile birds, what better addition to the “Difficult ID’s” pages than a very detailed description of how to tell apart Buteo hawks?  I’ve just uploaded the following new page:

How to differentiate between “Buteo” Hawk species

On these pages, I’ve restricted myself to the more common Buteo species that are found in South Dakota and the U.S. as a whole. The more rare or geographically restricted species, such as Gray Hawk, Zone-tailed Hawk, or Short-tailed Hawk, were excluded, so the page could concentrate on the more common species in the U.S.  Species included are Red-tailed Hawk, Ferruginous Hawk, Swainson’s Hawk, Rough-legged Hawk, Red-shouldered Hawk, and Broad-winged Hawk.

For these 6 species I have several pieces of information to assist birders in identification challenges.  That of course include photos that offer a variety of angles, color morphs, bird ages, etc., as well as identification keys and species range maps.  The Buteo Hawk page is undoubtedly the most comprehensive of the “difficult ID’s” pages that I’ve put together to date…I hope that people find it helpful!

Given how much attention those pages are getting, I will likely add new categories of “difficult ID’s” in the coming weeks. If you have any suggestions, let me know!  In the meantime, here are the other species groups that are offered on the difficult ID’s page:

Revisiting Dowitcher Identification

Short-billed Dowitcher - Limnodromus griseus

Photo of a Short-billed Dowitcher. At least now, after 15 years, I’m finally making a call that this is one, given the advice of several folks. Click for a larger view.

Ok, after much debate and consulting with other folks, I think I have a better handle now on identification of Short-billed Dowitchers vs. Long-billed Dowitchers. It’s still not an easy call, but after 15 years of birding, I’d never mentally/physically “checked off” Short-billed Dowitcher on my life list.  Long-billed Dowitchers are the ones that are more often found in fresh water areas, and are more often found on the interior of the continent, and until this point, I’d just mentally called any Dowitcher I saw in South Dakota as a Long-billed.

I’m now adding Short-billed Dowitcher to my list, based on the top photo here and the advice of several folks.  I had a photo of about 10 different Dowitchers, but this is the one (a crop of the photo showing 10 birds) that most people pointed to as being most clearly a Short-billed Dowitcher  What’s interesting is that opinions varied as to why, but the ID points hit the ID points provided in the exhaustive SurfBirds page on Dowitcher identification.  For this bird, ID keys are the following:

 

  • V-shaped lower coverts with white running up the sides of the feather more than a Long-billed Dowitcher.  Long-billed Dowitcher lower coverts are described as more “squared off”, with white that doesn’t run up the side of the feather a bit.
  • Droop in last 1/3rd of the bill.  You definitely see that on this bird.  I’m not totally sold on this ID mark though, as I’ve seen conflicting information online about whether this is diagnostic.
  • Primary projection.  Short-billed Dowitchers are supposed to have slightly longer wings, and have primaries that extend out from the tertials more. This guy has long primaries.
  • Slimmer shape than a Long-billed Dowitcher.  I forget whether I read it or whether it was an ID key someone sent me, but supposedly Long-billed Dowitchers are chunkier looking, with the description being that they look like they “swallowed a grapefruit”. In terms of shape/structure, this also results in a straighter back for the supposedly slimmer Short-billed Dowitcher, while in profile a Long-billed Dowitcher has a kink/dip/indentation in the back towards the tail.
  • “Arched” supercilium. This is a mark from the SurfBirds article online, and there are also other sites that note Long-billed Dowitchers seem to have a straighter, less steep slope on the forehead than Short-billed Dowitchers. The result is supposedly a straighter supercilium on a Long-billed, with a Short-billed Dowitcher having the “arch” in the supercilium shape.
  • Light looking underparts with modest barring/spots.  Hard to see in this angle, but the bird does seem to be relatively light-colored underneath, with lighter/white areas.  Long-billed Dowitchers are supposed to be more uniform and colorful below.

 

Dowitcher Tails in Flight

Three dowitcher tails captured while in flight. Black-and-white barring thickness is supposed to be diagnostic for Dowitchers, with Short-billed Dowitchers having wider white bars than Long-billed Dowitchers

One other potential difference between the two species is the width of the black-and-white barring in the tail (visible in flight).  As this group of birds flew by at one point, I did get a (rather bad) photo that captured parts of 6 birds. For Long-billed Dowitchers, the black bars in the tail are supposed to be significantly thicker than the white bars.  For Short-billed Dowitchers, the white bars are wider, and can be as wide as the black bars.  This 2nd photo shows the 3 tails captured in that bad flight photo.  To me, the white bars in that bottom photo are definitely wider than the white bars in the top 2 photos.  I of course have no idea which bird may be the wading bird depicted in the top photo, but it could be possible 2 of these 3 birds are Long-billed Dowitchers, and the bottom one is Short-billed.

I also find it interesting how the relationship between leg length and tail differs between the top 2, and the bottom image.  In the bottom image, the legs appear to stick out further from the tail than in the top 2 photos.  It could just be the poor quality of the photo, or the fact that in the bottom bird, the tail isn’t fanned out as much.  But Long-billed Dowitchers ARE supposed to a have a longer tail than Short-billed Dowitchers.  Could that be while the tail seems to cover more of the legs and feet int he top two birds, compared to the bottom one?

Whew.  If you take just one of any of the ID keys above, there’s no way I’d make a call, particularly on my own.  But given the “match” of several different ID keys, and given the opinions of others, I’m (finally) comfortable calling the bird in the top photo a Short-billed Dowitcher.

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