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Gulls, Gulls, Gulls

November 13, 2007
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The title’s supposed to be a reference to the Mötley Crüe song. I hope that’s how you read it, it’s much funnier that way. 

Here’s an update on my museum Larid aging project. I’m done with terns, thank ye gods, and now onto the real fun. Gulls man, gulls. For that I’m using the phenomenal Howell/Dunn Gulls of the Americas from the Peterson Reference Series. It’s enormously useful for situations like this as both the photos and text are extremely comprehensive. If you are at all interested in getting serious about Gull ID, then it should be the number one reference for you. I may do a complete review of it at some point I like it so much, and it’s also on my Channukah/X-mas list (we do both around these parts) so it may not be long before I get my own copy in my hot little hands rather than the museum’s copy.

I decided to start slow, with the museum’s considerable collection of Bonaparte’s Gulls. Bonies are relatively simple as gulls go, they only go through three cycles as opposed to four so the differences are not very subtle. The vast majority of the Bonies in the collection I looked at are basic plumaged gulls, as those are the only ones we’re going to find in North Carolina in any numbers. I had either Basic I birds like the one below (what Howell/Dunn would call first cycle), or Definite Basic (adult birds). There were alot of them but I cruised through them all in an afternoon. Piece of cake. Incidentally, I chose this particular individual to take a picture of because it clearly shows the nice terminal tail band on a classic Basic I Bonie. I love it when the bird preppers spread the tail like that, cause they don’t always. The tail can be such a useful tool for parsing those tough IDs (I found this especially true when aging terns), and I just felt this skin was very nicely done. I hope you all can appreciate it too.
The museum also has a couple Little Gull skins, and thought it would be nice to put a Basic Little Gull next to a Basic Bonie so you could really see that when they called that bird a Little Gull, they aren’t messing around. That gull be tiiiiiiiny. A Bonie is not a substantial gull in any way but it dwarfs the Little Gull. I wish the collection included a Black-headed Gull so I could have lined that up too but we don’t have one. There has been one hanging around Lake Mattamuskeet for the past few winters, maybe this year we should go shoot it for the collection. I keed, I keed… kinda…

 

So feeling flush with triumph after my successful completion of the Bonie collection, I decided to up the ante a bit. I started pulling out the Glaucous Gulls. I may be sorry I did that.

Here’s the skinny. Glauc is a classic four-year gull, which means roughly, it has nine different plumages from four full molts. The differences in Alt vs Basic are differences mainly between body molt and wing molt as I understand it. I could be on the wrong track there though. Fortunately, Glauc is an arctic breeder, so unless the bird was collected in the arctic (and it would say so on the tag) we can thankfully ignore the alternate (breeding) plumages. So what I’m trying to do is parse the ages of the birds in the collection by plumage, of which I have four to choose from. Also I don’t really have soft tissue to work with as obviously iris color, a useful tool in the field, is lost to me because my birds no longer have eyes. Sometimes iris color is noted on the tag though, but not often and it depends on the whim of the collector. I’ve pulled birds out that were originally taxidermied and when they still have the glass eyes it seriously freaks me the hell out (I should get a picture of one).

So let’s put this in practice shall we? At left are examples of (from left to right) Basic I, Basic II, and Basic III plumages, all from early fall I should add so the plumage is more or less fresh. That’s important because the middle bird was very tough for me to place to Basic II. If there are any Gull people out there feel free to help me out on that if I’m wrong, but because the bird was collected in September as opposed to say, April, I felt comfortable calling this individual a fresh Basic II rather than a worn Basic I. I thought maybe the tail was a little strongly patterned for the birds listed as Basic II in Howell/Dunn. But, and this is my one complaint of this book thus far, there aren’t any pictures of a bird from different times of year to compare. I was stuck comparing these skins to birds in the book who were from later in the cycle (spring) and had plumage much more worn. Not shown in this pic but obvious in the hand were the undertail coverts, strongly barred in the Basic I bird and more amorphous in the Basic II. Plus the Basic II bird had a pale tip to the bill where Basic I is completely bicolored. Anyway, I’m fairly confident on my identification but willing to hear other opinions. You guys still with me?

Ok, so the pic to the right here shows why date is so important for these birds. Both of these birds I identified as Basic I. You may ask why? The bird on the right looks remarkably like the Basic II bird in the above shot. You’d be right to wonder that, and it bugged me for a some time but here’s the deal. The left bird is a fresh Basic I from September. The right bird was collected in April so it’s plumage is worn, and Glauc is known to really wash out when the feathers are worn, especially in their first cycle. Some differences can also likely be attributed to the fact that the left bird is from the barrovianus ssp from the west coast and the right is from the nominate hyperboreus ssp from eastern US, but it’s not clear to me exactly how much that would matter.

So there you have it. I spend a ton of time on only five Glaucous Gulls, I’ve got several drawers more to go. These suckers are tough, but if I get one out on the Outer Banks this winter I hope to god this makes me ready for it.

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5 Comments
  1. slybird permalink
    November 13, 2007 10:12 am

    Whats your objective in studying these larid skins?

  2. November 13, 2007 11:02 am

    I’m a volunteer in the ornitology lab at the museum. None of their Larids are aged and it’s been a project they’ve wanted to do for a while but noone had the time. Then I showed up and they stuck me with it.

    They’ll eventually include all this information in their new database.

  3. slybird permalink
    November 13, 2007 11:22 am

    Cool!

    What kind of confidence must you have before you can assign a gull plumage age? Ie… you name it a SY, its actually a worn HY, but then the next person comes along and says ‘oh this looks like a HY but I guess its actually a SY’… just wondering – I worry about post hoc judgments such as these 🙂

    Do you do any skinning too? I sometimes do specimen prep for the Cornell collections.

    Cheers,
    Nick

  4. November 13, 2007 5:04 pm

    Yeah, getting them wrong was a concern an first but by and large I’m confident of the calls I make. The way I see it, if a Glaucous Gull expert comes along and looks at our collection and points out one of the few I made a mistake on than it can relatively easily be changed.

    I’m amazed actually at the misinformation that is on some of the tags, especially the older ones. It’s not so much wrong as it is just an obsolete way of thinking about birds and plumages and a lck of understanding of what constitutes good information. We have some skins that are 100 yrs old or older and I’m lucky if they ever write “immature” on them, which that even when you think about it is a pretty imperfect way to judge age, especially in Larids when they go through 3 or 4 “immature” plumages.

    So I have no problem with someone down the road making post hoc judgements on the birds I’m looking at, cause it’s really no different than what I’m doing.

    They haven’t got me on skinning yet, my schedule doesn’t allow for the time it would take right now. Soon though…

  5. slybird permalink
    November 13, 2007 5:49 pm

    Very true, very true.

    I look forward to more museum posts!

    Sometime soon I’m going to get back to CUMV and start skinning again (it has been over a year for me) and I’ll be sure to post some when I do.

    Cheers,
    Nick

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