Thursday, November 3, 2011

terns ~ 11/03/11 ~ Morro Strand Beach



edited 11/11/11 - These were the funniest looking birds I've seen in a long time, like gulls with clown outfits on. It's too bad we lost sight of the Morro Bay Winter Bird Festival leader who pointed out the surfbirds for us.

I originally posted these as all being elegant terns, but I was unsure and considered royal terns as an option. I asked if anyone could help me tell the difference between the two species, because I was pulling my hair out thinking they all had to be either elegant terns or all royal terns. I tried to convince myself the variations I spotted were due to some being younger birds. As I've blogged before, I'm aware I often make the incorrect assumption that similar looking things near each other must be the same. Thanks to commenters Neil and Jennifer, I agree there are actually two species of birds hanging out together. Neil provided an excellent link to the San Diego Natural History Museum Focus On Royal and Elegant Terns. Thanks to you both!


royal terns with 1 elegant tern 2nd from right
S. maxima with 1 Sterna elegans 2nd from right

The royal terns have white tops of the heads, like a man balding on top, and thicker, pumpkin-colored bills. They look stockier than elegant when standing side by side.

elegant terns with 1 royal tern 2nd from left
S. elegans with 1 S. maxima 2nd from left

The elegant terns have heads with black hoods that touch their eyes, thinner, sharper bill, and slightly smaller overall size. Note the yellow legs of the juvenile elegant tern.


mixture of elegant and royal terns

Now, can you spot the differences above? With all the variations in plumage within a species, depending on time of year, age of the bird, and sometimes sexual dimorphism (other birds), I hope my confusion can be easily understood. Now that I know what to look for, the differences seem obvious. It'd be more of a challenge distinguishing these terns in their breeding plumage. I'm just glad a caspian tern (Sterna caspia) was not in the mix, too.

Somehow it's comforting to know other people have a hard time IDing these terns, e.g., Ben's Blog - In Search of Nature, Birds, Butties & Bugs, and John Wall's Natural California (does he have a mix of both species, too?).

8 comments:

Neil said...

Ha, I think I see why you are having problems but I almost don't want to spoil it. Pay attention to relative body size, relative bill size and shape and the amount of white on the head. That last one might be the best clue. This website might help:

http://www.sdnhm.org/research/birdatlas/focus/terns.html

Also, allow me to kick myself again for not paying better attention to birds, plants and bugs when I was growing up in SLO county. Too much snake and lizard chasing, not enough careful observation of field marks.

Jennifer said...

Wow, that's a tough one. Ok, here is my guess....
The first photo is a royal, the second photo the second one from the right is elegant and the rest royal, the third photo half are elegant and half are royal, and the last photo they are all royal. Then again, that last photo could be all elegant....I seriously am having a hard time telling. If I had to pick I would say the last photo is all royals...also the beaks seem stockier to me.

Katie (Nature ID) said...

No wonder I was having such a hard time narrowing these down to one species. Phew! Got it, I think. I edited the above, added an extra picture, and moved them around. Thank you both for your help!

Jennifer said...

I love these photos. The one with them flying off is especially cool, and also the ones where they are all facing the same direction. Neil's link was really helpful. I think the one thing that helps me the most is noticing the way the black on the elegant tern bleeds into the eye. I wish we had realized the differences when we were there!

Imperfect and tense said...

Lovely photos, Katie. Two species of tern in the same picture, very nice!

Katie (Nature ID) said...

Jennifer, I think there's a bird term for when birds all face into the wind or towards the sea. Do you know it?

Thanks, Graeme. This was a tough post for me to figure out.

thebuggeek.com said...

That's a lot of terns!
One good tern deserves another?
(Sorry, that was terrible.)
Seriously though, I think I've only ever seen maybe one or two species of tern in my life, and never at the same time. Very cool.

Katie (Nature ID) said...

Thanks, TGIQ. I'm still trying to get used to your new blog name. I loved Fall to Climb and thought it was appropriate for how some beetles do fall and climb (even though I know that's not why you named it that).