So, how do I know this avocet is a female?
1/4000, f/6.3, ISO 500, Canon R5, Canon EF500mm f/4L IS II USM + 1.4 tc, not baited, set up or called in
Five days ago at Bear River MBR I watched this female American Avocet foraging near her nest as her mate was incubating their eggs. When she took off, I figured she’d circle around and come back immediately to land near the nest again, which is something that nesting avocets of both sexes often do. So I was ready for her when she came in to land.
As she approached her intended landing spot near the nest I got about a half dozen shots of her in flight but some of them weren’t quite sharp enough. I chose to post this one because she’s sharp and I like her flight posture. It also clearly shows their typical nesting habitat.
In case you’re wondering why I’m so confident that this avocet is the female of the pair, it has to do with the shape of her bill.
This is an older photo of courting avocets taken just prior to mating. In avocets, sexes are similar in plumage but different in size and in bill shape. Males are larger than females but that trait can only be used reliably when a male and female are seen together. In this photo the male is the larger bird in front.
But there’s a second trait that can be used to sex lone avocets fairly reliably – females have slightly shorter and more strongly recurved bills than males.
In this photo both traits are obvious, confirming that the male is the bird in front. And that the avocet in the first photo is a female because of her strongly recurved bill.
Ron
Wonderful shots Ron! Thanks for sharing!
Charlotte Norton
I knew the answer. Years of reading your blog gave it to me, though I am grateful to Dan for some extra information.
❤️
Thanks, EC. I figured the lesson was worth repeating, especially because I thought that second photo was excellent for reinforcing my point.
Nice photos and lesson. The difference is well seen. But why is the female bill more recurved? One possible answer – Even in the shallow water they feed in they are often taking slightly different prey (with much overlap). Females feed slightly deeper than males. The birds dip their bills into the water and sweep it back and forth. When held roughly parallel to the water’s surface, the male’s less recurved bill is then just below the surface. To be parallel to the surface, or bottom, the female must put her bill slightly lower in the water. Doing so can allow her sometimes some different prey. It’s subtle but at times does make a difference. Try it yourself. Bend your fingers slightly back and hold them parallel to the floor. Now bend them slightly more. To be parallel to the floor you will need to lower your hand.
Wow! More fabulous info! That makes for a great day.
Thanks Dan, that makes a heap of sense, though I can’t help wondering whether the beak shape is the chicken or the egg in an evolutionary sense.
That’s an interesting theory, Dan. The drivers of evolution are often difficult to figure out “after the fact”.
Thanks for that information about sex difference! We see lots of avocets on a marsh near us and I never even noticed the difference. I will pay more attention now😊
“I will pay more attention now.”
Good. That was exactly my intention for that last part of this post. Thanks, Catherine.
Great photo of very striking bird but I was especially interested to find out about the bill shape as an aid to identifying the sex. I’m happy to be a student in this “class”.
Thanks, Granny Pat. And you’ve always been one of my better students… 🙂
Nice takeoff and very nice courting shots. Such elegance; those long bluish legs certainly add to that.
I thought you might say you saw them mating and the male was on top.
Perhaps the bill difference is their way of telling male from female. Yeah, no.
“I thought you might say you saw them mating and the male was on top.”
I did that too, Lyle. And he was of course.
I paused at your question before I scrolled down and was able to search my memory for the correct answer. The only way I knew about the bills was because of your blog. You may be retired, but you’re still a fabulous teacher and teaching this “old dog” some new tricks. ❤️
Good memory, Marty. And thanks for the kind words, especially from another teacher.
Every year I taught, I’d go around to other teachers’ classrooms (with their permission, of course) during my prep period to watch and learn. Watching good teaching is among my favorite memories of being a teacher. I know I would have loved visiting your classroom!
I did that too, Marty. Sue Southam, who sometimes comments here, is one of the teachers I visited regularly. She was an English teacher. I also did it with a chemistry teacher and an art teacher.
Excellent photos as always and another educational moment for me. I was not aware that with these wading birds that the male was larger than the female. I think I assumed that they were like our raptors where the female was always the larger. Right now we have two 11 week old recently fledged Bald Eagles and the female is huge. Nature gives them added wing and tail feathers to help them fly, and this gal perched next to mom is really large.
The second photo makes me think of two kids who did something bad quietly trying to sneak off without being seen.
Everett, regarding your last sentence I definitely see what you mean.
Ron – I have never mentioned before, but it is always educational to read Dan’s responses. Glad he has been a long time follower.
‘Recurved’ not just ‘curved?’ Curious 😄
Kathleen, recurved means “curved or bent backward”. As opposed to bent forward I suppose, like the bill of an ibis.
Thank you! Always learning something new and interesting from you Ron 😄
I didn’t know the different genders had different bills. I must say that the curve of her bill enhances the gentle curves in your wonderful photo.
Thank you, Kent.
In guessing the answer to the “female marker” question, I was about to type–
but then I read Judy’s comment, and I agree with her speculation.
Except… in avocets, both sexes incubate so they both presumably perform the same incubation-related duties. So I don’t see how that could be responsible for their differently-shaped bills.
Interesting! I wonder what the advantage of the more recurved bill is? Arranging stuff while on the nest/food gathering/turning eggs perhaps…….
New one between here and GF the past couple of days – a vulture! First on road kill in a ditch and then on a post. I’ve never seen one in this area!
I’ve wondered the same thing, Judy. Often.
Good news about the vulture. I’ve never seen one in the Cut Bank area either.
Learned something today about the “marshmallow” bird. Thanks.
Good. Thanks, Marcia.