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New kids on the rock

For the second year in a row (that I am aware of, anyway), the Brandt's cormorants (Urile penicillatus) have claimed the last remaining arch at Natural Bridges as a breeding rookery. I remember being so excited at "discovering" them in 2021. Anyway, they're back again, building piles of algae into nests.

Rock with dozens of black birds, some sitting on nests of algae
Brandt's cormorants (Urile penicillatus) on top of the arch at Natural Bridges
© Allison J. Gong

BTW, if you're keeping score at home, the genus name for the North Pacific cormorants has been changed from Phalacrocorax to Urile. A 2014 study showed this North Pacific group to be a sister clade to those in the genus Phalacrocorax, and in 2021 the International Ornithologists' Union formally adopted the genus Urile for them.

Adult cormorants with white breeding plumes on neck and back
Brandt's cormorant (Urile penicillatus)
© Allison J. Gong

During the breeding season the Brandt's cormorants develop long, wispy white plumes on the cheeks and in two smaller tufts over the shoulder blades. In my head I've been calling them Einstein plumes because although they probably do have a real name, I don't know what it is. When you see a face portrait of one of these birds, you'll know what I mean.

Male cormorant bringing algae to mate on top of rock
Brandt's cormorants (Urile penicillatus)
© Allison J. Gong

The color blue also features in the breeding phenotype of Brandt's cormorants. Cormorants are related to pelicans, which of course have that huge gular pouch that can hold gallons of water. The gular pouch of cormorants isn't nearly as large. For the Brandt's cormorants, the blue gular pouch indicates sexual maturity. And can you see the color of the eye of the bird that is bowing? The eye of a sexually mature bird turns a brilliant cobalt blue during the breeding season. Brandt's cormorants nest on rocks or cliffs, with the male gathering most of the nesting material. At Natural Bridges, the nests are made up mostly of algae, but I've seen a few birds flying by with surfgrass in their mouths. This male above has brought back a nice clump of red algae (a species of Cryptopleura, maybe?) to an appreciative mate.

So those are the Brandt's cormorants.

This year there is a second species of cormorant hanging out on the sides of the rock. These are pelagic cormorants (Urile pelagicus).

Three cormorants on rock cliff
Pelagic cormorants (Urile pelagicus) at Natural Bridges
© Allison J. Gong

I first noticed the pelagic cormorants early in March. I saw those white patches on the flanks and thought, "But that's not the right body shape for a pigeon guillemot!" I came home, looked them up, and sure enough, they are pelagic cormorants. The pelagic is a little smaller and more slender than the Brandt's, and has a red face and glossy black-green plumage with the white rump patches during the breeding season. These three pelagic cormorants are on small ledges on the side of the same rock where the Brandt's cormorants are nesting, providing a nice demonstration of resource partitioning.

So, are these pelagic cormorants really the new kids on the rock? Going by my photographs from 2021, I'd say yes. I looked back through the photos I took when I discovered the Brandt's cormorants, and did not see pelagic cormorants in any of them. Of course, absence of evidence is not necessarily evidence of absence, and it could very well be that the pelagics have been there all along with the Brandt's and I simply never noticed them. Given that my area of expertise is absolutely not birds, I'm quite prepared to learn that I am wrong about this. But the pelagic cormorants are new to me, and that's reason enough to be delighted by them.

5 thoughts on “New kids on the rock

  1. Trish (QAGeek @ Ravelry)

    Well, I'll start using it in all my cormorant conversations! And how interesting the changes that sexually mature Brandt's cormorants exhibit. That certainly makes them easier to spot!

    1. Allison J. Gong

      I do believe it! I've known forever that pelagic cormorants are here. But for me this was the first time I'd seen them on the arch at Natural Bridges. As I said, they're new to me at this site.


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