It’s Cormorant Monday! Three—count them, three—species! Reader and biologist Bruce Lyon sent a bunch of photos from California, and some useful information.
I would have sent these earlier but I am swamped because I am teaching Ornithology (including a lab) while trying to run a full on field season on the winter social behavior of migrant golden-crowned sparrows. I will send some sparrow photos at some point as well.A head shot of a Pelagic Cormorant (Phalacrocorax pelagicus). The dark red facial coloration is diagnostic among the three local species, as are the prominent crest feathers on the top and back of the head. Note the iridescent plumage. All of the cormorants have beautiful jewel-like eyes too.
Below: Several nesting pairs of Pelagic Cormorants just beginning nests on a cliff face, their typical nesting habitat. They often nest on ridiculously skimpy ledges.
A Double-crested Cormorant (Phalacrocorax auritus) with a fish. The facial coloration is much more orange than that of the Pelagic, and is more extensive on the throat (gular pouch). Don’t waste time looking for the “crests”—the crests are nuptial plumes donned only during the breeding season. Cormorants are “foot propelled divers” that hunt for fish under water using their feet for propulsion. Double-crested Cormorants are less coastal that the other two species and often frequent lakes. Unlike the other two species, they also nest in trees.
Below: A Double-crested Cormorant dries its wings. Cormorants apparently have wettable plumage, presumably to make them less buoyant during their foraging dives. A brief check of the literature suggests there has been a debate over whether this wing-spreading behavior functions to dry wings or is used in thermoregulation. One paper I found suggest that the main function is to dry the wings.
During the breeding season Brandt’s Cormorants (Phalacrocorax penicillatus) have gorgeous blue throat coloration, with striking blue eyes to match. The blue gular pouch coloration largely disappears at the end of the breeding season, and based on photos on the web, it seems that the eyes may become less colorful as well. The white hairlike facial plumes are also grown for the breeding season. This might make a great (nerdy) Halloween costume?
A Brandt’s cormorant nesting colony at Año Nuevo State Park just north of Santa Cruz (with California Sea Lions in the background).
A male Brandt’s Cormorant giving a ‘flutter display’—this is a courtship display males use to attract females to check out their nest site. If courtship goes to the next step and the female is serious about pairing with the male, both sexes engage in mutual displays, some of which include displaying the blue gular pouch, which females also have.Mutual sexual selection is one hypotheses for why both sexes are ornamented in a given species. Darwin proposed this idea but then instantly rejected it as unlikely: “…., this view is hardly probable, for the male is generally eager to pair with any female. It is more probable that the ornaments common to both sexes were acquired by one sex, generally the male, and then transmitted to the offspring of both sexes.” Darwin missed the boat on this one, and mutual sexual selection has been confirmed in several animals. Notably, the first demonstration was in a socially monogamous seabird, the Crested Auklet (Aethia cristatella). Brandt’s Cormorants are also monogamous and both sexes help raise the kids.
A male (center) apparently being visited by a few females who are checking him (and his nest site) out.
A bird returns to the colony with nesting material, most of which comes from the sea.
More nesting material:
In Moss Landing Harbor, half way between Santa Cruz and Monterey, Brandt’s Cormorants use wooden pilings and a decrepit wooden pier as the site for their nesting colony. Baby Cormorants are born naked and helpless (‘altricial’ in the official ornithological terminology).
This is wonderful stuff. Thanks.
Stunning….
I’ve always enjoyed watching cormorants. Their odd body proportions give them a prehistoric look. They fly with very fast wing-beats just above the surface of the water. And they hang out their wings like wet sails. They are pretty amazing birds.
Ah yes – like Hesperornis
https://en.wikipedia.org/wiki/Hesperornis
And vaguely reminiscent of Azhdarchids perhaps? Anyway, I saw this recently and it is an amazing image. “It’s one of those images that really kicks you in the brain the first time you see it.” http://svpow.com/2015/10/19/how-light-could-a-giant-azhdarchid-be/
Very cool links, thanks Dom & Torbjörn!
This anonymous was mine, sigh.
Yes, quite a resemblance. Parallel evolution, but displaced by 83 million years.
Great Pics – we have cormorants in King’s Lynn, and I have loads of pictures of them on aspiblog.wordpress.com.
Bruce says that mutual sexual selection is possible, but is that so in this particular cormorant case? Darwin was surely right that males WILL mate with any available female, pretty much…? Or is that wrong? It may well be true of humans…
It is unknown for cormorants (and most birds) whether mutual ornamentation is explained by mutual sexual selection or some other mechanism. Darwin’s idea that genetic correlation (selection is on males and the traits just get carried along for the ride in females) seems to be true for some animals, I think.
Unknown for cormorants or most other animals. Darwin’s idea that “genetic correlation’ — i.e. that selection is on males but because both sexes share genes the trait is dragged along for the ride in females — can explain some of the ornaments we see in females probably holds in some cases.
I don’t see why mutual sexual selection wouldn’t exist in species that are primarily monogamous. If a male is going to invest his reproductive success heavily in a single female, why wouldn’t he be choosy?
Actually, mutual sexual selection is more likely to apply in monogamous species, it seems to me.
Sexual selection doesn’t have to be based on access to mating opportunities. There may be other costly resources that the other sex may contribute other than gametes. In the case of mutual selection, parental care is probably the most common resource. Females compete to be the social mates of males who offer the best parental care, though they may also solicit extra-pair copulations from other males who offer better gametes.
I agree with you John but not everybody agrees about what constitutes sexual selection. I tend to think of it having to do with fitness that comes with mating, which includes mate quality (and parental care) but some folks have recently suggested that sexual selection should include all of reproduction, as long as it involves reproductive competition. With this definition, competition within all female social insect colonies becomes sexual selection. Some forms of brood parasitism (within species) become sexual selection. This could get messy. The problem is that no matter how one slices things, sexual selection involves semantics. It is a subset of natural selection but where to draw the boundaries….
What beautiful birds, and photographs! Double-crested cormorants are common on the Maine coast, though I understand their numbers are declining.
Looking forward to sparrow photos!
Sorry about this repeat. Jerry warned about some posts being unintentionally anonymous, but mine at first did not appear so I tried again, shortened a bit, below.
What beautiful birds and photos! Looking forward to the sparrows.
Wonderful!
That was cormorant unlimited and three species.
I think of them as flying submarines.
Sub
Sub
Excellent stuff, and highly educational. I did not know that Darwin did not figure out mutual sexual selection. He was very insightful about so many things that it is easy to forget that he was also wrong on a # of details.
Beautiful photos! I especially love the Brandt’s; I rarely get to see them around Vancouver.
There are three large urban cormorant colonies here in Vancouver, all underneath large steel bridges. The two downtown colonies house about 80 pelagic cormorant nests each, and the other one further out houses over 200 double-crested cormorant nests. Fascinating birds that really will nest in the most precarious of spots.
Thanks for the wonderful photos and cormorant lesson.
I can see how the Brandt’s Cormorant’s blue coloration could attract based on displays of fitness, but the facial plumes are a mystery to me, like much of natural selection’s selections.
Fantastic photos and commentary, thanks so much, Bruce!
I see the double-crested here in Michigan, and the other two when I visit Oregon, but I almost never see them in breeding condition so seldom see their beautiful colors. (Or in the case of the d-c, crests.) (Nor would I ever be close enough to see or photograph all that interesting behavior!)
In the wing-drying photo: are the large feathers at the “shoulders” tertials and their coverts? Or some sort of scaps?
Their having altricial young makes those “ridiculously skimpy” nest ledges even more so! 😀
“… there has been a debate over whether this wing-spreading behavior functions to dry wings or is used in thermoregulation.”
I’ve read that cormorants (& Anhingas) do not spread oil-gland oil over their wing feathers, although presumably they do over the rest (or most) of their body. This permits the wing feathers to become wet & lose buoyancy, making it easier for the bird to swim underwater. Wing feathers would be easy to dry, it seems to me, as you just hang out your wings, something you can’t do with non-wing feathers.
I SCUBA’d for many years, and can attest to the energy it takes for a buoyant body (e.g. cormorant or human + wetsuit) to stay submerged when in shallow (30 ft or less) water. In deeper water, pressure compresses the body, wetsuit & feathers enough so that buoyancy can become negative.
Interesting. Frigatebirds, which are a sister group to cormorants, have very reduced uropygial glands and spread little oil on their feathers; consequently, though sea-birds, they can’t land in the ocean or they become waterlogged and drown. It’s harder to imagine why that’s adaptive than the adaption-for-diving that you explain!
Please fill in your name and email address in future comments; you have several posted as “Anonymous”
So sorry! That was me!
Looking back over this thread, only one other of the many anonymous links was mine. Apparently WP gave all the anon posters the same avatar.
Like things weren’t already annoying enough! 😀
Frigatebirds also have the largest wing area to mass ratio of any bird, and are thus the most buoyant (in the air) bird on the planet. I suspect there’s a connection between that and their not oiling their wing feathers, but I don’t know what it is. Sounds like a good topic for a PhD thesis.
Thank you for that important piece of the puzzle! Fascinating birds!