Let's all speculate about the lesbian birds

OK, so that title is a bit glib, but that is definitely how the press is going to spin this story about birds who have stable female-female mating pairs:

Almost a third of Laysan albatross nests in the Oahu colony have two mommies.

That's the surprise in Lindsay Young's genetic analysis of breeding pairs on Oahu. Like many other birds, two Laysan albatross court and pair up to form a nest and share the work of feeding a chick. But the males and females look so much alike in this species that the sex of the nest tenders only became clear after genetic tests, Young and her colleagues say in an upcoming Biology Letters.

About a third of the two-female nests managed to raise chicks, says Young of the University of Hawaii at Manoa. The genetic analysis also identified some of the fathers, males elsewhere in the colony. In the female-female pairs the egg-laying moms had had brief encounters with these males at some point even though the males may have had their own nests. The female-female pairs have shown up in other bird species, but Young says the previous record for female-female pairing in an animal was only 14 percent (in western gulls).

What makes this finding really unusual, says Young, is that even in a good year a Laysan albatross pair can raise only one chick. Even that single beak takes two parents a lot of work to fill. It's not unusual for an adult from Oahu to fly as far as Alaska on a single fishing trip to collect baby food. In a two-female nest, therefore, only one female gets to be the genetic mom. The other is just busting her tail feathers to spread somebody else's genes.

This one-mommy-at-a-time household looks tricky in view of reciprocation. "It doesn't pay to be the helper first, especially if there's a long delay between when you give the help and receive it, because you're never sure the other individual is going to reciprocate," says Young.

On Oahu, the two-female nests do include pairs that have been together for multiple years, Young and her colleagues report. And during those years, evidence shows that at least some of the pairs ended up raising a chick for each mom over the course of the partnership.

Oahu's female albatross nesting could reflect the skewed 59 to 41 female to male ratio that turned up in the analysis, the researchers say. The birds started to breed on the island only in the early 1980s, and more females have arrived than males, Young says. Among animals, one sex often tends to move away from home more readily than the other. The female-female pairs have only half the success in raising chicks that other pairs do, but that's better than failing without any kind of mate, Young says.(Emphasis mine.)

Let's break this story down. There are many angles to this phenomena, and I am interested to hear what people have to say about them.

1) There is the evolutionary angle. From an evolutionary perspective, you have to ask why female-female matings would be selected for in species. Why would a species with female-female matings be more successful than not? From what they said, it sounds to me like a founder population effect that would vanish if there were equal females and males. Considering the founder population had a disproportionate female to male ratio, the birds are more reproductively successful in a female-female pairing than when a female raises the chick alone.

2) There is the ethological/behavioral angle. From an ethological/behavioral perspective, how does a female bird mistake another female bird for a valid mate in this environment? Kate can probably speak more to this, but I feel like in mammals opposite sex identification and mating have a strong element of pheromones (except in people...read this by Kate). I am no bird specialist, but maybe ethological triggers are primarily visual. If the male and female birds look so similar, the females could misidentify the other females a potential mates.

This mis-identification hypothesis would contrast the alternative that the animals no full well that they are raising a chick with another female. The question really hinges on whether the birds are capable of identifying another individual. This would be critical to reciprocity -- you helped raise my chick not I will help raise yours. The results do suggest that some mating pairs are stable over multiple seasons, but this might just be some statistical process where some pairs lasted longer than others. In order to figure out the answer to the ethological/behavioral question, you really have to work out how these birds identify possible mates and their particular mate.

3) There is the socio-political question. This gets to my glib title. Why do we immediately focus on the female-female element here as unnatural, and why do we attempt to apply humanistic labels to these birds' behavior? While I know that evolutionary biologists may be critical of her work on substantive grounds, Joane Roughgarden has documented numerous examples of sexual behavior that does not fall into the frankly misogynistic "man-on-top, get-it-over-with-quick" rubric (to quote George Carlin). Given the prevalence of strange sexual behavior in the animal world -- for further reading, pickup Dr. Tatiana's Sex Advice to All Creation -- why are stories like this even news?

Animals are many and various in their techniques for surviving in a oft hostile world, and it doesn't even surprise me that one technique they cooked up is female-female mating.

So let's here it. Any other angles people can think of?

Hat-tip: Mike Dunford

UPDATE: I just had a thought. I wonder if there is any evidence that the female-female pairs actually...you know...do it. Has anyone observed false copulation attempts in female-female pairs? That would certainly clear up the mis-identification issue.

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Well, I'm no ornithologist, but I think it's perhaps slightly stronger than "birds are more reproductively successful in a female-female pairing than when a female raises the chick alone." From what (little) I understand of albatross, it is simply impossible for a bird to raise a chick alone - their feeding patterns simply don't allow it.

I also seem to recall that in many bird species the parenting drive is so strong that birds without their own young will adopt any youngsters they can, so perhaps reciprocation isn't that big a deal. I definitely recall David Attenborough describing how amongst some penguins (I can't recall which penguins) the competition between prospective adoptive parents is so fierce that orphans frequently get killed in the scrum.

On the gender identification issue - just because the sexes look alike to humans does not mean the birds cant tell - as birds can see in uv several species are known to have different patterns of uv reflectance in males and females. Also, albatross courtship involves a long series of choreographed displays - possibly males and females sound differently (at least to each other).

You know, I'm really not sure how well most bird species can identify each others' gender by sight alone. You'd have to use some sort of distal cues, such as pheromones (as you aptly pointed out), without allowing the birds to see each other, then measure the nature of their vocalizations and any other physiological changes that might come along with courtship and/or sexual receptivity. Wouldn't be surprised if it's been done, but can't speak to it.

I tend to agree w/ Dunc and your first point. If you can partner up with another conspecific in the animal kingdom to boost the chances of successfully raising your offspring, I don't think sex has much bearing at all. Some help is always, ALWAYS better than no help.

So, you're quite right - perhaps what's most unnatural is our still-pervasive anthropocentric unwillingness to understand that same-sex dyads can be an extremely advantageous means of raising offspring.

Kate: perhaps what's most unnatural is our still-pervasive anthropocentric unwillingness to understand that same-sex dyads can be an extremely advantageous means of raising offspring.

Why would this be anthropocentric? It's not a general human quality that children be raised by a father and a mother; polygamous and polyandrous societies clearly act differently. I think you're reaching for "ethnocentric" here. That's much more unnatural than anthropocentric -- it would be weird enough to think that non-humans think like humans, but it's so much weirder to believe that non-humans think like middle-class Americans.

This is a good time for the nation to step back and consider whether or not they are going to continue to use examples from nature in their debates on societal issues.
Either this bird scenario must be admitted as an example that a family with "two moms" is natural, or the "nature vs. nurture" arguement which cites examples in nature must end today.
I much prefer the first option, as I am a strong supporter of Science.

I just came across this conversation, and am surprised that none of the comments points to one source of the female-female pairings: environmental endocrine disruptors. It has been discussed by wildlife biologists for many years. Our environment is contaminated by many chemicals that disrupt hormonal mechanisms; for example, organochlorine pesticides such as DDT. The presence of environmenal endocrine disruptors is now seen as a significant threat to human health. Bisphenol A, the plasticizer now being removed from polycarbonate baby bottles is an estrogenic chemical. A useful source of information is www.ourstolenfuture.org, which originated from a seminal book published in 1996--Our Stolen Future--which noted phenomena such as same-sex pairings in contaminated environments such as the Great Lakes.

my sister have 2 female bird that did try to copulate each other. both put egg ("empty" eggs).
Since some years ago that she have this birds.