Saturday, 3 January 2009

More moorhens

Teenage moorhens feed their younger siblings. Not only that, but in some species they also sit on eggs and chase off intruders. They probably even keep their bedrooms tidy and are unfailingly polite to other members of the family. Teenage moorhens set an example to us all.

Teenage dusky moorhen (Gallinula tenebrosa) looking for an old bird to help across the pond

But why are they so helpful? There are numerous hypotheses about the roles of different individuals in co-operative breeding. The benefit to the youngest chicks is obvious — they get care from siblings as well as parents. The benefit to the parents is also pretty clear. But where does that leave the teenagers?

Moorhen chick prepares itself for teenage-hood.

On the lookout for more food

Here's my hypothesis. Feel free to test it. Maybe they're just rebelling against their parents who live in communes and engage in a spot of free love. That's right — it's always the 1960s for moorhens. Given that they lay their eggs in shared nests, not only are the males not sure which chicks belong to them, but neither are the females. This is the stuff of A Current Affair. Teenage moorhens, according to my hypothesis, are the stockbroking kids of the hippy generation.

Adult taking some responsibility for its actions. Or possibly that of another pair. Who knows? Certainly not this moorhen.


mick said...

lol But I guess that hypothesis only works until the teenagers become adults themselves!

Snail said...

Good point! :)

sarala said...

Interesting. You do wonder how the behavior evolved.

Denis Wilson said...

Hi Snail
I did not know about the group nesting behaviour in Moorhens. Choughs certainly do something similar.
As for the hypothesis about the young stockbrokers - surely not. They would sell all the better looking chicks to their rich uncles.
Richard Dawkins "Selfish Gene" seems to work better as an explanation.

Kevin said...

Interesting stuff, prompting me to see if Common Moorhens, which I don't see in UT but were quite common in Florida, engage in similar behaviour. And it turns out they do.

Plus, I also learned that they can be both victims and perps of nest parasitism - the strangest (from Birds of North America Online) just had to be a moorhen in South Carolina parasitizing a grackle's nest! You just have to love the internet.

Snail said...

You've all inspired me to look deeper into this cooperative breeding business in moorhens and their ilk.

Denis, I was going to talk a bit about the idea that this sort of behaviour by the juves might be explained by relatedness but with all that promiscuity goin' on, there's a chance that they might not be very closely related to other nest mates. Maybe they're hedging their bets? At that point I went blank and got flippant!

Kevin, the notion of nest parasitism by and of moorhens is really odd. A grackle?! I'd like to see how that turned out.

A cursory glance through the internet (Yes, I do love it!), throws up a lot of info about Tassie native hens, which are also Gallinula. I'll see what I can dig up.

Kevin said...

I ended up writing a rather long-winded post about brood parasitism; even though only 1% of species, I had no idea the behavior was so widespread in birds.

Kevin said...

Sorry, goofed the link with an extra "/", hopefully this one will work . . .

Sherrie Y said...

Sorry, this is totally unrelated, but did you see THIS on Boing Boing today?

I want one.

Dave Coulter said...

As the youngest of four I know now that I am not a moorhen ;)

Snail said...

Excellent stuff, Kevin. There's so much to know.

Sherrie, I want that car. This Nissan S-Cargo pops up here now and then as a goods vehicle but it's not quite the same.

Given moorhens' other attributes, Dave, that might be a good thing!

Jamie said...

I have many many moorhen families near my home. I have spent literally hundreds of hours photographing them and watching their behavior. I have observed the exact opposite .. Mother and father build their own nests and lay their own eggs in it. They fiercely defend their area from intrusion by other moorhens and birds. Mother and father moorhen share equally in sitting on their eggs and raising their own young. The first clutch will often stick around as juviniles (teenagers) to help raise their younger siblings.They are a very tight family bird.And no 60's free love is goes on.

r. gere said...

Moorhens rock! Unfortunately the babies are "sitting ducks" for predators like the always hungry hawk, vulture, osprey, alligator, otter, etc. If the female has 6 chicks -- it would be miraculous for one to survive adulthood, hence all the mating. Since they only skim across the pond (not fly) they're kinda trapped in their moorhen existence. You gotta love 'em -- he'll chase her night and day to impregnate. Very fun to watch ;)