Written for the Los Angeles Arboretum.
Meep meep? More like “Honk honk!”
Arboretum regulars will no doubt recognize the call of a startled peahen, but you may not be aware of the clever ways they use it. Not that they try to boast or taunt the enemy, necessarily, but I’m starting to think that the birds at the Arboretum owe a lot to their version of the Road Runner’s call.
How do I know? Some background is in order here: I’m the tall blond woman who has been hanging around the Arboretum morning and night for the past few years, overdressed and hauling a camera, a pair of binoculars, some peanuts and, if I was lucky, a peacock. Working at the park each spring, I often wished I had more time to chat with visitors. But I was preoccupied, and the life of an ornithologist can sometimes feel like that of Wile E. Coyote on a bad day.
For the past four years, I’ve been chasing peafowl across the continent – from Arcadia in February to Winnipeg, Toronto and New York in May and June. Incidentally, the Bronx Zoo is the only place in North America that even comes close to the Arboretum in sheer number of peafowl. Three years into my PhD in biology, and I’ve spent literally hundreds of hours watching these birds.
You may be wondering what got me into this mess.
It all began with a question: why do peacocks have all of those fantastic colours on their train feathers? Note that I didn’t say tail – if you look closely, you’ll see that the beautiful elongated feathers are located on the bird’s back; the tail is underneath, and it’s what the birds use support the raised train.
Only males have these ornamental feathers, and they play a special role in reproduction. During the mating season, it’s the males who put on an elaborate performance, rapidly vibrating their train feathers in front of females. The plain-looking females – or peahens – seem less than impressed, but if you watch them for long enough, you’ll find that they always take the time to look closely at a male’s vibrating “eyespots” before they are willing to mate with him. Indeed, this dance is about all females get out of the bargain, since after mating a peahen raises her brood completely on her own. Charles Darwin was first to suggest that the hens might be doing something extraordinary, for an animal: choosing to mate with a specific male based solely on appearances1.
So far, research suggests that this is indeed the case. At the Arboretum and in several other populations around the world, the males with the brightest and most iridescent eyespot feathers achieve the most matings – and most other males never mate at all. Taken on its own, this doesn’t rule out the possibility that females are paying attention to some other characteristic that happens to be correlated with iridescence. That’s why I messed with peacock colours at the Arboretum back in 2008: I ran an experiment where I manipulated the train display of some of the males using black and white stickers to see whether colour really made a difference for females2.
The first challenge, though, was figuring out how to catch the beasts; they’re a lot smarter than they look. It didn’t take us long to figure out how to nab the males – we just waited until they were distracted by the effort of showing off. The females were another story, leading me to wonder whether Home Depot is the new Acme. We tried all kinds of snares, nets, blinds and traps, and spent hours tying knots and spray-painting before we’d realize that the latest contraption wasn’t much better than the last. A peahen may be no match for the fleet-footed Road Runner, but they sure have a way of cutting down your mammal superiority complex.
If you’re lucky, you might get to see the birds at the Arboretum work together to evade a real coyote. I watched a gaggle of peahens chase one across the Bauer lawn early one morning; Susan Eubank, the Arboretum librarian, has seen males doing something similar. When groups of animals team up to harass a predator like this, it’s called mobbing, and it’s a typical behaviour for a lot of birds – not to mention group-living mammals like California ground squirrels, meerkats and even some fish.
And that chorus of honks that seems to spread whenever a siren or some other threat sets one of the peafowl off? Think of it as a community alarm signal3. This kind of group warning is also typical of animals that mob. Biologists who study animal behaviour suspect that mobbing is quite useful: by grouping together, animals can drive a predator away, or at least confuse it, thereby protecting offspring and kin. Drawing attention to the enemy might also prevent stealth attacks. Another idea is that mobbing helps young animals learn, since their parents are effectively pointing out the sources of danger – and there is some evidence for this theory in blackbirds4-5. I wouldn’t be surprised if mobbing is one of the reasons peafowl thrive in strange places like Arcadia, so far from their native Indian habitat. Their ability to learn a new predator deserves some respect. The few times I accidentally set off a honk alarm myself, I couldn’t get anywhere near the birds for days.
While I’m no expert on predation, I have done a fair amount of work on those curious peacock dances. During the mating season, the males shake their wings and sidle up to females, sometimes even shuffling backwards right into them, before they start vibrating their train feathers. One of the most exciting things to come out of my work at the Arboretum was evidence that males maneuver themselves to present their feathers at an angle of about 45° to the sun, on average, and that they use their dances to corral females into viewing them from that orientation6. I suspect this enhances the iridescent eyespot colours, and that over time males learn to present themselves in the best possible light. In the years since, other researchers have found that great bustards and snowy owls also orient their brightest feathers towards the sun7-8.
This is just the beginning, so stay tuned9-10. I’m working on some new projects to look more closely at the “how” side of things. That is, how do females decide on which male to mate with when there are so many to choose from at the Arboretum? More on this to come.
In the meantime, a few acknowledgments are in order. Dr. Mark Wourms helped me get started. Jim Hendrich provided tremendous support and helpful advice over the years. Of course, I couldn’t have caught a single bird without my supervisor, Dr. Bob Montgomerie of Queen’s University in Canada, and our lively crew of field assistants: Rob Ewart, Adriana Johnston, Myra Burrell, Bonny Chan, Will Roberts, Daisy Luc and Rebecca Kandilian. Our team was very lucky to find Shih Chen back in 2008. Somehow, Shih made a group of Canadians feel at home in Arcadia in the middle of winter. The same could be said of the wonderful staff and members at the Arboretum. It turns out that most of our time working on these birds involved watching them do very little, for hours on end – and you made it easy.
The following notes are for anyone interested in finding out more about the research described here.
Notes
- Darwin discusses his view of peacocks in The Decent of Man, and Selection in Relation to Sex (1871, John Murray, London). It’s available here: http://darwin-online.org.uk/contents.html#descent
- My work on peacock colour is not yet published. For now, you can access an earlier study of a population in France led by Dr. Adeline Loyau. See Loyau et al. 2007. “Iridescent structurally based coloration of eyespots correlates with mating success in the peacock.” Behavioral Ecology 18: 1123-1131, available here: http://www.adeline-loyau.net/publications/publications.html
- For more on peafowl calls and their potential functions, see Takahashi et al. 2008. “Seasonal and diurnal use of eight different call types by Indian peafowl (Pavo cristatus).” Journal of Ethology 26: 375-381. http://www.springerlink.com/content/1j662768l435x3u0/
- For more on mobbing in blackbirds, check out Curio et al. 1978. “Cultural transmission of enemy recognition: one function of mobbing.” Science 202: 899-901. http://www.sciencemag.org/content/202/4370/899.short
- A good place to start for mobbing and antipredator behaviour is the book Animal Behavior: An Evolutionary Approach (John Alcock, Sunderland, currently in its 9th edition).
- For more on peacock courtship displays, see Dakin and Montgomerie. 2009. “Peacocks orient their courtship displays towards the sun.” Behavioral Ecology and Sociobiology 63: 825-834. This paper, along with some of my videos of male displays, can be found here: http://roslyndakin.com/publications
- For more on great bustard displays, see Olea et al. 2010. “Bottoms up: great bustards use the sun to maximize signal efficacy.” Behavioral Ecology and Sociobiology 64: 927-937. http://www.springerlink.com/content/73g5304lx105840t/
- For more on snowy owls, see Bortolotti et al. 2011. “Wintering snowy owls Bubo scandiacus integrate plumage colour, behaviour and their environment to maximize efficacy of visual displays.” Ibis 153: 134-142. http://onlinelibrary.wiley.com/doi/10.1111/j.1474-919X.2010.01067.x/full
- It’s a story for another time, but another neat thing to come out of the Arboretum peacock research is a resolution to a controversy about how important it is for a male to have lots of eyespots in his train ornament. See Dakin and Montgomerie. 2011. “Peahens prefer peacocks displaying more eyespots, but rarely.” Animal Behaviour, in press, available here: http://roslyndakin.com/publications
- You can also read about the eyespot number controversy in the popular press. See brief articles from Nature News ( http://www.nature.com/news/2011/110418/full/news.2011.245.html ) and Wired ( http://www.wired.com/wiredscience/2011/04/peacock-mating-feathers/ ).
From May 31, 2011