Here’s where the story gets interesting.
In 1962, game farmers introduced 67 kalij pheasants to the Pu’u Wa’awa’a Ranch on the island of Hawaii. With most native birds on the decline thanks to invasive predators, the pheasants stretched their little legs and settled in. They’ve done so well in the last several decades that kalij pheasants can now be found on Hawaii in densities up to seven times higher than those found in Asia.
But density isn’t the only thing that differs among the transplants. Instead of conforming to the monogamous nuclear Pheasant family described above, kalij pheasants on Hawaii run around in little breeding packs. These groups are made up of one female and up to six males, the oldest of which is dominant.
If you were to sit and watch these pheasant groups, as ecologist Lijin Zeng did for three years while she completed a doctorate at the University of California-Riverside, you’d notice that they’re more than just friends. (The findings were published in The Auk: Ornithological Advances earlier this month.)
For instance, when a mongoose or hawk or even a male from another group comes sniffing around, the pheasants make all kinds of squawks and screeches until the intruder leaves. And if that doesn’t work, they’ll even attack. Zeng once saw a female pheasant charge a mongoose after it ignored her warnings.
But this pheasant assemblage is about more than defense. While the dominant males do most of the mating, they and the subordinate males all help raise the chicks together. This includes ringing the dinner bell for the young’ins by making special food calls, pointing out tasty morsels with their adorable little beaks, and even picking up pieces of food and placing them in the chicks’ mouths. (D’aww.)
Obviously, it’s not uncommon for animals to take care of their young. But what is unusual is the way the subordinate male pheasants chip in. They’re basically free babysitters and bodyguards for the female’s brood. And what’s even weirder is the fact that back in the Himalayan foothills, these young males would probably be off starting families of their own.
Zeng wanted to know what was up with these Hawaiian pheasant communes. After all, nothing in nature is free.
By taking DNA samples from 170 kalij pheasants, Zeng was able to match chicks with their likely fathers. And the results come straight out of Maury Povich.
While the dominant male in each group fathered a vast majority of the chicks, Zeng found that around 17 percent could trace their paternity to one of the subordinate males. What’s more, seven out of the 82 chicks sampled were fathered by dominant males from another group, and four chicks were fathered by subordinate males from another group.
So it’s true: Everybody does get lei’d in Hawaii. If your a kalij pheasant, anyway.
Now remember, most evidence points to the kalij pheasant being monogamous back in its native range, with perhaps a little dabbling in polygyny (a male mating with multiple females). But Zeng’s evidence shows that Hawaii’s pheasants are engaging in straight up polyandry — or a female mating with multiple males. This is only the third documented case of cooperative breeding reported for Phasianidae, the family of birds that includes pheasants, chickens, quail, and partridges.
“We often think of a species' social structure as being characteristic,” says John Rotenberry, a professor emeritus at UC Riverside and co-author of the study.
In other words, we tend to categorize animals in absolute terms — elephants have matriarch-led herds, albatrosses mate for life, and so on. “But the more scientists look the more we see that that structure can vary from place to place for a species, depending to a considerable degree on local ecological conditions,” says Rotenberry.
The question of why the pheasants should employ a totally different baby-making strategy in a new habitat is still up for debate. But there are a few hints that their unusual population density has something to do with it.
For instance, an earlier study Zeng conducted found that when you remove a bunch of pheasants from an area, the subordinate males of the groups that remain no longer have any interest in communal living. Instead, the young bucks go off and establish their own troops in the newly-vacant territories.
Kalij pheasants may not be the first birds to go down this path. A 1992 study of the Seychelles brush-warbler found that cooperative breeding could appear in as little as two years when the birds became too many and the mating opportunities became too few.
It’s interesting that cooperative breeding only seems to occur as a backup plan in both kalij pheasants and brush-warblers, but this also makes sense, genetically speaking. One male and one female means both get the best odds that their DNA will be passed on to the next generation. But if there are simply too many pheasants around to get that kind of exclusivity, teaming up makes the best out of a less than ideal situation. Cooperating with a dominant male bird — making themselves useful by providing protection and caring for chicks — means a shot at fathering a chick or two of their own, which is better than not having a mate at all.
There’s some evidence that the Hawaiian pheasant commune may be even stranger still. Of the 82 chicks sampled in the study, three did not match the genetics of the mothers from the nests they were found in, nor did they match any of the females tested in the entire study. Does this mean kalij pheasants on Hawaii may also practice brood parasitism, where a female plops an egg or two into another female’s nest, like a baby left on the doorstep?
The researchers don’t know. What happens in Hawaii stays in Hawaii, I guess.
Jason Bittel writes about weird animals for a living. You can find more of his work at his website.