Laura Erickson's For the Birds

(Recording of a Jacana)

Whenever I want information about the fast-breaking world of ornithology, I read the current issue of The Auk—the journal of the American Ornithologists’ Union. The first paper in the January 1989 issue is titled, “Experimental Induction of Infanticide in Female Wattled Jacanas.” Yes, you heard me right– -infanticide, defined by the authors in the first sentence as “the killing of conspecific young.” What the Cornell and Smithsonian researchers did was to remove five females—I presume by shooting, though presumably not with an AK47—from mated pairs of tropical shorebirds to see what would happen.

The Wattled Jacana, like phalaropes, is polyandrous, and shows sex role reversal—the female is the territorial and mating aggressor, and the male is the one who performs all the parental care duties. He incubates the eggs for a month, and then cares for the chicks until they become independent about 56 days after hatching. In this study, the ornithologists discovered that if a female was removed, other females appeared on the scene almost immediately to console the bereaved widower. And these females were usually successful. Of the five widowers the researchers studied, only one remained true to his departed mate’s memory throughout the study period, which only lasted a few days. The rest not only quickly allowed themselves to be wooed by a new mate, but also passively sat back while these brazen hussies killed their chicks. It takes three months to raise baby jacanas from laying the eggs through the young growing independent, and apparently the females don’t want to spend their lives taking care of other females’ babies. I wonder if the tales about evil stepmothers weren’t inspired by this species.

As gruesome and downright rude as this behavior seems to us, it makes sense for jacanas. A dead female is logically less fit for survival than a living one, and it would be wasteful for a healthy female to allow her mate to spend three months caring for the genetic offspring of a dead female, instead of raising her own possibly superior young. Yes, the system of jacanas is logical and good in the overall scheme of the universe, but I’m awfully glad I’m married to a person instead of a jacana.

The second paper discusses the fall migration of the Blackpoll Warblers. There have been two theories about their route from Canada down to South America. Some scientists believe that they cross the northern US and Canada heading almost due east, and then fly over the Atlantic Ocean to their South American wintering grounds. Other scientists believe that they follow the coast down to Florida and Georgia before crossing the ocean. This article supported the second theory, which makes more sense to me—I find it hard to believe that a half ounce bird would really fly non-stop over a dangerous ocean from the Maritime Provinces to Brazil.

Wisconsin ornithologists are studying the dispersal of juvenile Ruffed Grouse–they report in The Auk that in autumn female juvenile partridge move more than twice the distance of males. In spring the males show their wanderlust.

Birds never file paternity suits, but ornithologists use several tests to determine whether the birds caring for an egg or nestling are actually its parents. One paper in the Auk discusses improved techniques for determining parental relationships.

Yes, the Auk is the place to learn about the field of ornithology, and also quite a bit about the people who study it.

(Recording of a Jacana)

This is Laura Erickson, and this program has been “For the Birds.”