Laura Erickson's For the Birds

Birds in the News

This week’s “Birds in the News” has yet more evidence that this has been a hard year for birds the world over. In Israel this Monday, August 23, at least 200 migrating storks dropped down exhausted to drink and rest at pool of water in the Negev desert, only to be poisoned by toxic flows from a chemical plant. The birds, on their way from Europe to their winter quarters in Africa, arrived in southern Israel earlier than usual, catching nature officials and staff at the Rotem chemical works off guard. Usually workers put up nets and bird-scarers to keep migrating birds out of danger.

“We found around 100-150 dead storks throughout the pools and dozens more which were unable to fly,” Peter Rabin of the Israeli Parks and Nature Authority told Israel Radio. “They apparently landed to drink water there, and that what was what harmed them.” Although they tried to save those that were still alive, later reports indicated that all the birds died. Ornithologists say about 700,000 storks make the trip from western Europe through Turkey and the Middle East to Africa every fall, retracing their route in the spring. Although the journey would be much shorter if they flew over the Mediterranean, the heavy birds lack the endurance for long, uninterrupted flapping and so use the warm updrafts rising off the Mideast landscape to glide their way back and forth.

“A flock arrived a year ago, not at these pools but at another place nearby, and I managed to chase them away,” Nadav Bloch, head of the plant’s environmental department, said. “This time they landed in an unexpected spot, in dried out pools which had little puddles.”

In Canada, ornithologists were conducting research to make chickens taste bad to hawks. When British pigeon fanciers heard about it, they suddenly decided it would be cool to develop a diet supplement to make their pigeons taste terrible enough for Peregrine Falcons to take them off the menu, and are encouraging scientists to search for a food product that will do the trick..

The Peregrine Falcon population is growing in Britain, with numbers now over 2,800. And racing pigeons make up 85% of a falcon’s diet. In May, when baby falcons are hatched, the peregrines eat two a day. The researchers note that they will lose some birds initially, but hope that in the long run making pigeons taste bad will get Peregrines to search out other prey.

They’re searching for a substance that won’t have a harmful effect on either pigeons or birds of prey. The pigeon fanciers are currently receiving proposals from scientists who could carry out the research into their ‘taste aversion’ tactic. They also hope to receive a grant from the European Union to fund the research. News releases didn’t say what source of food the peregrines will have to turn to when they stop feeding on pigeons.

Closer to home, in the American West, ornithologists are teasing out the reason that Townsend’s Warbler seems to be displacing its endangered sister species, the Hermit Warbler. Apparently Hermit Warblers thrive in high quality northwestern fir forests, but when they become degraded, Townsend’s Warblers out-compete their meeker relative simply because they produce more testosterone. Townsend’s warblers have always been more aggressive, and have been displacing Hermit Warblers for thousands of years in less than . But now, Luke Butler, a biologist at the University of Washington, says the Hermit Warblers “are running out of places to go.”

Tests show the Townsend’s males have higher levels of male hormones, notably testosterone. Writing in Biology Letters, a journal of Britain’s Royal Society, scientists believe that the Townsend males seem to be stealing away hermit warbler females, especially in less-desirable habitat. “In low-quality habitat, Townsend’s males are more able to attract females than hermits are,” Butler said in a statement.

In Washington and Oregon, the researchers found hybrid zones where the birds have mixed plumage. Blood tests show they have the higher hormone levels typical of the Townsend’s species. “Many of these are presumably the result of hybrid matings between the ‘tough-guy’ Townsend’s and the females of the ‘wimpy’ hermit species,” Butler said.