Scientists are trying to figure out why there are a bunch of dead robins in Central Texas. The leading theory is...well, see for yourself:
Pesticides, a common killer, were ruled out. So was West Nile virus because the mosquitoes that transmit the disease have been zapped by cold weather. Tests run by two laboratories were inconclusive.
Now scientists are wondering whether the birds succumbed to a junkie's fate -- overdosing on alcohol-spiked berries or hallucinating on fruits plucked from exotic bushes in the back yards of suburbia.
"The bird gets stoned," said Cliff Shackelford, an ornithologist with the Texas Parks and Wildlife Department, which has been investigating reports of dead robins along the Interstate 35 corridor since mid-January.
Each year millions of robins born in southern Canada, the Great Lakes and Northeast make the trek to Texas, settling for the winter in areas with the most abundant food.
Die-offs happen periodically, due to bacteria flare-ups and the stresses of migration.
But this particular death spell was more pronounced because of the size of the robin population, which was pushed higher this year by the harsh winter gripping the North, state wildlife biologists said.
With more competition, some robins gorge on foods that in a normal year are not as prevalent in their diet. Some of these plants cause the same side effects that college freshmen get after downing too many tequila shots, Shackelford said.
There is no equivalent to the blood alcohol test for birds, since their digestive system processes berries and alcohol rapidly.
"I don't know what other tests we can do," Shackelford added. "When they keep coming up negative, we don't have the resources."
And while it is a common belief that birds get drunk on berries that repeatedly freeze and thaw -- a process called fermentation that converts sugar to alcohol -- some scientists question whether the fruit is a high enough "proof" to kill them.
"The evidence that there is enough alcohol in the berries to kill them is not there," said Jesse Grantham, a biologist and director of bird conservation for Audubon Texas.
"They think grapes, berries, alcohol ... the birds are drunk. I've never seen a study saying birds are dying of alcohol intoxication"
Grantham said the cause is more likely that the birds are feeding on non-native ornamental shrubs that contain toxins that American birds weren't designed to stomach.
Examples include Chinese tallow, fire thorn (Pyrocantha coccinea) and chinaberry, he said.
"Most of the die-off is in suburban areas where people plant ornamental shrubs," Grantham said. "There are some hazards to planting non-native species in your yard."