The smarts pecking order is based not on a single bird-in-cage test, but on 2,000 reports of feeding innovations that have been observed in the wild and published in the world's ornithology journals.
"Initially, quite honestly, I didn't think it would work," says Dr. Lefebvre, an animal behaviourist at McGill University in Montreal, Canada, who first reported the bird bell curve system in 1997. "Scientists don't like anecdotal evidence. So if you're wary of one anecdote, why would you expect to find a valid pattern in 2,000? I've been waiting for something to come up that would invalidate the system, but nothing has."
The biologist, whose work is supported by Science and Engineering Research Canada (NSERC), will present his latest findings at the 2005 American Association for the Advancement of Science meeting in Washington D.C. on February 21.
The IQ index draws its strength from the world's legions of avid bird watchers. Professional and amateur birders alike report unusual sightings to refereed ornithology journals, such as the Wilson Bulletin in the U.S. and British Birds. These observations are published as "short notes." Dr. Lefebvre's innovation index uses short notes from 1930 to the present as the basis for counting the number of innovative feeding behaviours observed in the wild for particular groups of birds.
These bird-brained feeding feats are definitely clever. One of the most famous is the 1949 report of tits in England who learned to open milk bottles left on the stoop. Or there's the brown skua, an Antarctic bird that parasitizes nursing mother seals by angling in on drops of breast milk. One of Dr. Lefebvre's favourites is the report from a front-line soldier cum bird watcher during the Rhodesian war of liberation. The soldier reported observing vultures who'd learned to wait beside mine fields for an unsuspecting gazelle to get blown into a meal.
Dr. Lefebvre says that the IQ index meticulously avoids the factor that gets feathers ruffled with human IQ tests: cultural bias. The index statistically takes into account differences in the number of observations for commonly seen birds, such as crows, and rare isolated sightings. Even then, he says, there's a clear hierarchy for bird innovation ability. The crow and falcon families are at the top of the class, followed by hawks, woodpeckers and herons.
In 2002, the feeding innovation index methodology gained a higher scientific perch when it was successfully extended to primates by British researchers Dr. Simon Reader and Dr. Kevin Laland at Cambridge University.
The result, says Dr. Lefebvre, demonstrates links between the evolution of innovation-related brain structures in birds and primates. In both groups, greater feeding innovation, tool use and speed of learning are related to larger forebrains - the neocortex in primates and other mammals and the mesopallium-nidopallium complex in birds.
"So it all seems to provide a picture of convergent evolution. Similar solutions to brain-cognition organization seem to have evolved in the two groups, whose ancestors diverged more than 300 million years ago," he says.
And, says Dr. Lefebvre, the latest research by his former postdoctoral student Dr. Daniel Sol shows that those birds with greater "behavioural flexibility" do indeed rise to the top when it's a difference between life and death. Analysis of dozens of attempts to introduce bird species around the world reveals that species which were more innovative on their home turf were much more successful in taking up roost in new environments.
Says Dr. Lefebvre: "This data on bird introductions is at the moment the only good evidence we have for the fact that big brains and innovative behaviour make a life and death difference and therefore that they could have been selected for in evolution."
Dr. Lefebvre's AAAS presentation
Feeding innovations and forebrain size in birds
Monday, February 21, 2005
Part of the symposium: Mind, Brain and Behavior