But even when the hormone levels evened out between the two groups as the chicks got older, their behavior was different. Nearly fledged chicks in tourist areas did not flee until people were within two feet, while those in the areas not visited by tourists sought safety when people were still 30 feet away.
The research will be published in the October issue of Conservation Biology, a journal of the Society of Conservation Biology. Co-authors are Dee Boersma and John Wingfield, UW biology professors and Walker's doctoral advisers. The work was funded by the Wildlife Conservation Society, the American Ornithologists' Union and the American Museum of Natural History.
There is no evidence of short-term negative effects, such as different growth rates or weight differences at fledging, caused by distinct differences in corticosterone levels between newly hatched chicks in tourist and non-tourist areas of the reserve, Walker said. But it is unclear what later effects the elevated stress hormones might have.
"We don't know yet what it means ?it might mean nothing, but it will take more research to be sure," he said. "We are seeing evidence in other species, including humans, that some detrimental physiological changes that happen to adults can only be traced back to stressful situations or elevated corticosterone levels when they were young."