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Evolutionary biologist Romain Garnier could already hear the howling when he stepped out of his car on Gran Canaria, one of the Canary Islands. "They are definitely a loud bird," he says.

But Garnier hadn't traveled that far to bird watch. Syringe at the ready, he was there to vaccinate the shearwaters. Breeding bird colonies are extremely vulnerable to disease. With the birds in such close quarters, illness can be transmitted rapidly and cause massive die-offs.

A mother bird transmits antibodies to her offspring via the yolk of the egg, so a vaccinated female bird passes immunity on to her chicks. How long the immunity lasts, however, is still unknown for many species.

While in the Canary Islands, Garnier and his colleagues from the the University of Barcelona and the Centre d'Ecologie Fonctionnelle et Evolutive in France vaccinated 90 female shearwaters. They returned to the colony periodically to measure the antibodies in the offspring's bloodstreams.

The chicks exhibited antibodies for up to 65 days—long enough to mature and leave the colony. "It was much longer than we expected," says Garnier, noting that the immunity likely would have prevented a full-scale outbreak had a pathogen come to the colony.

Another surprise? The vaccinated mothers were able to pass immunity to multiple generations—for up to six years, the researchers found. The vaccinations really paid off.

Thanks to climate change, pathogens are spreading to new regions and new breeding colonies faster than ever. Birds often have no natural immunity to foreign pathogens, and many bird populations are already struggling in the face of global warming, notes Garnier.

So the , published in The American Naturalist last month, is good news. If researchers can learn about the avian immune system now, they'll be better prepared to protect threatened birds in the future, Garnier says.