Gannets abandoning chicks at Cape St. Mary’s

Josh Pennell
Published on August 29, 2014

Almost to the day, seabird biologist Bill Montevecchi got a call this August that was disturbingly similar to one he got two years ago.

In 2012, he received word the northern gannets at Cape St. Mary’s were doing something that nobody had seen them do in any colony in the world before.

Like somebody had thrown a switch, the adults, en masse, abandoned their nests, leaving their chicks alone, hungry and, ultimately, doomed.

The colony at Cape St. Mary’s has been observed for about 50 years,  but there are colonies in the U.K. that have been observed for centuries.

“Gannets never abandon their chicks,” Montevecchi says.

One parent stays with the chick while the other goes out to sea to feed and collect food for their young. There are simply too many predators around for a chick to be left alone.

Nevertheless, this year when a call came in about peculiar behaviour being noticed at the colony, it was again abandonment of the chicks by the parents, albeit on a smaller scale than the all-out desertion seen in 2012.

“What is happening this year is not as extreme, but it is extreme,” Montevecchi says.

 Montevecchi says one third of the chicks at the colony this year look as though they have been deserted.

It’s also something of a mystery. Once seabirds have invested the time and energy to have a chick, they don’t just forsake them for any reason.

The answer appears to be a rising ocean temperature and the consequences that has on the food available for the diving seabirds.

“The water temperature was outside the box extremely warm in 2012. It’s warmer this year in 2014,” says Montevecchi.

He describes it as a sudden pulse in water temperature that drives the gannets to desperately cast off — one day there and the next gone — but it’s a sudden spike caused by a long-term trend in climate change. The gannets seem to be going further and further to find colder waters and the types of fish that frequent them.

“What does that parental absence mean? It means those adults are out there hunting for food and they’re going a very long ways away,” Montevecchi says.

Those are survival trips, he adds. The adults are going a long way to feed themselves, but that means there will be nothing to feed the young when and if they come back. In the parents’ absence, the chicks become prey. They grow weak with hunger and fall off the cliffs. They starve.

Besides these long-range feeding trips, there have also been observations of gannets diving alongside fishing boats to grab smaller, discarded cod. They have also been seen scavenging fish guts, a very odd thing for a diving bird of prey to do.

“Gannets don’t go after fish guts,” Montevecchi says.

There have been incidents of kittiwakes dying on the nest due to parental abandonment.

All these factors speak to him of climate change. As far as Cape St. Mary’s is concerned, it is the most southern northern gannet colony in the world and so could be more susceptible to a rising ocean temperature. But the behaviour of these birds has big consequences for people, too, Montevecchi warns. If the fish they rely on aren’t there then the ones people rely on won’t be either.

As for the fate of the colony, there isn’t any way to undo what has been done this year. It’s a longer view and solution that needs to be found, he says.

“There’s really nothing we can do,” Montevecchi says. “But what we can do is try and understand it, which is really important.”