Sabine’s gulls are much smaller than your typical seagull, with slate-grey heads, black collars and pointy wings. They happen to be the only gull known to migrate from the Arctic to the Southern Hemisphere, traveling 29,000kilometers (18,000 miles) on its annual round-trip.
Some Sabine’s gulls travel from the Canadian Arctic to South Africa and Namibia in the Atlantic. Others migrate to the coast of Peru in the Pacific. Remarkably, biologists studying these birds on a remote High Arctic island discovered one mated pair that reunited over successive years after splitting up to winter in opposite oceans.
It seems the island in question sits along the border of two different wintering populations of the gull. What’s more, both birds traveled nearly the same distance: about 15,000 km (9,000 miles) each way. “It’s remarkable the distance is almost the same,” said Mark Mallory, a Canada Research Chair at Acadia University involved with the the study.
This is just one of several interesting findings that has stemmed from work Mallory has recently been involved in. He’s also helped identify the wintering grounds for Canada’s ivory gull, which was recently declared an endangered species following the bird’s massive population drop in recent decades. It turns out that the ocean between Greenland and Labrador is critical habitat for the bird’s global population.
The same broad area is also important for the rare Ross’s gull, according to other research Mallory helped with. Both these findings point towards the importance of protective measures for an area that’s also vital for hooded seals, polar bears and other species.
Arctic Deeply spoke to Mallory about long-distance relationships, the decline of the ivory gull population and why maintaining their breeding grounds is so important.
On the Sabine’s gulls’ remarkable monogamy:
“A lot of these Arctic birds – well, a lot of seabirds in general – have long-term pair bonds. That means they’re not exclusively monogamous but generally monogamous, at least for quite a few years in a row. That’s a real advantage to them. Normally, for a lot of these seabirds, the more experienced they are with the mate, the higher a reproductive success they have. Often it takes them a couple of years to work out all of the kinks of timing and finding food and that, and then they have high reproductive success each year.
“The fact that they would go to such different areas with obviously not a hope that they would ever interact with each other in the non-breeding season, then come back, time it so that they’re close together and pair up, and away they go again for the summer – that was really quite remarkable. I’m sure it happens in other colonies, but at least at that point in time we hadn’t heard of any reports of that previously.”
Ivory gulls were recently classified as an endangered species in Canada, after the bird’s population declined by some 70 percent over three decades. (Photo Courtesy Mark Mallory)
On the suspected reasons behind the ivory gull’s population decline in Canada:
“In my mind, probably the big reason why Canadian birds declined so dramatically was harvest in Greenland. They used to migrate right down the coast of Greenland; we know that from old banding data. They were harvested for years and years. Greenland and Denmark has really done a good job of stemming down now. They’ve got a lot of education out for people not to shoot these birds. I think what happened was the Canadian population declined probably very heavily because of harvest in Greenland.
“Probably, although we’re not positive, the birds aren’t quite as healthy as they used to be because of the contaminants. We certainly know globally, circumpolar world ivory gulls have pretty much the highest contaminants, at least in terms of birds that aren’t right besides some point-source pollution location. They’ve got the highest contaminants of pretty much all of the sea birds that we know of. They’re basically little polar bears. They follow polar bears round, they eat what polar bears eat, and polar bears are at the top of the food chain and highly contaminated, and so are ivory gulls.”
On the importance of understanding the ivory gull’s wintering grounds in the Labrador Sea:
“In terms of the Species at Risk Act in Canada, and being able to define critical habitat, this is an area that’s essential for the maintenance and well-being of the species.
“With lots of birds that are colonial we can say, ‘Well here, if you wiped out this colony, that wipes out X per cent of the population if they can’t move.’ Now this is one of the few times we can say, ‘Here’s a key spot in the winter.’ Some of it is in Canadian waters and some of it is in Greenlandic waters, but now the next step is to see about some form of marine protection for that area.
“That would be my argument anyway. Certainly, if I wanted to see something come from the results of those studies, and with all the effort that’s gone into the satellite tracking, is to use that as one arrow in the whole quiver of proof to identify some of these Arctic at-sea hotspots, or key Arctic sites. Because it so happens that the ivory gull area overlaps very regularly and very highly for part of the year with the hooded seal whelping patches – where the hooded seals come out to have their young. We also know there’s a lot of polar bears who use that area in the winter as well. Clearly it’s one of those things that Canadians might not think of, but it’s a key wintering site for iconic Arctic species.”
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