Laura Erickson's For the Birds

Tuesday, June 28, 2011

Loon Wars

Common Loon
(Transcript of today's For the Birds)
A couple of weeks ago, when I was serving as one of the leaders for Hunt Hill Audubon Sanctuary’s first annual summer birding camp, we took a field trip to Crex Meadows, in Grantsburg, Wisconsin, where we came upon a group of five adult Common Loons. When people have told me over the years that they saw a flock of loons swimming together during spring or the early breeding season, I’ve told them the birds they’re seeing are much more likely to be mergansers, but this group was close and unmistakable.
Common Loon

When we first looked at them, they seemed to be getting along okay, but suddenly a couple of them started posturing aggressively, their heads lowered, muscular necks ready to strike. Then one reared up, its massive body rising out of the water as it charged, head lowered in striking position.
Common Loon

Water danced and splashed as wings and big webbed feet flapped. We didn’t see any actual contact, but we may have missed it in the mêlée. At least two of the birds were making the loud yodel calls that territorial male loons typically make at night. Finally, one bird started running on the water’s surface and flew away, and then a second did.
Common Loon

We had no idea which birds flew and which remained, and whether any of the birds were females. It was all a summer mystery.

Normally loons don’t leave the ocean or Gulf of Mexico to return to the north until they’re three to five years old, mature and aggressive enough to fight for a territory on a lake. There can be a lot of jousting for territory—now that they can color band individual loons and even follow some with radio tracking, we’re starting to realize that loons replace one another on lakes more often than people realized. It takes a lot of fish to maintain two adult loons while providing enough nutrition for their young over a long summer, so it’s imperative that they keep other loons off their territory. Loons once ranged as far south as Illinois, but development shrunk their range, and water quality isn’t good enough in even many lakes in Minnesota and Wisconsin, where agricultural and lawn runoff fertilize the water. Excessive plant growth makes the water murkier, and water clarity is the most important feature loons need in the lakes they use.

This year the loons nesting in Eagle River, Wisconsin, abandoned their first nest when black flies got just too bad. All the rain contributed to changing water levels which would have been disastrous for loons nesting on the shorelines—properly constructed floating nest platforms rise and fall with the water level, so those nests probably succeeded. But it’s possible there was more than average nest failures first time around. Loons do renest if they lose their nest during May or early June, but the later it gets into the season, the less likely it is for an individual to be capable of breeding again. But as the loons at Crex Meadows showed, even after loons are no longer trying to breed, they still have a lot of hormones surging in their blood, making it hard to get along peacefully for any length of time. By August, they’ll be far calmer. That’s when many adults leave their still-flightless young and move off to larger lakes. By October, the adults can be in pretty large groups in some areas, most often on Lake Superior, Lake Michigan, and especially Mille Lacs Lake. People witness fewer and fewer of these exciting territorial battles as summer wanes. This was the first time I’ve ever seen it, and I took a lot of photos. But I felt stressed wondering about the reasons these loons abandoned their breeding lakes in the first place. Rather than seeing five adult loons together, I’d much rather have been watching a distant pair of loons with two chicks.

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