Black flies make life hell for loons, too
Seasonal plague of flies can even drive iconic wilderness birds off their nests
This spring, Postmedia’s Tom Spears looks at our not-quite-warm, not-quite-cold season. oday we talk to a biologist who knows a type of black fly that won’t eat people, luckily.
Black flies that can create a private hell for campers are even more vicious to another species: the common loon.
May is the cruellest month for loons, breeding billions of flies that target loons in particular, showing them no mercy.
Yet in a twist, this is a specific type of black fly that doesn’t bother humans at all.
The attacker is a fly called the Simulium annulus, also known as the loon black fly for good reason. It won’t bite ducks or geese or curious biologists, but it swarms around loons.
“May is the month when black flies emerge, bite loons mercilessly on the nest, and generally make them wish they had hands instead of wings,” says loon biologist Walter Piper of Chapman University.
“They are loon specialists. They are really slamming the loons. We’ve got a lot of nest abandonment this year,” he said in an interview. Loons may try nesting again in a week or two once the flies disappear.
“It’s just dreadful. The flies are just horrendous. They need a blood meal to reproduce and they aren’t shy about getting it.”
“They don’t bite people. They are sort of attracted to us ... They will fly all around our head and sometimes land on us but never bite.”
On loons, however, they raises hundreds of “nasty” welts, many around the head and the back of the neck that make the usually sleek neck feathers look “all ruffled up and mussed.”
They stop biting at night and in cold, windy weather. But during a warm day the loon’s only defence is to dive, which takes it off the nest.
Two summers ago an unusual crop of the flies drove 70 per cent of the loons in Piper’s area off their first nests. In other years no loons are driven away. He doesn’t know what makes the fly population rise and fall.
Loons can abandon eggs for hours, but return often enough to incubate them successfully, Piper says. Otherwise the loons will have an easier time on a second nest in a couple of weeks, when there are no flies (but still raccoons and eagles and other predators).
Loons and their flies show that life in nature is never perfect, Piper notes.
“Everybody and every species has multiple things that are attacking you and chewing on you. Of course it’s an arms race. You have your own counter-adaptations in dealing with them.”