There’s good news in a bad year for baby loons
Our Science of Summer series continues as the August days become shorter. Today Tom Spears looks at a potential risk for baby birds born late in the summer.
This summer has been torture for loons, as a huge crop of biting flies drove the adult aquatic birds off their nests across the northern U.S. states and southern Canada.
Parents abandoned their eggs in large numbers, often returning a week or two later to lay new eggs when the flies had gone. Many had babies that hatched very late in the season — in mid-July rather than the usual late May or June.
This got loon scientist Walter Piper wondering, and then writing: “Are late chicks doomed?”
The short answer is no, so loon lovers can relax.
The longer answer is more complicated.
Piper is a biologist from Chapman University in California. He has studied loons on some 200 Wisconsin lakes for 30 years.
And, while he was happy when the “fuzzball” chicks finally hatched late this summer, he worried that they might be too late to gain skills and strength they’ll need to become independent and migrate in the fall.
“Logically, there must come a date in late summer beyond which chicks run out of time,” he writes in his blog.
His team has banded 983 chicks over the years. He was able to trace the dates they were born, and count how many returned as adults.
“At the very least, we can say that chicks hatching in mid-July survive at a rate no lower than those that hatch a month earlier,” he writes. “There is a hint of a decrease in survival from early to late hatches, but it’s only a hint.”
But he also has figures to show that biting flies do affect the number of surviving baby loons. What raised his curiosity was the observation that many loon families this year have only a single chick, rather than the usual two.
His idea: That adult birds must dive into the water for relief so often, they don’t do a good job of incubating eggs, and often only one chick hatches in a nest with two eggs.
Again, he ran the numbers, checking other years with clouds of flies. The numbers backed him up.
“It seems that black flies inflict a double whammy — they cause widespread abandonment of nests, and nests not abandoned suffer from a reduced hatching rate.
“To make matters worse, cold spring weather, which prolongs the lives of black flies, also causes hypothermia of loon embryos, endangering their survival.”
This spring, of course, was cool and wet.
What he calls black flies aren’t the same type that bite people. This is an insect that preys specifically on loons, not on humans, and not even on other birds. Footnote: As of Friday, Ottawa has lost one hour and 43 minutes of daylight since summer began. We’re sorry.