Weather gives a cold shoulder to songbirds
Here in the north, we tend to think we’re far removed from what happens in the southern United States.
Yet weather events along the Gulf Coast and Mexico border states can have ripple effects even up here, in the shadow of Canada.
Hurricanes may lead seabirds to wander far inland, resulting in such sights as a magnificent frigatebird cruising the skies around Wausau, Wis., and over the Straits of Mackinac in September 2017.
This year, the extreme cold that crippled Texas in February may have taken a toll on more than humans, one that now can be seen — or, more accurately, not seen — in Wisconsin and Michigan.
The Wisconsin Bird Conservation Partnership announced earlier this month that some songbird species that normally would be back in the region by now are conspicuously late or absent from their usual nesting sites.
“Have you noticed fewer bluebirds in your part of Wisconsin so far this spring? Many observers have,” the partnership said in a statement. “Although some are yet to return, especially up north, it appears overwinter mortality may have been significant this year due to freezing rain, ice storms, and prolonged periods of exceptional cold across the southern and central U.S., where this short-distance migrant spends the non-breeding season.”
Those conditions may have caught flycatchers such as eastern phoebes — a common summer yard bird in the region that frequently builds nests above lights and other places it can situate itself under eaves — out as well.
The biggest threat to these insectivore species was not exposure to the freezing temperatures but starvation, said Laura Erickson, an author in Duluth, Minn., who was science editor at the Cornell Lab of Ornithology and has the blog site For The Birds at https://blog.lauraerickson.com/.
Insects and other cold-blooded prey won’t venture out in such conditions, leaving birds with little to eat, Erickson explained. While some such as American robins can turn to berries and fruit, many of the insect-eating types are not adapted to switch up their diet.
She heard reports of people down south who found dead adult bluebirds inside nest boxes they were tending. Other species that might have been affected include several types of warblers, she said.
“It’ll be interesting — and hopefully not too depressing — seeing what kind of numbers we get this year,” Erickson said.
In this region, migration for some songbirds also has been slowed this year by persistent cooler temperatures and wind flows going the wrong direction, so it’s possible some of these missing birds got delayed.
The WBCP’s advisory wasn’t completely grim, either. Even if bluebirds took a hit this winter, “the good news is that populations of this species are healthy and capable of quick rebound because they often raise two to three broods of four-plus young each year,” according to the WBCP, which added, “Help them recover by providing nest boxes, avoiding pesticide use and planting native food sources.”
At Six Mile Lake, both the phoebes and now at least one bluebird have turned up. The phoebes actually have been present for a couple weeks, using a favorite nesting site in the fork between two lights on my mom’s quilt shop.
It led me to wonder if these might be the same pair that has raised young here in the past, or perhaps the offspring of past phoebes that nested in the same site under the eaves.
It’s possible these phoebes do have some past tie that drew them back to the location, Erickson said. Phoebes and robins will return to a site where they’ve had past nesting success.
But if something happens to the original pair, they might be replaced by an offspring — or another phoebe couple in the neighborhood may notice the empty nest and claim it as their own, she said.
A number of bird species that form stable breeding pairs and share in raising young will repeatedly use the same area and even the same nest if possible, Erickson said. This includes common loons — the world’s oldest loon pair is on its 25th year at Seney National Wildlife Refuge in Schoolcraft County — and Canada geese. Bald eagles are “famous” for sticking with the same nest.
“If it’s worked in the past,” Erickson said, “they’re happy to stay with it for life.”
But if it’s a species in which the male does little in terms of parenting, such as mallard ducks, the dynamics work a little differently, she said. While female mallards might venture back to where they hatched, young drakes from here will first begin forming a relationship with young hens at wintering grounds such as Louisiana, then follow the female to wherever she heads, Erickson explained.
Dispersing the males like this is “a really good way of keeping a species that’s fairly promiscuous from inbreeding,” Erickson said.
Though it offers stability and proven success, favoring the same nest does have some disadvantages, she added. “Yucky” parasites such as lice, mites and even fly maggots may manage to overwinter in these nests, posing a risk to the next brood of chicks.
It’s why chickadees will continue to excavate tree cavities, even ones that already appear large enough, to hopefully remove any parasites still lurking in the wood. Studies showed chickadees that used nesting boxes favored ones with fresh wood chips added “so they can feel like it’s excavated,” Erickson said.
Parasites are the reason as well that those who tend bluebird houses will remove the previous year’s nesting materials and scrape out the bottom of the boxes to evict anything still inside.
Erickson recommended taking down used phoebe nests in spring, if possible, before they’re sitting on eggs; the phoebes will quickly build a new one on the same spot. Their nests are a marvelous combination of mud, lichens, woven grasses and hair or fur, with a fringe of green moss, she said.
Phoebes, by the way, reportedly were the first birds banded in North America — by ornithologist and painter John James Audubon, no less, who wound a light silver wire on the legs of fledgling phoebes to determine if they would return to the same area, Erickson said. He claimed they did, although that has been challenged by modern researchers who maintain the percentage of young phoebes that come back to their hatch site is fairly small.
Those researchers were willing, however, to give Audubon credit for the leg band idea.
Betsy Bloom can be reached at 906-774-2772, ext. 240, or firstname.lastname@example.org.