The 10,000-plus North Carolinians who answered Audubon NC’s recent call and established nest boxes for habitat-challenged brown-headed nuthatches may be wrestling with a puzzle this spring.
Are those tiny white and blue-gray birds zipping into the box, their beaks full of squirming cankerworms a hard-pressed parental pair?
Or could they be offspring from last year’s brood, or the year before that, or the year before that – who never left home and are helping Mom and Pop with the feeding chores?
You guess is as good as anybody’s, says one scientist who can keep the generations apart only by reading the color-coded leg bands she put on 600 of the birds at north Mecklenburg County golf clubs.
Brown-headed nuthatches (Sitta pusilla) all look exactly alike, except perhaps to each other, says Esther Niemasik, who studied them on her way to a doctorate this spring at Cornell University in New York.
And, in a departure from typical bird behavior, they practice cooperative breeding.
Grown birds from one nesting, usually male, often hang around home for at least another year, where “all group members work together to feed the nestlings.” Niemasik has seen as many as eight adults handling the chores.
Only nine percent of bird species are cooperative breeders, including the American crow and the federally endangered red-cockaded woodpecker of the Sandhills/Fort Bragg and Camp Lejeune areas.
Niemasik, who studied neurobiology and bird behavior, had always been curious about the practice, and when her former Davidson College professor, Mark Stanback, put up nuthatch boxes at six golf clubs, she asked in 2011, “How would he feel about me stealing his nuthatches for five years?”
Stanback has long been a fan of nuthatches and what he described as “their squeaky-toy, rubber-ducky voices.” He told her to go ahead, and with nets and tiny banding strips – the 4-inch birds’ leg-banding size is listed as zero – she made a big swath through north Mecklenburg’s nuthatch population at Northstone, Birkdale, The Peninsula, Trump National, Mallard Head and River Run golf clubs.
“They’re so personable and fun to work with,” she said. “They have great personalities... very chatty. They’ll sit next to each other on a branch and allopreen (groom) each other all the time.” It’s like humans touching hands, she said, but it smooths and oils feathers.
Nuthatches will “bury their beaks in the spots that are hard to reach for the other bird,” she said, but only for family members. Otherwise, “It would be like you walking up to a stranger and hugging them.”
The woodpecker way
Red-cockaded woodpeckers “treat as kin anybody that was there in the (family) territory when they were hatched out.” said Jeff Walters, a Virginia Institute of Technology ornithologist who has studied them for more than 30 years.
These woodpeckers don’t allopreen, but one dominant male from each generation helps feed successive nestlings and, in a bird version of primogeniture, inherits the parents’ nest box if it should become vacant.
While crows’ stay-at-home ways are mostly seen as a maturing process for the young, nuthatches and woodpeckers have their temporary helper roles forced upon them by the scarcity of suitable nesting sites, a result of both species’ peculiar nesting needs. Most eventually start their own broods, though Walters said, “We’ve had birds still living at home that were 12 years old.”
Only pines 100 years old or older have the amount of relatively soft heartwood that the woodpeckers (Picoides borealis) need to drill nest cavities in. An entire family will spend years drilling the hole and pecking away at surrounding bark to make snake-discouraging sap flow in silvery rivulets down the tree.
In the case of nuthatches, it’s a matter of competing for a site. Even when a nest-box entrance hole is downsized to exclude larger birds, as the Audubon-promoted boxes have been, chickadees and house wrens can be formidable competitors.
Though the helper role may be involuntary, Nature offers some help.
Helper woodpeckers, who sit on the eggs just like the parents, undergo the same hormonal changes parents do, developing brood patches on their breasts before the eggs are even laid. Lots of close-to-the-surface blood vessels create extra warmth there.
Niemasik was amazed to find that helper nuthatches not only bring food to their parents’ nest, but they’ll also assist other family members. If feeding help is needed, they’ll fly over another bird’s territory – about 400 square yards – to get to the relative, she said.
She thinks that perhaps the hippocampus – the part of the brain that in both birds and humans remembers locations – is involved. The nuthatch hippocampus is one of the largest, relative to size, among birds, she said.
Want to help?
If you want to host nuthatches and have nearby pine trees – they eat pine seeds and pine-dwelling insects –Audubon NC offers free devices to downsize entrance holes in bluebird boxes. Info: email firstname.lastname@example.org.