Image of mockingbird nest

Untimely Evictions: Dangers of Tree Trimming

Trim trees now to avoid harming animals in spring

Image of squirrels orphaned by tree removal
These babies were victims of poorly timed tree removal. (Photo by Humane Wildlife Services)

To most people, the tiny voices rising above the din of traffic would have registered as everyday birdsong. But to Lori Thiele’s finely tuned ears, the high-pitched staccato emanating from a neighbor’s yard last spring was unmistakable, a sure sign of distress.

“I was getting ready to go out on a job,” says the longtime rescuer and wildlife biologist. “I walked out my back door and immediately heard the babies.”

Image of baby squirrels almost orphaned by tree removal
Thiele placed them in an accessible box, hoping their mom was still nearby. (Photo by Humane Wildlife Services)

She also heard chainsaws. Crossing the street to investigate, she found young squirrels who’d been placed inside a plastic cat carrier by workers removing a tree. Knowing their mother was likely frantic to retrieve them, Thiele relocated the babies to a cardboard carrier with holes cut in the side for easier access.

When the mom failed to reappear, Thiele waited for the noise to stop and got even more creative, playing these pre-recorded baby squirrel vocalizations from her phone:

“I couldn’t even get out of the way fast enough before the mom started grabbing them—boom, boom, boom,” she says. “She came down looking for them so quickly that I just started putting them out on the sidewalk, and she had them all three tucked back in the next tree over in like 30, 45 seconds.”

Image of oriole's nest in palm frond
Orioles in California often nest behind palm fronds. When tree care workers don’t take a few minutes to inspect the tree and watch for activity, many babies end up in wood chippers. (Photo by Gillian Martin/Cavity Conservation Initiative)

Given the chance, wild parents often carry displaced babies to alternate nests. But countless animals never have that opportunity. Though it’s best to prune and remove trees after they’ve gone dormant, many babies end up orphaned because of poorly timed tree maintenance at the height of breeding season. Entire nests are inadvertently—or sometimes intentionally—thrown into wood chippers. Some are so camouflaged that losses are impossible to quantify: Tree trimming is a significant threat to the tiny, lichen-covered nests of hummingbirds. In southern California, orioles raise their young under palm fronds that are often cut away. Woodpeckers nesting in dead limbs are also lost to obsessive pruning.

Image of mockingbird parent with food for babies
To check a tree for nests, first watch for busy parents and listen for the chirping of their babies.  (Photo by Mike Fried/Comprehensive Tree Care)

Simple observation can prevent harm, says Gillian Martin, founder of the California-based Cavity Conservation Initiative, dedicated to preserving dead wood for habitat and encouraging mindful maintenance of live trees. The presence of active parents, combined with the sounds of their young, can alert tree trimmers to a growing family in their midst.

Timing is also key. As an arborist and animal rescue volunteer who helps renest raptors, Mike Fried of Comprehensive Tree Care in Frederick, Maryland, doesn’t hesitate to postpone certain tasks in his clients’ yards if he finds a nest. Last spring, he only partially pruned a dogwood after discovering catbird families, being careful to avoid the nests and the shade that protected them.

Image of hawk family taken with wildlife camera
Fried delayed pruning at his daughter’s house when he discovered this hawk family nesting. A wildlife camera tracked their development. (Photo by Mike Fried/Comprehensive Tree Care)

Pruning or removing trees in summer can harm more than just animals, often scalding surrounding plants that are unaccustomed to direct sunlight. “The majority of trees are best pruned in the dead of winter when they’ve gone dormant and don’t have any leaves,” says Fried.

Even if branches must be pruned sooner for pedestrian or structural safety, sometimes carefully reducing their lengths can keep nests intact. “The more you leave in place,” says Martin, “the better.” On a recent job, Fried left enough tree trunk for a resident mouse to continue his occupancy. “Typically dead wood is removed for aesthetic reasons,” he says. But provided it’s safe, “it’s still a good source for habitat … and there’s no reason not to leave those things up.”

A version of this article originally appeared in the November-December 2016 issue of All Animals magazine. For great advice about helping birds and squirrels who’ve fallen from nests, see the information on orphaned wildlife compiled by the Humane Society of the United States.

*Featured image of hungry baby mockingbirds by Mike Fried/Comprehensive Tree Care

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