In March 2021, a Facebook post circulated, warning readers not to leave certain materials for birds to use in their nests:
Please DO NOT offer yarn, string or human hair for birds to build nests! Every year we see both young and adult birds…
The post offered text alongside a screenshot of an image from the page “Wildlife Rescue Nests” showing a box containing colorful scraps of yarn and string:
Please DO NOT offer yarn, string or human hair for birds to build nests! Every year we see both young and adult birds being admitted to wildlife rehabilitators due to this. It can sometimes result in the bird losing their foot or entire leg from the yarn/string/hair slowly tightening and cutting off circulation[.]
DO NOT offer laundry dryer lint either. The lint collected in your dryer filter may seem like ideal nesting material, but it isn’t. It will soak up water and may be steeped with chemicals unhealthy for birds, such as remnants of detergent and softener.
Also a warning about offering pet hair. Many of our pets are treated with specialty shampoos or tick/lice treatments which stay on the hair and can be harmful to birds collecting it for nesting material. DO NOT offer pet hair that has been exposed to any shampoo treatments or chemicals.
In the second part of the post, the user listed six purportedly safe alternatives to yarn, string, or dryer lint for birds’ nests:
For birds looking for small twigs, almost any tree or shrub you plant will do. When small branches or twigs fall from a shrub and gather at its base, leave them for birds to pick up, preferably in lengths under 4 inches.
Some birds line nests with soft plant matter. You can provide this accoutrement by growing catkin-bearing trees and shrubs such as cottonwood, maple, mulberry, willows, poplar and beech.
Many birds—hummingbirds spring to mind, but other songbirds as well—gravitate toward fluffy material, such as seeds with silky attachments designed to waft them on the wind or seed pods with a soft, hairlike covering. You can provide these items via cottonwood trees, lamb’s ear (ground cover), milkweed (also good for attracting monarch butterflies), honeysuckle, and clematis.
If you have a pesky spot in your garden that refuses to grow anything but dirt, try adding a little water and see if you can grow mud. Mud is a favored nesting material for swallows and swifts and even the common robin.
When you trim your yard, perhaps you can find a spot in your garden for laying out a selection of dried grass stems cut 2 to 4 inches long. Grass is a common ingredient in songbird nests, used by species from native sparrows to robins.
If you have a shady spot in your yard, trying growing moss; with its velvety green growth, moss is a beautiful highlight for any moist garden and is a favored building material of some hummingbird species.
The screenshot appeared to be a very popular February 28 2018 post by “Wildlife Rescue Nests.” The text from that post was identical to that of the February 28 2021 post, down to an extra space before the first period:
This photo has been making the rounds again this year…
Please DO NOT offer yarn, string or human hair for birds to…
An “About” tab for Wildlife Rescue Nests read:
The home of “Wildlife Rescue Nests” for licensed wildlife rehabilitators. Join our volunteers who provide nests to over 500 rescues in 14 countries!
A 2019 blog post (“Safe Bird Nesting Material”) from the site OurHerbGarden.com indicated that advice to save scraps of yarn, string, and dryer lint is common on social media — and that another wildlife rescue organization had also warned about the risks:
OK, who hasn’t seen the suggestion to put scraps of yarn, twine, string and even human hair out for the birds during nesting time? In principle, it sounds like a great recycling idea. Make use of the little bits and pieces that would normally be thrown out and help the birds make sturdy and comfy nests for their eggs and hatchlings. And, how fun is it to see bits of color in the nests?
A Facebook posting from the folks at Carolina Waterfowl Rescue quickly educated me that this act of kindness is anything but kind to our feathered friends.
Our good intentions have led to some horrendous outcomes.
Every year, the rescue organization takes in baby songbirds that have terrible injuries from these good intentions. The fibers may tangle around the bird’s legs, neck or wings. They act like a tourniquet and cut off the blood flow and cause injuries that can lead to loss of limbs and even death.
We visited the “Carolina Waterfowl Rescue” Facebook page and found a version of the image of “nesting materials” in a February 29 2016 post, which began:
We’ve been seeing a lot of online posts lately suggesting using yarn scraps, twine or other material as outside nesting material for songbirds. While the intentions are good, please do NOT do this.
Birds should be able to find their own nesting material and do not need our help. If you insist on providing nesting material please look for natural materials.
Yarn and any type of string, twine and even human hair can easily become tangled around birds legs, neck etc. and cut off circulation causing serious injury or even death. We get in many baby songbirds every year missing limbs due to string like materials in a nest. These are also choking and obstruction hazards when other animals eat them.
A post on the U.S. Fish & Wildlife Service’s site (last updated in December 2019) included a “staged photograph” of a suet cage of yarn scraps; it explained:
Avoid: String, twine, yarn, dryer lint and pet hair
Providing lint and yarn in a suet cage can be hazardous to birds. Staged photo by Courtney Celley/USFWS.
String, twine and yarn can get wrapped around the legs and necks of birds and nestlings, cutting off circulation and often resulting in death. Stringy items can also become a choking hazard if mistaken for food. Never offer dryer lint as it could contain chemicals that are harmful to birds. Pet hair may also be dangerous due to chemicals from flea treatments and shampoos.
An April 2019 Audobon.org “News” post (“What Nesting Materials Are Safe for Birds?”) concluded with a “Materials to Avoid” section:
Materials to Avoid
Human hair: According to Gordon, human hair is a triple threat for birds: It’s long, thin, and strong. These characteristics can be a deadly combination, allowing the hair to easily ensnare a bird’s leg or wing and sever it. “You can wrap [hair] around your finger and cut your circulation off,” she says.
Yarn or string: Long strands of yarn and string can wrap around a bird. Hatchlings are particularly susceptible to such entanglements, Gordon says. Yarn in a nest can get caught around a baby bird and cut off circulation as it grows.
Dryer lint: Although it is popular to put out and seems like the perfect lining for a nest, dryer lint quickly loses its fluffiness and structure when wet. Dryer lint is unsustainable in the rain, crumbling and leaving holes in an otherwise solid nest.
Cornell University’s Cornell Labs All About Birds site also referenced the popularity of leaving dryer lint for birds, placing the substance on their “Don’t Provide” section. As for the six items listed in the Facebook post’s “safer alternatives” section, it was (as indicated) from a 2014 National Wildlife Federation blog post titled “How to Offer Bird-Nesting Materials in Your Garden.”
Another section simply stated:
Don’t Use Dryer Lint!
The lint collected in your dryer filter may seem like ideal nesting material, but it isn’t. It will soak up water and may be steeped with chemicals unhealthy for birds, such as remnants of detergent and softener.
In 2016, 2018, and 2021, a photograph of a hanging cage containing colorful scraps of string and yarn circulated, alongside warnings about inaccurate social media posts advising the materials be left accessible to birds as materials for nest-building. The claims were accurate — wildlife rehabilitators and advocacy groups repeatedly warned that yarn, string, twine, and dryer lint could pose serious risks to birds. The same organizations recommended twigs, moss, plant matter, mud, and dry grass as safe alternatives for people who wished to leave nesting materials out for birds.