Spring is in the air — which means nest-making season is upon us!
Birds build their nests out of everything from twigs and mud to spider silk. Some birds don’t even build a nest, and the places where they do build them can vary.
For this month’s Chirp Chat, Lake Effect’s Xcaret Nuñez spoke with Holly Walz, a park naturalist with the Wehr Nature Center, a division of the Milwaukee County Parks department.
Walz explains the role nests play and the different types of nests that birds in Wisconsin make.
Why birds build nests
Nests aren’t homes birds build to live in year-round. Instead, Walz says, birds solely use nests to protect their young from the elements and predators until they fledge.
“It's all about reproduction,” she says. “It's a very energy-expensive process… they have to have been eating well and getting the right nutrition before they can reproduce. So when [a bird] starts building a nest, they might do that together with their mate, or they might do it alone and then attract a mate. It depends on the species.”
Birds build a variety of nest types, and Walz says that’s because they’ve been able to evolve and adapt to different environments and use the materials around them.
“So birds living on the beach, they don't really perch in a tree, so they wouldn't gather sticks to take up into the tree to build a nest. Instead, they lay their eggs on the ground, and their eggs are camouflaged into, for instance, rocks around the beach or the sand. In a forest area, you have Robins who have access to mud and worm castings and grasses and twigs that they use to build their nest. So different habitats warrant different types of nest building.”
While nests are great to admire from a distance, it’s important that people leave nests alone, Walz says.
“If you do see a nest, it's OK to look at it a little bit, but when you repeatedly come back to a nest, there are certain types of predators that actually follow human scent, like cats and canids, and they could eat the birds in the nest just because you had walked there. So it's a good idea to not revisit a bird nest once you've seen it.”
Most nests are also protected by the Migratory Bird Treaty Act, which makes it illegal for anyone to keep, move or destroy a bird nest without a permit issued by the U.S. Fish and Wildlife Service.
Different types of bird nests
Walz describes a variety of nest types that certain bird species will make when nesting in Wisconsin, including:
Cup Nest
A variety of birds build cup nests, which are often held steady by a base of twigs, bark shreds, grasses and mosses. They’re also held together by a layer of mud, spiderwebs, fur and hair.
“The cup is shaped by the female bird's body,” Walz says. “It’s fashioned that way so that the eggs are kept warm enough. And most protected birds like Goldfinches and Northern cardinals and American robins, they all build cup nests, but they all use different types of materials according to where they live. Goldfinch, they live in the grassland, so their cup nests are made out of plant fibers and different types of downy seeds. And Northern cardinals build cup nests out of twigs in the forest as well.”
Weaving Nest
Some birds, like Red-winged blackbirds, build weaving nests by intertwining plant fibers with knots and loops around branches.
“I like [Red-winged blackbird] nests because they're really just kind of hammocks hanging over the water,” Walz says. “They build them with wet vegetation, grasses, cattails, anything that's been soggy for a while, and they weave it in between plants that are in the water or very close to the water. As those plants dry, it just holds into a great little hammock that she can sit in and disappear. The female red-winged blackbird is brown and speckled and not at all like the male. She’s so camouflaged she blends right in.”
Cavity Nest
Cavity nests can be naturally existing holes in a live or dead tree, or made by birds that excavate holes into a dead tree, log or pole.
“They'll either enlarge [a hole in a tree] with their beaks, or they'll make their own in the case of woodpeckers,” Walz says. “If the wood is really soft, a chickadee can hollow out their own nest, they are cavity nesters as well. Sometimes they line those nests with plant materials and feathers, but sometimes they just leave the wood chips in there and lay their eggs right on the wood chips, in the case of Red-bellied woodpecker.”
Scrape Nest
Scrape nests are small indents, holes or divots dug into open ground in sand, dirt or gravel environments, and they’re sometimes lined with soft material like leaves and feathers.
“We have wild turkeys at the (Wehr) Nature Center, too, and they do not do much of nest building,” Walz says. “I wouldn't call them lazy. It's just that they're ground nesters, and maybe there's just not much that they can gather around. So they'll scrape away the leaves that are on the ground and lay their eggs there. They're perfectly camouflaged to blend in with the surroundings, so they build a type of scrape nest.”
Mud Nest
Mud nests are primarily made from mud and dirt and are often mixed with materials like grass, hair and feathers. They’re also usually found on the sides of vertical structures like inside barns, under bridges and cliffs.
“Can you imagine carrying all of that nesting material, mud in your beak, to the eaves of the building,” Walz says. “They'll even reuse their nest that they've built, it's so energy-intensive. So if there are no parasites or mites in their nest, they’ll reuse the same nest in another year just by removing any feathers or previous year’s nesting materials inside.”
Chirp Chat’s Bird of the Month for March
Walz says Sandhill cranes are among the oldest living bird species, with fossil records dating back to 2.5 million years and some scientists believing they may have existed up to 6 million years ago.
“[Sandhill cranes] are really dinosaurs walking around us,” Walz says. “And they signify spring — when you hear Sandhill cranes, you know it's right around the corner.”
Walz also says Sandhill cranes mate for life and build their nests in wet, marshy areas.
“I have only been lucky enough to see a Sandhill crane nest once, and it was in the Vernon Marsh, and it looks like a hammock,” Walz says. “So it's a bunch of plant material that they heap together, and then the female will make a cup in the center of it with her body. So it just looks like a mound in the middle of the marsh. It's hardly even visible.”
