YOU MAY HAVE SEEN bluebirds slugging it out with tree swallows over the season’s lease on a particular nestbox, or a robin flying by with a beak-ful of grass, back and forth and back again to the same spot. Everybody’s nesting—but what’s the best nest material, and to a bird, what’s the definition of prime real estate? In Part 8 of our popular ongoing series, Ellen Blackstone of the BirdNote public-radio program teaches us about the diversity of birds’ nests, helping us understand what’s going on as we look skyward.

“Location, location, location,” says Ellen. “It’s important when people choose a place to raise a family, and every bit as important to a bird.” (This archived BirdNote show explains just how much so.)

“When we think of birds’ nests, we may picture the classic robin’s nest, a twiggy little cup formed with mud and grasses, holding a clutch of sky-blue eggs,” she adds. “But with more than 10,000 species of birds in the world, there are many, many more kinds of nests–some simpler, some far more complex.”

In the Q&A that follows, Ellen’s answers contain green links to audio files from BirdNote’s archive that you won’t want to miss. Next week, we’ll look at the nests of larger birds than those covered here. A recap of earlier stories in our series is at the bottom of the page, along with information on how to get BirdNote daily.

robins and the heroics of cup nests

Q. The most-visible nests here in the garden year in and out are the robin’s—sort of your basic model of what I think of as a nest. So let’s start there: What’s the robin’s approach? 

 A. Picture what the building of that “cup nest” takes: What would be the human-sized equivalent of a robin’s nest? An average robin weighs less than 3 ounces. Let’s say an average person weighs 170 pounds, or 1,000 times as much. A robin’s nest, made of grass and mud, weighs about seven ounces, so yours will weigh 450 pounds. You’ll need to collect about 350 strands of grass, each about four feet long. And don’t forget the mud: 150 pounds of it. You have five days to complete the job. Of course, being a robin, you’ll have to carry all these materials in your beak. That’s 300 mouthfuls of mud. (This popular BirdNote audio tells the story.)

Hummingbirds build petite cup nests, decorated with tiny bits of natural materials to help them blend in, like this, or like the Anna’s hummingbird feeding her young in one in the photo above.

woven, bag-like nests

Q. I’m always thrilled to see local orioles nesting way up in the biggest trees here, in their preposterous hanging pouch-like nests. Do other birds weave such nests?

A. Yes, various birds work even harder than those cup-nesting robins–orioles, as you mention, and bushtits and the Montezuma oropendola of Central America, among others, build intricate hanging bags.

The female oriole weaves her nest of grass and adds in manmade materials she finds close at hand; here’s how she does it. That’s a Bullock’s oriole nest, above. Bushtits use spider webs and other fibers in their nests.  And those oropendolas hang their nests way out from the tips of branches, the better to avoid marauding monkeys!

a roof over their heads: nests in cavities

Q. What about so-called cavity nesters?
A. Some birds nest in natural cavities, and the competition can be fierce.  Tree swallows, violet-green swallows, and bluebirds, among others, nest in holes left by broken tree branches or cavities in dead, or rotting snags. (Tree swallows love feathers in their nest, by the way.)  Many of these birds are happy in manmade nestboxes, too. Here’s how you can help,  or read our whole story on nestboxes.

Other birds excavate their own cavities. Woodpeckers are famous for that–watch out! (What’s that flicker doing to your siding–drilling, drumming, or excavating?) But much smaller birds, including chickadees and nuthatches, are also skilled excavators. And trees aren’t the only target for excavators. In the Southwest, many a bird makes its home in a cactus (like the Gila woodpeckers, above).  (An extra note on life inside a cactus: Cactus wrens orient their nests in tune with the season, to avoid the cold winds of spring and the hot sun of summer, like this.)

Other birds excavate, too–but in the ground, rather than in trees. The belted kingfisher burrows into a bank, sometimes as far as 15 feet (above photo). Burrowing owls take their very name from their nest-building habit, but they also may use a burrow once held by prairie dogs or other such creatures. (Small seabirds known as auklets also burrow into banks, as do many types of penguins.)

Some birds take the easier route, enlarging or adapting a hole abandoned by another bird that nested there the year before. Perhaps one of the most interesting switcheroos is when a bufflehead, our smallest diving duck, nests in an abandoned flicker cavity! The gaudy wood duck also prefers tree cavities or a nestbox several feet off the ground. Watch that first step, ducklings!

Q. Do all swallows prefer cavities for their nests, the way tree and violet-green swallows do?

A. No; barn swallows and cliff swallows shun cavities and instead build mud nests. Barn swallows are right at home nesting over your back porch–forgive the mess and remember how many mosquitoes they eat!

Cliff swallows construct their gourd-shaped nests out of mud, side-by-side and all jumbled together (as many as 3,700 nests in one colony in the West!).  Purple Martins often nest colonially in the East, with several pairs in a large group. In the West, the birds nest in natural cavities and also in gourds put out especially for them, often near water.

nesting on the ground

Q. What about ground nesters? It seems so unsafe, but I know some species do it.
A. It may seem strange to think that some songbirds–all of which can fly–would choose to nest on the ground, but a few do! Dark-eyed Juncos are ground-nesters, hiding their nests under a log or root or shrub. Ovenbirds take their very name from their nest–a woven dome that resembles a Dutch oven, right on the ground (photo above). Gardeners with ground-nesters in mind can create layers in their plantings.

Many other types of birds nest on the ground, often without the luxury–or trouble–of a nest. Most sandpipers nest in a shallow scrape, a hollowed-out depression on the beach or open ground, with or without any additional lining. Killdeer, a type of plover, happily nest on gravel roads, driveways, parking lots, and lawns, where their eggs enjoy natural camouflage (above photo). (And if you get too close to a nest, you’re likely to witness their “broken-wing display,” designed to draw your attention away from the eggs or young.)

Snowy plovers and piping plovers both nest on the beach, and this puts them at great risk. If you’re lucky enough to see these tiny shorebirds on a nest, please give them a wide berth.

(There’s an exception to every rule, they say. And a few sandpipers prove it, by nesting in trees. The solitary sandpiper, a bird that winters in South America and breeds in the far north, lays its eggs in the abandoned nests of songbirds!)

By the way, rooftops are fair game, too, and you might find gulls or–if you’re especially lucky–common nighthawks, nesting in the gravel on your flat roof.

‘those wacky wrens’

Q. To me the classic improviser is the wren, which I swear nests almost anywhere, often to my surprise when I come upon her accidentally.

A. Those wacky wrens deserve their own separate chapter. The marsh wren builds multiple nests. After choosing his territory, the male weaves up to 15 dome-shaped shells, known as “courting” nests, lashing together cattails, grasses, or reeds. The winter wren and its western cousin, the Pacific wren, hide their nests, topping them off with moss or twigs, like this. A Bewick’s wren nest might turn up on the rung of a ladder, long ignored in the shed, or in a can tucked away in the carport, even an old boot left in the yard. The Carolina wren, too, is not too fussy, and may choose a flowerpot or an out-of-the-way nook or cranny to raise its family.

nesting in private, or with neighbors, or not at all

Q. Do birds tend to pick a private spot, or nest near one another?

A. While some birds are territorial and won’t allow another pair into their nesting territory, other birds actually prefer company. Red-cockaded Woodpeckers of the Southeastern U.S. nest in family groups with several nest cavities in the same area, like this.  The Groove-billed Anis of southern Texas not only nest close together, but as many as five females may lay their eggs in one nest (the details)!  Red-winged blackbird males court an entire harem in their marshy domain.

Q. Anybody who doesn’t care about building, or at least claiming, a nest of its own?

A. Brown-headed cowbirds not only don’t bother to build a nest, but don’t even bother to raise their own young. Instead, they lay their eggs in the nests of other unsuspecting songbirds. Many cuckoos do the same.

how to get birdnote

FIND ANSWERS to other bird questions in the BirdNote show archives, or on their FieldNotes blog.

Meantime, listen to BirdNote’s latest podcast anytime on the player below, or by visiting their website. Subscribe to the podcast or RSS, free. More than 100 public radio stations playing BirdNote are listed here; if you like what you hear, why not ask your local station if they’ll carry it.

The BirdNote backstory: In 2002, the then-executive director of Seattle Audubon heard a short public-radio show called StarDate. “We could do that with birds,” she thought. In 2005 the idea became a two-minute daily public-radio show. Lucky for all of us!

past installments of our series

IN CASE YOU MISSED anything from my ongoing series with the daily public-radio show BirdNote:

• Week 1: How do birds make themselves at home—even in winter?
• Week 2: hummingbird migration, and on flying in formation.
• Week 3: on daring behavior, such as when a mob of small birds chase after a bigger one, or a woodpecker drums on a house.
• Week 4: whether birds mate for life, and how long they live.
• Week 5: What senses birds of prey use to hunt.
• Week 6: Bird houses, or nest boxes.
• Week 7: Bird songs and calls! What you’re hearing.

(Photos courtesy of Tom Grey, Idie Ulsh, Mike Hamilton, Kent McFarland; used with permission.)