Back in the '50s, a great horned owl was using an old hawk's nest adjacent to the "City 40," a plot of land the city of Bend used for sewage affluent, and I took a librarian out to see the nest, hoping to impress her with my acumen and coolness. She, however, impressed me with her keen interest and wanted to climb up and see the baby owls. "You bet!" I said, and up she went. Just about the time that lovely young women peeked over the lip of the nest - right out of nowhere - a magnificent, very large golden eagle swooped over her head.
The adult owl leaped into the air with the eagle in hot pursuit, and crashed into a willow thicket along the irrigation ditch. Needless to say, this was an unexpected event for all participants. When the shaking librarian arrived back on the ground she said, "Don't call me, I'll call you," and I never saw her again...
Anyway, about nesting birds: A bird nest is a place (location or object) in which (or where) a bird deposits its eggs to incubate them and feed nestlings to fledgling age. The grass and mud cup made by robins is just one example. Long-eared owls use the top and inside of magpie nests. Short-eared owls, on the other hand, are ground-nesters. In fact, I do not know of any owl that actually "builds" a nest.
Woodpeckers are famous for the cavities they excavate in trees and stumps as a place to raise their young. In our part of the country, such cavities are vital to other birds (and bats), such as saw-whet and pygmy owls, chickadees, nuthatches, fly-catchers - and the damnable house sparrows and European starlings. The latter two are competitors for native birds, both for food and nesting substrate.
I am not an advocate of killing animals (except for legal food), but if we don't do something to curtail the growing population of these two species, we will lose a lot more than our native birds. Please do all you can to eliminate house sparrows and starlings. It is legal to destroy them.
Hummingbirds build a tiny cup nest held together with spider webs and soft plant tissue. When you observe a hummingbird dipping into a flower for nectar, you don't see the other things they eat, such as tiny insects and spiders - one cannot live on sugar alone. (Speaking of hummingbirds, if you have a feeder up, please do not use red food coloring in the sugar syrup; it is not good for hummingbirds, or people.)
Cowbirds lay their eggs in other birds' nests - such as the brewer's blackbird or robin's cup nest. Why, you ask? Because cowbirds are a transit species, never stopping to build a nest and raise babies. They use surrogate parents to do it for them. Mom cowbird then watches patiently for the foster parent to raise her nestlings, and just as the young cowbirds fledge, mom and dad cowbird come back to get them.
Swifts build a nest out of spit, grass and small sticks. Chimney swifts glue the whole shebang to the inside of a chimney, lay one or two eggs in the tiny cup and probably hope no one gets cold in the house and builds a fire.
Swallows use spit and soil to make mud nests they glue to rocks, under eaves of houses and other handy spots. Swallows are akin to bats at snatching up mosquitoes and other tiny flying insects. It is not exaggerating to say swifts and swallows will devour tons of mosquitoes and gnats in one nesting period.
Great blue herons and others of their ilk build a clumsy stick nest in trees and shrubs. Never go near such nesting areas! Young herons are notorious for leaping out of nests when disturbed. Robins do the same. While it's relatively easy to put a robin in (or near) a nest, hauling a heron or egret back into the nest will cause more problems that you can imagine. It's a really a good rule-of-thumb to leave all nests alone.
Springtime in our neck of the woods is usually cold and windy. Baby birds that hatch in nests are reptilian all through their young and tender weeks. Unable to manufacture any body heat for themselves, they therefore depend entirely on mom or dad to keep them warm. Spook the parents off the nest on a windy, cool or rainy day and its curtains for the kids - even hawks, eagles and owls.
The common nighthawk(s) we see swooping around at sunset, scooping up insects in their gaping maws, nest on the ground. I think they're like the killdeer; the female will fly around until suddenly she says, "Uh, oh, it's time, dear!" Down they come and lay their eggs, sans nest. Unlike the killdeer, which is noisy with babies running around minutes after hatching, nighthawks depend on camouflage to hide them. You can't see a baby nighthawk unless it opens its jewel-like black eyes, so please, be careful where you step if a nighthawk suddenly flies up into your face.
If you would like a free nesting box guide, send me a 5x7 SAS envelope (two stamps), and if I don't forget, I'll send you my booklet, which includes bird feeders and a bat roost. P.O. Box 1513, Sisters, OR 97759.