This is the most important time of the year for our backyard birds. This is what it was all about, the hard work of surviving the winter or chancing mile after mile on migration to get here. Songbirds barely have time to settle onto a branch, put back some of the weight lost in winter's cold or on long flights, choose a summer territory, and then it's time to dive into nesting season.
They fill the spring with song, but it's not meant to entertain us. Song is how they stake out a claim and work to catch the attention of a mate. Next, birds scour the area for building materials, using grasses, sticks, mud, feathers or moss to build the kind of nest particular to their species.
Many of us put up birdhouses for birds to nest in, but may not realize that only about 10% of birds are "inside" nesters, making use of tree holes or birdhouses. (If there aren't enough spaces to go around for the "insiders," they simply won't be able to raise a family that year.) Most birds build in the outdoors, creating a nest on a branch or on the ground.
If things go right, when the time is right, a male and female will mate, then she settles down to egg laying. Most females produce one egg a day and don't begin to incubate them, using body warmth to develop the embryos, until the last egg is laid.
Once tiny birds tumble out of their eggs, and fill the nest, generally after about two weeks of incubation, the really hard work begins, as parent birds hustle to find enough food (almost invariably insects) to stuff down their begging youngsters' throats. On average, a bird nest will contain four young, so adult birds need to bring in hundreds of caterpillars, beetles, flying insects, sometimes even tiny frogs or toads, each and every day to meet their insatiable demands.
Parent birds begin to look a bit tattered, as they go without daytime rests and sacrifice bathing and grooming to keep up with the intense feeding schedule. Think of the American robin, a species that raises two batches of youngsters each summer: While the female starts the second nest, the father bird takes care of their fledglings, now scattered around the yard, loudly demanding feedings. He must fly from youngster to youngster to keep them fed, a much tougher job than caring for confined nestlings.
It's a similar story for most of our backyard birds, although only a few — notably cardinals, robins, house wrens, ruby-throated hummingbirds and house sparrows — raise more than one batch of youngsters during breeding season.
Surprisingly, even though their nests are well-built, designed to survive bouncy young birds, many parental landings and summer storms, birds almost never re-use their nests. Once the youngsters leave, the nest is abandoned.
