Flight Lines: When it comes to nesting, the sky's the limit
It's empty now, exposed to the elements and slowly deteriorating. It's assuming the look of unkempt hair, messy, scraggly, loose pieces swaying to the whimsical breeze. I see it every morning when I open the kitchen blinds; about 10 feet above ground, it sits atop a lateral branch stemming from my neighbor's crabapple. It doesn't seem that long ago when this delicate structure was the hub of bustling activity. The American robins that raised a family here are gone. But their nest remains, an ephemeral monument to those precious few frantic weeks.
It was a shielded and shadowy place then, nearly invisible in a cocoon of apple leaves, the ideal location for bringing off a family. It's still a magical place even today. To think that in those few short weeks, this nest was built, eggs laid, young hatched and raised, and ultimately fledged from this temporary location now abandoned. The pace alone is staggering, the mystery behind it even more so.
Nests are critical for bird parents. They keep the eggs in one place aiding incubation, shield the eggs from predators, and protect the precious packages from storms, heat, and cold.
Our robins build a nest type all of us are familiar with called a cup. Scientists describe and classify, however, about a dozen nest styles from floating platforms (think loon or grebe) to a simple scrape on a cliff (peregrine falcon) or even on the ground (killdeer).
Nesting habits among birds run a stunning gamut. There are species familiar to North Dakotans that nest underground. Burrowing owls are among the few that raise their brood there. Usurping burrows from other animals such as badgers, the lanky owls to not themselves excavate, nonetheless have adapted to life below the surface. Belted kingfishers and bank swallows actually perform the digging themselves.
Most nests are fleeting temporary arrangements designed to last a single nesting attempt. Bald eagles, though, erect structures on a more permanent basis. The large raptors can't seem to turn off the building instinct and add sticks to their large platform nests every year. Some weigh a ton or more.
Outside my window robins built then abandoned their nest in less than five weeks. Contrast that with a nest site on the British coast that has been continuously occupied by peregrine falcons since the Elizabethan era, over 400 years.
There are some species that have so adapted to life with humans they show an overwhelming nesting preference for manmade structures. Barn swallows, house sparrows, and chimney swifts come to mind.
Some species recognize the security from proximity to raptors and will actually nest within the structure of eagle or hawk nests. There was even a case in Florida where a great horned owl nested inside a bald eagle nest and both incubated eggs within a few feet of each other!
It would be a misnomer to call a nest a home. Birds really have no homes, per se, instead occupy a certain amount of space for various purposes throughout the year. No, nests could more aptly be called nurseries, the place for the critical raising of the next generation.
The work required at these nurseries can be as simple as finding an okay spot on a gravel road in the case of a killdeer mother or making tens of thousands of pokes weaving filaments of grass and other fibers into an oriole's dangling hammock nest. Or bringing back hundreds of mouthfuls of mud from the nearest wallow used in the adobe nests of cliff swallows.
We once believed the blueprint for nests was hardwired into a bird's DNA. Newer research is finding that, while the basic plan stems from that source, learning actually takes place. That is the older a bird gets the better its choice of location, the more sound the nest construction. The birds are probably even learning from observing others of their kind.
There is still a lot we don't understand about nesting birds, most choose to do it rather secretly. Your observations could actually add to the body of knowledge. But be cautious during this critical period. If a bird flushes or quits feeding young, you are too close. Back away. But be that vouyer, be the nosy but discreet observer, you just might be the one to witness some previously unknown behavior and share it with the rest of us.