Birdwatch

Nesting Season

There’s no place like home

By Susan Campbell

It is almost that time again for our feathered friends: nesting season. Pairs of birds will team up to bring forth the next generation. In some cases, they will even repeat the process once or twice before the days shorten and temperatures begin to drop.

As with so many behaviors, reproduction is triggered by hormonal changes, which are the result of changes in day length. Females will become responsive to the advances of males as daylight increases. And before long, the hunt for a spot to nest will begin. Interestingly, the strategies vary among the bird species we find in central North Carolina.

The investment in nest building for some species is minimal. Killdeer, for instance, only create a slight scrape in a sandy or pebbly surface. They are ground nesting birds whose splotched eggs blend in perfectly with the substrate. Furthermore, killdeer young are precocial, meaning that they are mobile as soon as they hatch and will instantly begin following their parents. There is no nestling phase, so protection of the young birds is unnecessary.

In the Sandhills it is not unusual for mourning doves to nest at ground level in a layer of grasses or small twigs. Even when doves nest in small trees or shrubs, their nest platform is minimal. It is amazing that the eggs or young do not fall through the nest. Then again, this species is known to raise young in virtually any month of the year, so losing an egg or youngster through the cracks is not problematic in the long run.

Cup nests are a very common strategy for nesting — especially among songbirds. Northern cardinals, blue jays, American robins all form a typical nest from small branches, twigs and grasses. Such nests can be visible through the leaves and are not infrequently depredated. As a result, some species, such as blue-gray gnatcatchers and ruby-throated hummingbirds, have evolved to use camouflage in the form of mosses or lichens on the outside of the cup so that the nest is not obvious to predators on a bare limb.

Hawks and eagles have taken nestbuilding to the next level and may create an enormous, cupped platform for their young. These huge stick nests, placed high in a live tree or snag, typically are enlarged with more material every year. They can be very noticeable given their bulk. However, given the size and ferocity of these birds, the strategy is not problematic. Furthermore, one of the adults typically guards the nest until the young are close to fledging.

And then there are the species that use holes: the cavity nesters. Woodpeckers and nuthatches can carve out a cavity in dead wood using their powerful bills with little trouble. Species such as chickadees, titmice, bluebirds or wood ducks will move right into these spaces when the architects move on. It is these birds that many of us have been giving a helping hand by erecting bird boxes. Box design varies by species, of course, given the different reproductive requirements of different birds. The height, the depth of the box and, most importantly, the size of the entrance hole will determine who will move in.

So, if you have not yet done so, this is the time to be cleaning out and repairing nest boxes for the breeding season. Old nests should be removed, and the boxes should be aired out for a day or two.  It would not hurt to give them a rinse with the hose as well — but do NOT use cleaning products. And then stand back: It will not be long before your first feathered tenants will be moving in!  PS

Susan Campbell would love to receive your wildlife sightings and photographs at susan@ncaves.com.