We recently had some roof work done that included having the old shingles stripped off and replaced with new ones. Such activities are a normal part of maintaining a safe, dry, and warm home. Not long after, we began to see more birds gathering and carrying various kinds of their own construction materials. They were building their “homes,” nests where they could raise their young, ideally safe from predators, relatively dry (or at least not prone to being flooded), and warm (with the biological “furnace” provided by one of the parent birds).

Some of the earliest nest-building activity that we saw this year was done by bald eagles. Several times in March we saw them carrying hefty sticks. Since eagles are one of the few birds that reuse nests—in their case, sometimes for many years—they often are just adding new sticks to what may be an already impressively large and heavy nest platform. American crows also are often seen carrying small sticks and twigs, beginning in late March and early April, for their relatively bulky platform nests.

In late April we started seeing our backyard song sparrow flying by with pieces of dry grass and disappearing into a thick shrub. Song sparrows build open cup nests that may be on or near the ground or a few feet up in a shrub.

While watching our son’s tennis matches, we began hearing in April the insistent loud “kill-deer kill-deer” calls of the aptly named killdeer, a pair of which was setting up housekeeping on top of the school roof nearby. The killdeer, slightly larger than a robin, is plover—and an example of a bird species that takes nest building to the opposite extreme. Like all plovers, the killdeer lays its (usually) four eggs in a slight depression in the ground (or in this case, the flat roof of the school). It doesn’t try to cushion the eggs with soft grass or feathers but ensures they stay warm and dry by sitting on the eggs and covering them with its breast feathers. They rely on their camouflaged brown and white bodies to make it hard for predators to spot them. If a potential predator comes too close they will feign a broken wing to draw it away from the nest. When the predator is far enough away from the eggs, the bird suddenly goes from appearing to be seriously injured to being miraculously cured and flies away.

The killdeer that nest on the roof top of our son’s school have no mammalian predators to worry about up there but they do have another, likely unforeseen, problem to deal with when the young hatch. Young killdeer are born fully feathered and able to walk within hours after hatching, and they feed themselves. The mother killdeer shepherds them around to safe places where there is available food. She broods them when it’s cool, shades them when it’s hot, and continues to try to protect them from predators. Unfortunately when the young are born on the top of a building (and this has become quite common for these and some other bird species), it’s a long way down to the ground, yet there is likely not be much food for birds should they decide not to make the leap. We know that at least three of the killdeer that were hatched on the school roof top last year made it to the ground safely (it takes a number of weeks before they can fly) and presumably made it to fledging.

Just last week we had the pleasure of watching an industrious female black-and-white warbler gathering dry leaves and carrying them into a hole under an overhanging root in a dirt bank. She was getting a new piece of construction material every 20-30 seconds then darting in with it and popping out of the hole within a few seconds for another load. Black-and-white warblers build an open cup nest on the ground but often place it in a cavity of sorts, gaining some of the benefits that cavity nesting birds like woodpeckers and chickadees derive from that nesting strategy.

As the nest-building season continues, don’t be surprised to see our feathered neighbors zipping about with all kinds of materials. Perhaps it will inspire you to fix that back fence!

Jeffrey V. Wells, Ph.D., is a Fellow of the Cornell Lab of Ornithology. Dr. Wells is one of the nation's leading bird experts and conservation biologists and author of the “Birder’s Conservation Handbook.” His grandfather, the late John Chase, was a Boothbay Register columnist for many years. Allison Childs Wells, formerly of the Cornell Lab of Ornithology, is a senior director at the Natural Resources Council of Maine, a nonprofit membership organization working statewide to protect the nature of Maine. Both are widely published natural history writers and are the authors of the book, “Maine’s Favorite Birds.”