Beaks and Bills
by Joe Meche
Joe Meche is a past president of the North Cascades Audubon Society and was a member of the board of directors for 20 years. He has been watching birds for more than 60 years and photographing birds and landscapes for more than 40 years. He has written more than 145 articles for Whatcom Watch.
Try to imagine needing to build a new house every year to accommodate a new family of two to four offspring, and then feed and nurture them until they leave home … in two to four months. Consider the process involved in building this temporary home that you’ll occupy only long enough to see the entire family leave, just after it becomes comfortable … and then do the same thing next year. Millions upon millions of birds do this annually and even though some species remodel and reuse old nests, most of their efforts involve new construction.
Unlike most animal species, birds do not give birth to live young. We know they lay eggs, but before there are eggs, a space needs to be created, not only to hold the eggs but also to protect them throughout the incubation period and until the young of the year have fledged. Nest building is a necessity for birds and is the single most demanding commitment of time and energy that a bird will ever make. In many species, the entire process of building and maintaining nests involves both sexes. The very survival of their species depends on them to carry on the next generation.
When the time comes for nest building, every bird has a specific design that is the epitome of form and function for that particular species. From simple cup-shaped nests to elaborate stick construction, nests are remarkable feats of avian engineering. An important thing to keep in mind is that all of the construction is done using the simplest of tools. Birds use their beaks and bills along with their feet to gather the perfect building material to create their nests. From the swallows that make elaborate mud nests by the mouthful, to eagles and ospreys that create huge stick nests, all of the work is done methodically using techniques that have been passed down through multiple generations.
The wide diversity of birds calls for an equally diverse choice of nest sites. The often heard mantra of realtors everywhere is “location, location, location.” The same concept applies to bird nests. Birds have a large amount of control when it comes to finding suitable habitat for nesting in the right climate, and that is one of the primary goals of migration during the spring. When these requirements are met, protection from predators then becomes the highest priority. According to noted naturalist Alexander F. Skutch, the main factors that contribute to nest safety are “invisibility, inaccessibility and impregnability.”
The cryptic coloration of many birds’ nests and eggs make them practically invisible to most potential predators. Nests are built on sheer cliffs and behind waterfalls, on floating platforms and in deep burrows and cavities to provide safety for the nest and the nestlings as well as the incubating adults. These are very important safeguards when you consider that nest predation accounts for the highest percentage of breeding failure in most species.
Birds that nest on the ground are more vulnerable than other species, for obvious reasons. Colonial nesting has provided success for many ground nesters, but there are drawbacks to this approach. The increased demand on the site itself to support large numbers of birds is critical. There is much competition within the colony for food and nesting material, but the tradeoff comes in the apparent safety in numbers. Predators are often discouraged when set upon by an entire colony of angry birds.
The entire nest building process is a major part of courtship and pair bonding between males and females. After the nest is complete and the female is incubating the eggs, the male is at his territorial best to protect his mate and the eggs from predators and other males. When hatchlings are in the nest both sexes participate in the care and feeding of the young birds. In some waterfowl species, on the other hand, the males abandon the females when nesting time rolls around.
Again, the design and shape of individual nests is species dependent. The size of nests runs the gamut from the miniature nests of hummingbirds to the large nests of bald eagles. Nests of large predators like eagles, ospreys and hawks are often added to year after year creating massive structures that last for several generations. The single best way to find these structures is to locate them in winter when the trees are leafless and the nests are open to view. If you’re diligent about monitoring these large nests, make note of their locations in winter and keep tabs on them as the nesting season progresses.
One of our largest and most recognizable species, the great blue heron, builds a stick nest in trees. Herons and other large wading birds are often colonial nesters and such is the case with the herons at the wastewater treatment plant on Bellingham’s southside. The city of Bellingham has done a wonderful job of cordoning off the nesting area while simultaneously providing ample viewing opportunities for the public.
In May and June, the local nesting scene is quite busy across a broad range of species. Gulls are prolific breeders and can be found nesting on rooftops and marina breakwaters, often competing for breakwater space with double-crested cormorants. Killdeer utilize a mere scrape on the ground to lay two or three eggs that blend perfectly with the surrounding gravel. Adult killdeer engage in their unique broken-wing distraction display to lure would-be predators away from their nests.
Most of our songbirds conform to the general concept of a bird nest, building simple cup-shaped structures to lay their eggs. Two notable exceptions are the Bullock’s oriole and the bushtit, which build more elaborate hanging nests that can be found in suitable habitats. Woodpeckers build their nests in trees and begin with a perfect entry hole, after which they excavate constantly until the interior dimensions are perfect. Old woodpecker holes often provide nesting cavities for smaller birds like chickadees and nuthatches.
The swallows that nest locally are quite diverse within the family. Tree swallows are cavity nesters, barn swallows build shelf nests, and rough-winged swallows nest in burrows or holes that they create in sand banks along streams. The most creative and ambitious of all swallows are the cliff swallows. Nesting in dense colonies under bridges or the eaves of houses and barns, these marvels of the avian world build their nests entirely out of mud. They make numerous round trips to and from the nest site to find the perfect mud and carry one mouthful of mud on every trip.
Waterfowl make use of any material that might be available near their chosen nesting sites. Mallards, it seems, are quite content to nest in just about any place that meets their broad criteria. The proximity to water is a prerequisite ,and a frequent sighting in spring is a female mallard with as many as a dozen ducklings trailing behind her. Two local nesters, wood ducks and hooded mergansers, are a little more selective when they choose their nesting sites. Both are cavity nesters and will take advantage of manmade boxes placed in suitable locations.
From eagles to hummingbirds, bird nests are engineering marvels that are as diverse as the birds that build them. Old nests might be recycled or reused, but the majority of nests are newly built every year. Birds are driven to reproduce and over thousands of years have evolved into master builders. If you tend to balk at small remodeling projects around the house, consider the birds and the incredible efforts they make every year to ensure that there will be future generations for us to enjoy.