ZOO-ology column: Name that nest
By Judie Farnsworth
March 4, 2012 at 11:02 p.m.
Updated March 3, 2012 at 9:04 p.m.
Birds are not much different than we are when a family-site is needed. They use accessible materials, the nest size fits their size and the site fits family needs. Using only toes and bills, they are wonderfully creative little engineers.
So, you see a nest. Who built - or didn't build it? For starters, where is it - high, middle, low? How big is it? An enormous nest of twigs high in a tree would surely rule out a woodpecker. Likewise, a hole in a tree trunk would (hopefully) rule out an eagle.
Does it contain twigs, leaves, grasses, lichens, moss, spider webs, pine needles, string, cotton, feathers, shed snake skin, fur, flower petals, trash?
What about shape? Cup nests are most familiar with deep depressions for eggs. Tiny hummingbird nests often contain lichens that are waterproof and held together with sticky spider web threads.
The cupped, mud nests under bridges or eaves on houses belong to swallows. They collect and apply mud pellets to a wall and then line with feathers and grass.
Vireo's pensile (suspended) nests are cupped, but almost always hanging in the forks of twigs.
Nests of some birds, including shorebirds, may be unrecognizable as nests. They're called scrapes, merely a scratched out area on the ground. Species like gannets or boobies simply stand on their eggs, pulling a few stones or sand close.
Flamingos build cone-shaped mud piles sometimes called mound nests. A small depression on top holds a single egg and the elevated cones are often surrounded by watery moats where the mud has been excavated.
A few birds, like kingfishers, burrow nests horizontally into a vertical dirt bank. The tunnel created leads to a chamber that holds the eggs. Excavation may begin by flying headfirst into the dirt wall. Ouch! Idle burrows of animals like rabbits or prairie dogs may be used by some birds (burrowing owl). It sure seems healthier.
Cavity nests may be in natural or excavated areas - most often trees. In the west, saguaro cacti are readily used. Cavities may be lined with leaves, moss or soft materials. Pine pitch or other pest or predator controlling material may be smeared around the opening. After nesting, cavities may offer shelter for some birds during bad weather.
Orioles build pendant nests - elongated sacs suspended from a branch. They're firmly woven with grasses and plant fibers.
Platform nests may be on the ground, highly elevated or even floating. They're often much bigger than the builder and may be used for many years, growing to enormous proportions. This is the case with raptors (osprey, eagles etc). Eagles nests (eyries) have been know to topple trees.
Male jacanas build flimsy floating platform nests (lily pads on vegetation). They also tend the eggs and raise the chicks. When pop steps onto the nest, it often sinks down dunking him and the eggs. Luckily the eggs are waterproof.
Some birds nest just about anywhere. Carolina wrens have been known to build in long johns on a clothesline.
You may already feed birds, but try offering nesting material. Collect combed pet fur, short bits of string, Easter grass, dryer lint, bits of hair, flower petals, cotton bits, etc. Put them in a wire feeder basket or where accessible to birds. Later in the year, you may see a nest with your material in it.
Judie Farnsworth is a longtime volunteer at the Texas Zoo specializing in educational programs.