Nature News

By: Carol Suits
Liberty Wildlife Volunteer

By: Gail Cochrane
Liberty Wildlife Volunteer

Bird nests in Arizona may be as tiny as a thimble or as big as a compact car.

Intricacy of nest designs range from a few sticks scratched together on a ledge (dove) to a woven pouch sewn to a palm frond (hooded oriole). Nests are built in thickets of cacti bristling with sharp spines and in the hearts of mistletoe.

Consider the challenges of providing a suitable location to raise a troupe of ever-famished baby birds in an arid desert where springtime temperatures normally reach triple digits. Desert plants don’t have the luxury of available water to help them soar tall and leafy, so native birds find other ways to shelter their young.

The cactus wren does her best for her kids. She places her nest in the arms of the forbidding cholla cactus, a fortress of barbed spines. The football shaped nest is completely enclosed but for a hole in one end and provides shade and protection from predators. That’s not enough for the cactus wren though. As soon as mom is sitting on eggs, dad starts building a decoy nest.  These secondary nests confuse predators and provide shade for the adult birds later in the summer.

Another species that builds an enclosed nest is the verdin. These nests are like softballs, round twiggy spheres with tiny awnings over the doors. Placement of the door near the bottom of the nest, and placement of the nest on the outer ends of tree branches ensures the parents easy access to their begging nestlings.

Way bigger nests belong to raptors. A red-tailed hawk pair builds a sizable platform of sticks for the basic framework of their nest and finishes with a lining of soft grasses and bark. This edifice may be more than two feet across and at least as deep. The nest platforms often become a foundation that is used season after season by red tails or other raptors who may add their own modifications.

If no one’s at home when you spot a raptor nest, subtle details may reveal the identity of the current residents. Red tailed hawks sometime add interesting features such as a snake skeleton or devil’s claw pods. Red tails generally prefer easy access and a view so build their nests in the highest sturdy crotch of a tall tree, on a cliff ledge, or sometimes on transmission tower platforms.

Ravens are rambunctious and messy, and sticks and bits of building material may be found on the ground beneath their nest. They will also excrete more whitewash on the sides of the nest.

Bald eagle nests can become enormous, as large as 65 square feet as annual renovations add to the bulk. Arizona’s bald eagles live near waterways and favor nest sites in the tallest trees, where they build in a crotch near the top. Lacking available trees, bald eagles sometimes nest on cliffs.  Eagles line their nests with plant material such as soft grasses and fibers of cacti.

It’s the hummingbird of course that constructs the thimble sized nest. The Anna’s hummingbird nests in December and January. She constructs her nest from downy materials such as thistle and feathers bound together with rodent hair and spider webs. Only an inch and a half across, it’s thick walls insulate both eggs and mom from the cold.

The Sonoran desert’s amazing diversity is exemplified by the astounding range of size, building materials, timing and location of bird nests.