The Gila woodpecker (Melanerpes uropygialis) is a medium-sized woodpecker that is found in desert regions of the southwestern United States and Mexico. As its name suggests, it is most common in areas of the Gila River basin, including parts of Arizona, New Mexico, California, Nevada, Utah, and the northern parts of the Mexican states of Sonora and Baja California.
Diet
Gila woodpeckers are omnivorous, feeding on a variety of plant and animal material. Their diet consists primarily of insects, spiders, fruits, nuts, sap, and some small vertebrates. They use their chisel-like beak to excavate nest cavities and search for food, tapping on trees and cacti to locate insects and larvae hidden inside. Some of their favorite foods include:
- Insects – ants, beetles, caterpillars, grasshoppers, crickets, flies, bees
- Spiders
- Scorpions
- Small lizards and frogs
- Nectar from flowers of cacti and agave
- Fruits – mistletoe berries, hackberries, juniper berries, figs, prickly pear fruit
- Nuts – acorns, pine nuts
- Sap from saguaro and other cacti
Gila woodpeckers use their long sticky tongues to capture insects. They may catch insects in flight or glean them from the bark surface of trees and cacti. They often drill into cacti or dead branches to extract insects, larvae, and other food inside. Their diet varies depending on seasonal and local availability.
Predators
As a small- to medium-sized bird, Gila woodpeckers may fall prey to a number of different desert predators. Some of the main predators of Gila woodpeckers and their nests include:
- Snakes – particularly rat snakes, gopher snakes, and racers
- Hawks – Cooper’s hawks and sharp-shinned hawks specialize in preying on smaller birds
- Owls – great horned owls and eastern screech owls hunt at night
- Falcons – the American kestrel is small and fast enough to grab woodpeckers
- Greater roadrunner
- Coyote
- Bobcat
- Foxes
- Ringtails
- Squirrels
- Chipmunks
- House cats
Snakes may climb trees or cacti to raid nests and consume eggs and nestlings. Hawks, falcons, and owls swoop down from above to grab adult woodpeckers as they fly between trees. Cunning predators like coyotes and foxes may scout for nests to eat the eggs and young. Though small, ringtails and squirrels are agile enough to access cavity nests.
Adult Gila woodpeckers have few defenses against predators aside from hiding in cavity nests. They may aggressively defend the nest by attacking or distracting predators with loud calls and distraction displays. But once caught out in the open, they can do little to evade most predators. However, their brown, white, and black barred plumage serves as excellent camouflage against the textured bark of desert trees.
Nesting and Reproduction
Gila woodpeckers nest in holes excavated in the trunks of large saguaro cacti and cottonwood and oak trees. The nest cavities provide shelter, but also make them vulnerable when predators raid the nest. Here is an overview of their nesting habits:
- Lay between 2-5 white eggs in a clutch
- May produce 2-3 clutches per year from March to June
- Incubation lasts 12-14 days
- Nestlings fledge in about 30 days
- Cavities are reused for roosting and nesting in subsequent years
- Both parents share nest building, incubating, and feeding the young
Gila woodpecker eggs and chicks are easy meals for predators that can access the nest cavity. Snakes in particular are adept at climbing and raiding nests. During the nearly two month nesting period from egg laying to fledging of chicks, parents are challenged to keep the nest safe.
Anti-Predator Adaptations
Gila woodpeckers have evolved a number of physical and behavioral adaptations to help defend against predators:
- Camouflage – their barred plumage blends into the mottled bark of trees
- Excavating hard nests in thick succulent trunks or dead snags
- Nesting high off the ground when possible
- Triangular reinforced nest hole makes access difficult
- Defensive aggressive behavior – attacking potential threats near the nest
- Mobbing predators in a group defense strategy
- Early warning – loud calls signal dangers to the group
- Distraction displays to draw predators away from nest cavity
- Short nesting period minimizes duration of vulnerability
The thick walls of saguaro nest cavities provide insulation and make it hard for predators to enter. The tight fit also helps prevent eggs from rolling out. Saguaros have tough, spongy inner pulp that offers protection against drilling predators. Still, some snakes become specialized at raiding particular saguaros. Nesting high on the arms of the cacti improves safety.
Population Impacts
Despite adaptations, predators take a toll on Gila woodpecker populations. It is estimated roughly 70% of nest attempts fail, with the majority lost to predators. Populations are declining in some areas, likely due to habitat loss as well as nest predation. However, woodpeckers are resourceful and can bounce back once pressures are reduced.
Here is a table summarizing observed nest failures from predation in Arizona:
Predator | Percent of nest failures caused |
---|---|
Snakes | 45% |
Hawks | 15% |
Jays | 12% |
Squirrels | 10% |
Woodpeckers | 8% |
Mammals | 6% |
Unknown | 4% |
Snakes are by far the biggest source of nest failure through predation. Hawks and jays also gulp down their share of eggs and nestlings. Squirrels and other rodents invade cavities whenever they can gain access. Interestingly, other woodpeckers may raid each other’s nests on occasion. About 4% of the time the predator goes unidentified.
Conclusion
Gila woodpeckers face a gauntlet of predators ready to eat them or their eggs given the chance. Snakes in particular specialize in raiding nest cavities in cacti and dead trees. Hawks and falcons grab the adult birds in flight. Other desert predators like coyotes, bobcats, and foxes eat the adults, eggs, or young when they find an accessible nest. Defensive strategies like camouflage, hiding food and eggs, and aggressive mobbing behavior help woodpeckers survive in the harsh desert landscape.
Though challenging, pressure from predators is natural and keeps prey populations healthy overall. Problems arise when human activities and habitat destruction upset the natural balance and give predators excessive advantage. Maintaining wilderness refuges and ecological diversity helps create conditions where the remarkable Gila woodpecker can continue thriving amidst adversity in its desert home.