The mountain bluebird (Sialia currucoides) is a small thrush found in western North America. Its bright blue plumage and melodious song make it a favorite among birdwatchers. But even this beautiful songbird has natural predators that feed on it. In this article, we’ll take a look at the main predators of the mountain bluebird and examine how they hunt this petite prey.
Raptors
Raptors, or birds of prey, are perhaps the most significant predators of mountain bluebirds. Their keen eyesight, powerful talons, and sharp beaks make them expert hunters. Several species regularly prey on mountain bluebirds.
Sharp-Shinned Hawks
Sharp-shinned hawks are small woodland hawks that specialize in catching smaller songbirds. Their short wings and long tail give them agility to pursue prey through dense thickets. Mountain bluebirds are vulnerable when moving through open areas near woodlands, where sharp-shinned hawks will ambush them.
Cooper’s Hawks
Slightly larger than sharp-shinned hawks, Cooper’s hawks also prey regularly on small birds like mountain bluebirds. A study examining the diet of this hawk found that small songbirds made up 90% of the prey items. Agile flyers, Cooper’s hawks surprise and overwhelm smaller birds from cover or while patrolling open habitat.
Red-Tailed Hawks
The common and widespread red-tailed hawk sometimes feeds on mountain bluebirds, although small mammals are their primary prey. Most predation happens when mountain bluebirds are on open ground foraging. The red-tailed hawk will soar overhead, keeping watch for any unlucky bird that wanders too far from cover.
Great Horned Owls
These large and adaptable owls hunt at night, preying on all manner of small animals. They regularly take roosting songbirds, including mountain bluebirds. Nestlings and fledglings are also vulnerable to great horned owl predation if the nest site is not well concealed.
Other Avian Predators
In addition to raptors, several other bird species sometimes prey on mountain bluebirds.
Crows
American crows are intelligent opportunistic feeders. They will eat eggs and nestlings if they find an unguarded mountain bluebird nest. Adults are occasionally captured if they mob a crow that ventures too close to the nest.
Steller’s Jays
These resourceful jays supplement their diet with eggs and nestlings stolen from songbird nests during the breeding season. Mountain bluebirds must be vigilant against these nest raiders while incubating eggs or raising young.
Merlins
This small falcon is a fearsome predator of larks, warblers, finches, and other small birds. Merlins migrate through the range of the mountain bluebird and capture them in mid-air after spectacular stoop dives at speeds up to 200 mph.
Mammals
Mammalian predators also pose a risk to mountain bluebirds.
Foxes
Foxes, including red foxes and gray foxes, are carnivorous predators that feed on small birds when the opportunity arises. They raid nests to consume eggs and nestlings. Adults may be captured when feeding on the ground.
Coyotes
As opportunistic feeders, coyotes sometimes prey on mountain bluebirds. The predators use fencing as hunting perches to search for birds and other small animals moving through open terrain.
Squirrels
Tree squirrels are mainly herbivorous, feeding on nuts, seeds, and fruit. But they are also opportunistic and will consume eggs and nestlings left unattended. Grey squirrels and red squirrels may ransack mountain bluebird nests.
Raccoons
With their dexterous paws and omnivorous appetites, raccoons can be destructive nest predators. They feed on eggs and chicks from songbird nests, including those of mountain bluebirds. Raccoons are expert climbers and will access nests along cliff crevices or in tree cavities.
Domestic Cats
Free-roaming domestic cats kill billions of wild birds in the U.S. every year. Mountain bluebirds feeding on open ground are vulnerable to predation by feral and pet cats. Nestlings can also fall prey if the nest site is accessible.
Reptiles
Reptilian predators eat mountain bluebirds more rarely. But they can be a concern in some regions.
Gopher Snakes
Also called bullsnakes, these large nonvenomous snakes occasionally prey on birds, especially eggs and nestlings. Gopher snakes are adept climbers and can access nest cavities of mountain bluebirds and other hole-nesting species.
Racer Snakes
Like gopher snakes, racers sometimes include birds in their varied diet. Adult mountain bluebirds may be targeted if they nest low in shrubs or on the ground. Racer snakes are common in mountain forests inhabited by these songbirds.
Other Predators
A few other predatory animals attack mountain bluebirds when given the chance.
Chipmunks
While mainly herbivorous, chipmunks occasionally eat eggs, nestlings, or adults. They can access cavity nests and may ransack shallow cup nests built in shrubs or trees.
House Sparrows
The invasive house sparrow competes aggressively with native cavity nesters. They may peck adult mountain bluebirds intruding near their nest sites. House sparrows also consume eggs or overwhelm nestlings.
Brown-Headed Cowbirds
Cowbirds lay eggs in other birds’ nests. The cowbird chick often outcompetes host offspring. Mountain bluebirds may abandon parasitized nests or raise cowbirds rather than their own young.
Defense Against Predators
Mountain bluebirds have some behavioral adaptations to reduce the risk of predation.
- They remain alert and scan surroundings constantly for danger.
- Their wary nature makes them difficult to ambush.
- They emit alarm calls to warn others of predators.
- They harass potential nest predators like crows and jays.
- Adults may perform distraction displays to lure predators from the nest.
- They nest in cavities or placed behind foliage to stay concealed.
Importance of Predators
While predators may seem harsh to beautiful songbirds like the mountain bluebird, they serve important ecological roles.
- Predators help stabilize prey populations and prevent overuse of resources.
- They remove old, ill, or weak individuals, improving the gene pool.
- Predation is a strong selective force that hones physical and behavioral adaptations.
- Scavengers and decomposers benefit from predators that do not consume their entire prey.
- Predator-prey interactions link food chains and energize ecosystems.
Conclusions
The mountain bluebird faces predation pressure from a wide array of natural predators. Raptors are likely the most significant predators, but mammals, snakes, and even other birds also pose threats. However, mountain bluebirds have evolved behaviors to lower their risk of predation. And predators certainly play vital roles in maintaining healthy ecosystems.
Understanding these predator-prey dynamics provides critical insights into the natural history of the mountain bluebird. This knowledge can help inform conservation plans for maintaining sustainable populations of this and other vulnerable songbird species into the future.