Quick Answer
Northern harriers do occasionally eat squirrels as part of their varied diet, but squirrels are not a primary prey item. Northern harriers are opportunistic hunters and will eat small mammals like squirrels, rabbits, mice, voles, rats, and shrews when the opportunity presents itself. However, they rely more heavily on birds and reptiles. Squirrels make up a very small percentage of the northern harrier’s overall diet.
Northern Harrier Diet
The northern harrier (Circus cyaneus) is a medium-sized bird of prey found throughout the northern parts of North America, Europe, and Asia. It is sometimes known as the “hen harrier” or “marsh hawk.” Northern harriers have a diverse diet that includes small mammals, birds, reptiles, amphibians, and insects.
Some of the main prey items in the northern harrier’s diet include:
– Voles: Voles are small rodents that are common prey for northern harriers, especially in grasslands. Voles make up a substantial part of the northern harrier’s diet.
– Mice: Various species of mice are taken opportunistically by northern harriers. Mice can be abundant in fields, grasslands, and wetlands where northern harriers hunt.
– Rats: Rats are larger rodent prey that northern harriers will catch when available.
– Rabbits: Both young and adult rabbits may be hunted by northern harriers. Rabbits are especially important prey in open habitats like grasslands and agricultural areas.
– Birds: Small birds like larks, sparrows, starlings, blackbirds, quail, and shorebirds are common bird prey. Northern harriers often locate bird prey by sound as well as sight.
– Reptiles: Snakes, lizards, turtles, and frogs are readily consumed by northern harriers. Reptiles and amphibians can be significant prey, especially during the breeding season when birds are less available.
– Insects: Large insects like grasshoppers, dragonflies, beetles, and caterpillars supplement the diet, especially during the summer months.
– Squirrels: Squirrels are opportunistic prey for northern harriers but make up a relatively small percentage of their overall diet. The most common squirrel prey are ground squirrels like chipmunks.
So in summary, northern harriers are dietary generalists and eat a wide range of prey including both vertebrates like small mammals and birds as well as invertebrates like insects. Squirrels are not a primary prey item but may be taken opportunistically if encountered by a hunting northern harrier. The abundance of squirrels in a particular habitat determines how often they are preyed upon by northern harriers.
Hunting Techniques
Northern harriers have several specialized hunting techniques that allow them to take advantage of the diverse prey found in open habitats like marshes, fields, and grasslands. These include:
– Low flight: Northern harriers often fly low over the ground, using their acute hearing to locate prey by sound. Their owl-like facial disk helps funnel sound waves towards their ears. Low flight allows them to surprise prey on the ground.
– Hovering: Once prey is sighted, northern harriers will abruptly stop beating their wings and hover in place to zero in on prey. The position of the eyes on the sides of the head gives them excellent binocular vision for judging distance and position while hovering.
– Stealth flight: The soft, owl-like wing feathers of the northern harrier allow them to fly and hover very quietly. This reduces disturbance of potential prey. Their muted coloration also provides camouflage when flying low over grasslands.
– Pounce attack: From a hovering position, northern harriers will drop quickly down onto prey in a surprise attack. Their long legs and talons are effective at securing prey immediately upon impact.
– Perch hunting: Northern harriers sometimes use an elevated perch to spot potential prey, then launch an attack. This technique is used occasionally for hunting squirrels and other small mammals.
These specialized hunting techniques make northern harriers effective predators of agile, fast-moving prey like squirrels. A northern harrier that spots a squirrel while flying low over an open field may quickly hover and then execute a pounce attack before the squirrel detects danger.
Habitats Where Northern Harriers Hunt Squirrels
Northern harriers inhabit open environments like grasslands, marshes, pastures, wet meadows, drained marshlands, croplands, shrublands, and riparian areas. These habitats provide favorable conditions for hunting squirrels:
– Grasslands: Open grassy areas like prairies, pastures, hayfields, and meadows. Ground squirrels like chipmunks and prairie dogs are vulnerable prey in these habitats.
– Croplands: Farmland, especially with low, open vegetation, creates ideal hunting grounds. Northern harriers often follow plowing tractors to take advantage of prey disturbed by the activity.
– Marshes: Wetlands with tall grasses and sedges harbor small mammals. Harriers cruise over the marsh vegetation searching for voles and muskrats.
– Young forest/shrubland: Northern harriers hunt along forest and shrubland edges. Squirrels moving between forest patches for food are at risk.
– Riparian areas: River and stream banks lined with grasses, reeds and shrubs are prime areas for stalking squirrels moving near water.
– Parks/suburbs: Harriers adapted to human activity may hunt squirrels in open suburban parks, golf courses and other green spaces.
Northern harriers frequent these open habitats across their range, increasing the likelihood of encountering and preying upon squirrels during daily hunting. The abundance of squirrels and the success rate of attacks determine the actual amount of squirrel prey taken by northern harriers.
Squirrel Defense and Evasion of Northern Harriers
Squirrels have several advantages that help them minimize predation by northern harriers:
– Vigilance: Squirrels are always on alert for danger from above. Their upright stance gives them a wide view of the sky to spot approaching raptors.
– Speed: Squirrels are extremely quick and agile. They can dart rapidly to trees, burrows, and other cover when threatened. This makes a successful surprise attack more difficult.
– Hiding: Squirrels will flatten themselves against the ground or a tree trunk when a harrier is sighted, relying on camouflage to avoid detection.
– Burrows/dreys: Safety is found in tree cavities, leaf nests, and underground burrows where squirrels take refuge from danger.
– Noisy alarms: Loud alarm calls alert other squirrels to danger when a northern harrier is spotted hunting. This makes nearby squirrels more wary and attentive.
– Zigzag running: Squirrels use evasive zigzag running patterns to make targeting more difficult for an attacking northern harrier.
– Tree climbing: If caught in the open, squirrels can quickly escape to the safety of trees by rapidly scurrying up trunks and out onto branches.
These defenses likely reduce northern harrier predation success on squirrels substantially compared to more vulnerable prey like voles. But harriers continue to opportunistically hunt squirrels because successes, though infrequent, provide a nutritious reward.
Conclusion
In conclusion, northern harriers are opportunistic predators that occasionally eat squirrels as part of their diverse diet. Squirrels are vulnerable when moving through open habitats frequented by harriers, especially grasslands, marshes, and areas near forest edges. Northern harriers use stealthy, low-flying hunting techniques to surprise squirrels on the ground. However, squirrels have effective defenses like speed, vigilance, hiding, and escape to trees that likely limit their predation by northern harriers in most cases. Although not a primary prey source, squirrels provide a beneficial supplemental food item when successfully caught by the adaptable northern harrier.
