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Raptors

Broad-winged Hawk Migration Peaking

9-17-18 juv. broadwing_U1A7043The migration of raptors has begun, and one of the first species to migrate in the fall is the Broad-winged Hawk (Buteo platypterus). While it is quite secretive when nesting, it is one of the more conspicuous species of birds when migrating.  This is for two reasons. They are one of the few North American raptors that flocks during migration, and much of their migratory behavior is concentrated in the Northeast in a two-week period around the middle of September.

Migrating Broad-wings conserve energy by frequently soaring in thermals and mountain updrafts. Flocks of birds, or “kettles”, soar up the heated columns of air, peel off and glide to the next thermal where they repeat the process. Very little wing-flapping is necessary in order to cover a lot of ground. The flocks, or “kettles,” range from several individuals to thousands of birds (larger kettles generally occur nearer their Central and South America wintering grounds).

The number of birds migrating often grows following a cold front, when winds die down and thermals increase. Fall migration of Broad-wings in the Northeast is associated with good visibility, moderate favorable winds, high temperatures, and afternoons (vs. mornings). (Photo: juvenile Broad-winged Hawk)

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Snowy Owl Gets Mouthful When Hunting In Tall Grass

12-8-17 snowy owl and meadow vole3 049A9802Only Naturally Curious readers would come up with flossing!

If lemmings are in short supply and you’re a Snowy Owl, head for tall grass where small rodents dwell. This juvenile female Snowy Owl successfully caught a Meadow Vole (along with a footful of grass) in its talons and proceeded to swallow the vole whole, along with some of the grass. However, most of the grass remained hanging from the owl’s mouth after the vole had been consumed, so it proceeded to grasp the grass with its foot and pull it out of its mouth (yesterday’s Mystery Photo).

Although many people are under the impression that hard weather forces Snowy Owls farther south some winters, the reason for Snowy Owl invasions or irruptions turns out to be linked to either prey population crashes in the north, high productivity breeding years (producing more predators than the prey can support) or a combination of the two. New research has shown that the abundance of Snowy Owls seen in the eastern U.S. during the winter of 2013-14 was the result of a particularly good nesting season on the Arctic tundra. A population boom of lemmings, the Snowy Owl’s primary food source, translated to a population boom of owls.

 

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Barred Owl Parents Providing Fledglings With Food

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Young Barred Owls are fed from the time they hatch (four to six weeks old) until late summer or early fall, months after they have fledged and long after they are capable of flight. When first out of the nest, the fledglings cannot fly, and thus are totally dependent upon their parents’ continued delivery of prey. The fledged young initially stay near one another and the nest site. The parents continue to feed them, and as the young become more mobile they slowly move away from the nest tree. Flight is attempted between the ages of 12 and 15 weeks. The first attempts are, as you would imagine, rather awkward, but as their wings strengthen, the young owls’ flying skills improve. Even so, the parents continue to feed them through the summer and often into the fall, when prey deliveries slow down and eventually cease, forcing the young to disperse. (Photo: Recently-fledged Barred Owl chick eyeing the Flying Squirrel its parent is delivering.)

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Barred Owl Chicks Fledging

5-25-17 barred owl fledging2Unlike most young birds, Barred Owls fledge before they can fly. On average, they leave their nest when they are around eight weeks old, and don’t master flight until they’re about 12 weeks old. Fledging for a Barred Owl consists of climbing up out of the tree cavity where they spent their first two months, onto a nearby limb where its parents will tend to it. More often than not there is a nearby branch which it can hop to.

In the fledging depicted, the closest limb was a good 10-15 feet above the nesting cavity. With the help of its strong talons, beak and wings, the fledgling managed to scale the tree trunk up to a somewhat horizontal stub where it could get a good purchase. It may not have been the most graceful ascension, but the fact that it could manage to climb straight up for this distance without the assistance of any grasping fingers was impressive, to say the least.  Fledged Barred Owls continue to be fed by their parents until they can fly and capture their own prey.  (Photo: Barred Owl chick fledging – clockwise, starting from upper left)

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Barred Owls Parents Tending Chicks

5-12-17 adult owl in nest hole 241For about a month the female Barred Owl sits on her 1-5 eggs (usually 2 or 3) until her white, downy chicks hatch, usually around the end of April or beginning of May. At about two weeks (mid-May) their natal down is being replaced by a white-tipped gray-buff secondary down, and primary feathers are beginning to grow in.  They remain in their cavity nest for their first month.

It is pretty safe to assume that the adult owl in this photograph is a female as she is in constant attendance during the chicks’ first two weeks. The male brings her food which she tears into little bits so the chicks can swallow it. At the beginning of the third week, the female begins leaving the nest frequently to hunt. When she is at the nest, she often takes breaks from the kids and sits at the entrance surveying her surroundings.  At this point the chicks start consuming prey (that is delivered to them) on their own. In a week or two the chicks will also start appearing at the cavity entrance.  By their fourth or fifth week, the still-flightless chicks will leave the nest, but parental provision of food continues until fall.

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Feathered Fishermen

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Using their keen eyesight and sense of hearing, Barred Owls typically sit and perch on a branch, surveying the ground beneath them for whatever morsel appears, small mammals and birds being at the top of their list during the winter, with more emphasis on amphibians, reptiles, fish and invertebrates during the warmer months.

Several times I have observed a Barred Owl taking advantage of a vernal pool that was teaming with life, specifically Wood Frogs and Spring Peepers. Perched in a nearby tree, the owl kept an eye out for any sign of movement in the water.  When ripples appeared near the shore it would swoop down to the water’s edge in an attempt to grasp a frog with its talons. Although it met with repeated failure, success was inevitable due to the plethora of distracted mating frogs.

Because they lack hair and feathers, frogs may be underestimated when scientists dissect owl pellets to see what Barred Owls eat. Given the frequency with which I have observed these feathered fishermen, I would think that might be very likely.

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Red-tailed Hawks Building & Refurbishing Nests

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Red-tailed Hawks are on eggs, or soon will be.  Whether their nest is in the canopy, on a building ledge, transmission tower or elsewhere, it usually has a commanding view of the surrounding area and unobstructed access from above.

Both members of a pair share in nest site selection, which is often in mixed woods adjacent to open fields. They build their nest together, working most diligently in the morning, and construction is completed within four to seven days. If a nest is re-used, which it often is, it is refurbished with sticks and greenery. Red-tails are very wary during this nest-preparation period and may discontinue nest-building if humans are detected, so should you come upon a nest during this stage, best to remove yourself quickly.

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