northeast naturalist: hawks

Showing posts with label hawks. Show all posts

Thursday, March 27, 2014

Story in the Snow

[scanned Kodachrome II slide]

A Story in the Snow

Birder's journal March 21, 1971: I was following the redtail along the ridge, not so much to get a photo of it as we were both heading in roughly the same direction. I was a minute or two behind the hawk when I exited the woods and entered a partly-scrubby opening on the north end of the drumlin. More by luck than anything else, I came upon the story written as clearly as if words had been used. The mouse tracks ended in a depression, surrounded by the hawk's wing and tail feathers imprinted on the surface as it lifted into the air, prey in tow, while a drop of blood on the snow was all that remained of the hapless creature.

This could have been written a week ago; we've had no shortage of snow and cold weather this winter. There is a timeless element to many of nature's stories. It's likely a story that has been written over and over again across the intervening years.

immature Red-tailed Hawk (note barred tail)

For more information on Red-tailed Hawks, photos and sounds, visit the All About Birds website. An interactive range map (zoomable to your location) can be found in the eBird Explore Data section.

Corrections, comments and questions are always welcome at ebirder_14432@yahoo.com or connect through my Facebook page and photo page. There's also a community-type page for The Northeast Naturalist. Other nature and geology topics can be found on the parallel blogs Adirondack Naturalist, Heading Out, and a Naturalist's Viewpoint.

Thursday, February 21, 2013

Accipiters

Juvenile Cooper's Hawk eating what might have been a Red-winged Blackbird(?)...
(It's hard to tell at this point, especially with some Norway spruce twigs in the way.)
Note that it's wings are spread out to "mantle" (hide) it's prey.
- All photos and editorial content © Dave Spier -

What birds are visiting your feeders? Probably cardinals and jays and chickadees and juncos and doves and the usual winter mix that comes to partake of seeds and suet. What do all these birds have in common? They attract what many people consider uninvited guests -- the bird hawks, members of the genus Accipiter, a word that comes from the Latin verb meaning "to seize." I know one is around our yard when the feeder birds become very still or suddenly disappear. Hawks are a natural part of the web of life and they help keep everything in balance. I'd prefer they catch starlings and house sparrows, but it seldom seems to work that way.

In much of the United States, from Washington to Iowa to Massachusetts and south, there are two Accipiter species likely to visit your yard in winter, the Sharp-shinned (Accipiter striatus) and the Cooper's Hawk (A. cooperii), but they are difficult at best to separate. Male Sharp-shinned Hawks are about 11 inches long, roughly the size of a blue jay. Like most hawks, the females are significantly larger. Female sharpie's are 14 inches long, about the size of a pigeon, but slimmer. Here's the problem. Male Cooper's Hawks are about the same size as female sharpie's and maybe an inch longer. The larger female Cooper's is approximately the size of a crow.


An adult Sharp-shinned Hawk eating what might have been a Mourning Dove (judging by the color of the feathers on the snow after the hawk left - but its hard to tell).

Plumages of our two bird hawks are virtually identical, making it that much harder to tell one from the other. Juveniles of both are brown on top and streaked lengthwise underneath. Juvenile Cooper's have thinner, darker, tear-drop-shaped streaks, but that is subjective and requires some experience for comparison. The juvenile's yellow eyes turn orange and then red as Accipiters mature. Adults are gray or blue-gray on top, hence the nickname "blue darter." The cap or crown is darker like charcoal, especially on Cooper's. (Sometimes a Cooper's Hawk will raise its hackles giving it a small crest.) Sharpie's have more of a hood, meaning the dark crown extends down the nape, wheras Cooper's have a lighter nape.

Underneath, adults of both species are light colored with rufous cross barring on the chest giving way to white under the tail. At all ages, the tail is coarsely barred with dark bands. Under ideal conditions, subtle differences in the tail can be discerned. Sharp-shins have a square or notched tip on a slightly narrower tail. Cooper's tails are slightly wider or fanned with rounded ends due to the outer tail feathers being shorter than the inner ones (but molting could confuse the issue). A white tail tip is more noticeable on Cooper's, but this can be masked by feather wear. Cooper's have white bellies whereas sharpie's tend to have more smudged or "dirty" bellies (another subjective call).

juvie Cooper's again showing a slight crest and making the eye appear closer to the front
(by comparison, Sharpie's eyes appear larger and more centered on the head)

The third and largest member of the Accipiters, the Northern Goshawk (Accipiter gentilis) is a bird of Canada, the north woods and the Rockies. The name "goshawk" comes from the Old English word goshafoc, meaning "goose hawk." I have no photos of this species, but a distinguishing characteristic is a light line (called a supercilium) above the eye. This line is white in adults and it contrasts with a dark line through the eye. Adults are also gray on the back and light gray on the belly, but never rufous like the smaller bird-hawk adults. Juvenile goshawks are brown and streaky and have pale-tipped greater coverts overlapping the inner (secondary) wing flight feathers.

All of these raptors have relatively short wings for maneuvering between woodland trees. The small sharp-shin can even adeptly chase prey through bushes. I watched as one hunted chickadees. It was an aerial acrobat making contorted maneuvers, weaving and diving through the sumac and other shrubs in hot pursuit of black-caps. Accipiters have long tails to aid in sudden, sharp turns. Although small birds are the staple diet of our Accipiters, they will take other prey. Sharpie's will take mammals up to Red Squirrel size; Cooper's up to Gray Squirrel.

adult Sharp-shin again, showing square corners on the tail and a small, rounded head
with the crown extending down the back of the head and forming a "hood"

Mouse- and insect-eating hawks like the kestrel and redtail perch in the open and watch the ground for signs of motion. Accipiters prefer to hide in a tree or bush while they eye your feeder. When they attack, their flight is swift and low. From the side, sharp-shins appear "neckless;" they keep their heads pulled in and wings pushed forward, compressing their short necks. Overhead, this gives them a "T" shape. Cooper's have longer necks and larger heads, and overhead have the appearance of a cross. During migration, sharpie's will intersperse bursts of rapid flapping with glides and they may circle briefly if they encounter a thermal (an updraft). Cooper's flight is more direct and determined.

To the birds at your feeder, it makes no difference what species is chasing them. It's strictly a matter of life or death. The faster birds survive; the slower stragglers (read "old, sick or injured") don't. Remember the old saying, "Survival of the fittest?" If you want to help your seed eaters survive, locate your feeder(s) close to escape cover. The denser the better... Discarded Christmas trees can be staked next to the feeder and also serve as a wind break. (You also might consider placing a baffle or skirt around the bottom of the tree to prevent cats from hiding underneath.) In my younger days, when I had fewer back problems, we bought a live Christmas tree every year and planted it in the spring. Some of those trees are pretty big now and several of our feeders hang from the inner branches. If your zoning regulations permit, a loose brush pile also provides escape cover and winter storm protection for birds and small mammals. At least the House Sparrows will appreciate it and roost there overnight. Our Carolina Wren also uses the brush pile -- when it's not in the thicket across the road.

Okay, look out the window again at your feeder. Now, what do you see?

For more information, photos and sounds, visit the All About Birds website and type in the species of interest. An interactive range map (zoomable to your location) can be found in the eBird Explore Data section. Again, type in the species.

Corrections, comments and questions are always welcome at northeastnaturalist@yahoo.com or connect through my Facebook page and photo page. There's also a community-type page for The Northeast Naturalist. Other nature and geology topics can be found on the parallel blogs Adirondack Naturalist and Heading Out.

Tuesday, January 17, 2012

Mourning Doves

Pair of Mourning Doves on the snow at the Montezuma Audubon Center

I call them "bobble-heads" because of the way their heads bob as they walk across the ground in search of seeds dropped by other birds from the hanging feeders. Small buffy head, large buff-colored body, darker gray-brown on the wings and back, dark spots on folded wings, long-pointed tail with white along the edges… They prefer to feed on the ground, usually in small flocks, but if there’s enough room they’ll land on a platform feeder. When they take off, the whistling of the wings is diagnostic. In the morning, flocks try to catch the early rays of sunlight by lining up on utility wires strung between poles along country roads. We are of course talking about Mourning Doves (Zenaida macroura), named for their sorrowful cooing sometimes mistaken for the call of an owl.

Doves are the preferred prey of the Cooper’s Hawk, that long-tailed, short-winged, fast and maneuverable accipiter that visits our bird feeders.

The doves, related to domestic pigeons, are mainly vegetarian. You may see a flock picking up waste grain in a winter cornfield if there’s not much snow, but they also eat seeds from grasses and weeds. A few insects are fed to nestlings during the warm months. In late summer they eat the dark-purple, almost black, berries of pokeweed. Many doves head south to agricultural areas for the winter, and a few birds banded in New York have gone as far as the Gulf-coast states.

In early spring, watch for them to begin pairing up as they prepare for a long nesting season, and listen for their "song," a series of five coos with the second one rising and falling. Once they set up housekeeping, a skimpy handful of loose twigs barely qualifies as a nest and it looks like the eggs are in danger of falling through or rolling off. Mourning Doves nest repeatedly through the summer, and I’ve seen them sitting on eggs as late as October in New York. That particular nest, in one of our spruce trees, may have been the fourth brood of the year. It’s a good thing, because half the chicks don’t make it out of the nest; they fall victim to various predators, both avian and mammalian. Of the half that survive the nest and fledge, three-quarters don’t make it to their first birthday. Past that point, only 5% of the adults make it to five years old or beyond.

Mourning Doves were historically birds of the Southern states. They adapted to rural farmland where there was a combination of grain fields and watering holes or slow creeks to get a drink twice a day. During the 20th century the Mourning Dove population began expanding northward until it reached an estimated 10 million birds in New York State. They can live on the edge [called an ecotone] between woods and fields, but they are absent from large tracts of continuous forest. In the 1800’s Passenger Pigeons were the dominant bird in the forested Appalachians and north into New York, but that species was hunted to extinction.

The Mourning Dove is named for its sorrowful cooing, which is sometimes mistaken for the call of an owl. -- © Dave Spier

To get an idea of the Mourning Dove's range, visit eBird's "View and Explore Data" page, click on "Range and Point Maps" and type in "Mourning Dove" [or just click the link]. You'll notice there's a concentration of sightings across the South, the Great Plains and the Eastern United States. Zoom in for detail. The process works for any species anywhere in the world, but many areas like Asia and Africa and much of South America still lack data.

For more information, photos and sounds of the Mourning Dove, visit All About Birds.

In the Southern and Western States, you might encounter the similar Eurasian Collared-Dove. Check the eBird range map for this species if you have a question about your location.

Eurasian Collared-dove in Red Rock Park, New Mexico

Tuesday, November 25, 2008

Harriers

At this rate, it just might spend the winter here. Sometimes it flies close to the building, passing the west windows, and then disappears across the field. I doubt it's hunting the birds at the feeder, but they are within the realm of this raptor's diet. Mostly it flies low over the grasslands and the marsh while it looks for small mammals, especially Meadow Voles (also called field mice) which are caught with a sudden pounce. Sometimes this large bird's flight drifts lazily back and forth, then stops momentarily to hover. In warmer weather it hunts snakes, frogs and insects. When all else fails, carrion is eaten.

The Northern Harrier, once known as the marsh hawk, is a slender and buoyant hawk with a somewhat owl-like face. The hawk's long wings and tail are designed for life in the open. If it tips a bit sideways toward you, watch for the distinctive white rump patch. When soaring, the wings are held in a shallow V with the tail fanned. At low altitudes, the tail is usually closed and the wings held flat to the sides. In a steep glide, the wings are sharply bent and swept back like a fighter jet.

In the winter, harriers hang around with Short-eared Owls and share the same fallow, grassy fields where mice have had time for a population explosion. Both raptors will use fence posts as hunting perches while they listen for prey. Though unrelated, the facial disks of both harriers and owls are thought to help focus sounds on the ears.

The harrier's Latin name, Circus cyaneus, refers to its circling flight and the supposedly blue plumage of the males. The color is actually gray, but that's only half accurate because females and juveniles are brown, an unusual disparity for raptors. Juvenile harriers are orangish underneath, like the two photos. The name "harrier" is Old English for "harassing with hostile attacks." Other colloquial names include blue hawk, mouse hawk and white-rumped hawk. Males are smaller and more agile and catch smaller prey, including birds. The harrier flying past the Montezuma Audubon Center (Rt. 89, Savannah, NY) was a larger, brown female probably more intent on a larger meal than the tiny goldfinches at the feeder.

Harriers nest in the marshes at Montezuma National Wildlife Refuge (between Rochester and Syracuse, NY). Last April I watched a female repeatedly carry nesting material in her beak and then drop down into the same patch of heavy vegetation. There are indications harriers also may nest in the Northern Montezuma Wetlands Complex around Savannah (Wayne County, NY). They almost certainly nest in the Lakeshore Marshes Wildlife Management Area near Lake Ontario in northeastern Wayne County as well as Howland's Island in Cayuga County. The female does all the incubating while the male brings food. After the eggs hatch, the male continues supplying prey, but only the female tears it up and feeds the young. If something happens to her, the nestlings will starve, even though the male continues to drop whole prey into the nest.

Harriers breed from Alaska across Canada to the Maritimes and south into the United States as far as a line from California to Pennsylvania. Most harriers head south for the winter and return in the spring.

Contact me at northeastnaturalist@yahoo.com More nature photos can be seen at http://picasaweb.google.com/northeastnaturalist and http://www.flickr.com/photos/dave_spier and now my Facebook photo page.

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