Birds of Prey in the NWT
Birds
of prey or raptors are the hunters of the bird world. They typically have large, strong feet with which they seize and
kill their prey as well as powerful, strongly hooked beaks that are used
to tear prey into bite-sized chunks. Diurnal raptors are active during the
daylight hours and reply upon their keen eyesight to spot their prey,
whereas nocturnal raptors (such as owls) are usually active after sunset
and use their acute hearing to locate their prey.
The
specific body structures of the diurnal raptors allow them to exploit most
efficiently one type of habitat and are adapted to hunt one type of prey.
Raptors are incapable of digesting bones, fur, feathers or insect
skeletons and each day cough up a small pellet consisting of those indigestible
remains. Often pellets can be
found around the next site and near favourite perches.
Prey of birds larger than robins are usually plucked before being
eaten, whereas smaller birds and rodents are swallowed whole.
Among
most species of raptors, males are smaller than females.
The
degree of size difference depends on the species.
Species that scavenge or take slow moving prey (such as bald eagles) do
not show as much size difference as species that hunt agile prey (such as
peregrine falcons). Male falcons
are typically 1/3 smaller than female falcons so are sometimes called tiercels,
the Latin word for one-third.
When outlined against the sky,
each raptor group has a similar shape of body, wings and
tail. In the NWT, the dirunal birds of prey can be classified into five groups:
 Woodland
hawks (accipiters)
The body structure of woodland hawks
is
adapted to forested areas. Their
short rounded wings and long tail allow them to dodge
branches while in pursuit of small birds, squirrels or mice.
They are often seen sitting quietly on an exposed tree
limb in the forest waiting to spot a mouse or small bird. This group
Includes:
Goshawk (Accipiter gentilis)
Sharp-shinned hawk (Accipiter
striatus)
Soaring hawks and eagles
These heavily built raptors have wide broad wings and a fan shaped tail,
which allow them to prospect for prey as they ride the air currents. They have powerful beaks and feet, especially the much larger
eagles, and hunt in more open country than the accipiters. Soaring hawks and
eagles in the NWT include:
Golden eagle (Aquiola chrysaetos)
Bald eagle (Haliaeetus leucocephalos)
Red-tailed hawk (Buteo jamaicensis)
Swainson's hawk (Buteo swainsoni)
Rough-legged hawk (Buteo lagopus)
Harrier
hawks
Harriers
are slim-bodied hawks with slim long wings, long tail and long legs. They fly low over open marshlands hoping to flush a small bird or
mouse from cover and frequently hover over their quarry before pinning it
to the ground.
There
is only one type of harrier hawk found in the NWT:
Northern harrier
(Circus
cyaneus)
 Osprey
Osprey are fish-eaters and inhabitants of river and lake country.
Their powerful long, narrow, slightly crooked wings can lift them out of
the water after having plunged in after a fish. Their feet have spiny scales, long curved talons and a reversible outer
toe, all of which increase their ability to hang onto their slippery prey.
Osprey (Pandion haliaetus)
 Falcons
Falcons
are swift, aerial hunters. Their
streamlined bodies, short narrow pointed wings and slim tail enhance this
lifestyle. Unlike other raptors, they have a small tooth-like projection
behind the hooked tip of the upper bill which characterizes them as
falcons. Three types of falcons are found in the NWT:
Gyrfalcon (Falco rusticolus)
Peregrine falcon (Falco
peregrinus)
Merlin (Falco columbarius)
American
Kestral (Falco
sparverius)
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