Monday, September 30, 2013

Northern Goshawk

Northern Goshawk - Accipiter gentilis

These raptors have a reputation for relentless pursuit of Snowshoe Hares and Ruffed Grouse, their traditional prey. However, anything smaller that moves is at risk when this talented hunter is in the neighborhood. In years when the Snowshoe Hare population falls, Northern Goshawks might migrate south. 

Accipiters have long toes and the prey is killed with the talons. After capture, and during flight, the Northern Goshawk extends long legs away from the body to minimize injury from the prey, and repeatedly stabs the prey with the talons until a vital organ is penetrated. The beak is only used for feeding.  
The location at the edge of a coniferous forest, the broad tail with a fourth tail band, and the distinct white supercilium confirm this as an immature Northern Goshawk.
References

The Atlas of Breeding Birds of Alberta. Federation of Alberta Naturalists. 2007.

Dunne P, Sibley D, Sutton C. Hawks in Flight. Houghton Mifflin. New York. 1988.

Fisher C, Acorn J. Birds of Alberta. Lone Pine Publishing. Edmonton. 1998.

Sibley David A. The Sibley Guide to Birds. Alfred A Knopf, Inc. New York. 2000.

Sibley David A. The Sibley Guide to Bird Life and Behavior. Alfred A Knopf, Inc. New York. 2001.

Friday, September 27, 2013

Mountain Goat

Mountain Goat - Oreamnos americanus


Recently, we saw a mother and her kid foraging in a rocky gully along the Kananaskis Highway. The mother bounded up the grassy hill and ran past us. However, the kid was intimidated by our presence, and as soon the young goat was about ten meters from us, the kid turned and ran back down the hill. The young goat repeated the run-up-to-us, pause and bleat, and then run-back-down manoeuvre about five times before the mother finally returned to the gully.
The mother's fur looked mangy because the autumn moult had started. Mountain Goats moult twice a year. The short 1 cm summer coat moults in autumn to allow the long 20 cm winter coat necessary for a Canadian winter in the mountains.

Male and female goats look the same and are difficult to tell apart. We presumed this was a mother, since kids and even yearlings stay with the mother. The pictures otherwise confirm the female gender. The circumference of the male horn is much larger at the base than the eye of the goat.

Female goats squat to urinate and males "stretch." The mother obliged us by peeing before she ran past us and down into the gully to rejoin her kid.   
The main predators include grizzly bear, wolf, and cougar. Golden Eagles prey on kids and juveniles. These large raptors swoop by and and knock the smaller animals off the cliff-sides and then feed on the fallen carcass. The most common cause of death is avalanche. Mountain Goats forage at higher elevations in the summer and lower elevations in the winter. Except during autumn rut, adult males and females live in separate groups.
References

Gadd Ben. Handbook of the Canadian Rockies. Corax Press. Jasper, Alberta. 1986.

Naughton Donna. The Natural History of Canadian Mammals. UofT Press. 2012.

Wednesday, September 25, 2013

Cooper's Hawk


Cooper's Hawk - Accipiter cooperii

A gang of young crows hang out in my backyard. They enjoy the husked sunflower seeds I set out. These black adolescents are not endearing. They make a lot of racket and they scare off the smaller birds. Periodically I chase them off.

Recently, a Cooper's Hawk did the job for me. At dawn, I looked out and saw several of the crows sitting on the metal arch at the back gate. Suddenly, they scattered. A Cooper's Hawk arrived and for a few moments, the sky above the gate was a flurry of birds as the crows disappeared in a variety of directions. The Cooper's Hawk took up the same perch on the metal arch.

The Cooper's Hawk arrived from the East, and was likely perched along the fence in my neighbour's yard. The fence is a favoured perch for the Cooper's Hawks and Merlins who prey on the smaller birds who enjoy the sunflower seeds. Smaller birds avoid the yard when the crows are present. A such, the crows were inconvenient for the Cooper's Hawk.
The short rounded wings of accipiters are well-adapted for quick maneuvering in dense forests, and the tight turns the Cooper's Hawk made above my fence were a perfect example of this attribute. Surprise is the hallmark of an accipiter.

References

The Atlas of Breeding Birds of Alberta. Federation of Alberta Naturalists. 2007.

Baicich PJ, Harrison CJO. Nests, Eggs, and Nestlings of North American Birds. Princeton UP. 2005.

Dunne P, Sibley D, Sutton C. Hawks in Flight. Houghton Mifflin. New York. 1988.

Fisher C, Acorn J. Birds of Alberta. Lone Pine Publishing. Edmonton. 1998.

Sibley David A. The Sibley Guide to Birds. Alfred A Knopf, Inc. New York. 2000.


Sibley David A. The Sibley Guide to Bird Life and Behavior. Alfred A Knopf, Inc. New York. 2001.