adventure for the outdoor enthusiast
Squamish - Whistler - Vancouver

Eagles Brackendale Eagles Park

Falcons, Stawamus Chief Park - Squamish BC - StawamusChiefPark.ca
Photo Credit: Bill McComish, WestCoastPhotos.com

The Bald Eagle

Scientific name - Haliaeetus leucocephalus

Eagles are a member of the Accipitridae family, which also includes hawks, kites, and old-world vultures.

Scientists loosely divide eagles into four groups based on their physical characteristics and behavior. The bald eagle is a sea or fish eagle.

There are two subspecies of bald eagles. The "southern" bald eagle, Haliaeetus leucocephalus leucocephalus, is found in the gulf states from Texas and Baja California across to South Carolina and Florida, south of 40 degrees north latitude. The "northern" bald eagle, Haliaeetus leucocephalus alascanus, is found north of 40 degrees north latitude across the entire continent. The largest number of northern bald eagles are in the Northwest, especially in Alaska. The "northern" bald eagle is slightly larger than the "southern" bald eagle.

Studies have shown that "northern" bald eagles fly into the southern states and Mexico, and the "southern" bald eagles fly north into Canada. Because of these finding, the subspecies of "northern" and "southern" bald eagles has been discontinued in recent literature.

Bald eagle body description

Color - The adults have a blackish-brown back and breast; a white head, neck, and tail; and yellow feet and bill.

Juvenile bald eagles are a mixture of brown and white; with a black bill in young birds. The adult plumage develops when they're sexually mature, at about 4 or 5 years of age.

The bald eagle is the only eagle confined to North America, and there are no other large black birds in North America with white heads and tails.

Size - The female bald eagle is 35 to 37 inches, slightly larger than the male. With a wingspan which varies from 79 to 90 inches.

The male bald eagle has a body length from 30 to 34 inches. The wingspan ranges from 72 to 85 inches.

Bald eagles weigh from ten to fourteen pounds. Northern birds are significantly larger than their southern relatives.

The golden eagle is larger than the bald eagle in average height and wingspan, but there isn't much difference in their average weight.

Life expectancy - Wild bald eagles may live as long as thirty years, but the average lifespan is probably about fifteen to twenty years

Eagles sit at the top of the food chain, making them more vulnerable to toxic chemicals in the environment, since each link in the food chain tends to concentrate chemicals from the lower link.

Body Temperature - 102 degrees Fahrenheit (38.8 degrees Celsius)

Tolerance to cold temperatures - A bald eagle's skin is protected by feathers lined with down. The feet are cold resistance because they are mostly tendon. The outside of the bill is mostly nonliving material, with little blood supply.

Fidelity - Once paired, bald eagles remain together until one dies, the survivor will not hesitate to accept a new mate.

Voice - Shrill, high pitched, and twittering are common descriptions used for bald eagle vocalizations. Eagles do not have vocal cords. Sound is produced in the syrinx, a bony chamber located where the trachea divides to go to the lungs. Bald eagle calls may be a way of reinforcing the bond between the male and female, and to warn other eagles and predators that an area is defended.

Skeleton - It weighs about half a pound (250 to 300 grams), and is only 5 or 6 percent of its total weight. The feathers weigh twice that much. Eagle bones are light, because they are hollow. The beak, talons, and feathers are made of keratin.

Detailed diagram of a bird skeleton Another diagram of a bird skeleton

The wings and soaring - An eagles wings are long and broad, making them effective for soaring. To help reduce turbulence as air passes over the end of the wing, the tips of the feathers at the end of the wings are tapered so that when the eagle fully extends its wings, the tips are widely separated.

To help them soar, eagles use thermals, which are rising currents of warm air and updrafts generated by terrain, such as valley edges or mountain slopes. Soaring is accomplished with very little wing-flapping, enabling them to conserve energy. Long-distance migration flights are accomplished by climbing high in a thermal, then gliding downward to catch the next thermal, where the process is repeated. Several eagles soaring in a thermal together is described as a "kettle of eagles".

The tail - is very important for flight and maneuvering. While the bald eagle is soaring or gliding in flight, the tail feathers are spread, in order to attain the largest surface area and increase the effect of thermals and updrafts. The tail also helps to brake the eagle when landing and assists in stabilization during a controlled dive or swoop toward prey. The strength of the feathers and the follicles holding the feathers is quite impressive, while watching the tail move back and forth and up and down during maneuvers.

Bald eagles have 7,000 feathers. Eagle feathers are lightweight yet extremely strong, hollow yet highly flexible. They protect the bird from the cold as well as the heat of the sun, by trapping layers of air. To maintain its body temperature an eagle simply changes the position of its feathers. While an eagle suns itself on a cold morning, it ruffles and rotates its feathers so that the air pockets are either opened to the air or drawn together to reduce the insulating effect. Feathers also provide waterproofing and protection, and are crucial for flight.

Feather structure makes pliability possible. Overlapping feathers can form a dense covering, which the birds can open or close at will. The bald eagle has several layers of feathers, each serving a different function. Under the outer layer of feathers is an inner layer of down or smaller feathers. The inter locking of feathers is an astonishing design of nature.

The feathers enable eagles to live in extremely cold environments. Eagles do not have to migrate to warmer areas each year to fulfill temperature requirements, they migrate to available food supplies.
A lone eagle feather is believed to convey great power. North American Indians incorporated the eagle's primaries and tail feathers into their ceremonies and legends.

Respiratory system - Eagles have external nares opening on both sides of the bill. A bald eagle never reaches speeds that would interfere with normal breathing. The eagle's lungs and air sac system is adequate for its size. Air moves in through the lungs and on into the air sacs before moving back through the lungs and out again. Air passes through the lungs twice with each breathing cycle - twice that of mammals. More about the respiratory system of birds

Beak - The hook at the tip is used for tearing. Behind the hook, the upper mandible, the edge sharp enough to slice tough skin, over laps the lower, creating a scissors effect. A bald eagle's beak is a strong weapon, but is also delicate enough to groom a mate's feathers or feed a small portion of food to a newly hatched chick.

The beak of a female eagle is deeper (distance from top to chin) than the beak of a male.

The beak and talons grow continuously, because they are made of keratin, the same substance as our hair and fingernails. The beak of a captive eagle is not warn down naturally, so must be trimmed annually.

Talons - Talons are important tools for hunting and defense. Eagles kill their prey by penetrating its flesh with their talons.

 

#  AREA NAME  ADULT JUVENILE UNKNOWN  TOTAL
1 Elaho (north of mile 30)  35 9 0 44
2 Upper Squamish 68 10 0 78
3 Ashlu 74 0 0 74
4 Pilchuk to Ashlu (walk + raft) 93 28 0 121
5 Cheakamus to Pilchuk (rafting) 284 0 0 284
6 I.R. Bluffs to Sunwolf 323 150 67 540
7 Judd Slough to I.R.Bluffs 201 75 1 277
8 Easter Seal to Judd Slough 86 17 1 104
9 Mamquam to Easter Seal 136 68 8 212
10 Training Dyke to Mamquam 35 21 1 57
11 Downtown Squamish 0 0 0 0
12 Railway to Art Gallery 6 2 0 8
13 Stawamus 0 0 0 0
14 Inlet 0 0 0 0
15 Mamquam 25 9 0 34
16 Lower Cheakamus 221 80 0 301
17 Upper Cheakamus 8 6 0 14
18 Garbage Dump/ Airport 15 3 0 18
19 Baynes Island 151 66 0 217
 20 Old Main Channel 132 92 0 224
  TOTALS 1892 636 78 2607

 

TOTALS FOR PREVIOUS YEARS

 1986 / 537 1987 / 952 1988 / 2500  1989 / 1560 1990 / 737
1991 / 875 1992 / 1675 1993 / 1574 1994 / 3769 1995 / 2597 
1996 / 1859 1997 / 1319 1998 / 1352 1999 / 1847 2000/2607 

 

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Copyright 2003 Bill McComish
All images on this website are legally protected from unauthorized use by international copyright law. The images may NOT be used in other websites, published, copied to another computer or used as the basis for other photographs or illustrations.

 

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