Bird Migrations
I know that during the winter you migrate. But where do you come from in the spring?
Winter Summer
-this is an example of Bird Migration, which for most migratory birds involves flying south each fall and returning north in the spring -why fly south in fall? to escape the cold weather and the resultant lack of food -why fly north in spring? (good question!) -less competition, more food available -longer days provide more time to find food for chicks
-most birds (especially those living in warmer regions of the earth) do not migrate (i.e. 8,200 species out of 10,000)
-most birds (especially those living in warmer regions of the earth) do not migrate (i.e. 8,200 species out of 10,000) X X -much less land in south -many birds (living in cooler regions) breed in north regions in summer and migrate south in winter (i.e. 1,800 species out of 10,000)
-but even in cooler regions of the earth, some birds do not migrate In our area, these include: crows and ravens chickadees blue jays woodpeckers starlings northern cardinals rock pigeons mourning doves nuthatches sparrows
Black-Capped Chickadee: a Resident (Sedentary) bird
Migrating Birds -from Canada, some of our birds migrate south only as far as the USA -these include: goldfinches canada geese grackles loons wood ducks merganser ducks bald eagles
American Goldfinch
Canada Geese
Bald Eagle
Wood Duck
-other birds migrate further south to Mexico and Central America -these include: ruby-throated humming birds robins bluebirds baltimore orioles red-winged blackbirds mallard ducks great blue herons ospreys peregrine falcons ring-billed and herring gulls
American Robin
-some birds migrate all the way to south america -these include: swallows purple martins scarlet tanagers red knots
e.g. Cliff Swallows
Cliff Swallow Migration
Swallow is symbol of happiness. Song: When the swallows return to Capistrano
Red Knot migrates from arctic to terra del duego -stops on way north at Delaware bay and feeds on eggs of horseshoe crab; threatened by harvesting of crabs
-Arctic Tern migrates from north pole to south pole and back (travels 22,000 miles each year)
Longest non-stop flight: Bar-Tailed Godwits: from Alaska to New Zealand (11,000 km) 11,000 km 8 days non-stop!! -prior to flight 55% of body weight is stored as fat to fuel flight
Highest Fliers: Bar-headed Geese (fly over Himalayas) Wintering Area Himalayas Breeding Area
Bar-Headed Geese flying at 21,416 feet while crossing Himalayas
Birds tend to migrate along specifically named flyways -visual landmarks: coast lines, rivers, mountain ranges
Mechanics of migration -use sun, stars, lines of earth s magnetism -youngsters learn from adults -return to same nest or barn (swallow)
Mechanics of migration -broad-winged gliding birds ride on rising thermals of hot air which exist only over land
These thermals of air lie beside mountain ranges Rockies Andes
-broad-winged gliding birds avoid large bodies of water such as Mediterranian Sea since these have no thermals and these birds cannot maintain active (wing flapping) flight for long periods Med
-birds travel in flocks -for protection against predators -for efficiency of flight 20% less energy used
Hazards to migrating birds -threatened by hunting Passenger Pigeon (hunted to extinction) -flocks were one mile wide and 300 miles long -darkened sky -took three days to pass over
Other hazards to migrating birds Wind farms - collision Power lines collision and electrocution
Conservation Measures -set up sanctuary on his farm in 1904 -first to band geese and ducks in North America -led to U.S. Migratory Bird Treaty in 1918
Conservation Measures Jack Miner Bird Sanctuary Point Pelee National Park Point Pelee National Park
Ducks Unlimited: Since 1927, 700,000 members Wood duck restored from almost extinction -greatest current threat comes from loss of habitat (e.g. wet lands, especially for shore birds such as sandpipers and red knots)
Issues are highlighted in two excellent BBC productions (available on DVD from Ottawa Public Library) BBC BBC 6 hours 1 hour THE END