Monday, September 28, 2009

Fall Bird Migration

In my last post I covered the antics of robins in Central Alberta as they migrate south. I should have first written about bird migration in general.

Migrating birds can be divided into large groups . There are water birds, boreal birds and grassland birds. In each group there are a large number of species and a wide variety of migration habits. To complicate matters many birds, particularly the males, look different than their spring plumage. In the fall I keep the Sibley's bird book nearby as the spring and fall plumage are covered as well as juveniles. Identifying birds in the fall is challenging as you see a bird hat looks familiar, but you can't quite place them. This is because the fall plumage is different.

Some of these birds leave us by the end of August. Others spend more time here as there is abundant food. Much has to be learned about migration, but birds seem to move in a narrow time line each year no matter what the conditions are . I keep a yard bird list . Each year the birds return at about the same time .

Boreal birds, such as warblers , busily work their way south by feeding in trees, brush and plants. They feed in the daytime and fly at night . Many times they crash into tall buildings and are found the next day at the bottom of the building. While they are in our yards they are interesting to watch. In my yard the most common warbler is the yellow rump. They feed on aphids on the back of leaves.

Water bird migrations are spectacular as we see the flocks of geese in their familiar vee formation. Ducks are in loose flocks and tend to fly rapidly. These birds feed for weeks in central Alberta grain fields.

Once again these birds are consuming huge amounts of high energy foods . They are also conditioning themselves for major flight. As a result the birds are energetic and we see all kinds of antics which attract our attention.

My childhood was spent in central Saskatchewan where there are main flyways for ducks and geese. When the wetlands were full of water it was perfect habitat for these birds. Sad to say many of these wetlands have been cleared and plowed for farmland.

A migration that most people try to ignore is the flight of crows. All through September we have massive numbers of crows which fly out to fields each day to feed on seeds and insects. In the evening they fly back to a common roosting area.

Several places on the edge of the Rocky Mountains provide perfect places to watch the migration of eagles . If you sit in the one spot you can count many eagles in one day.

So folks get out and enjoy the fall migration. These birds will soon leave us and we will be left with the few hardy species of winter birds.