Spring Migration is Underway

Right this moment spring migration for North American land birds is well 
underway starting from South and Central America. Some of these migrants will 
just gradually move north, then use the Panamanian Isthmus follow the 
topographic features of Central America then entering North America. 

Eastern oriented birds are apt to take a long distance route over the Caribbean 
Sea before entering North America. At that time of year the prevailing winds 
are from the southeast, giving those migrants an added boost. Depending upon 
weather conditions their migration can be very exciting for bird watchers. 

Since there are few visible land features to guide them over the ocean 
migrating birds will rely on celestial cues, such as the sun and stars. In the 
northern hemisphere, the sun lies in the south and moves during the day from 
east to west, and at night the stars rotate counter-clockwise. (In the southern 
hemisphere, it is all reversed). For course direction they will rely on the 
degree of geomagnetic pull for re-orienting their course. Some of the 
over-the-ocean migrants will enter North America via the southeastern states 
and then move north, but most of the migrants will enter the country via the 
Gulf Coast states and then branch out in all directions north. Some like the 
Dickcissels will drift to Colorado for nesting. Many of Colorado’s nesting 
birds winter in Central America so their migration north in spring is shorter 
and is less dynamic, but equally as welcomed.

Bob Righter
Denver, CO

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