Saturday, April 2, 2011

Spring Bird Migration in High Gear! (Radar Map) *April is migration peak*


American Redstart (male)
I knew this species was migrating through an area where I conducted bird species surveys in northeastern Oklahoma. Finally, after 3 years, I saw one in a Spring Migration "fallout". I had seen a female during the prior Autumn Migration.

Spring Bird Migration in High Gear!

A wondrous event is occurring every night on Earth and right above you! Unseen and silent, the spring bird migration is in high gear! Millions of birds will leave, are leaving, and/or have left the Caribbean, Central America, and South America to begin the annual journey northwards to nesting grounds throughout North America. These are the songbirds and summer residents in your backyard and hometown you see arrive each year.

The birds normally leave within an hour after dark, weather permitting, and continue flying northwards. Depending on where the journey started, the migration time and distance for species can be from a few weeks to a few months, from hundreds of miles to thousands of miles. Most birds migrate at night and stop during the day to rest and feed.

Spring Bird Migration 2011

Below is snapshot of the National Weather Service national radar mosaic at 9:08 p.m. CDT on Saturday, April 2, 2011. The blue and green circles around radar sites are "bird rings". Studying birds via radar is called radar ornithology. These bird rings can be seen below on the Gulf coast and inland in Georgia, Alabama, Mississippi, Louisiana, Texas, Oklahoma, Arkansas, Missouri, Nebraska, Iowa, Nebraska, and central to eastern South Dakota. The bird rings are millions of birds flying northwards, many ultimately to the Boreal forest in Canada and to Alaska. The Boreal forest of Canada is critical habitat for North American birds.

The Central Flyway, the migration path through the middle of the United States, is very evident on the map below. Rain is occurring in western South Dakota and North Dakota, which has cut off the overnight migration in these areas. Birds "drop down", wait for the weather to clear, and continue the northward migration the next permissible night. These are called "fallouts" by birders and some avidly seek these areas during the day to observe an abundance of species in a relatively small area.

The almost continuous blue along the Gulf Coast are birds making landfall from flying across the Gulf of Mexico plus birds leaving the coastline, after rest, to continue their journey northwards. Some stop very soon upon reaching land, exhausted. These birds then rise up in a night or two to continue the journey, now overland, northwards to their breeding grounds.

There is not much evidence of birds from Savannah, Georgia northwards along the east coast of the United States. The Spring Migration is underway but most of the birds fly parallel to the coast over the Atlantic Ocean. More evidence of migration will be seen in later weeks.

National Weather Service
National Radar Mosaic (for images as presented above)

The Yellow-throated Warbler is an early arrival of the Spring Migration, in March, to northeastern Oklahoma to begin nesting

Cornell Lab of Ornithology

Clemson University Radar Ornithology Lab

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