Fall Bird Migration

It's almost that time of year when the migratory bird species that call the mid-latitudes of North America home all summer begin to move back to the tropics and subtropics for winter.  The trigger for this southward migration is shortening day lengths and cooler weather.  Over the span of a couple months billions of birds will make the journey, and some of those birds will fly through your backyard.

Why do birds expend the energy to fly thousands of miles, sometimes risking dehydration and starvation to fly across the open waters of Gulf of Mexico?  As colder weather develops across temperate North America food supplies dwindle.  In addition many birds simply aren't adapted to survive sustained cold weather, particularly cold weather of the magnitude experienced in Canada and the northern United States.  Snow covers up any food on the ground.  The tropics and subtropics offer mild temperatures, plentiful food supplies, and a safe place to wait out the cold winter weather to the north.  But that begs the question "if it's so nice in the tropics, why fly north each spring?"  So many birds packed into so little space in the forests of Central America eventually would lead to stress on the naturally occurring insect and plant food sources here too, especially as the birds tried to breed and raise hungry young.  Temperate North America offers relatively uncrowded territory with ample food -- at least for the summer months.

I live in a great area to view the various bird species during fall migration.  Prevailing wind directions during the fall begin to acquire a more northwesterly component across the Eastern U.S., constricting the southward-moving stream of migrating birds up against the Atlantic coast.  Contrast this to the spring migration where the stream of northward migrating birds fans out well to my west.  During spring migration I invariably will see much lower numbers of migrating species.

The reason I'm writing this today (August 30th) is I saw my first Red-Eyed Vireos of the year. While Red-Eyed Vireos do breed across Southeastern North Carolina they do not breed in my neighborhood.  (At least not that I'm aware of)  When I start to see Vireos show up it means this species is beginning its movement  out of its typical breeding habitat and the migration season can't be far behind.

The list of fall migrants I typically see here is unique:  Red-Eyed Vireos, White-Eyed Vireos, American Redstarts, Black-and-White Warblers, Gray Catbirds, and Black-throated Blue Warblers. It's even arguable that some the Black Vultures I've seen in fall are southward-moving migrants.  There are many, many more species that move through this area I'm just waiting to see.

Here are some photos taken in my backyard from previous fall migration seasons:

Red-Eyed Vireo

Black-and-White Warbler

White-eyed Vireo

Black-throated Blue Warbler (never faced in my direction)

American Redstart

Toward the tail-end of the migration season in late October I start to see my typical winter birds return:  Baltimore Orioles, Yellow-rumped Warblers, and White-throated Sparrows among others.