Tuesday, September 5, 2017

Nighthawks on the Move

As summer winds down [the first day of autumn is just three weeks away] forests, fields and wetlands have fallen silent of bird song, and with another nesting season behind them, many of the bird species that nest in Vermont and north are either in the midst or preparing for their annual southward migration to winter ranges in the southern U.S., Caribbean islands, Mexico, Central and South America.  Warblers, flycatchers and shorebirds are currently on the move and can pass through unnoticed to the untrained eye.  Currently two bird species, Common Nighthawk and Broad-winged Hawk, are wrapping up and beginning their fall migrations, respectively, at our latitude.  Both birds undertake spectacular flights: Common Nighthawks passing through from mid August to late August or early September, and Broad-winged Hawks primarily in September.  The nighthawk is the focus of this post with more to be said of Broad-winged Hawk migration in a future post.

The Common Nighthawk is not a hawk at all but rather a close relative of the Eastern Whip-poor-will, both members of the taxonomic family Caprimulgidae (nightjars) which translates from Latin to goatsuckers, in its own right is a misnomer.  Nighthawks are insectivorous birds feeding nocturnally on the wing and almost exclusively on flying insects.

Photo taken by Lloyd R. Bunten and is used with his permission.
Although nighthawks during migration may be observed in early evening hours just about anywhere in Vermont but especially along river corridors, the very best location to see them in high numbers is at Westminster Station in Windham County, Vermont.  This location is located next to a migration corridor, the Connecticut River, and is an area dominated by open agricultural fields, both features favoring an abundance of insects.  Annual surveys to estimate nighthawk migration abundance have been conducted here since 2010 by Don Clark, the principal counter and an experienced and well respected Vermont birder and naturalist.  Below are count data collected by him over the eight years since monitoring began.

The summer range of the Common Nighthawk includes much of the lower 48 states of the U.S. and the southern Canadian provinces.  Winter range extends from southern Columbia to central Argentina, and migration distance between summer and winter ranges spans 2,500 to 6,800 miles.

Each speck in the above photo is a nighthawk migrating over Westminster
Station, VT.  Place cursor on image and tap to enlarge.  Photo taken by 
Lloyd R. Bunten and is used with his permission.

Observing a thousand birds over several hours, not to speak of the nearly 6,000 counted in one evening this year, is amazing.  So, if you haven't experienced a nighthawk fall migration, mark your 2018 calendar.  You won't be disappointed.