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Wind, climate change and raptor migration

Posted on Oct 4, 2014

Earth’s climate and weather play a direct and constant role in the lives of birds. At no point is this impact from mother nature more widely observable than during migration. Global winds shape the timing and track of bird movements across the continents and the sea. In this case I wanted to take a look at September 2014 and how it seems to have been a climatic “throwback” in the Northeast for our birds.

If you talk to folks in many portions of New England the Mid-Atlantic about the weather in 2014 you often hear how it was very average in terms of temperature and precipitation. It was downright “boring” at times after years with massive blizzards, hurricanes, numerous severe thunderstorm outbreaks, and so forth. Certainly some areas were further from average than others during the year (very wet in some parts of the Chautauqua-Allegheny region!) but September was a quiet month with little precipitation that allowed avian migrants to move through slowly and steadily along historic routes and corridors along the Atlantic Coast.

Boothe Park clocktower sky cirrus clouds 0366

September 14, 2014. Northwest winds? Check. Light cirrus clouds to help us see raptors? Check. What you can’t see – the wind strength – is what hurt migratory counts in September at our hawk watch at Boothe Memorial Park in Stratford, Connecticut.

Raptors like the Broad-winged Hawk were mostly able to follow what we have perceived over time as “preferred” inland routes without being pushed to the coast, coasting over the hills rather than soaring along the shore. If they can glide over Litchfield County and make a shorter, more direct route south then why take a longer southern detour towards Long Island Sound when they have to go west no matter what? This was because of weak cold fronts passing through frequently and light winds making optimal flight easy for the birds. When we on the coast have a good day of raptor migration we have to literally hold on to our hats and weigh down our chairs because of the wind.

My question is this – have we had surprisingly significant counts of Broad-winged Hawks at coastal watch sites in recent years more frequently because of climate change aiding the increased frontal strength and more powerful high pressures making for stronger winds? We certainly have had atypical, in comparison to historic norms, years where inland sites have had hundreds of birds while we count thousands (such as 8,041 Broad-winged Hawks out of 8,234 raptors on 09/16/11).

There is no certain answer here…only an abundance of questions that deserve answers. I hope we will be able to devote the time and resources to this research and study because if climate change and a warming planet play a role in altering major migratory corridors, shifting the highway south (or north) for billions of birds each year then we will have to be ready for it and plan accordingly. Our coasts may become even more important than they already are.

Scott Kruitbosch
Conservation & Outreach Coordinator