Within the column “Since You Requested” in each situation of BirdWatching, Contributing Editor Julie Craves solutions readers’ questions on birds and hen conduct. Here’s a query from our September/October 2019 situation.
Q: What makes a gaggle of hawks a “kettle?” — Clair Van Buren, Bloomington, Indiana
A: Hawks and different raptors migrate through the day. Because the solar heats the bottom, heat air rises from the earth. Sure geographic options, together with pure topography or human-built areas, can fluctuate the speed and placement of heating, creating columns of heat, ascending air. Birds can enter these updrafts, and by flying or hovering in a circle inside the column, they are often lifted excessive into the sky. Because the birds attain a top the place the column dissipates as a result of it meets more and more cooler air, they will merely set their wings and glide down into one other thermal within the course they’re headed. Utilizing this technique, the birds can journey fairly far whereas conserving vitality, because it takes far much less effort than fixed flapping.
The sight of a gaggle of hawks profiting from a thermal, all swirling and spiraling, is harking back to objects being stirred or boiling in a pot — therefore the phrases a “kettle of hawks” or “hawks kettling.”
Thermals don’t type till the solar is sufficiently excessive within the sky, normally mid-morning, so observing kettles of hawks doesn’t require rising on the break of day. Nor do thermals type over water. Notably, migrating hawks will lose altitude as they cross a lake or massive river, so websites situated close to shorelines are nice locations to look at migrating hawks as they arrive onshore at decrease altitudes earlier than they’re in a position to “catch” a brand new thermal to journey.
Study extra about raptor migration on the web site of the Hawk Migration Affiliation of North America, and uncover nice fall hawk-watching areas on this BirdWatching article.