How Migrating Hawks
Use Air Thermals
Migrating hawks sometimes form a kettle of hawks, or groups, that will swirl in small flocks overhead.
Hawks swirling in a kettle are actually circling tightly in an air thermal.
When a kettle of birds is tightly circling in a thermal, they look from a distance like something boiling in a cauldron, which may explain the origin of the word kettle to describe a thermaling flock.
Thermals are what the hawks rely on to assist them on their traditional migratory pathways, which are determined by both geography and weather patterns.
geographic features, known as leading lines, include
mountain ridges, coastlines or lake shores. For instance, in parts of
the Appalachians, the mountain ridges form nearly parallel
lines. Wind following a cold front blows from the northwest,
and it strikes these ridges at about a 90 degree angle.