Hawks fly in circles because they use thermals to glide without using a lot of energy.
This type of flight is an effective way for hawks to stay in the air for long periods. Circling in thermals gives hawks plenty of time to search for food and patrol their territory.
When utilizing thermals, moving in circles allows the hawks to stay within the natural flow of the updraft.
Thermals are naturally occurring columns of warm air that rise up from the ground. The difference in air temperatures causes the warmer air to rise and this creates an updraft of air.
Hawks and other birds often use thermals to their advantage as they can use the rising air to fly higher while conserving energy.
Hawks utilize thermals so they can glide without needing to flap their wings, this reduces their energy output.
When using these updrafts of warm air, hawks will circle to gain altitude and cover more ground while remaining within the bounds of the thermal.
The Harris’s hawk uses soaring as their most common flight mode; they rarely flap their wings.
This is because hawks are large birds and flapping their wings requires a lot of energy making soaring considerably more energy-efficient.
The hawk’s large wing surface and broad feathers allow them to easily maneuver through the wind.
Searching For Food
When you see a hawk circling, they could be searching for food as most raptors specialize in active-searching (aerial hunting).
Red-backed hawks were observed soaring (flying in circles) almost 30% of the time, with the rest of the time in the air spent between wind hovering and gliding.
Circling in thermals allows hawks to cover more ground so they have more energy to catch prey.
Hawks have excellent eyesight, so they are able to continue looking for prey even while circling high in the sky.
Flying in circles could also be part of a courtship display. Red-tailed hawks are known to use soaring for courtship in late winter.
If you see a pair of hawks circling together they are likely performing a courtship display.
When courting, pairs of black-and-white hawk-eagles glide in circles at low altitudes while one of the pairs calls with short, sharp notes.
Similarly, the mantled hawk courtship behavior includes gliding together either on thermals in circles or as a horizontal glide before free falling in a spiral.
Patrolling Their Territory
Finally, many hawks glide on thermals as part of territorial behavior.
The white-necked hawk also glides on thermals as part of territorial behaviors.
If the hawk is patrolling their territory, then you may also hear them calling. This is the hawk’s way of letting others know it is their territory and they should stay away.
Why Do Hawks Screech While Circling?
Typically, hawks will screech while circling to either mark territory, attract a mate, or as part of a courtship display with a partner.
Hawks will screech loudly as they patrol their territory to warn others away.
Some hawks soar in circles while calling as part of their courtship flight, this is either performed with or directed towards a partner/potential mate.
Why Do Hawks Circle In Groups?
Hawks may be seen circling alone or in groups. If there is a group of hawks circling, then it is a sign that the hawks are flying in the same thermal currents.
During migratory seasons there is more chance of seeing multiple hawks gliding together through thermals.
Why Don’t Smaller Birds Circle?
Smaller birds have a different wing shape from hawks and are lightweight, so flapping their wings does not use as much energy.
Small birds are also safer closer to the ground as they can more easily evade predators. Larger birds such as hawks don’t have to worry about being vulnerable, so they can confidently soar at heights.
This is why small birds will flap their wings rather than soar and circle.
Hawks will soar in circles because it’s one of the easiest ways for them to fly. They can patrol their territory, find food, and attract a mate while flying in circles.
If you hear them screeching while circling, they are either letting potential threats know where they are or attracting a mate.