When someone is referring to hawks as a kettle of hawks the meaning of the kettle of hawks is used to describe a group of birds or hawks that are wheeling and circling in the air.
The kettle of Hawks may not always be just hawks flying in that Kettle but also may be composed of several different species of birds at the same time.
Hawks and other birds usually begin their kettle flying in September before flying south for the winter.
Hawks form “kettles” in thermal updrafts during migration.
When the hawks find a column of warm, rising air they stretch out their wings to rise with it and then other hawks in the area see the kettle of hawks forming and join the crowd.
Then the kettle of hawks grows and grows.
As each hawk reaches altitude at the top of the thermal the hawk sets their wings and glides away toward their destination.
Then one by one, each hawk leaves the kettle from the top while others join below.
During their glide the hawks lose altitude so they find another thermal and repeat the process.