Do Eagle-pairs escort each other as territorial marking?

Abstract

For 15 minutes we watched November 2020 two pairs of White-tailed Eagles Haliaeetus albicilla in Schleswig-Holstein (Schlei-Fjord) flying one after the other over a distance of about 2.5 kilometer. Partners flew at a distance of 30 meter, while pairs were spaced about 100 meter apart. Then they turned and the spectacle went in the opposite direction. This happened four times. In between, the pairs landed on trees for a short moment and started screaming. The action ended when both pairs flew to their adopted nest sites. We assume that this occurred at the foraging habitat used by both and was intended to delimit the boundary.