SINE

Birds are Aura’s department, but when I'm outside looking for rocks, I’ve seen them sing to warn off intruders. I guess that’s easier than taking on every one that crosses your path. Aura came up with some reading matter on the subject if you’re interested.

Eliot Howard, Territory in Bird Life

Predecessors Altum (1868) and Moffat (1903) also made similar observations, though their ideas were not accepted at the time

Ernst Mayr, Bernard Altum and the territory theory

C. B. Moffat, Spring rivalry of birds

GET BOOK