If I remember right the study attributed Cooper hawks feeding mainly on birds to them having a very narrow size range for the prey they targeted……They were basically targeting that baseball size diameter of birds and that’s all……compared to something like a red tail hawk who had a much wider range of anything from golf ball to volleyball……If that’s true then it means there would be a fairly narrow window for which Coopers would target poults as they passed through that specific size range.


Just an example of what I'm talking about with targeting specific size ranges........

https://feederwatch.org/learn/artic...-and-coopers-hawks-pick-different-foods/


"Miller and colleagues found that Sharp-shinned Hawks took smaller-bodied birds, such as juncos and Pine Siskins most often. Cooper’s Hawks also took smaller-bodied birds, but they mainly took medium and larger-bodied birds, such as European Starlings and pigeons. Miller explains that a focus on different size prey may be one component that allows these species to coexist. "