We have a lot of birds visit our yard that are the same size and roughly same shape as a hawk, eg cockatoos, ravens and corellas. But when a hawk shows up and perches nearby my girls go nuts until I go scare it off. It must be instinct becuase a bird of prey is a threat to chicks but how do they know? Anyone have a good explanation or link to an article? In the same vein, from day one they are fine with the dog but the cats spook them more.