We dont fear birds but we fear snakes, even if both tried to predate us for millions of years. Most mammals dont care about small theropods. we lived in our burrows and hid away from them, and even if we engaged in direct combat we had a chance because a large squirrel could sorta grip a chicken and bit it in some way the thing cant kill you. But a snake? Those shits are weird. And if they got you is game over. They also search inside burrows... they are devils and theres no way to fight them... we grip.