A while ago I heard the following anecdote:
"On some tropical island, explorers infested the island with rats that wrecked the native ecosystem. To get rid of rats, people introduced cats that instead of hunting rats killed off the entire island's bird population".
The explanation given is that birds could not recognize cats as predators and/or did not have natural predators in the environment. This made me think - is there any part of a bird that on a genetic level knows that some other organism is a predator and is to be avoided?
For animals that live surrounded by predators, for example a house sparrow - how does a bird learn that cats are predators, but squirrels are not?
An example might help illustrate my question: Let's say someone takes house sparrows from America and breeds them for 3 generations on the same tropical island with no predators - would such 3rd generation sparrow still recognize cats as predators?