Male house sparrows (a bird species) sing a different song than do male tree sparrows (a different bird species). Based on this information alone, what type of prezygotic isolation mechanism might be acting to keep the species separate?

Behavioral isolation

Explanation:

The prezygotic isolation mechanisms are ecological, temporal, mechanical, behavioral and gametic. The mechanism shown here is behavioral because the birds sing a different song and their songs are used to attract mates as part of their mating behaviors. The different songs attract different species, thus the females of each species will only be attracted to the song of their own species, preventing mating between different species of birds.