Final answer:
The two bird species' different song patterns are an example of a prezygotic barrier, as these song patterns are essential for mate recognition and thus prevent inter-species mating before fertilization can occur.
Step-by-step explanation:
The example of two bird species with very different song patterns for mate recognition represents a form of reproductive isolation, specifically a prezygotic barrier. In these birds, the unique song patterns are an essential part of courtship and mating behavior. If the birds do not recognize the songs of another species as potential mating calls, they will not attempt to mate with each other. This is a clear case of behavioral isolation, which is one of the mechanisms under the broader category of prezygotic barriers that prevent interbreeding between different species.
In the case of two bird species with different song patterns for mate recognition, it is a prezygotic barrier because the differences in songs prevent the birds from attempting reproduction. This prevents the formation of a zygote and ensures reproductive isolation.