Answer:
The birds do not breed with each other where their territories overlap.
Step-by-step explanation:
The correct answer would be that the birds do not breed with each other where their territories overlap.
A species consists of organisms that are phenotypically similar and are capable of mating to produce fertile progeny.
Hence, the first thing to establish that two organisms are not of the same species is the inability to breed with each other. If an eventuality occurs and they are able to breed, the resulting progeny would be invalid.
Therefore the fact that the golden-cheeked warbler and the black-throated green warbler do not breed with each other where their territories overlap is enough information to determine that the birds are separate species.