system
Given the following post, respond as if you're commenting on Reddit:
human
How/why do separate species breed?

It's rare but different species have bred in the wild. But how? Why don't they attack one another like they normally would?

For example, coyotes and wolves are two separate, but closely related, species that have bred without human interference. But they're rivals with different behavior. 

I assume they mate and then part. They can't rear the pups together, right? On that note, do coywolf pups get raised by single mothers or do males of their mother's species help, despite not being their pups?

Another example I know of is Big Bird, the cactus finch. He somehow bred with completely different finches. How did he attract the females despite having the wrong call and being of the wrong species? I know his children couldn't attract anyone but each other despite having his call. Why couldn't they breed with other finches but Big Bird could?
gpt
You're placing a lot of stock in the intellectual reasoning of creatures with brains sometimes the size of a grape. "Because sex" is sometimes all the reason wild animals need. It was there, it was available. 

Not even wild animals, some pets will have sex with a mate, a cushion, and their owner's leg with equal enthusiasm.