grammaticality - Singular or plural form of verb

Which of two following sentences is correct?

1. Depending on whether
   
   a birth or a death occurs , we have...




2. Depending on whether
   a birth or a death occur, we have...

Update I changed the title.

Answer

OP's example #2 looks a bit unlikely, but in certain contexts it could be valid. As they say, it all depends on the "whether" - in this case, whether the two possibilities are...

1 A: a birth occurs, OR B: a death occurs
2 A: a birth or death occurs, OR B: neither of those things happens (happen??!!!)

If OP intends the second distinction, the plural verb form in #2 is fine.

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I wouldn't have a problem with a hotel manager saying...

"It all depends on whether the King or Queen turn up - if not, we might be able to let you have the Royal Suite tonight"

In that context, the two possibilities referenced by whether are that either a senior royal arrives (and thus gets the best room in the house) or neither of them do (in which case you will get the accommodation upgrade).