Answer:
You could have many hypothesis...
Explanation:
A hypothesis is a guess as to what is going to happen in a situation. Without knowing the exact question you are developing a hypothesis for I can't give you an exact answer and the hypothesis takes place before the experiment. So you wouldn't know why the birds didn't come.
But if I had to give a bs answer I would say that the conditions weren't ideal for the birds (ie not right location or type of food)