Could you setup birdfeeders on the site as far away from the pws as possible and near trees and bushes? You might be able to relocate the birds to a more favorable location for both them and yourself. Do you know what kind of birds they are?
If the feeder was aprox 100' -- 400' away and in an area where there are trees and/or bushes, I think it would be easy to move
certain types of birds away from the pws and have them focus much attention on the food and surrounding flora. Let's say they were goldfinches; they travel in flocks and love thistle so if they had a source of thistle they could very well move as a group away from the pws and to the area where the feeder is located.
I have my pws out back of my house didn't have any trouble with birds. (Fingers crossed for 2018). There are plenty of trees around the area where the pws is and I also have birdhouses up nearby (and feeders about 500' away and on the opposite side of my house). Birds find food easily and quickly.
BTW, it's a federal offense to shoot a songbird
Here's my thistle feeder good for goldfinches, purple finches, juncos, and etc:
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