I had the following post on a thread regarding "fox problem" and it would apply here as well; If you are up to taking a dog, it's the best solution in guarding a flock in my opinion. You need one of the sheep type dogs,
not herding (definitely not hunting), ie. Great Pyreneese, Maremma, Kuvaz, Akbash, etc. I think even a mix of one of these would work. I got a Great Pyreneese from a local shelter almost 3 years ago and haven't lost a bird since (used to loose up to 5 birds a year to foxes and minks - we have coyotes too, but haven't seen any close to the house). I doubt she's a pure bred but I didn't need to train her, I just put her in with the birds and the was off to work. We have chickens, geese and a peacock. My dog stays out with the birds from morning till the birds get locked up in the coop for the night. She sleeps nights inside on our bed, which I don't recommend unless you have a king size bed

. But, I'm sure they would be ok outside for the night as well, it's just our choice to bring her in at night. She instinctively guards the yard and everything in it from all critters. And, since I live in Canada, she can easily tolarate even -30deg temperatures, she's ok in heat too except she likes to take an occasional dip into the mud in the summer and you can just imagine how she looks after that

. She has a dog house with straw facing the bird yard, but only goes in it if it rains or snows. She's the best investment I ever made. I've seen other's post about Great Pyreneese as well, so I would definitely recommend a GP for your coyote issue. They have basically no prey drive. They guard a yard (not from people though, just strange animals) and she's the best at it!