What to do to help them?

For the third year in a roll these beauties are setting up nest in my terrace. They have been hatching for the last two years, however, last year was very sad and not one chick made to maturity.

I am so excited to see them back today and looking for advice on how to protect them better.

It is not a garden, just a long strip of bedding. West facing with plenty afternoon sun, nest is closer to the shaddier end.