Since it's a cold, damp spring - and also because some birds have two
broods - it's still worth putting out nesting material. We put out RG's
hair after a trim and I gather some of the moss from the lawn. Pet hair
is also a possibility, and dog hair would help to keep squirrels away
from nests containing eggs.

Do you really think that squirrels haven't worked out that Dogs can't
climb trees?