I don't know about Reggie's blue birds, but ours are little
wimps.  If a sparrow or chickadee fights to nest in the blue
bird house they always get it without much resistence [with
no outside interference of course], but even if I get pissed
because I bought that damn thing for blue birds and by God
blue birds will nest there or nothing will nest there and I
chase off the offending bird, the little shit ass blue bird
does not take up residence in that house that nesting
period.  Neither will the offending bird.  I have to wait
for their next nesting period.  They do not thrive on
stress.  Actually, they avoid stressful situations.   That's
why it is difficult to get them to nest in a bird house that
is near tall bushes, trees, or bird feeders, especially when
it faces those doohickeys.  Blue birds are pretty, but
wimpy.