Miriam, thanks for the very interesting detail.  I'm picturing the 
typical bluebird/swallow nestbox, though, and having a hard time 
imagining nestlings being unable to get out when they're ready to 
fledge.  Since they're darn close to adult size at that point, what 
would keep them from getting out if the adults can get in and out?  Are 
they that much weaker?  I would think that most of them could get out 
just by using the backs of the rest as a starting place.  Even if it 
took a little longer to manage it, wouldn't the parents continue to 
respond to their food begging for at least a while past the usual time?

Owls and swallows may be very different in this, but I know of a 
situation where a nesting barn owl was inadvertently trapped in an open 
church steeple cupola in a town southeast of Boston when workmen put up 
chicken wire to keep pigeons from roosting inside.  She apparently 
hunkered down on her nest in a dark corner and wasn't noticed by the 
workmen.

The situation wasn't discovered until well into the fall, and all that 
time, the male owl had continued to bring mice and small snakes and 
other goodies to his imprisoned family, by that time four full-grown 
birds, with of course, no help from the female.  He had to work even 
harder because much of the food he left for them was dropped just out of 
reach of the birds inside, and the little roof terrace just below the 
sill of the cupola was thickly littered with the unreachable and uneaten 
meals he had so faithfully been dropping off.  I'm exhausted just 
thinking about the job that poor bird did so dutifully for so long!

Amazingly, all four birds inside appeared healthy and well-fed, and even 
the youngsters were able to fly right out once the chicken wire was 
taken down, having apparently gotten enough practice flying around 
inside the cupola.

Jane



Lawrence, Miriam wrote:

> I've had 9 nest boxes on my property for going on three years.  All have
> been occupied by Tree Swallows and Bluebirds (as well as a couple by House
> Sparrows, a problem I'm trying to solve now).  
> 
> My understanding is that smooth walls more commonly cause problems for Tree
> Swallows than for Bluebirds, because the swallows have weaker legs.  And the
> problem is that the fledglings can't get out. I've never heard of adult
> birds of either species having any such problem.  
> 
> We lost a large number of swallow nestlings to cold rainy weather two
> summers ago, but the Bluebirds did not have a problem.  The knowledgeable
> bluebirders I consulted attributed this discrepancy to the fact that
> Bluebirds eat insects from the ground, but the swallows catch them on the
> wing, and rain suppresses insect activity.  This means the swallows have to
> travel much farther for food and either can't get enough to feed the
> nestlings, or can't keep them warm enough, or both.
> 
> But these are all problems that occur AFTER nesting and breeding are
> underway. Based on what I'm hearing and seeing, what's happening right now
> is that the Bluebirds are not showing up or nesting in the first place.
> 
> As of yesterday, we still had our one pair of Bluebirds (I saw the female
> for the first time yesterday) aggressively defending a nest box from
> swallows. I did not see the Bluebirds today--but it was also very quiet on
> the swallow front.
> 
> Miriam Lawrence
> Monkton