Wow.  That's a shocker.  I wonder if the same thing holds true for tree 
swallow boxes, since a lot of boxes, including my two, are used by 
either bird.

Damn, I wonder if I have time to go retrieve those old nests I just 
tossed out the other day and put them back in.

Thanks for the info.


On 4/22/2016 11:23 AM, Janet Watton wrote:
> I just read in Mary Holland's quite excellent nature blog, "Naturally
> Curious." that we apparently don't need or even want to clean out old
> bluebird nests:  Here's what she writes:
> Contrary to what those of us who clean out our bluebird boxes have
> been led to believe, Cornell Lab of Ornithology states that
> experiments show preferences for nesting boxes containing old nests.
> In a paired experimental design bluebirds chose boxes containing old
> nests in 38 of 41 cases in which boxes with old nests were paired
> with empty ones.  Scientists conjecture that this may be because the
> old nests often contain wasp larvae, an easy source of food for the
> bluebirds.
> Who knew?! Janet Watton Randolph Center