While I'm on the subject of bluebirds, it's a good time to warn all bird 
lovers about tree tubes.  These are used to protect saplings from deer.  
Usually consisting of a plastic tube about 4' high held up by plastic ties 
and wooden stakes, these tubes are attractive nuisances for bluebirds: the 
male EABL wants to explore all possible nesting cavities, so he will go into 
the tube and fall to the bottom and not be able to get out (this kind of 
thing doesn't exist in the wild).  I have freed quite a few trapped 
bluebirds (along with occasional EUropean STarling) from these infernal 
devices, and have removed even more dead ones.

The tree tube manufacturers sell (or include) woven plastic tops, or "socks" 
to go over the tops of the tubes.  These will effectively prevent male EABL 
from going into the tubes.  If you see tops on the tubes, you're okay.

If not, you can use some means to create a small exit slot or hole at the 
bottom of the tube, such as pulling the stake out of the ground 1.5 inches.  
I don't want deer to eat saplings, but even more than that I don't want any 
birds, much less native birds already suffering from competition from 
invasives, to die of starvation/dehydration due to thoughtless human 
activity.

Paul Kilduff, Baltimore

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With tax season right around the corner, make sure to follow these few 
simple tips. 
http://articles.moneycentral.msn.com/Taxes/PreparationTips/PreparationTips.aspx?icid=HMFebtagline