Last year I posted an information request for information regarding 
trees to attract warblers.  While I received many good suggestions, I 
ran into a dead end finding a source for the tree I decided I wanted to 
purchase unless I was willing to drive 1.5-2 hours.

I finally purchased my Hackberry (Celtis occidentalis) from Herring Run 
Watershed Association who was holding an Earth Day sale at Mt. Pleasant 
Golf Course 5 minutes from my home!  

Moreover, this same group will be participating in another plant sale at 
Cromwell Valley Park along with Cromwell Valley C.S.A. (CVCSA) and 
Therapeutic Alternatives of Maryland (TALMAR). 

The sale will be held Saturday, May 9th and Sunday, May 10th, rain or 
shine, in the historic Sherwood Barn inside Cromwell Valley Park, 2002 
Cromwell Bridge Road (21234).  Sale hours are 10 am to 4 pm both days.

http://www.cromwellvalleypark.org/

Furthermore, you can get a $10 off coupon for trees from the "Growing 
Home" link on the last page of Baltimore County's Recycling Newsletter, 
"The Re-Source".

http://resources.baltimorecountymd.gov/Documents/Public_Works/solidwastemanagement/resource/resourcemarch2008.pdf

Happy gardening for birds---

Georgia McDonald   Towson, Balt Co