We have lost our "warbler tree" and are looking to plant a replacement.  
I am looking for advice with respect to which trees are most attractive 
to migrant warblers. 

Historically, all our yard warblers tended to end in one tree on a 
neighboring property.  I never had a firm id on the tree itself, though 
its seeds & leaves looked like a type of elm.  It appeared to be in need 
of protection from afternoon sun since it died in stages, as the larger 
tree sheltering it first broke and then, a couple years later, was removed.

We are looking for a species that will attract bugs for warblers and 
deal with full sun and heavy clay soil.  I have had one recommendation 
for hawthorn.  We do already have one hawthorn, planted perhaps 6 years 
ago, which is still rather modest in size and in which I have never 
noticed any warblers.

Any other suggestions? 

Georgia McDonald   Towson, Balt Co