Very sorry to hear that Diane.  I guess the only good thing is that it 
sounds like it was natural predation--not a feral cat or the result of 
human interference.  Read the BNA account on YCNH, and they don't even 
mention predation by hawks or owls as a significant factor in 
reproductive success.  Predation of eggs or very young birds by crows or 
mammals such as raccoons or opossum are the primary causes noted.  
However, most YCNH nest in colonies.  I wonder if solitary nesters, such 
as "your birds", might be more vulnerable to avian predators.

Best,
Jim Moore
Rockville, Maryland
PLEASE REPORT YOUR BIRD SIGHTINGS to http://ebird.org/

On 6/27/2010 2:21 PM, diane Ford wrote:
> Hi all,
>
>    I talked to a neighbor later this morning and got more info on the nest attack. Apparently, it happened yesterday afternoon.  The person saw a 'large brown bird' fly into the tree (I asked if it was 'hawk-like' he thought so) it flew off with one of the young and kept coming back, amid
> loud squawking and a terrible fight with the parent heron.
>
> D.Ford/Bethesda.
>
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