Heron rookery locations are dynamic, depending on conditions they
can last for 20 years or just a few years. The Sleepy Hollow rookery
is pretty much over. With all the beaver activity in Eastern
Massachusetts there are plenty of options, new locations are
occupied by herons every year.
An Osprey pair has been nesting in an abandoned GBH rookery in
Concord, MA going on three years now.
Probably redundant to say this but observers should keep good
distance from rookeries, disruption can cause abandonment. Probably
not a good idea for anyone to create an accurate "Rookery Hotspot"
on eBird. Maybe that's why the "hotspot" location in Concord was not
directly on the rookery location.
Andrew Joslin
Carlisle, MA