Arborists and tree services should know how to identify an avian rookery.

A rookery is a place where a group of birds or social mammals (such as penguins or seals) breed, nest, or raise their young.  The name ‘rookery’ comes from the rook (Corvus frugilegus), the most abundant bird in the crow family in Europe and Asia.  These crows commonly build nests and roost in treetop colonies.

Rookeries are used by several bird species such as herons, egrets, cormorants, and even turkey vultures.  Large trees or groups of trees are generally the preferred locations for rookeries.  Island trees can be especially sought after by nesting wading birds, as seen in the photo.

Common egret rookery    

 
Photo: Jacqueline Pine Savage    

It is very important that arborists and tree service professionals be able to identify potential rookeries.  An arborist should always perform a pre-work survey before beginning any pruning, maintenance, or removal project.  Keep an eye out for multiple nests or groups of birds in or around the tree.  Look for white wash and down feathers around the base of the tree.

If an arborist or tree service professional identifies a rookery, it is very important to avoid disturbing the birds in any way.  Rookeries may be used by the same birds for many years.  These locations are often protected areas to ensure a safe location for birds to nest and raise their young.