Info on Grackle Roosts

A perfect picture of the Pulitzer Fountain, All that's missing is the grackles.
The statue at the top of the fountain, by the way, is Pomona, Goddess of Plenty.

Below, a paragraph from the Common Grackle account in that authoritative resource, The Birds of North America. [Emphasis mine].Our grackle roost at the Grand Army Plaza of merely one or two thousand birds seems chump change next to a New Jersey roost containing, let's say, 167,000 grackles. [33% of 500,000].

From about Jul to Apr, Common Grackles gather at night in roosting congregations with Red-winged Blackbirds, Brown-headed Cowbirds, and European Starlings. American Robins and Euphagus blackbirds are rarer constituents of these roosts . Roosts are frequently near agricultural fields and orchards; location and formation probably reflect food eaten at this time . Roosts also located in trees lining streets in urban areas , hardwood thickets, conifer groves , or marsh vegetation (including cattail and common reed [Phragmites communis; . Fall roosts in New Jersey (containing 3,000–500,000 birds, 33% of which were Common Grackles) were located in early successional stands of various hardwoods with high tree density, closed canopy that was compact vertically, and mean twig heights from 5 to 12 m . Appears to switch roost sites regularly ; forages during day in agricultural fields and in suburban and urban areas.

Citation:

Peer, B. D., and E. K. Bollinger. 1997. Common Grackle (Quiscalus quiscula). In The Birds of North America, No. 271 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists’ Union, Washington, D.C.