Pittsburgh and its confluence of rivers are experiencing another bird spectacle this year, this a rare one, thanks to the polar vortex and frigid weather.
Species of migrating gulls that typically spend the whole winter on the Great Lakes have been forced south to Pittsburgh as those lakes freeze over.
Bob Mulvihill, an ornithologist with the National Aviary of Pittsburgh, said Pittsburgh area birders have counted as many as 8,000 gulls of varying species roosting together each night near the Point and displaying social habits somewhat similar to crows.
Local birders typically might travel to Niagara Falls just to watch the gulls. Now the gulls, mostly ring-billed gulls, roost each night on ice floes between Heinz Field and PNC Park on the Allegheny River. Birders have been setting up their spotting scopes to view them from in front of the Fred Rogers and Bill Mazeroski statues.
"Up to seven species of gulls have been spotted -- ring-billed and herring are the most common, but birders scattered among them have carefully identified much rarer glaucous, Iceland, Thayer's, lesser black-backed and greater black-backed gulls," Mr. Mulvihill said.
Several other uncommon water birds also have been seen from the Point, including red-throated loons, com- mon and red-breasted mergansers, white-winged scoters and long-tailed ducks.
"Winter has been severe, but we have open water," he said. "But that's not all. The rivers provide a safe resting place overnight, but each morning smaller groups of gulls fly off in every direction in search of food."
The gulls, like crows, in early March will return to northern states and as far away as Canada's northernmost borders, to feed, breed and raise their young.
"Before they do, it is worth a bit of shivering for the chance to view the truly beautiful spectacle of so many of these graceful birds gathering each evening at the Point, with the lighted Downtown skyline as a backdrop," Mr. Mulvihill said.