American Robin
© Bruce Di Labio / OTTwpAmerican Robin eating Sumac fruit since there are no worms out yet.
Birds have migrated north in large numbers in recent weeks - an early gamble that is now forcing some to do a U-turn, and others to starve.

A number of people in Ottawa have heard Canada geese fly over noisily, beginning in late February's mild spell.

"Thousands of geese showing up in eastern Ontario. A lot of them are actually still here," birder Bruce Di Labio said. But with snow covering the cornfields and freezing temperatures at night, they aren't going any farther north.

Many are spending nights in the Ottawa River near the Deschênes Rapids. There are also snow geese, Ross's geese and greater white-fronted geese, as well as ducks such as American widgeons, pintails and wood ducks.

"If I think back 40 years, a lot of these geese didn't show up until towards the end of March," Di Labio said. "Their spring migration movement has moved back a number of weeks now.

"Some of these birds don't go as far south as they did 45, 50 years ago. So they are wintering farther north, so it just takes a little mild spell to encourage them to move up.

"If we get more snow, they will definitely have to retreat because there is nowhere to feed. All those exposed cornfields that we have in Richmond, Munster, southeast and southwest of the city - that is where they are feeding right now."

Smaller birds are arriving, too. Red-winged blackbirds started to arrive by Feb. 24.

"They were on territory in cattail marshes, singing away as if spring was here," he said.

"They can eat anything. Yes, they eat insects in the summertime, but they also eat berries and seeds and can go to bird feeders and survive." Common grackles, robins, Eastern bluebirds and song sparrows are around, as well.

Di Labio did see American woodcock at the end of February, birds that eat worms and bugs that they dig out of the soil. But the freezing weather has probably cut off their food supply, he said.

"The likelihood is they're not going to do too well. They likely starved."

There has also been an appearance of turkey vultures.

With the forest continuing seasonably cold, the northward flow will likely stop for now, he said. But geese at least are hardy and will not suffer - although some may head back to the St. Lawrence River in search of milder weather and the open water that gives them safety from predators at night.

"This is the new face of things," said Bridget Stutchbury, who studies migratory birds at York University.

"A number of scientific studies have looked at arrival dates of various species and found advances of two or three weeks" as our climate grows warmer, she said.

Robins and bluebirds can survive the snow and cold by eating berries, she noted. "We don't think of sumac as a fruit, but it is. It would be like eating dry cardboard I'm sure, but it persists on the trees all the way through winter." Buckthorn bushes also have long-lasting berries.

"And if things get really bad, they can fly. They just turn around and leave. They only have to fly a few hundred miles to get somewhere habitable. They are well adapted to tracking warm spells."

The birds that are at greater risk if they fly north too early are insect-eaters, such as tree swallows.