You can do more than feed the birds this winter. You can count them.

For the 23rd year, Project FeederWatch is under way. Regular citizens count and identify the birds that arrive at their feeders from November until early April and then send the data to Cornell University or Bird Studies Canada, where scientists track the health and habits of North American birds.

Last year, Cornell received more than 117,000 data sheets from every state in the union and every Canadian province. Most of them, ahem, from women like me.

"I have to say our demographic is biased toward women, 50 and older, highly educated," said project leader David Bonter of Cornell. "That's my crowd."

There are plenty of scout groups, home-school students, nature centers - even retirement centers - that participate as well. "From hard-core bird-watchers to people who never even took a biology class," Bonter said. "The Internet has really made this thing happen."

Participants can do more than watch birds this year. They can watch out for birds. Particularly the Eurasian collared-dove, an invasive bird with an interesting back story.

In the late 1970s, this bird, native to Asia, was released by a pet dealer in the Bahamas. It spread rapidly, first to Florida, where it liked the warm climate.

But soon, this dove was soaring up the East Coast, crowding native dove species as it went. It was soon spotted as far north as British Columbia.

"It is spreading like wildfire," said Bonter. "You may not have too many in Maryland right now, but it is going to invade and it is going to invade in a big way."

Invasive is not a positive term when referring to plants or animals, but so far, Bonter says, the collared-dove does not seem to be "interacting negatively" with the three native species: the mourning dove, the common ground dove and the white-winged dove.

"But we're not sure how it will be in the north, in winter, when food is scarcer," he said.

The flocks are large, he said. "and it will be noticed when they arrive."

To participate in Project FeederWatch, go to the Web site at birds.cornell.edu/pfw/ and sign up for the kit, which costs $15. There are also helpful pictures to aid in the identification of the birds at your feeder. (If you can tell a song sparrow from a house finch, raise your hand.)

Attracting birds is easier than ever. Feeders and seed, as well as suet and suet cages, are sold in grocery stores, right in the pet food aisle. And bird seed projects such as peanut butter dipped pine cones rolled in seed are a way to entertain housebound kids.

This bird-counting project produces surprises every year. Last year, a Green-tailed Towhee, native to western North America, showed up in New Jersey and spent all winter at the same feeder.

With birds, you just never know.