Dozens of bird watchers participated in the 100th Ottawa-Gatineau Christmas Bird Count, an annual census that seeks to count every species and individual seen that day.

More than 100 Ottawa-Gatineau residents spread out across the area in the early morning last Sunday to stand and watch for birds.

They were participating in the 100th Ottawa-Gatineau Christmas Bird Count, an annual census that seeks to count every species and individual bird seen that day.

"You can put together a picture of bird populations from year to year," organizer Bernie Ladouceur told 1310 NEWS' The Rick Gibbons Show.

The event started in 1900 in the northeastern United States and soon grew into something much larger. There are now around 2,000 such counts held across North America every year between December 14 and January 5.

The count in the Ottawa area started in 1919 with only five participants, when there were a lot more farms and countryside in the area. This year's event was organized by the Ottawa Field-Naturalists' Club and the Club des ornithologues de L’Outaouis.

It saw dozens of bird watchers divided into six different sectors in a 12-km radius around the Peace Tower. Participants were given different areas to watch so that the same birds aren't counted more than once.

The bird count can provide some useful data and information for researchers about where populations are in late fall and early winter, Ladouceur said.

The Ottawa bird count recorded 75 species this year, which was a bit higher than the ten-year average of 72, and 30,000 individual birds. Ladouceur said the count provides a good snapshot of bird populations for the same three-week period every year.

He said the trends from the data can show how the growth of the city has had an effect on the bird populations.

"When you destroy where a bird lives, that's going to have an impact," he said.

The first time a cardinal was recorded on the bird count in Ottawa was in 1940. But now, Ladouceur said they're seen very regularly in backyards. He said it is fairly common to spot bald eagles in the region now, but thirty years ago they would have been extremely rare.

While some birds are becoming more common in Ottawa, others are becoming more rare. Great horned owls were once the most common type of owl in the region, but have been replaced by barred owls. The count also recorded snowy owls this year.

The only bird species that has been on every single count in Ottawa is the black capped chickadee, said Ladouceur.

Listen to the full interview here: