Ontario's Ministry of Natural Resources is asking for the public's help conducting a provincewide survey of peregrine falcons.
The peregrine was virtually wiped out in Ontario in the 1950s by the chemical DDT.
But over the last 25 years, the bird of prey has been slowly returning to Ontario's cities and wilderness.
Every five years, the ministry conducts a survey to monitor the population.
"We are asking for birders to report any peregrine falcon nesting activity that they observe, and we'd like to know if there are signs of an occupied territory or single bird," said Lisa Nyman, a biologist in the ministry's Nipigon district.
"If you see a territory with two birds, if you observe a nest, we would like to know the nest's location, the number of eggs or young that are observed."
Nyman told CBC News the peregrine population is getting larger every year, partly thanks to organizations like Thunder Bay Field Naturalists.
Brian Ratcliffe is with the group that for the last 20 years has helped the ministry reintroduce the birds to Ontario.
"This has been one of the best recovery strategies, on the recovery of a species, or of an endangered species, that there's ever been," said Ratcliffe.
Four years ago, the peregrine's status was upgraded from endangered to threatened by a provincial committee on endangered species.
The peregrine falcon is the fastest animal on the planet, reaching speeds of more than 300 km/h, with nostrils so adept at breathing during its phenomenal dives that scientists mimicked the function for use in fighter jets.