cktimes.ca Archives for Nature Link


Nature Link

With Blake Mann

Breeding bird season

Tuesday, April 22, 2003

We are now into the breeding season for birds. Robins are already starting to build nests. Actually, some birds have young already. Owls nest early, some starting in early February. Great Horned owls quite often use the large stick nests of Red-tailed Hawks. They will have young in the nest now. Screech Owls, a cavity-nesting species, may have fledged young already. Two and three years ago, I had a family of five or six roosting in the cedars about this time of year. The Screech and Great Horned are the only owls that nest regularly in this area.
The past two years I have been volunteering to survey for breeding birds, as part of the Ontario Breeding Bird Atlas Project. It is a five-year study to document the birds occurring in Ontario. It was last done in the early 1980's, so an update was needed. Hundreds of birders from all over Ontario are taking part.
The southern part of the province is divided into 10 km squares. Someone is assigned to each square to record breeding evidence. There are three main categories to record. These are possible, probable, confirmed. Certain criteria determine which category can be attached to a certain bird. The goal obviously is to confirm breeding.
It is interesting work, as you don't know what you will encounter in the field. I am doing three squares in the Wallaceburg area, and have recorded much data in the first two seasons. We are already ahead of the first atlas in terms of data.
Some species have obviously increased, while others have decreased in population. Many have decreased mainly due to habitat loss. With an increase in urban pressure, and the clearing of land for agriculture, many species have dwindled in numbers.
Some species are more abundant than you may first think. Once you start looking, you can find many types of birds that were not previously very obvious. Cliff Swallows, for example, can go by unnoticed. They nest in "oven-type" mud nests under bridges and other structures. The attached photo show one such nest under the Duthill bridge on Holt Line. I took this photo this past February while standing on the ice under the bridge. I saw a couple of Cliff Swallows flying around there last summer, but could not see under the bridge to confirm. Many swallows are colonial, and can nest in groups of several dozen. Last summer I was able to confirm a colony of several dozen under the McKeough Floodway Outlet bridge at the St. Clair Parkway.
The Ontario Breeding Bird Atlas website is at  HYPERLINK "http://www.birdsontario.org"; www.birdsontario.org and has up-to-date maps of the breeding birds found so far.