April 4, 2026

by Bill Read

I was out checking nest boxes yesterday and found one pair of bluebirds at a nest box. I did see lots of Tree Swallows checking out boxes. Last year 2025 was an exceptional breeding season for the swallows as they were able to get by the cold weather of May 22-24  with very little nestling mortality. They were either on eggs or had very small nestlings that could be brooded. The bluebirds had very poor first brood reproductive success in 2025. We had almost 100 % nestling mortality at most boxes because of the cold wet weather from May 22-24th. Unlike the swallows the bluebirds had much older young that required large amounts of food items that were just not available. The rest of the season we had ideal weather which allowed failed first nest pairs to nest successfully. Usually bluebirds are able to establish nesting territories before the Tree Swallows return, this does not seem to be the case this year. There also are fewer bluebirds at this date compared to last year.  The bluebirds that migrated last fall experienced a number of severe storms along the eastern seaboard and inland that may result in higher overwintering mortality than usual. These storms or polar vortexes reached all the way down to Texas. In Tennessee the trees were covered with ice and there were power outages across the state. The ones that attempted to overwinter in Ontario may not have fared much better as we had  a much colder winter than usual with record snow fall. This made it more difficult to find food especially winter active insects. Sumac is there number one food source in the winter. I expect that there will be fewer bluebirds this year in Ontario.  Weather has always been the number one factor affecting both overwintering success and breeding success. 

Now is the time to make sure that your boxes are free of Deer Mice and nest material from last year. Especially House Wrens that may have nested after the bluebirds left and filled the box with twigs. Make sure to record each visit to a nest box in a small binder. It is also a good idea to number each box or record the location by the property that is beside the box. If you have no bluebirds don’t despair they move through all the time and eventually one will show up. Good luck and remember to send me a note to let me know how you made out.