Chipping sparrows and red cardinals appear to be holding up the Lansdowne Park redevelopment plan.
Some 60 trees were scheduled for removal to allow work crews to move the Horticulture building to a spot east of its current location. A small protest on Tuesday halted the work.
The Canadian Wildlife Service distributed an email to Holmwood Avenue residents on Friday, informing them they have documented evidence of some migratory birds nesting in the trees.
Because of that, the wildlife agency said tree cutting will have to be put off until later this summer, when the birds move on.
The email also said two wildlife officers will head to the site early Monday morning to "ensure compliance with the Migratory Bird Convention Act."
Kanata Coun. Allan Hubley said he was disappointed by the news.
"The reality is these trees won't be there next year. We're taking this down, we'll do replanting as needs be, but the project is going ahead," he said.
City officials had no response Friday night.
A delay of several months could be a costly setback for the redevelopment project, which is working within a specific timeframe to get CFL football up and running.