Birds are facing a crisis — nearly three billion birds have been lost across North America since 1970 as a result of human activities impacting birds and their habitats.Each year, billions of birds migrate across vast ranges spanning the Americas. For many, the journey is fatal. In Canada, tens of millions of birds are killed annually by crashing into glass on buildings, most of which are low-rise or residential. This makes collisions with glass a leading direct cause of bird fatalities. Yet governments lack momentum to address the causes. Nearly two decades after Toronto became the first city in the world to consider bird safety in its planning process, Canadian cities are now trailing behind global peers in protecting birds from colliding with buildings.The Ontario government recently passed legislation that prohibits municipalities from enforcing green building standards, including bird-safe design, through their local planning process.This change appears to conflict with federal laws protecting birds that apply to building owners. Canada’s Migratory Bird Regulations and Species at Risk Act prohibit killing birds by causing collisions, even unintentionally. Fines can range up to $1 million per animal for killing a listed Species at Risk.Our new research explores strategies for designing bird-safe cities. Using Toronto as a case study, we examined how collaborative planning can balance development with ecological sustainability, reducing bird collisions with buildings.Lessons from building professionalsReducing bird collisions with buildings starts with following design guidelines during the planning process. Birds drawn to green spaces in cities do not understand reflections on glass and cannot see glass that appears transparent. In some Canadian cities, buildings have patterns of dots applied on windows and glass railings. These visual markers — first invented in Toronto — are proven to help birds detect glass and avoid colliding.Designing cities that are safe for birds also involves considering how birds move between habitats and interact with threats in the built environment. In our study, we convened experts and professionals who work in fields ranging from architecture, landscape architecture, engineering and facilities management to integrate perspectives on bird safety across disciplines.Through a co-design workshop, we identified key barriers and opportunities to promote wider adoption of bird-safe city building practices. Our paper translates lessons learned in Toronto for a global audience and highlights needs and progress at institutional, local and regional scales.Our results inform how professionals can be educated by our collaborators at FLAP Canada — a charity dedicated to raising awareness of bird safety in cities.Some real estate developers argue that bird-safe building design is too costly, “prescriptive” and is a barrier to housing construction. But researchers and architects point out that bird-safe glass represents a negligible increase in construction costs for typical buildings, and solutions involve using the same manufacturing techniques as popular privacy glass and heat-reduction coatings.The success of Toronto’s approach demonstrates how engaging across disciplines in the design of bird-safe planning tools results in more effective applications. Our research presents a model for bridging disciplinary silos to develop these tools.Cities where birds thriveAs Canada steps back, other countries are stepping up. Cities elsewhere are adapting, using design and policy to create environments where birds and humans coexist safely. In the United States, strategies originally developed in Toronto are now being applied more widely than in Canada. Bird-safe design is required by code in cities like New York and Washington, D.C., and other countries are following suit.This growth coincides with greater co-ordination between nations and sectors such as through the international Bird Collisions Prevention Alliance.The Canadian government recently adopted a 2030 Nature Strategy aligned with the Kunming-Montreal Global Biodiversity Framework. Numerous targets under this strategy align with principles behind bird-safe cities. While federal commitments are encouraging, the authority to regulate building construction lies with provincial and territorial building codes. It remains to be seen how governments will co-ordinate the strategy’s implementation between jurisdictions and policy areas.As governments set plans to build, now is a critical time for regulators and industries in Canada to adjust outdated building practices, mitigate their impacts and support ecologically resilient cities that are safer for people and for wildlife.Brendon Samuels is affiliated with FLAP Canada and serves as the charity's Bird-Safe Buildings Coordinator.Nina-Marie Lister receives funding from SSHRC and ARC-Solutions for related work on animal movement and ecological connectivity. Prof. Lister is affiliated with FLAP as a volunteer and has cofounded Bird Safe TMU, a community group monitoring the Toronto Metropolitan University campus for bird-window collisions. Sabrina Careri does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.