Window strikes kill hundreds of millions of birds annually worldwide and represent one of the most preventable human-caused sources of bird mortality, with simple and inexpensive solutions available.
Window collisions cause acute welfare harm. Birds that strike glass at full speed suffer traumatic brain injury, internal bleeding and broken bones. Those that survive the initial impact may die minutes to hours later from delayed internal bleeding or predation while incapacitated. Many birds appear to recover but die days later from internal complications. The scale of window collision mortality makes this one of the largest human-caused sources of bird death, yet most householders are unaware of the problem and solutions remain poorly known. Simple interventions including window films, hanging strings or netting can substantially reduce collisions at individual buildings, making this one of the most accessible wildlife welfare actions available to ordinary people.