Window collisions kill hundreds of millions of birds annually worldwide. Simple, low-cost prevention measures can dramatically reduce this source of bird suffering and mortality.
Window collisions cause acute trauma — skull fractures, brain injury, and internal haemorrhage — that may cause immediate death or delayed death after a period of suffering. Birds that survive initial impact may be stunned and vulnerable to predation, or may die later from internal injuries. The welfare harm is significant and largely preventable. Simple modifications — window films, exterior netting, closely-spaced external cords, or repositioning feeders — dramatically reduce collision frequency. The scale of the problem (hundreds of millions annually worldwide) makes this a priority welfare intervention achievable at the individual household level.