hey!! not a silly question! the cold is probably a factor in it. birds can lose their toes due to frostbite fairly easily. in cities, they also commonly have string or hair wrap around a toe and cut off its circulation, making it fall off over time. there’s also a few other possible factors:
- attacks from other pigeons or city animals like rats
- injuries in the nest
- infections from dirty environments
luckily, birds can live long and happy lives even with injured feet 🙂