Animal Birth Control is the only way to stop the endless cycle of suffering. Kittens born outside have extremely tough lives, most of whom don't survive past a few months. They are exposed to harsh weather, infections and viruses, some often get killed by dogs or get run over by cars. A single female cat can give birth to up to 3 litters per year with an average of 4 kittens per litter. Most of these kittens don't make it and those who do have extremely compromised lives. 

Spaying/neutering not only controls the population and prevents unnecessary suffering but also significantly improves the life span and overall wellbeing of the cat.