Nobody loves cats more than me so I post this as a cat lover and a wildlife lover in general! Cats are responsible for millions of bird deaths and this is even more true now during the migration times than other times of the year. There are two things you can do to cut down on this without keeping them inside all day.
1. Keep your cats indoors for the couple of hours surrounding sunrise and sunset, this is when birds are most active and killed. Migrating songbirds are on the decline and when they stop and rest in our yards, they are very susceptible to cat predation so keeping them indoors during this time is a big help!
2. Put a fitted collar with a bell or sonic device with a quick release to give the birds the notice and a chance to escape.
These two measures can reduce bird and small mammal deaths by 40%!
Bird diversity is important for many ecological reasons like pollination, ecosystem health, and insect control.
The earth thanks you! :)