Why so fewer birds in the yard come late summer and early autumn?

Question

We've enjoyed watching birds in our yard this past summer. We're in a suburb, fairly forested, inland northeastern USA hardiness zone 5. As we scaled up the amount of diversity and net primary production around the house, and added a bird feeder, we notice an uptick in various kinds of wildlife. However, we're surprised to see a stark decline in the amount of birds starting around late summer/early autumn.

What could cause the sudden decline in birds in late summer? Is there a migratory trend starting up around this time; it seems early to me for birds to be flying south?

The birds in question include a family of cardinals, occasional blue jay, downy and hairy woodpeckers mid-summer (some are still around), many various sparrows, yellow finches, chickadees, et al.

We continue to fill the bird feeder as usual. We haven't changed anything about our yard routine. We have a rescued feral cat which goes outside and hunts despite our efforts to stop it, and it has killed many mice and a few chipmunks mid-summer, so perhaps the birds have become wary of him and the dead bodies of small mammals left in forested edges around the yard.

Answer 1

One possible cause is Cooper Hawks. We are in east TX and put out a lot of seed ; we had more birds. Fewer in recent months due to the Cooper Hawk(s). Our yard is a buffet for them ,I hear them often, see them occasionally ;they will perch in the under story. And we hear birds hit the windows as they panic from the hawk ; it happens 0 to 4 times a day. The hawk has developed a technique of diving and after the small birds when they knock themselves out on the windows , the hawk walks on the patio to pick one up. I have been going out after a bird strike and picking up stunned birds and put them in a shoebox for 30 minutes. They usually recover, had a cardinal yesterday. If you are home during the day , listen for window strikes and watch for sudden flights of all the birds. The Sharpshin Hawk is also here but not a problem.......... And there is a degree of randomness to migrations: Some years we get many Goldfinches, Pine Siskins, Robins, and some years a few or none. And birds like Cedar Waxwings are notorious for their unpredictable movements.