The cats are curious, and hungry and they have no respect for nature.
A couple of years ago I had a sick 100 ft Douglas fir. I hired a guy to hack it down before it fell on my house, but asked him to leave 20 feet standing for wildlife. The guy left 40 feet. I guess I shouldn't complain, after all it is housing an entire ecosystem for even the tiniest wildlife. When the cats led me to the back window yesterday to point out our newest neighbor, I thought they were sweet. A beautiful Pileated Woodpecker was making his mark on the dead tree, and the three of us watched for a couple of minutes. But then I heard the cats doing the little clicking sound cats make when they want to pounce on their prey and eat it.
Good thing the window was closed.