It's not just exotic birds; common species such as robins, starlings and sparrows are taking big hits. The major culprits is us, of course -- specifically, human development encroaching on bird habitats and widespread use of pesticides. (In a cruel twist, pesticides known as neonicotinoids reduce the appetite of sparrows, causing them to slowly starve to death.) The connection to climate change can be specific; for instance, many migrating birds return in springtime to find conditions on the ground altered. Early onset of spring due to climate change can mean that the usual food sources have come and gone. The connection to climate change is general, too. All the expansionist, industrial activities that produce climate change also make the world less hospitable to birds.
House cats allowed to roam outside, poorly-sited wind turbines and glass skyscrapers also contribute to bird death. Three more things we're responsible for.
Anecdotally, fewer sparrows visit the feeder in my backyard these days. It used to be a feasting frenzy some mornings; now it's a casual brunch with friends -- until, that is, an impetuous squirrel comes by to jazz up the party. Thankfully, the family of starlings in one of our roof eaves are still camped there, and cardinals, mourning doves and blue jays continue to drop by. Blue jays often make a discordant, scraping call that sounds like the opening and closing of a rusty gate. It's a vaguely disturbing sound, repeated over and over and over. I wonder if they're trying to tell us something.