The story goes that someone imported English sparrows to control the insect population. Completely oblivious to the fact that the little birds eat seeds, not mosquitos. But wouldn’t there have been predators in place to control our native wrens and finches?
They do eat insects- in fact just about anything their little beaks can hold. Opportunistic feeders is the term.
Plenty of critters want to eat sparrows- Hawks (I have watched a Coppers hawk eat one), owls, cats, and many other things nab the eggs and young birds- racoons, ravens, etc.
But they breed so fast.
I was under the impression that house sparrows followed boats from Europe to the Americas. I can’t remember where I read that. I can’t imagine they’d be any better at eating mosquitoes than the native birds.
It was possibly a combo, but in North America deliberate introductions, were the primary culprit. Some potentially apocryphal like the goal of introducing every bird mentioned in Shakespeare. Some “practical” like the half-assed notion to control a variety of moth that was having an infestation that was defoliating Manhattan. Some just whimsical like the Shakespeare one, but more along the lines “let’s release these birds we like from back home.”
But yes, there are plenty of predators that eat house sparrows - they have no special immunities. I’ve literally seen with my own eyes a house sparrow getting snatched up by a suburban sharp-shinned hawk, so it happens. It’s just that they are very closely tied to human habitation which have a somewhat lower volume of bird predators (because people) other than stray/feral/free-roaming cats and they are very fecund.
Are we mixing sparrows and starlings? Those are the real pricks that up-ended a lot of other species’ places in the (pardon the pun) pecking order.
The Acclimitisation societies were complete arseholes - we had them here in Australia as well. They (and sole operating acclimitisers) have possibly caused more environmental damage and financial impact than mining. When we finally get that time machine and go back to kill Hitler, you know who I’m going to suggest goes on the list next?
May I borrow that time machine when you’re done with it? I’m gonna get the asshole(s) who introduced the Garden Snail to California.