Cowbirds are the worst! They’re the ones that will take over a nest, lay their own eggs there, destroy the original bird’s eggs, then the smaller birds EXHAUST themselves trying to keep the monstrous thing fed when it hatches!
And, it IS a native bird to North America, so we can’t blame immigration for this problem!
https://www.birdsandblooms.com/birding/bird-species/tanagers-and-blackbirds/brown-headed-cowbird/
Aim Small, Miss Small! ;)
I read an article last year where the DNR was actually setting up traps to catch the cow birds in an area in Michigan which is populated by the Kirkland Warbler. That didn't make any sense at all. Catch then kill them is what they should have done.....