Best Guess at Mystery Birds

We were a bit mystified by these unfamiliar-looking birds with thick-looking heads that are paler than their bodies, which we passed on a walk Tuesday evening. After doing some online sleuthing, my initial suspicion was confirmed and I'm almost certain these are female or juvenile Brown-headed Cowbirds. As allaboutbirds.org notes at the link above:

Even though Brown-headed Cowbirds are native to North America, many people consider them a nuisance bird, since they destroy the eggs and young of smaller songbirds and have been implicated in the decline of several endangered species.