Brown robin-sized bird with white specks on breast

by Chasya
(Denver, Colorado)

I'm east of Denver, Colorado. The bird I wish to identify is nearly robin-sized and shape, mottled brown with white specks on breast. No color other than browns and those white spots. At first, I thought these guys were were young robins but they're not developing color and their dark beaks are slightly slimmer than a robin's. They now visit as a small flock (a dozen at most), congregating at the bird bath and seeking to feed on small ripe tomatoes and berries. They also attempt to edge out the small birds at my safflower-seed feeder. I haven't been able to capture a photo. Any ideas? Thank you.