Well if the male was feeding it, i would go with cowbird. However in that first picture the streaking is really contrasting against a very white looking breast. The issue with photos are the light can look different as you captured one moment in time. Cowbird streaking in juveniles is usually a little more mottled and the breast not as bright white. However the second photo shows a different light. it also looks distinctly smaller than the cardinal. Top photo also looks like it has a distinct white supercillium but the bill looks too big. I was thinking female purple finch, but i think it is a cowbird based on the second photo