Bird Identification: CLOSED: Both Bonaparte's?, 1 by Elphaba

Elphaba wrote:
While I was at White Rock Park in the Dallas area, I saw my first Bonaparte's Gull. Turns out there were a lot of them there, but I only saw one for sure. I thought I saw some small gulls further down the lake, but the road turned and I forgot to hike down there to check it out. Anyway, someone who arrived just as I was leaving reported seeing a Little Gull in addition to Bonaparte's Gulls. I took this photo of a Bonaparte's and had a surprise mystery gull fly behind him. I tried to find the mystery gull again but could not, so this is the only photo. I think it's another Bonaparte's, but thought I'd check and see what you think.