Yesterday the "unexpected" bird was a juvenile Osprey in the Wasatch Mountains. I'd say it was unexpected because I'd been photographing songbirds and wasn't expecting to see North America's "Fish Hawk" in the same area.
I was photographing birds when I spotted a hairstreak butterfly land right in front of me and took some images of it, I didn't know at the time it was a Colorado Hairstreak butterfly, I found that out later after I got home.
White-faced Ibis are abundant at Bear River Migratory Bird Refuge during their breeding season and they can be easily seen from the 12 mile, self-guided auto tour route feeding in the water impoundments or flying in loose flocks overhead.
I like this photo for the eye contact, the fine details in the plumage of the bird, the stretched wing, light and how his one foot is raised, plus I think Horned Larks are beautiful songbirds.