Updated 5/29: This is definitely a goldfinch. But I was never very good at distinguishing American Goldfinch from Lesser Goldfinch. I remember posting what I thought was an American to eBird some years ago and getting a note from an editor ruling that it was a Lesser. So I’ve been inclined to see Lessers everywhere, including this one. And after I posted that it might nevertheless possibly be an American, my birder betters checked in and shot that down. It’s beyond question: a Lesser male. So be it.
Whatever it is, it was busy feeding on the west side of the park in the southern apron of the Native Plant Area. They can sing quite beautifully but this one had its beak full and remained silent. Manners.