Nice find, DK! And good eye noticing the birds - I think I would have missed that detail if you hadn’t pointed them out! I’m definitely no bird expert, but the long tail feathers make them look like they might be pheasants, which might imply a hunting motif and lend a little more masculinity to the buckle, at least from a Victorian era perspective. I’m leaning heavily toward calling your find a suspender buckle. Victorian suspender buckles often have a more ornate design, while garter clips are usually more utilitarian and plain since they would theoretically always be out of view
But the attachment method was also very different - your find has a small hook device on the bottom typical of a suspender clip. Garter clips tend to have an open slit to slide around a button.
I’d say late 1800s for the clip is a reasonable guess, putting it pretty consistent with the other finds at the site. Cool dig!
