Texas Gardening: Help! Imposter laying eggs in Redbird nest?, 1 by Indigoez

Indigoez wrote:
Hi all, I really know nothing about birds, but I've had two redbirds build nests this year very low to the ground, so I've been keeping an eye on them. The first one did quite well and the hatchlings have all left, but there's a new nest (constructed last week) in one of my Passiflora cages and there's an egg that doesn't look like the other ones that are in there; picture is below, the white one is the egg in question lol. If it is a foreign egg, what should be done? This may all be really dumb, but like I said, not a lot of bird knowledge here.