home of creature

~ Dog Effigy.

Culture: Colima

Date: 100 B.C.-A.D. 300

All three parents are very busy feeding the babies and keeping the nest clean! The OP briefly thought there might be another male coming by, but checking the markings seems it's just the one dad for the two moms, lol.

The mamas are getting along a little bit better - they're having to deal with the fact that a full nest makes it harder to stack at night, so they try to find different ways to get comfortable on the nest together without squishing the babies.

Also, the Facebook OP has put a hanging basket filled with nesting material below the nest, and a mattress on the ground, in case there's any falls or if the babies get too big to fit into one nest. The mattress actually saved two eggs when they got accidentally knocked out - she put them back in the nest, and they hatched a few hours later.

BTW, for those who wondered how you can tell the difference between the sexes, or saying the females don't look like certain artworks of female robins - no, you can't always tell adult robins apart. Though usually the males have slightly darker heads and slightly brighter chests, with more contrast between head and body, and the females have more white on their chests. In this specific case, the two moms both have a distinctive "brood patch", a featherless patch of skin on the lower abdomen that helps deliver the most heat to the eggs and/or babies. The daddy bird does not. He also doesn't sit on the nest, but he's a very attentive food-bringer.

Also, the OP just had an amazing article written up about her and the robins:

It's a great read, has even more pictures (if you don't have a FB account to check out the posts yourself), and the Audubon Society even found an article from the 1940s describing another robin throuple!

“During incubation both of the birds were frequently observed sitting on the nest together,” Howell wrote. “Sometimes one female would be on the back of the other, but more often they sat side by side. Usually both birds spent the night on the nest.”

As for these robin moms, a scientist at Cornell says:

Bailey said that there’s likely a simple explanation here: polygamy. “The typical relationship would be one female and one male for a breeding season,” she says. “But in the case where there might be a shortage of males, the females might have to just accept that they need to share this mate and their breeding territory. And if they’re going to do that, it makes sense to put the nests close together so that the male can feed both pretty close together or defend them more easily than if they were in two different spots. “But it does sort of make sense,” she says. “If you have to be polygamous, you might as well share a home.”

The Plankton Project: Living in Light and Dark by Lindsay Olson.