Nest with both Am. Robin and Common Grackle eggs, Crow Valley, Weld

[David Suddjian]

Yesterday a DFO field trip ventured out to the Pawnee NG in Weld County. While we were birding at Crow Valley Campground we found an active nest that had one American Robin egg and three Common Grackle eggs. The nest was in a Siberian elm north of the picnic area, and built in a natural niche at the base of a scar on the trunk,  at a height of about 6.5 feet. The nest appeared to have been constructed by a robin. Both species were present at the nest spot and interacting aggressively with each other at times (chasing and squabbling). We did not linger too long to ascertain more info about what was going on there. 

This seems like a fairly rare occurrence. A look at the Birds of the World species accounts did not provide much info, but the AMRO account has this under the heading Brood Parasitism by Other Species: "Although robins sometimes lay eggs in the nests of other species, they are generally not raised -- although House Wrens and other species have been raised by robins in a few robin nests. One record in Iowa of robin and Northern Cardinal (Cardinalis cardinalis) using the same nest at the same time; both laid eggs and both brooded eggs, but once the robins hatched the cardinals left the nest and their eggs were abandoned."

David Suddjian

Ken Caryl Valley

Littleton, CO