The Challenge: After observing two pairs of birds sharing a single nest in her yard, Jessy came across an article I posted a couple of years answering a question about American Robins hanging around a Northern Cardinal nest. In my answer, I suggested that the robins were probably looking to steal cardinal babies. Why is a Robin Hovering Around a Cardinal’s Nest?
Jessy challenges that answer “Robins are not generally known for ‘treating’ on young birds.” Based on what she was seeing outside her window, she suggested that the birds may actually be sharing the nest. “I have a robin’s nest with two young and one robin egg (until all the feathers come in I cannot be sure who the young belong to). It is always the robin I see on the nest during the day, but the cardinal male brings food to the nest. The female cardinal and male robin are also about frequently, but are more skittish and I cannot yet determine their roles.” |
The Discussion: Jessy makes a valid point in that eating baby birds is probably not a regular habit of American Robins (Turdus migratorius). However, most birds are opportunistic, and robins have been documented eating fish and snakes and even a shrew, so it doesn’t seem a stretch that they would eat a baby bird if given the chance. And though I had not heard of different species of birds truly sharing a nest, who knows what behaviors might be out there that we don’t yet know about. (We’re not, of course, talking about nest parasitism, such as is practiced by cuckoos and cowbirds, where females of one species lay eggs in the nest of another species and then abandon them to let the second species raise the chicks.)
With help from Jessy, I was able to find a source that described an incident of nest sharing between American Robins and Northern Cardinals (Cardinalis cardinalis). The authors of a 2009 article in the Wilson Journal of Ornithology observed a female robin and a female cardinal alternating at a nest where both laid eggs. This photo of the nest, in an arborvitae bush in a suburban neighborhood in Iowa, clearly shows three blue robin eggs and two speckled cardinal eggs.
The authors detail their search of the scientific literature for similar cases, and mention reports of sharing between two female cardinals and even a case of a cardinal feeding American Robin chicks. They state that “American Robins, however, are less tolerant of nest violations, generally rejecting Brown-headed Cowbird eggs, and have not been observed to exhibit intraspecific cooperative brood care.” They go on to say that actual nest sharing between two different species of birds is not common. One documented example, however, noted a tree cavity nest that included nestlings of both Red-breasted Nuthatches and Mountain Chickadees, after adults of both species were seen bringing food to the tree hole nest.
The rest of the brief article describes observations of the interactions between the birds at the shared nest. Apparently, the two females shared the nest fairly peacefully at first, but the interactions became more aggressive over time. The female cardinal would sit on the female robin’s back “… and scratch and kick until the robin fled the nest.” Eventually, the eggs began to hatch, with the result that two fledglings were seen, which turned out to be robin chicks. One cardinal egg was found on the ground and the other disappeared.
The authors suggest that scarcity of good nesting sites in this area might have led to the birds competing over that site, a contest that was eventually won by the robins.
Over the course of several days, Jessy monitored the joint nest in her yard and kept me updated by email. She wasn’t able to see whether there were eggs from both species, but as in the case documented in the Wilson Journal, the two eventual hatchlings were robin babies, as far as she could tell. The adult cardinals continued to hang around, and Jessy saw the male bringing food to the area of the nest, although she was unable to see if he was feeding the chicks or his mate. At one point, she noticed one of the hatchlings on the ground beneath the nest and she replaced it. A few days later, there was only one chick in the nest and shortly after that, Jessy found a dead chick on the lawn. She also found part of a wing of an adult bird, possibly a robin. The nest was empty and all the other adults were gone.
Jessy’s speculation is that a cat or raccoon or other predator might have ended the experiment in joint parenting.
So I guess I should modify my original answer about a robin hanging around a cardinal nest. I still think a good possibility is that a robin around a cardinal nest might be looking for unattended hatchlings to snack on. But another possibility is that it may be trying to compete for the nest. Unfortunately for the cardinals, in the two examples we have, that doesn’t seem to go well for the cardinals.
Sources: Govoni, P W, Summerville, K S, & Eaton, M D. (2009). Nest sharing between an American Robin and a Northern Cardinal. The Wilson journal of ornithology, 121(2), 424-426.
Sallabanks, Rex, and Frances C. James. Birds of North American Online. American Robin Turdus migratorius. Issue No. 462.
I read your comments with interest but I have a different question. I’ve been told of at least one specific instance where a great horned owl pair repeatedly alternated use of a large nest with a bald eagle pair at different times over several seasons. Has this been documented? Alan Meyers, Chicago
Owls commonly use abandoned nests. Their offspring fledge quite early in the year, so it’s possible that the nest was available early enough for the bald eagles (who probably built it) to return and use it again.
I have two nests in my front yard. One is a cardinal nest and the other is a robin’s nest. They each had one egg the first time I checked. The next time I felt 4 eggs in the robin’s nest and knowing that was an unusual number I took a look and found 3 robins eggs and one cardinal egg. I took the cardinal egg out and put it in the correct nest only to find, a couple of days later, the cardinal mom sitting in the robin’s nest. I’m not sure what to expect now. Since their diets are different how might that effect the babies if the wrong mom is feeding them?
I have witnessed robins taking over the cardinals nest. I hope there are no eggs or cardinal babies in it. It had been the cardinals nest for several years.
just recently: robin and cardinal build nest together.
Robin has an 3 eggs and they both sitting on them by taking the peaceful turns! All HD video documented starting from building stage.
I have a cardinal nest near a robins nest. Today I checked the cardinal nest and noticed 3 cardinal eggs and one robin egg. The robin has 3 eggs in her own nest. Should I move the robins egg from the cardinals nest and put it in right nest or leave it alone??
I have just observed a male cardinal feeding a baby sparrow. I was amazed. It did, it time and time again. Right outside my bathroom window in the burning bush, shrubs.
Hi
I clearly am witnessing a female cardinal started to build a nest in our trellis 1/2 way into the build the robin to it over but the female cardinal still comes back an now they are alternating sitting on nest when one flies out the other is in I have pics but only eggs I am seeing is robin
I have observed a cardinal building a nest and before it was
Finished a robin worked on the nest as well. The robin is now
On the nest but I don’t know what eggs are there yet.
Robert Morrison-I have been watching a Sparrow feeding what I assumed were baby Sparrows in a hole nest in tree, Today, I watched a Cardinal also feeding at same hole! I too am amazed. Eastern Pa.
We were watching a cardinal nest with 3 eggs next to our front door but when we returned from a 4-day trip were sad to find the empty nest out of the tree and sitting on the front porch. Empty. Now, one month later, we see a *new* nest in close to the same place! But it’s a robin. I’m wondering… Would the robin have forced out the cardinal in order to move in to that choice (?) real estate?
Hi Michele, it could have been any number of events. There are many critters that will raid a nest, including squirrels, cats, weasels, hawks, and even mice. Any one of those larger creatures could have knocked the nest down, either deliberately or in the process of raiding. And then the robins said, “Nice spot!” and built a new nest. It’s possible they knocked it down, but I think it’s more likely they would just take it over and use it as is, rather than build a new one from scratch.
I have witnessed a male cardinal coparenting with a chickadee at her nest. He did a very good job and was very attentive. This was years ago. Today I found a cardinal nest in my tomato bush. But 3 out of 4 eggs were speckled, and one completely unspeckled,pale blue– but otherwise looked very similar. Is the unspeckled egg from the cardinal or a different bird? If I could figure out how to post a photo, I would.
A couple of years ago, we had a Robin lay eggs in a nest where Cardinals already had eggs. The two mothers fought over the nest and the Cardinal won. Or more accurately, she sat on the eggs and refused to leave. The Robin finally left and the Cardinals raised the chicks.
I currently (May 2019) have a wren and chickadee sharing a bird house mounted on a post in my backyard. I have not confirmed the eggs/chicks.
Every year a robin builds a nest on my front porch. A male cardinal hangs around on the porch too. I wonder if they mate every year?
Hi Patti, it seems very unlikely that a robin and a cardinal would mate, since they are not particularly closely related. Tom
I have a nest on my porch that had 4 robin eggs and 3 cardinal eggs. It was a very small nest. I found one of the robin eggs broken on the ground. I took pictures every day. The Cardinals hatched first. I only ever saw a robin sitting on the nest. After they all hatched, I continued to take pictures. After about 2-3 weeks, there were only 2 left, huddling together. The others were destroyed. I still have all the pictures if your interested. I’m wondering if they were sparrows instead of cardinals.
Sure. Send the pictures to tom@askanaturalist.com. Thanks! Might be cowbirds.
We had a nest that originally had 3 cardinal eggs, then robins came in and added 3 robin eggs one at a time… then the cardinal eggs disappeared. The robins minded the nest, but the female cardinal hovered around and appeared upset. When the robins were hatchlings, I found the nest empty and the hatchlings all alive on the ground under the nest. I suspect that the Cardinal mother attacked the hatchlings to try to reclaim the nest while the mother robin was away gathering food, but this is just a guess.