|The Question: From time-to-time, birds fly into our picture windows and die. On two occasions, once last summer and then again just two days ago, a squirrel or a chipmunk retrieved the carcass and proceeded to devour it. This seems to be unusual behavior, and I wonder what triggers it, or if it happens more often than I am aware?
Submitted by: A. C., Georgia, USA
The Short Answer: Like most people, I once thought of rodents as seed eating herbivores, but it turns out that many, if not most, rodents are really omnivores that will eat insects or meat whenever they can get it. Gray squirrels (Sciurus carolinensis) and eastern chipmunks (Tamias striatus) are known nest raiders that will eat eggs or chicks. They also occasionally kill and eat adult birds. And gray squirrels are commonly seen eating road kills. So the answer to your question is that this carnivorous scavenging by a gray squirrel and a chipmunk is not unusual behavior at all. Great photos, by the way!
More Information: Scientific reports of predation by rodents list gray squirrels as eating other gray squirrels and birds. The list of observed prey for chipmunks also includes birds, as well as other chipmunks, voles, snakes, frogs and salamanders. Surprisingly, even small mice are significant predators of birds, mostly eggs and chicks, but they occasionally kill adult birds as well.
Given that squirrels and chipmunks are such frequent nest raiders, you might think that adult birds would defend their nests against them, but adult birds often simply abandon a nest if a squirrel comes near. This may be because, as mentioned above, squirrels are capable of killing adult birds. Under such circumstances, it might make sense for adult birds to simply give up and save their own lives in the hopes of nesting again in the future – especially under conditions where if the adult bird is killed while defending the nest, the chicks aren’t likely to survive anyway.
So, now you are going to have to view squirrels a little differently. And those cute little chipmunks are actually pretty good hunters. In fact, one study showed animal matter in the stomachs of 75% of chipmunks examined.
And all of this gives a new perspective to the Rodents of Unusual Size (ROUSes) that feature prominently in the satirical fairy tale movie, The Princess Bride. Turns out they are just imitating their relatives of usual size.
CALLAHAN. (1993). Squirrels as predators. The Great Basin naturalist, 53(2), 137-144.
LANDRY, SO. (1970). Rodentia as omnivores. The quarterly review of biology, 45(4), 351-&.
Bradley, JE, & Marzluff, JM. (2003). Rodents as nest predators: Influences on predatory behavior and consequences to nesting birds. Auk, The, 120(4), 1180-1187.
Pietz, PJ, & Granfors, DA. (2005). Parental nest defense on videotape: More reality than “myth”. Auk, The, 122(2), 701-705.
Lima, S L. (2009). Predators and the breeding bird: Behavioral and reproductive flexibility under the risk of predation. Biological reviews, 84(3), 485-513.
A C Baker Says:
Many thanks for the research, Tom. If someone had told me about this without pictures, I likely would not have believed them.
To (badly) paraphrase a famous writer: There are more things in this world than are dreamt of in our philosophy…
I once witnessed a really ferocious chipmunk battle over a massive frog carcass, and thought that the two involved must have been really vicious, street-hardened chipmunks. Glad to know that it’s not the case!
It is interesting that we don’t expect such behavior from these cutesy little guys – I bet that’s how they manage to sneak up on prey. The frog thinks, “Aw… look at that wee little chipmunk. Let’s feed it some br-” and BAM. No more frog.
Or, you know, something like that.
I was horrified today to see a chipmunk dragging a robin across my deck. I noticed because oodles of birds came dive bombing and pecking the chipmunk to drop the robin. At first it was about 5 robins, then a cardinal, a yellow bird, an oriel and then even chickadees stood by and watched. The chipmunk got away. Unfortunately the robin somehow in the scuttle fell off the deck and haven’t seen it, I believe it was dead.
Tom of AskaNaturalist.com Says:
Wow. That’s interesting. I wish we had a video of that.
I just saw a Chipmunk raid a cardinal nest and take an adolescent chick across my deck. I am not too happy about this. I wondered why the cardinals had been so crazy all day.
I saw a chipmunk attack a sparrow under the bird feeder. It would also hide under the low blue spruce branches in ambush. I also saw it run off another chipmunk. One day we found 3 dead sparrows and one large mouse under that tree. At first we thought something was wrong with the feed but did suspect that aggressive chipmunk. My son thought something was wrong with the chipmunk. We never saw them agressive before.
Was horrified to see one of the chipmunks attack a sparrow near the feeder. I went out to retrieve the bird and it was gone. Don’t know if the chipmunk dragged it away. Solves the mystery of another dead bird we found last week in the same spot.
Wayne Morgan Says:
While hunting in the Blue Mountains of Oregon 09/24/2015 I observed a Chipmunk eating a mouse. When I scared it away, rigor mortise had not yet set in. Did he also kill it??
Tom of AskaNaturalist.com Says:
Tough to know. It’s possible.
My daughter and I had a mouse that got caught in a waste basket of our barn. We decided to set it free in the woods (neither one of us has the heart to kill it). When we set it free, it went running off happily only to have a chipmunk run after it and kill it. It picked it up and spun it around like a nut while biting it and then ran off with it in its mouth! We were so shocked we just stood there with our mouths open. The funny thing is there was a second mouse that slipped out of the waste basket and hid under a leaf. We didn’t blame him.
Tom of AskaNaturalist.com Says:
Wow. I have not heard of that kind of direct predation. Thanks for sharing that.
C J Holm Says:
Just watched a grey squirrel climb a 15′ steel pole to get into a Martin house in winter. The house had 24 rooms and the squirrel checked each for a meal. It found a dead bird carcass which it took back to its nest for a snack.
Was in my kitchen this morning when a female cardinal bounced off of one of the windows. Went outside to check on her and she was standing motionless with dull eyes, obviously dazed. Didn’t want to frighten her so went inside to watch her where I didn’t think she could see me. A couple of minutes later, a chipmunk approached her from behind, put a paw on her back and moved its head toward the bird’s head. Not knowing the chipmunk’s intentions, I shooed it away. I kept watch over the bird until, after a few more minutes, her eyes became alert, she moved her head around and then flew off. Had to shoo the chipmunk away twice more before the cardinal had recovered enough to take flight. Later Googled chipmunk predation and found this string of posts. I knew chipmunks would take a chick but hadn’t before considered they would go after an adult cardinal. So I’m glad I kept watch over the bird until she was able to fly again.
Holy crap. I was surprised to see prairie gophers (not “prairie dogs”) engaging in road-kill cannibalism.
I had recently become curious about whether other squirrels would eat meat as well … I guess now I know. The chipmunks are surprising, didn’t think they were that aggressive. No wonder they can be such bold little guys!
Margo D. Says:
I came upon this site because I thought squirrels were herbivores and couldn’t believe it this morning when I watched a squirrel chowing down on a blue jay in my backyard! I was afraid that something was wrong with it like perhaps rabies! Lol Good to know it’s “normal”. I’m thinking that’s one tough squirrel to take on a blue jay!