American Kestrel - picky eater

This is a behavior I'm very curious about. I've seen it twice in kestrels but never in another raptor. This female very deliberately separated the small intestine from the carcass and discarded it. In fact she did it twice, with two pieces of the intestine. She ate all the other viscera with relish (the verb not the noun) :-).

This series was taken this past January - the temps were frigid and the ground snow covered so I suspect that food must have been at a premium. I was very surprised that she would discard anything at all.

Does anyone know if this is a relatively common behavior? And the explanation for it?

I posted a different shot of this bird in Avian last winter.

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Very interesting series. I have no idea why she would do that. Looking forward to other's expert knowledge on this behavior.

I don't know why either, Ron, but I did see a Kestrel separate part of the innards from a vole and discard them earlier this spring.

All I can hypothesize is if you were eating an animal - you would probably choose to discard of this section too. The only thing it's filled with is harmful bacteria - obviously the bladder/stomach etc. are filled with all sorts of bacterias as well, but I'm sure this section has some of the worst offenders and doesn't taste terribly well. What would be interesting is if this is a learned habit or an instinct... I'd have to believe it's learned, but I wonder if it's through experience or if it's taught by mom and dad. I

I witnessed an Osprey doing something similar with some of the nastier sections of a fish as seen in the photos. It severed this large chunk of the fish (looks like liver?) and then discarded it and continued eating.

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Luke, this is the small intestine, which would be filled mostly with incompletely digested food (in this case, plant material) and some digestive enzymes. The bacteria you refer to would be mostly in the large intestine and the kestrel consumed that organ. I've read that many strict carnivores get needed trace food components (carbohydrates for example) from the digestive systems of their prey which is part of the reason this behavior surprised me.

But you're right - if this mouse or vole was on my dinner plate I'd certainly "discard this section too".

Very interesting, and excellent shots as well.

I have a long series of a distant Red-tailed Hawk doing something similar with a ground squirrel.

Ron, "the small intestine ... would be filled mostly with incompletely digested food (in this case, plant material) and some digestive enzymes."
Can a kestrel's digestion break down cellulose?
Would the kestrel discard the small intestine of another carnivore?

Rosemarie,

"Can a kestrel's digestion break down cellulose?". It is my understanding than no member of the animal kingdom, not even termites, can produce the digestive enzymes required to break down cellulose - that must be done by bacteria living in the animal's gut, especially in the caecum of mammals. I also suspect that much of the diet of this rodent would be seeds, containing little cellulose.

"Would the kestrel discard the small intestine of another carnivore?" Good question. I don't know. I don't even know if this intestine discarding behavior is typical behavior for kestrels.

I guess I proved my utter lack of digestive system knowledge. . . :-). Needless to say I switched from being a Marine Bio major to Environmental Studies, which I guess was the right choice!

Terrific behavior series Ron. Great pics of the Kestrel which I think is one of the most beautiful of all falcons.

I don't have an answer either. I do know that animal behavior is often as complicated and illogical as human behavior (I separate the two for discussion purposes). I think we tend to believe that it always "makes sense", or has some biological imperative, but that's because we underestimate their complexity.

Peter

Ron -

We had a rehab female American Kestrel here a few years ago, and she did the same thing. Cricket was not a fussy eater, but always left the small intestines of whatever prey we gave her... Let me ask some of my professional ornithologist buddies and see if I can get any credible explanation.

Thanks very much Jim - that's very interesting to know. From what you said it seems that the behavior may be "typical". And I'd definitely be interested in any new info your buddies may be able to provide as to why they may do it.

Thank you Cindy, for the link and for posting Julie Crave's reply. Very interesting stuff. I've been out of town for three days and didn't see your comment until just now.

Strangely, I'm reading this thread while having breakfast (eggs, bacon, toast). Nice shots. I have seen owls do this. When they swallow prey whole, obviously it's take the good and the bad. On occasion when they tear prey apart, I have seen them leave the intestines behind.