Monday, September 24, 2012

Ruminants Eating Birds

Who would have ever thought that white-tailed deer (Odocoileus virginianus), which are herbivores, would have the occasional craving for bird flesh? I sure didn’t. I did some digging on this topic on SORA (Searchable Ornithological Research Database) and found articles from several ornithological journals speaking of this bizarre behavior.

From what I’ve discovered in the literature the first time this was noted was back in 1970 when researchers found bird remains in the rumen (first stomach) of a deer. (1) (6) In the Spring 1978 issue of Bird Banding it stated that previously in 1976, during a bird banding project, birds that had been captured in mist nets were being eaten. It was determined that deer were responsible due to their presence in the area and the fact that their tracks were found in the soil beneath the mist nest where the bird was partly consumed. (2) It wasn’t actually proven that this was happening until the years 1996-1999 when a white-tailed deer was videotaped depredating bird’s nests in grassland habitats in North Dakota. At that time it involved the nests of savannah, grasshopper, and clay-colored sparrow nestlings. Incidentally, some of the nests had been parasitized by cowbirds, which were also consumed. (3)

To take this odd behavior even further white-tailed deer have also been reported eating fish and insects.(2) (4) (5) There’s even photo evidence of deer eating meat at animal carcasses and gut piles left by hunters.(10) Another was seen eating at a dead rabbit in which it only consumed the legs and ears. (10) Here's a video of a white-tail deer I came across eating a bird:

This odd behavior has also been noted in other countries-Red deer (Cervus elaphus) on the Scottish island of Rum feed on the chicks of Manx shearwaters (Puffinus puffinus). And get this…..they’re only eating the heads, legs, and wings of the nestlings leaving feathers, flesh and skin intact. It is theorized this is due to mineral deficiencies found in the vegetation the deer consume on this island, and they eat the bony parts of the birds to supplement their diet with calcium and phosphorous that’s needed especially for antler growth. (7) (8)

Other ruminents have also been documented doing this- In southwestern Wisconsin from 2000-2001 cattle was believed to have consumed the eggs and nestlings of savannah sparrows and eastern meadowlarks. (9) On the isle of Foula in the Shetland Islands, scientists found sheep that were consuming only the legs of the unfledged nestlings of Arctic terns. (7) It is believed that the motivation for the cattle and sheep are the same as with red deer- for the minerals which are lacking in the soil and in turn the vegetation that they feed on.
Should deer, cows, and sheep now be considered as omnivores? And what effect could this have, if any, on bird populations? This is the type of odd, off the wall stuff I love reading about. There’s, I’m sure, so much more about nature that we still are totally unaware of.

References and Suggested Reading:

1) Stone and Palmateer. 1970. New York Fish & Game Journal 17(1):63 [cited by Carlson and Sloan].
      4) Olson, S.F. 1932. Fish-eating Deer. J. Mammal., 13:80-81.
      5) Shaw, H. 1963. Insectivorous white-tailed deer. J. Mammal., 44:284.
      6) IBBA News, 47:217-219, 1975.
    10) Meat-Eating Deer


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