Apparent chitin digestibilities in the Eastern Screech Owl (Otus asio) andthe American Kestrel (Falco sparverius)

Chitin, which is found in arthropod exoskeletons as a structural and defens ive material, is one of the most abundant carbohydrates in nature. Chitin d igestibility was studied in two partially insectivorous raptors, Eastern Sc reech Owls (Otus asio) and American Kestrels (Falco sparverius). When owls were fed crab shell chitin (5% or 2% of total dried food, by weight), 10.6 +/- 7.1% (SD) to 30.4 +/- 7.8% was digested (species digestibility means we re 26.2 +/- 4.4% and 18.6 +/- 6.6%). Kestrels consuming a 5% or 2% chitin d iet had 15.7 +/- 3.9 to 25.7 +/- 5.3 percent digestibilities. The mean appa rent digestibilities for kestrels were 18.5 +/- 2.5% and 22.3 +/- 3.0%, res pectively, for the 5% and 2% chitin diets. In an effort to improve chitin d igestibilities in owls and kestrels, chitin was added to daily meals for 3 or 6 weeks, but no statistically significant increase in digestibilities wa s found. Relatively low apparent chitin digestibilities in those two raptor ial species suggest that chitin is not an important energy source for rapto rs. Further investigation is required to clarify the magnitude of potential benefits. J. Exp. Zool. 283:387-393, 1999. (C) 1999 Wiley-Liss, Inc.