A comparison of the decomposition of raptor hair and feather pellets

Background/Question/Methods

Indigestible material is regurgitated in about 320 species of birds in 67 families, and birds of prey regularly regurgitate mucous-covered pellets with bone, fur, feather, chitin and scale remains of prey.  The objective of this study was to compare the ecology of the decomposition of hair and bone pellets with feather and bone pellets.  Pellets from laboratory Great Horned Owls (Bubo virginianus) fed on rats (Rattus norvegicus) and pigeons (Columba livia), and a zoo Bald Eagle (Haliaeetus leucocephalus) fed on rats were dried, placed in plastic mesh bags, and frozen. Sixteen to twenty-four pellets of each type were then set out in maple-oak hardwoods and in spruce forest sites in September in central New York.  One to four pellets of each type were then collected every eight days from each site for 48 days until mid-November.  Observed fungi were cultured individually and invertebrates were extracted using modified Tullgren funnels. 

Results/Conclusions

Five species of fungi were found on both hair and feather pellets.  The owl hair and bone pellets yielded 912 invertebrates of 88 species; the eagle hair and bone pellets yielded 441 invertebrates of 70 species; and the owl feather and bone pellets yielded 489 invertebrates of 68 species.  Thirty-four species were common to all three pellet types; 10 species were found only on the owl pellets; 10 species were found only on the hair and bone pellets, and 6 species were found only on the eagle hair and bone and owl feather and bone pellets.  The owl hair and bone pellets had much higher populations of collembolans, astigmatic mites and coleopterans.  The feather and bone pellets contained many more dipterans, while the eagle hair and bone pellets had the largest oligochaete population, incuding both earthworms and enchytraeid worms.  Feather pellets decomposed fastest but invertebrate communities on all three pellet types were similar.