Nutrient composition of the crop contents of growing and adult grey-faced petrels (Pterodroma macroptera):: a preliminary investigation

We investigated the nutrient composition of the crop contents of grey-faced petrel (Pterodroma macroptera) adults and chicks. Crop content samples were obtained from birds breeding at Bethells Beach, Auckland, New Zealand over a four month period (Sep-Dec 1997) and bulked according to age: 3-5, 6-10, 60-90 d old, and adults. Crop content samples were analysed for crude protein, amino acids, gross energy, lipids, fatty acids, ash and minerals. All four age groups contained high levels of crude protein (26-60%) and lipid (20-44%), while the ash level was highly variable between age groups (4-41%). In general, the amino acid pattern of the crude protein fraction was similar between the four age groups except for taurine and several other amino acids in the 3-5 d old group. The pattern of fatty acids was similar between the four age groups although myristic and palmitoleic acid were higher in the free fatty acid and triglyceride fraction of the 3-5 d old group. The calcium to phosphorus ratio in the fat extracted crop content samples of the 60-90 d old and adult birds was 2.5 and 2.9, respectively. The present study provides preliminary information on the nutrient composition of the crop content of growing and adult grey-faced petrels that can be used to formulate balanced artificial diets for the different life stages of growth and adulthood of the taiko or magenta petrel, a related, endangered species.