Fatty acid composition of depot fat of shorebirds collected at mid-continental stopover sites during spring migration
Despite the critical role of fat in providing energy for large-scale seasonal movements, little is known about the fatty acid composition of shorebird depot fat. Fatty acid composition is important because it may impact flight performance and seasonal migratory movements. We analyzed the fatty acid composition of depot fat of 12 species of shorebirds collected during spring migration at stopover sites in Kansas from two different subcutaneous fat depots (furcular and saddle depots). Five fatty acids (palmitate [16:0], palmitoleate [16:1], stearate [18:0], oleate [18:1n-9], and vaccenate [18:1n-7]) accounted for 70–96% of the total composition of depot fat despite the diverse foraging behaviors of the species sampled. This similarity in fatty acid profiles may be due to a limited availability of high-lipid food items in the shallow water and mudflat habitats where migratory shorebirds forage in the southern Great Plains. In addition, shorebird depot fat was composed primarily of long-chain saturated and monounsaturated fatty acids (i.e., 16- and 18-carbon), fatty acids thought to be more easily converted to energy during migration. Depot fat in the furcular depot was similar in composition to fat from the saddle depot, and we found no differences in fatty acid composition of the adipose tissue of males and females. Thus, our results suggest that representative shorebird depot fat fatty acid profiles can be obtained even if investigators are limited to sampling one sex, and that adipose tissue collected from saddle depots provide representative samples so biopsies can be limited to areas of the body with the least impact on flight performance.