O. Egeler et Td. Williams, Seasonal, age, and sex-related variation in fatty-acid composition of depot fat in relation to migration in Western Sandpipers, AUK, 117(1), 2000, pp. 110-119
The composition of depot fat in Western Sandpipers (Calidris mauri) was dom
inated by C-16 and C-18 fatty acids (palmitate, 16:0; palmitoleate, 16:1; s
tearate, 18:0; oleate, 18:1), which together comprised 80 to 90% of all fat
ty acids analyzed. Significant seasonal variation occurred in the relative
proportion of specific fatty acids and the ratio of saturated to unsaturate
d fatty acids in relation to the migratory cycle of the sandpipers. In adul
ts of both sexes, the proportion of 16:0 and 18:0 fatty acids decreased fro
m winter (December) to premigration (March) to spring migration (May), wher
eas the proportion of 16:1 and 18:1 fatty acids increased over these same p
eriods. Consequently, total unsaturated fatty acids increased by 34% betwee
n the winter and premigratory phase, and by a further 22% between premigrat
ion and spring migration. Therefore, biochemical modification of adipose ti
ssue in Western Sandpipers begins during the premigratory period in prepara
tion for long-distance flight but continues as migration progresses, perhap
s reflecting a training component of physiological modulation for migration
. Juveniles showed similar changes to adults in the composition of their de
pot fat during the "premigratory" period, even though most juveniles do not
undergo hyperphagia or rapid fattening at this wintering site. Potential p
rey species collected from a wintering site in Panama had a higher proporti
on of saturated fatty acids, less 16:1 and 18:1, and more 18:0 fatty acid c
ompared with those from a migratory stopover site in British Columbia, para
lleling the seasonal changes in depot fatty-acid composition observed in We
stern Sandpipers. However, the fact that Western Sandpipers show an increas
e in level of unsaturation and in the amounts of 16:1 and 18:1 fatty acids
in their fat stores on the wintering ground prior to migration suggests tha
t seasonal variation in fatty-acid composition is not entirely diet depende
nt.