Geographical variation of protein reserves in birds: the pectoral muscle mass of Dunlins Calidris alpina in winter

• Published in: Journal of Zoology
• Main Authors: Davidson, N. C., Evans, P. R., Uttley, J. D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1986
• Subjects: Midwinter; Calidris alpina
• Online Access: http://dx.doi.org/10.1111/j.1469-7998.1986.tb04714.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1469-7998.1986.tb04714.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-7998.1986.tb04714.x; https://zslpublications.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-7998.1986.tb04714.x

Pectoral muscle size (as an index of protein reserves) was measured in Dunlins during midwinter on five British estuaries, and examined in relation to latitude and midwinter air temperature. In adults, pectoral muscle size was greater on more northerly and colder estuaries. Pectoral muscle size of juveniles varied less than that of adults between estuaries. For both ages, pectoral muscle size correlations were stronger with temperature than with latitude. The size of protein reserves in the pectoral muscles differed by 26% (adults) and 14% (juveniles) between warmest (Menai Straits) and coldest (Firth of Forth) sites studied. Both pectoralis major and supracoracoideus muscles contributed to the protein store, but the supracoracoideus formed only 12% of the total pectoral muscle mass. The age‐difference appeared not to arise through the selective death of some juveniles. We propose that juveniles have a set‐point for pectoral muscle size in winter adapted to the broad geographical area within which they may settle. The set‐point may then be altered according to the weather conditions experienced at the site where they settle and return as adults.