Ardea
Official journal of the Netherlands Ornithologists' Union

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Davidson N.C., Uttley J.D. & Evans P.R. (1986) Geographic variation in the lean mass of Dunlins wintering in Britain. ARDEA 74 (2): 191-198
The lean dry mass and lean mass of 175 adult and 74 immature Dunlins wintering on 7 British estuaries were analysed in relation to body size, and latitude and air temperature of wintering site. Much of the individual variation in mass was a consequence of structural body size differences. Controlling for this variability, lean dry mass was poorly correlated with latitude, but was strongly correlated with midwinter air temperature so that mass was highest on coldest estuaries. The difference between mildest (Menai Straits) and coldest (Firth of Forth) sites studied was 0.64 g in adults and 0.94 g in immatures, and was partly due to variation in the size of protein reserves in the pectoral muscles. Lean mass varied in a similar way to lean dry mass, with between-site differences of 3.6 g (adults) and 6.3 g (immatures). This age-difference was largely a consequence of the high water content of immatures on the Firth of Forth. Erroneous interpretations of patterns of body condition based on total mass can be made if no account is taken of variations in lean mass, even over small parts of the wintering range such as within Britain.


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