Untangling causes of variation in mercury concentration between flight feathers

Bird feathers are one of the most widely used animal tissue in mercury biomonitoring, owing to ease collection and storage. They also principal excretory pathway birds. However, limitations our understanding physiology deposition has placed doubt on interpretation feather concentratoins. Throughout literature, moult sequence depletion body pool have been taken explain patterns such as decrease from innermost (P1) outermost primary (P10) wing. it suggested that this pattern is rather a measurement artefact result increased mass length ratio along primaries, resulting dilution effect heavier feathers. Here, we attempt untangle causes variation concentrations by quantifying concentration ?g (i) per gram feather, (ii) millimetre (iii) day growth Bulwer's Petrel Bulweria bulwerii chicks, effectively controlling for some axes may be acting adults, monitoring rate chicks. The chicks' primaries all three measures, following order emergence. These observations confirm across not an measure concentration, but likely growth, whereby earlier grown exposed higher blood than later moulted depletion.