ECOLOGICAL FACTORS INFLUENCING THE OCCURRENCE OF FLASH MARKS IN WADING BIRDS

1, Although the plumage of birds is important for flight and thermoreg ulation, it is also employed in inter- and intraspecific communication . The role in communication of particular plumage features can be stud ied by experiment or, as here, by correlational analysis. 2, The study was carried out on the 210 species of wading birds, such as plovers, sandpipers, thick-knees and allies, that are placed within the traditi onal order Charadriiformes. 3. Species differ in the location and exte nt of 'flash marks', patches of white on the plumage that are typicall y conspicuous when the bird flies. These patches occur, in various per mutations in different species, on the wing (primaries, secondaries, c overts), back, rump and tail. 4, Within a phylogenetic framework, it w as asked which of several broad ecological variables (migration, habit at choice, feeding technique, propensity to flock) were correlated wit h the occurrence of flash marks. Only flocking correlated significantl y. In particular, taxa that flock have flashier backs and coverts than their non-flocking relatives. 5, Three non-exclusive explanations for this correlation are: (i) individuals that take flight to avoid a pre dator may benefit from signalling their take-off to flock mates which themselves then take flight; (ii) flash marks could enhance the confus ion effect within flocks, making it more difficult for a predator to s ingle out an individual; and (iii) flash marks may facilitate co-ordin ated flight within flocks.