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Notes on the Flocking of Shore Birds

1931; Oxford University Press; Volume: 48; Issue: 2 Linguagem: Inglês

10.2307/4076784

1938-4254

John T. Nichols,

Scientific Research and Discoveries

ONE of the most striking phenomena of flocking in shore birds, although one that is in no wise confined to this group, is the way in which flocks at times fly holding a close ranked formation, and the seemingly instantaneous precision with which they wheel in unison, as though each individual were motivated by a common impulse, rather than adjusting itself to the movements of its companions. This has seemed to me something of a mystery until a recent observation suggested a simple explanation perhaps bearing on the mechanics involved as well as on the purpose of the maneuver. Two Dowitchers, young of the year, had been frequenting a narrow bit of favorable bay shore screened by sedge grass, for some days if not weeks. On the nearby ocean beach, reached through a short break in the dunes, Black-bellied Plover were usually to be found. This morning about a dozen Black-bellied Plover were alighted on the bay side with the Dowitchers, and sheltered by the grass, we detected a single Golden Plover among them, and had the pleasure of watching it at close range for as long as we desired. We then flushed the flock with the intention of picking out and comparing the Golden with the other Plover on the wing. Its flight was relatively fast, now it bounded off ahead of the flock, and as they wheeled finding itself in the rear, rose above them and dove down through to the front rank with a few swift wing strokes. Similarly the Dowitchers, naturally less fast than the Plover and straggling in the rear, were picked up as the flock wheeled and went off as an integral part of it. When flocks of shore birds are making a protracted straightaway flight they usually move in comparatively open formation and are particularly apt to straggle when more than one species is involved, the bunching and wheeling is most frequent when a flock takes wing and may well serve to hold it together until the faster and slower individuals have adjusted speeds.