Marking penguins with implanted transponders

Individual marking of birds is required in many studies. Lance Richdale pioneered marking of penguins in the 1930s (Richdale 195 1, 1957). His most reliable method was punching holes in the feet, but he also used homemade aluminium leg bands which had to be replaced every three years because of wear. Subsequently, researchers reported that leg bands used on Antarctic penguins caused injuries and that they experienced difficulties reading them in the field. Thereafter, flipper bands became the standard method for marking penguins (Sladen 1958). If applied correctly, these bands cause no visible injury other than some feather abrasion. Increased mortality over the winter was attributed to bands which were too narrow and restricted blood flow when the flipper swelled during moult (Ainley et al. 1983: 191). A different design with projecting fasteners caused serious injury, possibly death in a particular study (Sallaberry & Valencia 1985). In the latter case, a chinstrap penguin (Pygoscelis antarctica) colony of 180-210 nests declined to 40 nests within 11 years after birds in the colony were first banded (Valencia & Sallaberry 1993). Studies of energetics showed that the additional drag caused by flipper bands led to a 24% increase in energy expenditure during swimming in an artificial channel (Culik et al. 1993). However, no differences were detected in adult mortality, breeding