Flipper bands do not affect foraging-trip duration of Magellanic Penguins

Flipper bands are used to mark penguins because leg bands can injure their legs. However, concerns remain over the possible effects of flipper bands on penguins. We examined the effects of stainless-steel flipper bands on the duration of foraging trips by Magellanic Penguins (Spheniscus magellanicus) at Punta Tombo, Argentina, using an automated detection system. We predicted that, if bands were costly and increased drag, flipper-banded penguins would make longer foraging trips than those with small or no external markings. We tagged 121 penguins with radio-frequency identification (RFID) tags and an additional external mark. We placed either a stainless-steel band on the left flipper (N = 62) or a 2 x 10-mm small-animal ear tag in the outside web of the left foot (N = 59). We measured foraging-trip durations (N = 376 trips) for 68 adult penguins with chicks from 15 December 2007 to 28 February 2008. Contrary to predictions, trip duration was similar for banded and web-tagged penguins (P = 0.22) and for males and females (P = 0.52), with no interaction between tag type and sex (P = 0.52). No penguins marked in the 2007 breeding season and recaptured between 30 September and 30 November 2008 (N = 113) lost flipper bands or web tags, but three RFID tags failed between March and September 2008. Properly designed and applied flipper bands were a reliable marking method for Magellanic Penguins, had a lower failure rate than RFIDs, and did not affect foraging-trip duration.