THE EFFECT OF CARRYING DEVICES ON BREEDING ROYAL-PENGUINS

The impact of Time Depth Recorders (TDRs) and VHF transmitters, deploy ed on Royal Penguins (Eudyptes schlegeli) to examine foraging behavior , was assessed during all stages of the breeding season. Models of the devices were attached to penguins and compared to control birds with no devices. There were no impacts from transmitters on probability of return from a foraging trip, foraging trip duration, mass gained, wate r influx, or body composition, but substantial impacts from the TDRs. Attachment of TDRs (1) reduced the likelihood that penguins would cont inue the breeding attempt, (2) increased foraging trip duration, (3) i ncreased water influx, and (4) decreased fat levels. The effects varie d with sex and stage in the breeding season, which appeared to be rela ted to the energetic demands of the stage in the breeding season. TDRs probably increased drag, affecting swimming speed and foraging succes s. The differential impact of the devices is most likely related to th eir cross-sectional area and streamlining, with TDRs being larger and less streamlined than transmitters.