We attached black, white, blue, red, and yellow packages containing a peck pressure sensor and recorder to the dorsal feathers of free-living Adelie penguins (Pygoscelis adeliae). Packages were left in place for up to 14 days. Black packages, which matched the background feather color, were pecked significantly less (P < 0.05) than any other color except red during 24-hour trials with incubating birds. Other colors were pecked equally. The number of pecks given to packages worn at sea was positively related to the wearing time with no evidence of habituation up to the maximum wearing period. Researchers equipping penguins with external devices will have to consider device coloration as a potentially important source of irritation to the birds. J. WILDL. MANAGE. 54(3):447-451 The foraging habits of many seabirds are obscure due to the difficulty of observing birds at sea. However, attaching telemetric and other remote-sensing devices enables aspects of seabird marine ecology to be studied without direct observation. These devices have been used to de ermine avian foraging depths (Kooyman et al. 1982, Burger and Simpson 1986), foraging ranges and traveling speeds (Adams and Wilson 1987), dive duration (Trivelpiece et al. 1986), and total time spent underwater (Cairns et al. 1987). 'Present address: Centre d'Etudes Biologique des Animaux Sauvages, Centre National de Recherche Scientifique, 79360 Beauvoir sur Niort, France. This content downloaded from 157.55.39.223 on Wed, 24 Aug 2016 03:52:30 UTC All use subject to http://about.jstor.org/terms 448 PACKAGE COLOR * Wilson et al. J. Wildl. Manage. 54(3):1990 The necessity of packages to determine behavior of animals that cannot be observed also often precludes the possibility of directly assessing package-induced aberrant behavior (Perry 1981). Packages may affect seabirds either by physically impairing their capabilities, e.g., by reducing swimming speeds (Wilson et al. 1986) or by inducing extended time spent preening or trying to remove the device. Wilson and Wilson (1989a) described a simple device that uses a carbon paper sensor to determine the number of times that a packagefitted bird pecks at the device. We used this system to examine whether the reaction of breeding Adelie penguins to attached packages varied with the color of the package. We thank the Instituto Antartico Argentino for providing logistic help. Funding was provided by the Deutsche Forschungsgemeinschaft grant MZ/Ad 24/11-1. We are grateful to M.-P. Wilson for comments on the manuscript.