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Movements of animals provisioning offspring by central place foraging extend from short, highly local trips where food is brought back essentially unchanged from its normal condition to extensive interseasonal movement where the offspring are nourished from body reserves built up during the adult's absence from the breeding site. Here, appropriate strategies for maximizing lifetime reproductive success depend on the abundance and location of prey in relation to breeding sites and the energetics and speed of travel of the animal. Magellanic Penguins Spheniscus magellanicus undertake central place movements that are particularly variable during the incubation period; trips may last from a single day to over three weeks depending on colony locality. We reasoned that site-specific variability in prey distribution and abundance is responsible for this. Remote-sensing systems attached to 92 penguins from six different colonies over the species distributional range over the Patagonian Shelf were used to determine space use and foraging patterns in an attempt to understand the observed patterns. Birds in the north and south of the latitudinal range were essentially monophagic, feeding primarily on anchovies Engraulis anchoita and sprats Sprattus fuegensis, respectively, both species that are to be found relatively close to the colonies. Penguins in the center of the distributional range, where these pelagic school fish prey are essentially absent at that time of the year, traveled either north or south, to the same regions utilized by their conspecifics, presumably to exploit the same prey. A simple model is used to clarify patterns and can be used to predict which movement strategy is likely to be best according to colony location. During chick rearing, southerly movement of anchovies and northerly movement of sprats mean that Magellanic Penguins in the center of the distributional range may benefit, although the abundance of these fish is considered to be less than that closer to the Magellanic Penguin range limits. The extensive time involved in the foraging trips during incubation coupled with the postulated poorer prey conditions during the chick-rearing phase may help explain why Magellanic Penguin colony sizes in the center of the range are not elevated.

Adults and larvae of a new species of Skrjabinocerca Shikhobalova, 1930 (Nematoda: Acuarioidea) are described on the basis of light and scanning electron microscope studies. Specimens were recovered from Calidris canutus rufa Wilson (Aves: Scolopacidae) from the Southwest Atlantic coast of Uruguay. Data on the hosts, localities and main features of the four previously described species of the genus are provided. S. canutus n. sp. can be distinguished from its congeners by a combination of the following characters: non-recurrent cordons, shorter right spicule and possession of a delicate finger-like projection on the distal end of the left spicule. S. prima Shikhobalova, 1930 has a left spicule which is stilletto-shaped and sharply pointed, S. europaea Wong & Anderson, 1993 has recurrent cordons, S. americana Wong & Anderson, 1993 possesses two delicate digitiform projections on the distal end of its left spicule and S. bennetti Bartlett & Anderson, 1996 has subequal spicules. Fil: Diaz, Julia Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; Argentina Fil: Cremonte, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina Fil: Navone, Graciela Teresa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; Argentina Fil: Laurenti, Sonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina

The behaviour of Magellanic Penguins Spheniscus magellanicus commuting between their foraging areas and breeding areas in San Julian Bay, Argentina, was studied to examine whether tidal rip currents affected travelling patterns. Although there was no apparent relationship between departure and arrival patterns and the state of the tidal cycle, birds travelling against the current dived for longer periods and a shorter rests on the surface than birds travelling with the current. In addition, bird swimming against the current hugged the banks of tidal rivers much more closely than did birds swimming with the, thus, reducing the magnitude of the current against which they had to swim. In cases of extremely high current speeds, birds travelling upstream walked. Models regarding the energetics of movement indicate that the strategies adopted by Magellanic Penguins can result in substantial energy savings. Fil: Wilson, Rory P. Institut fur Meereskunde; Alemania Fil: Locca, R.. No especifíca; Fil: Scolaro, Jose Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina Fil: Frere, Esteban. Universidad Nacional de la Patagonia Austral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gandini, Patricia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia Austral; Argentina

Proctotrema bartolii n. sp. (Digenea: Monorchiidae) is described based on naturally and experimental obtained adults from the marine fishes Odontesthes smitti (Lahille), O. nigricans (Richardson) (Atherinopsidae) and Eleginops maclovinus (Cuvier) (Eleginopidae) off Patagonia, Argentina, in the Southwestern Atlantic Ocean. Its generic identification is based on the presence of a unipartite terminal organ with the metraterm uniting with its distal region, an unarmed genital atrium, a single testis, a vitellarium follicular lateral to the ovary and ventral sucker, and uterine coils occupying most of hindbody. The new species differs from P. bacilliovatum Odhner, 1911, P. amphitruncatum Fischthal & Thomas, 1969 and P. guptai Ahmad & Dhar, 1987 in having a smaller body (305-650 vs 1,600-3,080, 1,500-1,800 and 2,150-2,670 μm, respectively), a round vs funnel-shaped oral sucker, a smooth vs lobed ovary, a saccular rather than tubular excretory vesicle, the number of vitelline follicles (12-16 vs 8-9, 9 and 6-8, respectively), and wider eggs (25-31 × 15-20 vs 28-37 × 9-12, 24-28 × 7-10, and 24-30 × 8-10 μm, respectively). Moreover, the new species differs from P. bacilliovatum and P. amphitruncatum in having a saccular rather than a coiled seminal vesicle, and from P. bacilliovatum and P. guptai in having its tegument completely vs partly spined. Proctotrema Odhner, 1911 is considered to be restricted to these four species. This is the first report of a species of this genus from South American waters. Fil: Carballo, María Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina Fil: Laurenti, Sonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina Fil: Cremonte, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina

We looked at the routes taken by Magellanic Penguins up the beach while moving between the sea and the colony at a breeding site in San Julian, Argentina. Birds swam parallel to the shore for a period before leaving the water to cross the beach but trajectories over the beach were not perpendicular to the water's edge but at an angle of 39°. We examined the premise that birds might be optimizing for a trade off between time or energy by adopting this procedure and found that birds can gain little or no time by walking obliquely but can, under particular circumstances, save energy. These circumstances require that the previously-calculated costs of transport for walking have been over-estimated by a factor of two

The diet of Magellanic Penguins (Spheniscus magellanicus) was studied by stomach-pumping birds at five colonies (San Lorenzo, Punta Clara, Punta Loberia, Monte Leon and Punta Dungeness) over the species' latitudinal range in Argentina. A total of 159 birds were sampled during the period February 1986 to December 1988. Most prey items consisted of pelagic school fish, although squid and shrimps were also taken. At any one colony, birds appeared to be principally monoor bi-phagic and there were clear latitudinal differences in prey taken. Penguins in the northern colonies at San Lorenzo, Punta Clara and Punta Loberia consumed primarily anchovy (Engraulis anchoita) while birds at the two southerly colonies of Monte Leon and Punta Dungeness fed primarily on squid (Loligo spp. and Illex spp.), sprats (Sprattusfuegensis) and Hagfish (Myxine spp.). The strict dependence of Magellanic Penguins on commercially-exploited, schooling prey species makes the species particularly susceptible to changes in prey stocks, as has happened to congeners elsewhere that have suffered population crashes due to poorly-managed fisheries. Received iiJanuaryl 999, accepted 24 February 1999.