Effects of extra mass on the pelagic behavior of a seabird

Satellite transmitters and geographic-positioning-system devices often add substantial mass to birds to which they are attached. Studies on the effects of such instruments have focused on indirect measures, whereas the direct influence of extra mass on pelagic behavior is poorly known. We used 2.5-g geolocators to investigate the effect of extra mass on the pelagic behavior of Cory's Shearwaters (Calonectris diomedea) by comparing the traits of a single foraging trip among a group carrying 30-g weights, a group carrying 60-g weights, and a control group. The weights were attached to the birds' backs using typical techniques for attaching satellite transmitters to seabirds. The extra mass increased the duration of the birds' trips and decreased their foraging efficiency and mass gained at sea. These indirect effects may be related to foraging traits: weighted birds showed a greater search effort than control birds, traveled greater distances, covered a greater foraging area, and increased the maximum foraging range. Furthermore, the time spent on the sea surface at night was greater for weighted than for control groups, which showed that the extra mass also affected activity patterns. Our results underline the need to quantify the effects of monitoring equipment commonly used to study the pelagic behavior of seabirds. We suggest that geolocators can be used to obtain control data on foraging-trip movements and activity patterns.

Converses (extra)terrestres

El Nadal és una època plena de simbolisme, on les converses amb familiars i amics són protagonistes. Hi ha una frase bíblica,"I el Verb es va fer home i va conviure amb nosaltres" (Joan1,1-14), que sempre m'hi fa pensar, atès que en un context religiós el mot verb pot significar precisament això, "expressió d'idees i pensaments mitjançant la paraula" (DIEC2). Actualment al nostre planeta es parlen més de 6.800 idiomes. Hi ha idiomes tonals, com el mandarí i el ioruba, on el to amb què es pronuncia una paraula afecta el seu significat [...].