CADIC   02618
CENTRO AUSTRAL DE INVESTIGACIONES CIENTIFICAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Getting to know Magellanic penguins breeding in Staten Island: foraging behaviour and areas during chick rearing period.
Autor/es:
N ROSCIANO; K PÜTZ; A RAYA REY
Reunión:
Congreso; 8 International Penguin Conference; 2013
Resumen:
Studies of the foraging
behaviour of seabirds are important to establish their role in marine food webs.
In Penguins, foraging behaviour is known to vary with locality, sex and stage
of breeding. For the first time, we studied the foraging behaviour of
Magellanic Penguins (Spheniscus
magellanicus) breeding on Staten Island, Argentina, to evaluate differences
in the foraging behaviour between sexes and to characterize the core areas of
their distribution at sea. Fifteen Magellanic Penguins (PM) (8 males, 7
females) from the colony at Bahía Franklin were equipped with GPS data loggers
during the early chick rearing period in December 2011. Also, blood samples
were taken for stable isotope analyses. Foraging trip duration was 22.4+7.5
hs and all except one penguin performed overnight trips, where dive depths were
around 9 m. No significant differences between sexes were found for either diving
or feeding effort, except for diving depth and wiggle number per minute during
the bottom phase, being higher in males compared with females. PM initially headed
northwest and west towards their foraging areas, with a maximum distance from
the colony of 35.4+7.6 km, covering a trajectory of 110.6+29.7
km. Foraging areas (95% kernel contour) occupied 629.8 km2 for
females and 738.7 km2 for males, and females´ area overlapped with
males´ by 74%, revealing no differences in the areas for both sexes. Core areas
(50% kernel contour) were situated in rather shallow waters (bathymetry 94.5+60.9
m females, 74.8+51.1 m males) with a high primary production
(chlorophyll a, 1.7+0.8 mg/m3 females, 1.8+0.4 mg/m3
males) and temperate sea surface temperatures (8.1+0.2ºC females, 8.2+0.2ºC
males). Stable isotopes analysis revealed no significant differences between
sexes either for δ15N (15.8+0.3? females, 15.6+0.2?
males) or δ13C (-18.3+1.5? females, -17.2+0.7? males),
thereby indicating no dietary differences or contrasting feeding areas between
sexes during the study period. δ15N values were higher than those
for Sprattus fueguensis, the
preferred prey of PM, and δ13C values showed that PM foraged mostly
inshore, which was confirmed by the GPS data that showed most positions along
the Le Maire Straight near the coast of Tierra del Fuego. In comparison with
the nearest PM colony in the Beagle Channel, PM breeding in Staten Island
performed longer and overnight foraging trips and covered larger areas. Those
differences may be due to the larger density of birds feeding in the area and
thus intra- and/or interspecific competition since the Beagle Channel´s colony
holds around 3,000 pairs while in Staten Island more than 100,000 PM pairs and
about 120,000 Rockhopper Penguin pairs forage in nearby waters.