[First record of the runt eggs of the Imperial Cormorant Phalacrocorax atriceps and the Rock Shag P. magellanicus in the San Jorge Gulf, Argentina]

[The present study describes for the first time the abnormally small (runt) eggs of the Imperial Cormorant (IC) and Rock Shag (RS) observed during the breeding seasons of 1990/91, 1992/93, 1993/1994, 1994/95 and 1996/97 on the Isabel Island (45°07’S, 66°30’W) and the Galiano Island (45°06’S, 66°25’W), located in the northern San Jorge Gulf, Argentina. The frequency of occurrence of IC runt eggs was 0.2% (n = 995) and their average volume was significantly lower than normal eggs (t = 17.4, P< 0.0001, n = 824). The runt eggs were more spherical than those of normal size (Shape Index: 70.6 vs 64.5 for CI and 74.9 vs 63.9 for RS). The volume of the RS runt egg was 21.1 cm3. The cutoff between normal and runt eggs is between 30 and 35 cm3 for the IC and between 24 and 30 cm3 for the RS. The volume of the runt egg was 42.1% and 53.4% the average volume of the two remaining eggs of the clutch for CI and RS, respectively. None of the consistently observed IC runt eggs hatched and it seems that none of the eggs showing a volume lower than the proposed cutoff is destined to hatch]. [Article in Italian]

Dieta invernal del cormorán imperial Phalacrocorax atriceps (Aves: Suliformes) en Bahía Caulín, Chiloé, sur de Chile

The imperial cormorant (Phalacrocorax atriceps) is one of the most abundant cormorant species in the Chilean channels and fjords. Although its reproductive and non-reproductive distributions have been studied, works on its diet are inexistent. This paper describes the diet and determines the dominance and diversity of the prey consumed during the winter periods of 2011 and 2014 in Caulín Bay, Chiloé, southern Chile. A total of 73 pellets were collected (30 in 2011 and 43 in 2014). Prey were identified and classified into three categories: fishes (53.57%), cephalopods (39.29%) and crustaceans (7.14%). When prey consumption was analyzed according to their distribution in the water column, we observed statistically significant differences in a preference of benthic demersal over pelagic prey.