| WI - Cormorant Research Group | Meetings | last updated on 02/08/01 |
Abstracts of poster and oral presentations on cormorants at the
7th
Seabird Group Conference 2000
Wilhelmshaven - Germany
Esteban Frere & Patricia Gandini, Centro de Investigaciones de Puerto Deseado, Universitat Nacional de la Patagonia, Austral, Almirante Brown y Colón s/n (9050), Puerto Deseado, Santa Cruz, Argentina. Email: rqfrere@pdeseado.com.ar
Red-legged cormorants Phalacrocorax gaimardi breed in Argentina, Chile and Peru. In Argentina its breeding range is restricted a short portion of coast in southern Patagonia. This paper describes the breeding biology and causes of egg and chick mortality of this little known species. We worked at two colonies, Isla Elena and Cań adón del Puerto located at Ria Puerto Deseado, Argentina. Nests were located on high rocky cliffs 2 to 4 m from the high tide line. At Cań adón del Puerto the nests avoid prevailing winds whereas at Isla Elena most of the nests were oriented in the same direction as the wind. Mean clutch size was 3.04 ± 0.47 eggs per nest, and mean egg size was 6.03 ± 0.24 x 3.71 ± 0.14 mm. Incubation period varied between 34 to 38 days with chicks hatching between mid November to the first week of December. Clutch and egg size differed with two sympatric cormorant species, probably as a result of differences in foraging ranges. Egg mortality and the number of nests that suffered predation were higher at Isla Elena where predation pressure by aerial predators was higher. Our results suggested that predation seems to be the main factor of egg loss and extreme weather conditions result in high chick mortality for the red-legged cormorant in Argentina.
Daniela Guicking, Institut für Vogelforschung "Vogelwarte Helgoland", An der Vogelwarte 21, D - 26386 Wilhelmshaven, Germany. Email: peter.becker@ifv.terramare.de
Island Mocha (38°22'S 73°56'W), located about 35 km from the Chilean mainland in the South Pacific, is inhabited by the largest colony of the threatened pink-footed shearwater Puffinus creatopus, that otherwise breeds only on islands of the Juan Fernández Archipelago about 700 km north-west of the Island Mocha. Besides the shearwaters, very few seabirds breed on the main island. However, there are two rocky islets at the southern end of Island Mocha, and those are regularly visited by seabirds. Due to human disturbance and massive egg collecting in the past, one of the two islets, Islote Quechol, is no longer used as breeding site. The other, Islote Muertos, is less accessible and therefore almost free from human disturbance. On this islet, every year hundreds to thousands of Chilean pelicans Pelecanus thagus, Peruvian boobies Sula variegata, blue-eyed cormorants Phalacrocorax atriceps, kelp gulls Larus dominicanus and other species breed.
Ommo Hüppop & Anja Fründt, Institut für Vogelforschung "Vogelwarte Helgoland", Inselstation, P.O.Box 1220, D-27494 Helgoland, Germany. Email: O.Hueppop-IFV@t-online.de
The food consumption of fish-eating birds can be assessed from their pellet production. For this it is essential to know the average number of pellets produced per bird per day and to estimate the number and size of the prey items from remains in the pellets. However, the knowledge of pellet production in wild birds is extremely limited, especially in seabirds. In cormorants, several feeding trials on captive birds (fully grown) rendered quite contradictory results ranging from 0.3 to 1.75 pellets per day. In the only study on free living cormorants, (Russell, Wanless & Harris 1995, Seabird 17: 44-49) found that adult shags Phalacrocorax aristotelis produced less than 0.3 pellets per day during the breeding season. Pellet production in cormorants outside the breeding season is virtually unknown. Hence, we investigated the pellet production of great cormorants at a large winter roost on the island of Helgoland (south-eastern North Sea). With the aid of video equipment and with an image intensifier we recorded the time and amount of pellet production throughout the whole day. The study was supported by Hensoldt AG, ZEISS Gruppe.
Anja Liebert & Ommo Hüppop, Institut für Vogelforschung "Vogelwarte Helgoland", Inselstation, P.O.Box 1220, D-27494 Helgoland, Germany. Email: O.Hueppop-IFV@t-online.de
The offshore island of Helgoland in the south-eastern North Sea houses a large winter roost of great cormorants. Highest numbers (> 700) are found in late autumn and winter. This stands in contrast to other resting sites in Denmark and northern Germany where maxima occur during autumn and spring migration. Reasons for this diverging phenology may be: (1) differences in food choice and / or availability, (2) lower thermoregulatory costs in the ‘more marine’ habitat at Helgoland, or (3) the higher proportion of ‘Atlantic’ cormorants P. c. carbo compared to the resting sites at the mainland. To test these three hypotheses we studied food, time-budgets and energetics of great cormorants in autumn and winter. In this poster we present the diet based on pellet analyses. Main species found are: cod Gadus morhua, bull-rout Myoxocephalus scorpius, sea scorpion Taurulus bubalis, hooknose Agonus cataphractus and goldsinny Ctenolabrus rupestris. The proportions changed significantly throughout the study period.
Page created on
02/08/2001
by S. Volponi