Resumen

SAPOZNIKOW, Alexandra  y  QUINTANA, Flavio. Asynchronous laying and renesting in the Rock Shag (Phalacrocorax magellanicus): an evidence of the characteristics of their food sources?. Hornero [online]. 2009, vol.24, n.1, pp.21-30. ISSN 0073-3407.

We studied the breeding biology of the Rock Shag (Phalacrocorax magellanicus) at Punta Loma colony, Chubut, Argentina, during 2001 and 2002 breeding seasons. The egg laying period was long (3-4 months) and asynchronous, while fledging success was low (50%). During the first breeding season, the number of fledglings per nest was not related to laying date, while during the second breeding season there was a reduction in the fledging success of the pairs that laid their eggs late in the season. A high percentage of couples renested after loosing the first clutch (16-22%). In both seasons, the number of chicks fledged in replacement clutches was similar to that in first clutches. The extended and asynchronous egg-laying period, combined with a high rate of renesting (with a fledging success similar to that of single-laying couples), and the low relationship observed between breeding success and laying date, supports the idea of a highly stable and predictable food source for the Rock Shag.

Palabras clave : Argentina; Asynchrony; Breeding biology; Phalacrocorax magellanicus; Renesting; Rock Shag.

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