Status of the Red-legged Cormorant in Peru: What factors affect Distribution and Population size?

ZAVALAGA, C. B.; FRERE, E. & GANDINI, P.

WATERBIRDS (DE LEON SPRINGS, FLA.)

WATERBIRD SOC

Año: 2002 vol. 25 p. 8 - 15

1524-4695

The distribution and abundance of Red-legged Cormorants (Phalacrocorax gaimardi) were assessed by sampling 42 localities on the mainland and surveying most of the islands along 2500 km coast of Peru between October 1999 and December 2000. Cormorants were distributed in small discrete groups (Mode = 5 birds, range 1 – 69) from isla Foca (5º12’S) to Morro Sama (18º0’S). The southern (56% of the total population) and central (34%) coast held a larger proportion of cormorants than did the northern region (10%). The population was mainly located in unprotected areas either on islands (6%) or on the mainland (51%). The remaining was found in legally protected areas either guano bird islands (27%), guano bird headlands (3%) or within the Paracas Reserve (13%). We counted 658 birds (95% adults, 5% juveniles), but based on bird density, availability of suitable habitats and cliff lengths we predicted a total population size in Peru of approximately 1565 ± 282 birds. Red-legged Cormorants built their nests on narrow ledges only in vertical rocky walls falling sheer to the sea, located in average 17.8 m (range = 3 – 50, N = 56) above the sea level either in open cliffs, high-up in seacaves entrances or on small islets. They have undergone a spectacular decline over the last 30 years. Between 1968 and 1999-2000, the population at 10 localities in the northern and central coast decreased from 3229 to 69 birds. This negative trend shows that the population is currently in serious threat. It is likely that low numbers recorded in this study reflect the devastating effects of the strong ENSO 1997-98 as numbers prior and after this event at eight southern localities decreased by 73%. Because of the inaccessibility to their nesting and roosting sites and the lack of natural predators, Red-legged Cormorants are apparently not in danger on land. However, entanglement in fishing nets, competition for food in inshore waters, pollution, human disturbance, harvesting of kelp banks and reduction of their feeding areas are main problems (potential threats) at sea and could affect the population recovery.