- Order: Suliformes
- Family: Phalacrocoracidae
Data are from Millones et al. (2005) and Frere (personal observations)
In the Atlantic coast, diet of the Red-legged Cormorant is diverse, being composed mainly by benthic species, which is consistent with the diving behavior of this bird. Nevertheless, the occurrence of meso-pelagic prey also is important, especially during the breeding season. Fish are the most frequent prey: Patagonotothen spp. during the nonbreeding season, and the sardines Sprattus fuegensis and Ramnogaster arcuata during the breeding season. Other items in the diet are cephalopods (Loligo gahi), bivalves, polychaetes, and crustaceans (crabs). The seasonal changes registered in the occurrence of some of the prey and the shortage of dominant preys in the different periods of the year suggest an opportunistic feeding behavior in this cormorant.
Essentially solitary, but sometimes in flocks (Murphy 1936, Frere et. al 2002, Nasca et al. 2004). Red-legged Cormorants are efficient divers. They make foraging trips in inshore waters less than 15 m deep. Foraging consisted of short dives (27 ± 2 sec), followed by short intervals at the surface (9 ± 1 sec) (Frere et al. 2002).
Red-legged Cormorants are colonial. Aggressions subdued and overt fighting are common in south Chile but rare in Argentina (Frere, personal observations). Threat consists of silent, mild gape-thrust preceded or accompanied by lateral head-quivering often with retracted neck interspersed with ‘worrying’ nestmaterial (Nelson 2005).
Red-legged Cormorants are monogamous.
Social and interspecific behavior
Usually solitary, but sometimes in flocks (Murphy 1936, Frere et. al 2002, Nasca et al. 2004).
On the Argentinian coast, Kelp Gulls (Larus dominicanus) and Dolphin Gulls (Leucophaeus scoresbii) are the main predator of Red-legged Cormorants. Both prey upon Red-legged Cormorant eggs and chicks (Frere and Gandini 2001, Frere et al. 2005). In one colony, remains of Red-legged Cormorants were found in caves used by Culpeo Fox (Pseudalopex culpaeus), and fox tracks were observed at the base of cliffs (Frere et al. 2005). In Chile, the wild cat Kodkod (Oncifelis [or Leopardus] guigna) preys on eggs and young or Red-legged Cormorants (Frere and Ruiz, personal observations).
Data are from Frere and Gandini (2001), Frere et al. (2004) and Frere et al. (2005).
Nests are consisted of fronds of seaweed, feathers and guano. For some Argentinian colonies, egg laying occurs from mid-October to the third week of November, showing considerable asynchrony. Hatching occurred from mid-November to the first week of December. Clutch size range from 2 to 4 (mean = 3.04). Chicks fledge between late January and early February. After breeding, adults and juveniles remain in the breeding grounds.
Populations and Demography
The world population was estimated at 15,000 reproductive individuals (Frere et. al 2004). BirdLife International estimates a total population of 50,000 individuals.
In Peru (data from Zavalaga et al. 2002):
The main regions of concentration on the mainland were the southern and central coasts. Red-legged Cormorants are found mainly in loose aggregations or solitarily. In 2000 were predicted a total number s of 1,500-2,100 birds. Between 1968 and 2000, the numbers at ten localities in northern and central Peru declined from 3,229 to 69 birds. This sharp decline showed that the number of Red-legged Cormorants in Peru might be seriously threatened.
In Chile (data from Frere et al. 2004):
Red-legged Cormorants are found breeding in isolated nests or in small colonies in the north and central coast of Chile. However, in the southern area most of the colonies hold hundreds of nests. For the year 2000, the total population estimated for Chile ranged between 5,018 and 5,218 breeding pairs.
New breeding sites recently were described for southern Chile. Therefore, the total population of Chile might be increased in thousands of individuals.
In Argentina (data from Frere et al. 2005, Millones et. al 2008, Millones and Frere, unpublished data):
Colonies of Red-legged Cormorants are found at 13 localities. Colony size is variable; it ranges between 3 and 600 breeding pairs. Only two colonies have more than 100 breeding pairs. The rest of the colonies have less than 60 nests. Total population size is estimated between 900 and 1000 breeding pairs. The entire breeding population decreased by almost 20% between 1990 and 2009.
Frere, Esteban, and Ana Millones. 2012. Red-legged Cormorant (Phalacrocorax gaimardi), Neotropical Birds Online (T. S. Schulenberg, Editor). Ithaca: Cornell Lab of Ornithology; retrieved from Neotropical Birds Online: http://neotropical.birds.cornell.edu/portal/species/overview?p_p_spp=%0A%09%09%09%0921998