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 al 2008, Millones and Frere, unpublished data):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.