Flightless cormorant (Phalacrocorax harrisi)
|Also known as:||Galapagos cormorant|
|Size||Length: 89 - 100 cm (2)|
|Weight||2.5 - 4.0 kg (3)|
Classified as Endangered (EN B1+3d) on the IUCN Red List 2003 (1).
The flightless cormorant, also known as the Galapagos cormorant, is a large, blackish coloured bird. The tiny, scruffy-looking wings indicate the flightless habit of the species (2). This species is the only flightless cormorant and the heaviest member of the family (4). Like other flightless birds, the sternum (breastbone) has lost the pronounced keel, which in most birds is the site of attachment for the well-developed flight muscles (3). In fact, this species is so different to other cormorants, that some experts place it in a separate genus (Compsohalieus) (5). The upperparts of the flightless cormorant are blackish and the underparts are brown. The long beak is hooked at the tip and the eye is turquoise (2). Like all members of the cormorant family, all four toes are joined by webbed skin (6). Males and females are similar in appearance, although males tend to be much larger (2). Juveniles are generally similar to adults but differ in that they are glossy black in colour with a dark eye. Adults produce low growling vocalisations (2).
This unique cormorant is endemic to the Galapagos Islands, Ecuador, where it has a very restricted range. It is found on just two islands; Fernandina, where it is found mainly on the east coast, as well as on the northern and western coasts of Isabela (2). The population has undergone severe fluctuations; the 1983 El Niño event resulted in a 50% reduction of the population to just 400 individuals. The population recovered quickly, however, and was estimated to number 900 individuals in 1999 (2).
This species inhabits the rocky shores of the volcanic islands on which it occurs. It forages in shallow coastal waters, including bays and straits (1) and rarely ventures further than 1km away from the breeding areas (3).
It is thought that the loss of flight in this species is the result of a long period of evolution on isolated, predator-free islands, as well as the fact that they forage in a very small area (7). Unlike penguins, which ‘fly’ through the water using their flipper-like wings, the flightless cormorant propels itself by kicking its strongly-built legs (7).
The flightless cormorant feeds on octopuses, eels and bottom-dwelling fishes, which it hunts for by making pursuit-dives (3). All cormorants are aquatic predators, but their feathers are not waterproof. A behaviour characteristic of the family is to adopt a stance after emerging from the water in which the wings are held open in order to dry the feathers. Flightless cormorants retain this behaviour, and are commonly seen holding their small ragged wings at their sides (7).
Nesting tends to take place during the coldest months (July-October), when marine food is at its most abundant and the risk of heat stress to the chicks is decreased (2). At this time, breeding colonies consisting of around 12 pairs form (3). The courtship behaviour of this species begins in the sea; the male and female swim around each other with their necks bent into a snake-like position. They then move onto land. The bulky seaweed nest, located just above the high-tide mark, is augmented with ‘gifts’ including pieces of flotsam such as rope and bottle caps, which are presented to the female by the male (3) (7). Two to three whitish eggs are laid; they are incubated by both parents (3) (7). After the chicks hatch, the parents share the duties of brooding and feeding (7). If food is plentiful, the female may leave the male to continue to care for the chick as it approaches independence; she will then produce a second brood with another male (7). This high breeding potential allows the population to quickly recover from declines in numbers (7).
The fact the species cannot fly, coupled with its lack of dispersal tendencies mean that it is highly vulnerable to disturbance by humans and environmental disasters such as oil pollution (2). Furthermore, it is entirely fearless of humans, which further increases its susceptibility to disturbance (2). In the past, introduced feral dogs were a great threat to the species on Isabela, but they have since been eradicated from the island (3). Future introduction of rats or cats to Fernandina is a huge potential threat to the species (2). Fishing with nets poses a current threat to the species; this not only reduces the availability of the cormorant’s food, but also often results in birds becoming caught in the nets and killed (3). The fact that this uniquely adapted bird is found in such a small range and in such small numbers greatly increases its vulnerability to chance events such as environmental disasters, extreme climatic events and the introduction of diseases or predators. Unfortunately, marine perturbations such as those caused by El Niño events appear to be becoming increasingly extreme (1).
All populations of this endangered species are found within the Galapagos National Park and Marine Reserve; furthermore, the archipelago was designated as a World Heritage Site in 1979 (2). The Charles Darwin Research Station has monitored the species regularly to keep track of fluctuations in numbers over time (3). Conservation proposals include the continuation of annual monitoring programmes, the reduction of disturbance by humans and the prevention of fishing with nets in the foraging range of the cormorant (2).
BirdLife International 2003 BirdLife’s online World Bird Database: the site for bird conservation Version 2.0. Cambridge, UK: BirdLife International:
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- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
- Genus: a category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
- Keel: a structure that resembles the keel of a ship either in function or in shape. An example is the breastbone of flying birds, which have deep keels onto which the large breastbones attach.
IUCN Red List of Threatened Species 2003 (March, 2004)
BirdLife International 2003 BirdLife’s online World Bird Database: the site for bird conservation Version 2.0. Cambridge, UK: BirdLife International (March, 2004)
UNEP-WCMC/ WWF Species Fact Sheet – flightless cormorant (March, 2004)
Galapagos Conservation Trust – flightless cormorant (March, 2004)
- Livezey, B.C. (1992) Flightlessness in the Galapagos cormorant (Compsohalieus [Nannopterum] harrisi): heterochrony, gigantism and specialisation. Zoological Journal of the Linnean Society, 105: 155 - .
- Allaby, M. (1991) The Concise Oxford Dictionary of Zoology. Oxford University Press, Oxford.
The flightless cormorant – Prof. Robert H. Rothman (March, 2004)