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Blue-footed Booby Frenzy (Photo by Rebecca Holmes)
Blue-footed Booby Frenzy (Photo by Rebecca Holmes)
Island birds are one of the groups most subject to extinction worldwide following the arrival of humans. The loss of birdlife in the tropical Pacific may exceed 2000 species (a majority of which were species of flightless rails). Galapagos is the exception, primarily because humans arrived so much later than on other islands. While there are extinct bird populations on certain islands, Galapagos still retains all of its native bird species.
There are also six introduced bird species in Galapagos that have become naturalized in the wild, five of which were accidentally introduced and one was introduced for agricultural or other use. These include Smooth-billed Anis, Cattle Egrets, Quails, Guinea Fowl, Peacocks, and the Guayaquil Red-masked parakeet. One introduced bird species has been eradicated – the Rock Dove.
The Galapagos Islands are a mecca for tropical seabirds, including Blue-footed, Red-footed, and Nazca Boobies, Flightless Cormorants, Great and Magnificent Frigatebirds, Red-billed Tropicbirds, Waved Albatross, Swallow-tailed Gulls, Lava Gulls, Galapagos Penguins, and many more. Seabirds provide some of the greatest opportunities to observe wildlife in the islands – especially in the large breeding colonies.
While a large majority of the land birds are endemic, there are only six endemic species among the seabirds: the Galapagos Penguin, Flightless Cormorant, Waved Albatross, Galapagos Petrel, Lava Gull and Swallow-tailed Gull. While the two gull species are found on many islands, the others have more restricted ranges. Each species has evolved its own behavior patterns related to feeding and breeding, and in any month you will find some seabirds displaying, incubating eggs, or feeding their young.
Galapagos Penguins, one of the smaller penguins of the world, are the only penguins that live at or just above the equator. The penguin population of about 2000 individuals is concentrated in the colder, nutrient-rich waters in the western islands – Fernandina and Isabela (about 95% of the population). However, small isolated populations are found at some small satellite islands off the coast of Santiago and along small sections of the northern coast of Floreana.
Galapagos penguins breed throughout the year and nest at sea level in caves. They forage relatively close to shore and at relatively shallow depths. Long-term monitoring has shown that this species undergoes severe fluctuations, primarily related to El Niño events and their effects on the availability of fish. The extreme El Niños of 1982-83 (77% reduction in the population) and 1997-98 (66% reduction) caused a long-term reduction in the population over the last 30 years. Although the current population is relatively stable, the species is listed as Endangered by the IUCN due to small population size, restricted range, and its vulnerability to El Niños. Climate change may lead to an increase in the frequency and intensity of El Niño events further endangering this population.
Flightless Cormorants, with a population of approximately 1600 adults, are endemic to Fernandina and Isabela Islands. They live around most of the coast of Fernandina but only on the north and west coasts of Isabela. Their range is very similar to that of the Galapagos Penguin, centering on the cold, nutrient-rich waters of the western archipelago. Unlike other cormorants around the world, the Galapagos Cormorant has lost its ability to fly. With no predators, swimming ability was more valuable and after centuries of evolution, Galapagos Cormorants have only vestigial wings but very strong legs. Its food includes eels, octopuses, and fish. It usually nests in sheltered areas, mostly within 100 m of the shore, and in small groups, mainly during the cool season (July-October) when marine productivity is highest and the risk of heat stress to chicks and incubating adults is reduced.
As is true for the Galapagos Penguin, Flightless Cormorants are also negatively affected by El Niño events. However, after the 1997-98 El Niño, the population has grown more rapidly than ever during the years of censuses (1977 on). The population appears to be stabilizing and the IUCN has downlisted the Flightless Cormorant to Vulnerable.
Waved Albatross breed only on Española Island in the Galapagos, and perhaps on Isla de la Plata off Manabí province, Ecuador. On Española, the overall breeding population was considered to have been stable until recently. The Española population was estimated at approximately 12,000 pairs in 1970-1971, 15,600-18,200 pairs in 1994, and at least 34,694 adults in 2001. On Isla de la Plata, there are probably fewer than 10-20 pairs. Analysis of birds caught as intentional and incidental take in inshore fisheries has revealed that a disproportionate number of males are taken, which will result in further decreases to the effective population size given that this species has obligate bi-parental care.
Waved Albatross breed annually, arriving at colonies in late March and laying eggs from mid-April to late June. Pairs mate for life and, each year, perform an elaborate mating dance to ensure they have the right partner. Chicks fledge between late December and early January. Breeding adults travel to the Peruvian upwelling region to feed, and, in the non-breeding season, the albatross abandon Española and move mainly east and south-east into the waters of the Ecuadorian and Peruvian continental shelf. Waved Albatross feed on squid, fish, and crustaceans. This species is classified as Critically Endangered because it has an extremely small breeding range, is essentially confined to one island, and evidence suggests that it has experienced a substantial recent population decline related primarily to fisheries, especially long-lining.
Galapagos Petrels are the only seabird in the islands that breed in the humid highlands of the larger islands – Santa Cruz, Floreana, Santiago, San Cristóbal, and Isabela. The petrels nest in burrows or natural cavities usually on sloped hillsides. This nesting behavior makes them extremely vulnerable to introduced predators, including cats, rats, and pigs. By the 1980s all of the populations had plummeted. Conservation efforts, aimed at controlling the introduced predators at the nesting grounds, have resulted in the recovery of the petrel numbers. The global population estimate is now 10,000-20,000 individuals.
However, the IUCN continues to list them as Critically Endangered due to the continued presence of both rats and cats in the majority of their nesting areas, potential of nest destruction by goats, donkeys, cattle and horses, and impacts from agriculture and invasive plants on their habitat. Increased construction in the highlands and long-line fishing are also impacting these birds. In addition, El Niño events seem to have a detrimental impact on both nesting and productivity. Galapagos petrels feed mostly on squid, fish, and crustaceans.
Swallow-tailed Gulls breed mainly on the Galapagos Islands but also on Malpelo Island, Colombia. The population is estimated at 10,000–15,000 pairs and appears to be stable. When not breeding, these gulls can be found along the Pacific coast of South America from Ecuador to northern Chile. Swallow-tailed gulls, unlike all other gulls in the world, forage mostly at night, feeding on squid and some fish. They appear to suffer from periodic food shortages and are often observed feeding 500 km from the nearest land.
Swallow-tailed Gulls breed throughout the year and asynchronously across the Galapagos, with individual sub-colonies being synchronized by social interactions. They nest on steep slopes or broken cliffs, on ledges, and also just above the wave line on gravelly beaches and under vegetation. Adults leave the colony after breeding and become highly pelagic, returning in 4-5 months often to their previous nest site. Their range is very large and does not approach the threshold for the Vulnerable category – and thus Swallow-tailed Gulls are listed as Least Concern.
Lava Gulls are one of the least known of the seabirds. Although widespread throughout the archipelago, Lava Gulls do not form large breeding colonies and are usually observed in single pairs. The population is estimated at 900-1200 individuals. The reason for the tiny population and the solitary nesting behavior is not fully understood but is thought to be related to its feeding behavior. Lava Gulls nest solitarily in scrapes on sandy beaches or low outcrops close to water. The female lays two eggs. A gull’s territory is large and adults are extremely wary when nesting. They are scavengers but will also take seabird eggs, juvenile marine iguanas, small fish, and crustaceans. This poorly known species is considered Vulnerable because of its small population size. Although its numbers appear stable, there are numerous potential threats.
Three Species of Boobies
The three booby populations are the most common and most frequently seen of the seabirds. Similar in appearance to gannets, they are large birds (70-90 cm in length) with long narrow wings. Their long pointed beaks gave rise to their Spanish name piquero. Boobies have a strong direct flight movements, with several powerful rapid wing beats followed by a glide. All of the booby species feed by spectacular plunge diving into the sea and then catching fish on their way back to the water surface. All three species tend to live in groups, but in the Galapagos Islands, they range from widely distributed small colonies of Blue-footed Boobies to the larger, less frequent colonies of the Nazca Boobies, to the few huge colonies of Red-footed Boobies.
The number of eggs laid by each species is related to where they feed, with Blue-footed Boobies feeding near shore, the Nazca Boobies feeding further offshore, and the Red-foots feeding out in the open ocean. The farther they must go to their feeding grounds the fewer eggs they lay. Blue-footed Boobies lay 1-3 eggs. When times are good, they may successfully fledge all three chicks. Nazca Boobies lay two eggs with only a single chick surviving. The death of the second chick is usually due to siblicide (death caused by a sibling or close relative) by the older chick (born a few days earlier). Siblicide is apparently obligatory in the Nazca Booby species.
Although the smallest and least often seen by humans in Galapagos, Red-footed Boobies are the most abundant of the three species. However, since they feed far out to sea, they nest in the outermost islands with access to open ocean and lay a single egg. While the Blue-footed and Nazca Boobies nest on the ground, Red-foots nest in trees and shrubs. The Red-foots also have two color phases, the large majority (95%) with a brown body and the rest with a white-and-black body.
Two of the world’s five species of frigatebirds are found in Galapagos – the Magnificent Frigatebird and the Great Frigatebird. The frigatebirds or “man of war” birds got their name from their pirate-like habits. Large black birds with long wings, long hooked beaks and deeply forked tails, they are often seen soaring overhead. They are superlative flyers, and feed by snatching up flying and other fish, squid, and scraps from the surface of the ocean – and, most notably, by stealing from other seabirds in flight. When feeding off the surface of the sea, only their beak will touch the water as frigatebird feathers are not oiled and waterproofed like most seabirds. If their plumage gets too wet, a frigatebird can become waterlogged and drown.
Frigatebirds are occasionally seen “bathing” in the freshwater ponds in the highlands of some of the larger islands. While Waved Albatross and Blue-footed Boobies have a more elaborate courtship ritual, watching the courtship of Frigatebirds is spell-binding. The male frigatebird has a bright red gular pouch that usually sits tight to the bird but can be inflated when breeding to attract the female. The males sit together or singly in trees where they nest, waiting for females to fly overhead. On sighting a female, the males turn their head and wings upward, shake them vigorously, display their bright red pouches, and call loudly. If a female is attracted, she will descend to the nest and courtship continues. Females lay a single egg and both parents share incubation duties.
The most commonly seen shore and water birds include the Galapagos flamingo, the many heron species including Great Blue Herons, Yellow-crowned Night Herons, Lava Herons, Black-crowned Herons and Striated Herons, Oystercatchers, White-cheeked pintails, Gallinules, and Common Egrets.
The Galapagos Flamingo population is approximately 320-350 individuals. The small population size has resulted in changes in breeding behavior compared to other flamingo populations worldwide, which all need very large groups of birds for breeding to occur. Galapagos Flamingos can breed with just a few pairs present. They live in the saltwater lagoons close to the sea and filter feed primarily on brine shrimp. Young flamingos hatch with grey plumage. The pink color of the adults is due to aqueous bacteria and beta carotene obtained from their food supply. The population appears stable but they are threatened by introduced animals such as rats, cats, and pigs. Intense El Niños can affect their food supply and severely impact their habitat making nesting impossible.
The largest of the herons, the Great Blue, eats much larger prey than the other heron species. The Lava Heron catches fish by stealth, watching from a rock just out of the water until a fish passes and then grabbing it. The Lava Heron also eats small crabs, but the Yellow-crowned Night Heron, which hunts at night, could be considered the crab-eating specialist.
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