Birds of Seabrook Island




Species Acct.
NW Warblers


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The Islands
Ocean Currents
Field Guide

INDEX to Galapagos Birds in this Web

Birds Seen



©David Stevenson (with permission)

Between 18-25 May, 2008, our family joined a Linblad Expedition aboard the National Geographic Islander touring the Galapagos Islands, Ecuador. Virtually all the endemics characterizing the islands were seen and some of these are included in the web or indexed here. We visited the major islands with the exception of San Cristobal and Genevesa.

The Islands

    The Galapagos Archipelago consists of 4,897 square miles (7,880 square km) of land dispersed over 28,000 square miles (45,000 square km) in the eastern Pacific, straddling the equator. The largest of the islands, Isabela, measures 1,791 square miles (4,588 square km) and makes up half of the total land area. Volcan Wolf on Isabela is the highest point with an elevation of 5,600 feet (1,707 m). Isabela has 5 major shield volcanoes (Volcans Wolf, Darwin, Alcedo, Sierra Negro, Cerro Azul) and one smaller cone on the northwest corner (Volcan Ecuador). The newest active shield volcano is on Fernandina. These volcanoes have large calderas measuring several km across and up to 1 km deep.
   The group consists of 16 main islands, 6 smaller islands, and 10 rocks and islets. The islands are located at the Galapagos Triple Junction (a geological area in the eastern Pacific Ocean several hundred miles west of the Galapagos Islands where three tectonic plates - the Cocos Plate, the Nazca Plate, and the Pacific Plate - meet... It is an unusual type of triple junction in which the three plates do not meet at a simple intersection. Instead, the junction includes two small microplates, the Galapagos Microplate and the Northern Galapagos Microplate, caught in the junction, and turning synchronously with respect to each other.) The islands lie at the meeting point of two submarine ridges, the Carnegie Ridge running westward from South America, and the Cocos Ridge running south from Central America.
   It is also atop the Galapagos hotspot, a place where the earth's crust is being melted from below by a mantle plume, creating volcanoes. The oldest island is thought to have formed between 5 and 10 million years ago. The youngest islands, Isabela and Fernandina, are still being formed, with the most recent volcanic eruption in 2007. The Nazca plate is moving eastward at 2 cm/year, pushing up the Andes range along the western edge of South America. As the plate moves, the hot sport remains stationary so the youngest (and most eroded) islands are found to the east and the youngest to the west.
   Recent activity includes a major event in 1968 when the floor of the caldera on Fernandina fell over 300 m, accompanied by a large ash eruption covering the north-western slope of the volcano. There was a large eruption on the flank of Fernandina in 1995. On Isabela, Cerro Azul erupted in 1998 and Sierra Negra in 2005.
   The western islands are the tips of large submarine volcanoes but most of the eastern islands are uplifted submarine lava.
   In 1954, 5 km of coastline in the area of Urbina Bay (west coast of Isabela) was uplifted by up to 4 m. A further uplift of 90 cm occurred at Punta Espinosa and Tagus Cove in 1994.
   Types of lava include: Pāhoehoe - smooth and ropy lava, and A'a - clinkery, very rough lava that is hard to walk over. Black sand beaches result from degradation of lava. White "sand" beaches are covered in coral and shell remains (including sea urchin spines).
  Santa Cruz
Puerto Ayora, Santa Cruz. Harbor.


    The islands were discovered in 1535 by Fray Tomas de Berlanga, the Bishop of Panama, who drifted there while traveling from Panama to Lima. He noted some of the tame endemic fauna. The islands became a base for pirates - picking up the name Las Encantados or "bewitched islands" due to strong currents which, combined with the garua, made it seem as though the islands were moving.
   The islands were named by Abraham Ortelier in 1574 for the giant tortoises - galapago is the Spanish name for saddle, similar to the carapace of the saddleback tortoises from the drier islands.

Post Office

   The first resident was Patrick Watkins, as Irishman marooned on Floreana in 1807. The Post Office Bay had become a regular shopping place for whaling ships and arriving ships would leave letters for those returning home after voyages of 4-5 years. The first barrel appears to have been erected by Captain James Colnett in 1792. The Post Office of today is pictured to the left.
    The islands had been annexed by Ecuador and by 1832 there was a small settlement at San Cristobal as well as on Floreana (soon turned into a penal colony). Settlement at Villamil (Isabela) dates from 1893 and Puerto Ayora (Santa Cruz) was started in by a group of Norwegians who set up a fish-processing plant at Post Office Bay in1926. The plant failed and the Norwegians moved to Santa Cruz.

   The first commercial venture was a sugar plantation and mill in the highlands of San Cristobal in the 1880s. Many other ventures followed but most failed. Real commercial development followed tourism in the late 1960s.
     In 1942, the United States built a military base on Baltra - protecting the approaches to the Panama Canal. Two airstrips and many clapboard houses were built (but most were removed after the war - providing wood for most building on the islands until the mid 70s). The only stone building left on the island was the Officer's Club. The airstrip and dock are those that were built in the 40s but both have been renovated by Ecuador.
   Prior to 1968, the islands could be reached only by sea - taking 3-4 days and often shared with cattle, coffee and dried fish. No vessels were available to explore other islands.
   Regular weekly flights began in 1968 and there are now up to 5 flights a day either to Baltra or San Cristobal. The airstrip at Villamil (Isabela) is now being enlarged to accept flights from the mainland as well. Population has grown from 2,500 in 1968 to ~30,000 in 2006. Tourists numbers are approaching 100,000/year.
  sea lions
Sea Lions, Gardner Islet. Española.

Ocean Currents

      The Galapagos are remarkably cool and dry for an equatorial oceanic group of islands. The chief influence on climate are the ocean currents. Three influence the islands - the Humboldt (which turns into the South Equatorial current), the Cromwell (or Equatorial Undercurrent), and El Niño.
   The Humboldt brings cool, nutrient-rich water up from southern oceans. These fan westwards from the coast of Peru becoming the South Equatorial current which extends some 300 m below the surface. The deeper water is cooler and more saline sub-Antarctic water which upwells when it hits the Galapagos. The overall impact of this current which flows through the islands for 8-9 months is cooler temperatures and lower humidities than expected. This current is driven (in part, especially on the surface) by the southeast trade wings which blow toward the Equator from May - December.
   When the trades retreat southwards, much warmer water flows inward from the north - from the Gulf of Panama - bringing higher humidities and heavy tropical rains. This warmer water is the El Niño. It is a shallow current, less than 100 m in depth.
   El Niño occurs every year along the west coast of South America - usually in December (hence the name which means "the Child"). In the Galapagos, rains usually occur between January and March - the wet or rainy season. They may persist longer in some years (up to 6-9 months). With a prolonged El Niño, animals that depend on the sea for food (sea lions, boobies, marine iguanas) may die in large numbers. In contrast, land species flourish.
   Variations in the amount of rainfall can be dramatic - up to 3 m in Academy Bay and > 5.5 m at Santo Thomas (Isabela) fell in 1982-83. In contrast, the average annual rainfall at Academy Bay is 200 mm. The Grants report a period of > 500 days on Daphne with no rain (and heavy mortality of finches). The causes of this variability is unknown - global warming?
   The third current, the Cromwell or Equatorial undercurrent, is a submarine current flowing eastward from the central Pacific - it is cool and saline and creates very cool water conditions around Fernandina and western Isabela. This area is favored by whales and dolphins and yellowfin tuna.
  Vulcan Darwin
Isabela. From Punta Espinosa on Fernandina. Vulcan Darwin amid garua.


      The Galapagos have two seasons - the garua (cool season) from June - November, and the warm or rainy season from January - April. May and December are changeover periods that vary from year to year. On the coast, the garua is very dry - rainfall in Academy Bay, Santa Cruz, average < 10 mm in August - October and 50-70 mm in February to April. In the highlands, it is much wetter during the garua season. The warm season may include a rainy period, the El Niño, normally lasting 4-6 weeks.
   During the garua, cool water produces a temperature inversion trapping water vapor evaporating from the surface and forming clouds - usually between 500 - 1,000 m, forming strato-cumulus clouds. The light rain or drizzle from these clouds is known as the "garua."
   Strato-cumulus clouds gather around the tops of the higher volcanoes, staying for weeks or months. This produces a lush, fertile humid zone (the higher reaches may be so wet that they become bogs and moorlands). This habitat contrasts with arid coastal zones which receive appreciable rain only during the El Niño periods. Because the prevailing winds are from the south-east, the south sides of the major islands are moister than the northern sides (rain shadow) where vegetation zones tend to be compressed.
Floreana. Punta Cormorant.


     Darwin's visits and publications drew attention to the diversity of life in the Galapagos and attracted the attention of other scientists. In 1935, Ecuador passed the first legislation to protect this diversity but it was not until the centenary of the publication of the Origin of Species (1959) that the government made the islands a national par, A committee under UNESCO was also established - this became the Charles Darwin Foundation for the Galapagos Islands (CDF). The Charles Darwin Research Station (CDRS) was established at Academy Bay on Santa Cruz. It developed a coherent conservation program which was taken over by the Ecuadorian Natiional Park (PNG) in 1968. With modest budgets, early efforts were directed toward removing goats from Santa Fe, Española and Pinta and an attempt was made to eradicate rats on Pinzon. Early captive breeding programs focused on tortoises from Pinzon and Española. This has been expanded to include Land Iguanas.
   Recent programs have had to take into account rapid growth in the local population associated with increased tourism and tourism itself. Annual visitors now exceed 100,000 but their explorations are regulated and monitored. Each boat/yacht is required to have an Ecuadorian navigator and approved park ranger aboard and groups on land are limited to 17 individuals. There are no major facilities for tourists ashore so it seems that the overall impact of visitors may be relatively benign.
   One of the biggest threats to the biodiversity of the islands has been the introduction of foreign species - some eradicating the original habitat, some establishing new ones. Among the mammals, pigs, dogs, cattle, donkeys, horses, cats, black and brown rats, and mice have impacted a number of islands. Foreign invertebrates inclued a variety of ants, the blackfly, cottony cushion scale, two wasps and over 11 species of cockroaches. Plants new to the islands include quinine tree, guava, and elephant grass.
   The first systematic eradication program began in 1965 - an attempt to rid Sante Fe of goats. Ten years later the last goat was removed and the recovery of vegetation is impressive. The native rice rat and Land Iguanas are thriving. Volcan Alcedo is another success - in 1969 goats were introduced or crossed the lava flows from Sierra Negra to the south. By 2003 there were > 150,000 goats on Alcedo and the two volcanoes to the north (Darwin, Wolf). Operation Isabela begain in 1995 - using helicopters, dogs, and "Judas Goats" the project first cleared the remaining pigs and then the goats on Santiago and started on Isabela in 2004. The operation was completed in 2006. Unfortunately there are still some goats on Santa Cruz, San Cristobal and southern Isabela. Other smaller visitors may be even more difficult to eradicate but work is continuing.
    Puerto Egas
Santiago (San Salvador). Punta Egas. Islander - recent lava flow.

Field Guide

       Fitter, J., D. Fitter, D. Hosking. 2000. Wildlife of the Galapagos. Princeton University
      Press. Princeton and Oxford.


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