page_title: Socorro Island
section_title: Ecology
hierarchical_section_title: Socorro Island / Ecology
caption_attribution_description: English: Map made by PJ MInton Using Marplot Mapping Program
context_page_description: Socorro Island is a small volcanic island in the Revillagigedo Islands, a Mexican possession lying 600 kilometres off the country's western coast. The size is 16.5 by 11.5 km, with an area of 132 km². It is the largest of the four islands of the Revillagigedo Archipelago.
context_section_description: The lowlands of Socorro – except on the northern, more humid side – are covered with thick shrubland, consisting mainly of endemic Croton masonii and a cactus, probably Engelmann's prickly pear (Opuntia engelmannii). Above 650 metres (2,130 ft) and on the northern side, a richer vegetation occurs. This includes small trees such as Ficus cotinifolia, black cherry (Prunus serotina), and the endemic Guettarda insularis, which bear epiphytic orchids (Epidendrum nitens, E. rigidum and the endemic Pleurothallis unguicallosa).
  The native land fauna is depauperate, with birds predominating and mammals absent. There is one endemic species of iguanid lizard (Urosaurus auriculatus) and the land crab Johngarthia oceanica which also occurs on Clipperton Island.
  Sheep, cats and rodents were introduced to the island by human activity; more recently, the locust Schistocerca piceifrons has also established itself on the island. Unlike the mammals on Guadalupe Island or Clarión, their impact on the local flora was minor, but cat predation has had a drastic effect since the mid-1970s due to the fauna's island tameness, and the locusts that swarm twice a year seriously damage vegetation during that time. There have been no recorded extinctions of plants on Socorro; several birds have been drastically affected by cat predation however, and one taxon, the Socorro dove, has gone extinct in the wild.
  Socorro is an important breeding location for several seabirds, many of which have here one of their north(east)ernmost breeding colonies. The present status of these birds is not well known, and they presumably have suffered from cat predation. In 1953, the following taxa were present:
  Wedge-tailed shearwater, Puffinus pacificus (or Ardenna pacifica)
  Western red-billed tropicbird, Phaethon aethereus mesonauta – breeding suspected but not verified
  Nazca booby, Sula granti – breeding suspected but not verified
  Northeast Pacific brown booby, Sula leucogaster brewsteri – breeding suspected but not verified
  East Pacific great frigatebird, Fregata minor ridgwayi – breeding suspected but not verified; a doubtfully distinct subspecies
  East Pacific sooty tern, Onychoprion fuscatus crissalis – a doubtfully distinct subspecies
  East Pacific brown noddy, Anous stolidus ridgwayi
  Non-endemic landbirds and shorebirds occur mostly as vagrants or use the island as a stopover during migration; the northern mockingbird became established in the late 20th century. Among those that are recorded not infrequently are great blue heron, Hudsonian curlew, spotted sandpiper and wandering tattler. Unlike the situation on smaller and more isolated Clarión, wind-blown or vagrant birds seem to constititute the bulk of the recorded species, including brown pelican, osprey, peregrine falcon, semipalmated plover, willet, sanderling, belted kingfisher and buff-bellied pipit. It may be that this puzzling observation is due to the presence of the red-tailed hawks and cats, which has at least made the local Urosaurus more wary than its relative on Clarión, and might deter passing birds from stopping on Socorro.
caption: Map of Socorro Island
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