Clarion Island - Ecology

Ecology

As the topography of Clarión lacks any prominent peaks that could induce rains like Cerro Evermann on Socorro Island, the island is semiarid to arid all over. Consequently, the whole of the island is covered in shrubland, grassland and Opuntia cacti. Far away from land, endemic taxa are fewer than on Socorro but like there mainly consist of landbirds and plants. Rabbits and feral sheep are found on the island and have caused serious harm to the local vegetation; pigs introduced in 1979 have caused harm to the local fauna. Native vertebrates - except birds - are limited to one snake and one iguanid lizard, both endemic.

A few seabird species breed on Clarión or formerly did so. The island is near the north(east)ern limit of the breeding range of several of these, but their continued presence needs confirmation:

• Nazca Booby, Sula granti
• East Pacific Red-footed Booby, Sula sula websteri - a doubtfully distinct subspecies
• East Pacific Great Frigatebird, Fregata minor ridgwayi - breeding suspected but not verified; a doubtfully distinct subspecies

For reasons not fully known, Clarión seems to be more attractive to shorebirds and other vagrant or migrant birds than Socorro; perhaps this is due to the presence of Red-tailed Hawks on the latter island. Great Blue Heron, Snowy Egret, White-faced Ibis, Pacific and possibly American Golden Plover, Spotted Sandpiper, Wandering Tattler, Ruddy Turnstone, Black-necked Stilt, Western Gull and Barn Swallow are examples of the species that can be encountered on Clarión with some regularity; most of the shorebirds congregate in the sheltered shallows of Sulphur Bay. Others, such as Blue-winged Teal, Western Sandpiper, Least Sandpiper, Short-eared Owl, Belted Kingfisher, Northern Mockingbird and Brown-headed Cowbird have only been recorded on very few occasions, sometimes only once.