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Location Cape Verde, São Nicolau
Central coordinates 24o 36.00' West  16o 37.00' North
IBA criteria A1, A2, A4ii, A4iii
Area 700 ha
Altitude 0 - 164m
Year of IBA assessment 2001

Site description The island of Raso is primarily flat, with some small peaks in central-northern parts of the island, which rise to a maximum of 164 m. The entire south-western area is a flat, rocky plain, parts of which are covered with large boulders. Dry riverbeds cross the island. There is little vegetation except for a grassy area in the south-west. The coastline is entirely composed of rocky cliffs.

Key Biodiversity See Box and Table 2 for key species. The most famous bird of the island is, without doubt, the endemic Alauda razae, which is entirely confined to Raso and has a total population of c.45 pairs. The species roams all over the island, but breeding is largely confined to the grassy area in the south-west. Calonectris (diomedea) edwardsii is the most numerous seabird on the island, with thousands of pairs breeding on the cliffs along the southern shore and more breeding inland in holes under boulders. Other breeding procellarids are Puffinus (assimilis) boydi, Bulweria bulwerii and Oceanodroma castro. There is a colony of c.125 pairs of Sula leucogaster and 25–40 pairs of Phaethon aethereus, numbers which are only a shadow of those recorded c.100 years ago. Egretta garzetta, Pandion haliaetus, Falco (tinnunculus) neglectus, Tyto (alba) detorta and Passer iagoensis also breed.

Non-bird biodiversity: The endemic giant skink Macroscincus coctei is thought to have become extinct early in the twentieth century (see site CV010). The endemic geckos Tarentola caboverdiana and T. gigas still occur in good numbers. Other lizards include Mabuya stangeri and Hemidactylus bouvieri.

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
Cape Verde Shearwater Calonectris edwardsii breeding  1988  2,500-3,750 breeding pairs  A4ii  Near Threatened 
Red-billed Tropicbird Phaethon aethereus breeding  1986  25-40 breeding pairs  A4ii  Least Concern 
Raso Lark Alauda razae resident  1996  present  A1, A2  Critically Endangered 
Iago Sparrow Passer iagoensis resident  1996  present  A2  Least Concern 
A4iii Species group - seabirds breeding  1988  10,000 individuals  unknown  A4iii   

Protected areas

Protected area Designation Area (ha) Relationship with IBA Overlap with IBA (ha)  
Ilheu Raso Nature Reserve 700 is identical to site 700  

Land use

Land-use Extent (% of site)
nature conservation and research -
other -
Notes: Collection of eggs and young of seabirds.

Further web sources of information 

Alliance for Zero Extinction (AZE) species/site profile. This site has been identified as an AZE due to it containing a Critically Endangered or Endangered species with a limited range.

References Hazevoet (1989, 1994, 1995), Ratcliffe et al. (1999), Schleich (1982).

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Recommended citation  BirdLife International (2016) Important Bird and Biodiversity Area factsheet: Ilhéu Raso. Downloaded from on 22/10/2016

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