Justification This species is listed as Vulnerable because it has a very small range. Introduced herbivores are degrading habitat within its range, but it appears to tolerate some habitat modification and there is (as yet) no evidence of a decline in range or population.

Family/Sub-family Tyrannidae

Species name author Townsend, 1895

Taxonomic source(s) AOU checklist (1998 + supplements), Sibley and Monroe (1990, 1993), Stotz et al. (1996)

Identification 13 cm. Greyish flycatcher with rather long bill. Greyish-olive to dark brownish-olive above. Faint, dull buffy eyebrow. Dusky wings with two wing-bars and buffy edges to wing feathers. Pale greyish-buff to pale yellowish underparts. Brownish to olive wash to breast. Slender, dusky bill with pale horn lower mandible. Immature browner with tawny wing-bars and eyebrow. Voice Dry, descending and accelerating trill.

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

10,000-19,999

stable

25 km²

Yes

Range & population Nesotriccus ridgwayi is common throughout Cocos Island, c.500 km off the coast of Costa Rica.

Important Bird Areas Click here to view map showing IBAs where species is recorded and triggers any of the IBA criteria.

Ecology: It occurs in most habitats from sea-level to the highest hills, including the upper understorey and lower canopy of forests², Hibiscus scrub, Annona swamp, and wooded ravines. It is regularly observed in second growth², but degraded habitat may not sustain the species through its life-cycle. The diet consists of insects and, at least seasonally, fruits¹. Breeding probably takes place between January and May.

Threats Rats and cats are potential predators, and feral deer, pigs and goats graze suitable habitat. Pigs especially devastate the lower strata and understorey of native forests and inhibit forest regeneration^1,3. On many other islands, this combination of feral mammals has caused the extinction of numerous endemic plant and animal species. There is also low-level disturbance from increasing tourism¹.

Conservation measures underway Cocos has been designated as a national park, but no substantive measures have been taken to reduce populations of introduced mammals³.

Conservation measures proposed Estimate the population. Study the impact of introduced mammals. Eradicate introduced mammals where feasible.

References 1. Sherry (1985). 2. Stiles and Skutch (1989). 3. F. G. Stiles in litt. (1999).

Text account compilers Isabel Isherwood (BirdLife International), Simon Mahood (BirdLife International), John Pilgrim (BirdLife International), Rob Pople (BirdLife International)

Contributors F. Gary Stiles (Universidad Nacional de Colombia)

IUCN Red List evaluators Stuart Butchart (BirdLife International), Simon Mahood (BirdLife International)

Recommended citation BirdLife International (2009) Species factsheet: Nesotriccus ridgwayi. Downloaded from http://www.birdlife.org on 10/2/2010

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

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