State of the world's birds

Population trends of four formerly Critically Endangered species, 1965–2007

Black Robin Petroica traversi is endemic to the Chatham Islands (New Zealand). The rescue of this species from its tiny refuge on Little Mangere Island is one of the most remarkable successes in species conservation (Aikman et al. 2001, Butler and Merton 1992). Following human settlement of the islands, the species declined rapidly as its forest habitat was lost and degraded, and owing to predation by introduced rats and cats. In 1976, when the population had declined to just seven birds, the remaining individuals were relocated to nearby Mangere Island, where thousands of trees had been planted to provide suitable habitat. Nevertheless, by 1980, numbers had fallen to five (three males and two females): the smallest population of any bird species for which precise figures were known. Nest protection, supplementary feeding, and a cross-fostering programme (with the congeneric Tomtit P. macrocephala) were then established, and the population began to recover steadily. Individuals were later introduced to South East Island, and by 1989 the population had topped 100 individuals (Butler and Merton 1992), at which point management ceased. The population continued to rise until carrying capacity was reached in the late 1990s, since when it has been stable at around 250 birds (D. Merton in litt. 2004).

Rarotonga Monarch (or Kakerori) Pomarea dimidiata is endemic to the Pacific island of Rarotonga (Cook Islands). Although common in the mid-1800s, the species subsequently declined rapidly and, following the collection of a few specimens in the early 1900s, was not recorded again until 1973. In 1983, 21 birds were discovered, and a survey in 1987 estimated the population at 38 individuals, but declining (Robertson et al. 1994). A recovery plan was prepared in 1988, and implementation began later that year. Intensive control of predators (particularly black rats Rattus rattus) reduced adult mortality from 24% to 9% (H. Robertson and E. Saul in litt. 2004), with nesting success increasing from 15% to 63% (Robertson et al. 1994). By 2000, the population on Rarotonga had reached 221 individuals (see figure), leading to its downlisting from Critically Endangered to Endangered on the IUCN Red List. During 2001–2003, 30 young birds were transferred to the rat-free island of Atiu (200 km north east of Rarotonga) in an apparently successful attempt to establish a second ‘insurance’ population (H. Robertson and E. Saul in litt. 2004).

Mauritius Parakeet Psittacula eques had been reduced to fewer than a dozen birds in 1986, including just three females, owing to habitat destruction and alien invasive species (Thorsen and Jones 1998). However, captive breeding and release, control of invasive predators, provision of artificial nest cavities, and brood manipulations have increased the wild population to 343 birds by 2007, leading to its downlisting from Critically Endangered to Endangered.

Seychelles Magpie-robin Copsychus sechellarum was originally present on at least eight islands in the Seychelles, but in 1965, only 12–15 birds remained on Frégate (Gaymer et al. 1969). In 1994, following eradication of introduced cats, a recovery programme was initiated, involving habitat creation, supplementary feeding, nest defence, provision of nest boxes, control of introduced species and translocations to other islands. This allowed the population size to increase, and the most recent estimate totalled 178 birds on four islands (82 on Frégate, 46 on Cousin, 32 on Cousine and 18 on Aride) (N. Shah in litt. 2006). Three of the four populations are now at carrying capacity, with only small population increases anticipated as habitat continues to improve (R. Bristol in litt. (2005). Consequently, the species was downlisted from Critically Endangered to Endangered in 2005.

These remarkable recoveries show that species can be brought bank from the brink of extinction through sustained conservation action informed by detailed research when adequate resources and political commitment are applied.