State of the world's birds

Mosquito and native bird abundance in relation to altitude on Mauna Loa Volcano, Hawaii

van Riper et al. (2002)

The Hawaiian islands once supported over 100 endemic bird taxa, but more than half of these have been driven extinct by habitat loss, introduced predators and disease (Olson and James 1982, La Pointe 2000). For forest-dwelling native birds, the accidental introduction of mosquitoes Culex quinqufasciatus, bringing with them avian malaria Plasmodium relictum and avian pox Poxvirus avium, has had devastating consequences (Olson and James 1982, Brooks 2000, La Pointe 2000, van Riper and Scott 2001, Jarvi et al. 2001). For example, the prevalence of pox in ‘Elepaio Chasiempis sandwichensis is inversely related to the population density of this and other native bird species, suggesting that pox could be limiting their abundance and distribution, and hence playing a part in local extinctions (VanderWerf 2001). The mosquito is most common below 600 m (Warner 1968). The highest incidence of malaria and pox thus occurs in wet, mid-elevation forests where mosquitoes overlap with highly susceptible native birds (van Riper et al. 2002, see figure).