Nihoa reed warbler
| Nihoa reed warbler | ||||||||||||
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Nihoa reed warbler ( Acrocephalus familiaris kingi ) that was released into the wild in Laysan. |
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| Scientific name | ||||||||||||
| Acrocephalus familiaris kingi | ||||||||||||
| ( Wetmore , 1924) |
The Nihoa warbler ( Acrocephalus familiaris kingi ) is a songbird belonging to the reed warbler genus . It is the only surviving subspecies of the Hawaiian reed warbler , whose nominate form , the Laysan reed warbler , became extinct between 1916 and 1923. Due to morphological differences between the two forms, the Nihoa reed warbler is sometimes also considered a separate species. The subartepithet kingi honors Samuel Wilder King , the captain of the Tanager expedition and later governor of Hawaii.
features
The Nihoa reed warbler reaches a size of 13 centimeters and an average weight of 18.3 grams. The reins are whitish with some olive-colored tips and ribbons. The thin stripe above the eyes is whitish. The skull and neck are olive. The top is olive-brown, the rump is dark gray. Upper wing-coverts, hand wings and arm wings are mostly brown with gray and yellow-brown edges. The control feathers are hairy brown with yellow-brown-olive edges. Tail feathers and arm wings have dark brownish-olive bands. The underside is whitish. The sides of the breast are smoky gray, the flanks yellow-brown olive and the under tail-coverts light gray. The iris is dark. The upper beak is sepia colored, the lower beak cinnamon colored. Both halves of the beak have a noticeable dark tip. The legs are light gray to brown. The sexes are similar, but in females the underbust and belly may be whitish and cream-colored. The young birds are undescribed.
Occurrence and habitat
The Nihoa reed warbler was endemic to the only 63 hectare Hawaiian island of Nihoa until 2011 . Since then there has also been a population on Laysan Island, where the Nihoa reed warbler is supposed to replace the extinct Laysan reed warbler. The Nihoa warbler inhabits hill slopes dominated by bushes and prefers dense ground vegetation, especially around the shrub species Chenopodium oahuense and Sida fallax . However, it can also be found in other shrubs and in the clump grass .
food
The diet consists mainly of insects and their larvae, especially moths and caterpillars ( Lepidoptera , including owl butterflies of the genus Agrotis ), louse flies (Hippoboscidae), field locusts (Acrididae), small beetles from the weevil families (Anthribidae), leaf beetles (Chrysomelidae) , ladybirds (Coccinellidae), weevils (Curculionidae), beetles (Nitidulidae) and darkling beetles (Tenebrionidae) and from chinch bugs (Lygaeidae), leafhoppers (Cicadellidae), aphids (Aphidoidea), scale insects (Coccoidea), and from hymenoptera (including bees , wasps and Ants ). Also pseudoscorpions , spiders and grass seeds are food. The Nihoa reed warbler looks for its prey in bushes, clump grasses, in low vegetation, but also in the leaves and on the surface of the ground while it runs, hops or climbs. Sometimes he also catches insects in the air.
Existence and endangerment
The Nihoa reed warbler is classified by the IUCN in the “ critically endangered ” category . Surveys over the past 40 years have shown that the population is subject to strong fluctuations. Between 31 and 731 specimens were counted during this period. The population figures are presumably regulated by the weather. Droughts, storms and hurricanes inevitably have negative effects. The population level is also influenced by the fluctuations in the supply of insects. Climate changes and the unintentional introduction of predatory mammals could quickly lead to the extinction of the Nihoa warbler. Fires are also a potential hazard. The Nihoa honeycreeper ( Telespiza ultima ) sometimes destroys the clutch, but predators that seriously endanger the population of the Nihoa warbler do not exist on the island. The habitat is located in a strictly protected nature reserve that only biologists and other researchers are allowed to enter with prior approval. Strict rules are intended to prevent the unintentional introduction of neophytes and neozoa via clothing or equipment on the island. Resettlement projects are also planned. In 2011 and 2012, 24 and 26 specimens were released to Laysan . This population rose to over 100 in 2013.
literature
- J. Del Hoyo, A. Elliot, David A. Christie (Eds.): Handbook of the Birds of the World. Volume 11: Old World Flycatchers to Old World Warblers. Lynx Edicions, 2006, ISBN 84-96553-06-X .
