Nightingale Reed Warbler Acrocephalus luscinius Scientific name definitions

18 cm; male average 35·9g, female average 32 g. Relatively large reed-warbler with very long bill, head plumage often dishevelled. Nominate race has yellow supercilium, black eyestripe; crown and upperparts rusty brown, narrow buff edges on primaries and secondaries and on tips of rectrices; light yellow to cream below, flanks brownish-yellow to buff; iris dark; upper mandible greyish-black with yellow edges, lower mandible flesh-pink with yellow edges; legs greyish-blue. Sexes similar in plumage , male slightly (but significantly) larger than female. Juvenile undescribed. Race nijoi has shorter bill than nominate, also upperparts much less rusty, flanks and belly darker and more brownish.

Restricted to freshwater wetland and wetland-edge vegetation, this species is thought to have succumbed to a combination of predation by the introduced brown tree-snake (Boiga irregularis), wetland destruction, pesticide use and major fires. The last sighting was in 1969, and searches in the 1970s and 1980s failed to find it (3 Pratt, H.D., Bruner, P.L. and Berrett, D.G. (1979). America’s unknown avifauna: the birds of the Mariana Islands. Amer. Birds 33(3): 227–235. Close , 4 Savidge, J.A. (1987). Extinction of an island forest avifauna by an introduced snake. Ecology 68(3): 660–668. Close , 5 Reichel, J. D., G. J. Wiles, and P. O. Glass (1992). Island extinctions: the case of the endangered Nightingale Reed-Warbler. Wilson Bulletin 104(1):44–54. Close , 2 Saitoh, T., A. Cibois, S. Kobayashi, É. Pasquet, and J.-C. Thibault (2012). The complex systematics of the Acrocephalus of the Mariana Islands, western Pacific. Emu 112(4):343–349. Close ).

Guam, in S Mariana Is.

Mosaics of elephant grass and tangan-tangan (Leucaena), also mangroves (Bruguiera gymnorrhiza), reed (Phragmites karka) marshes, Hibiscus thickets; also typhoon-created forest openings with meadow vegetation and thickets , and groves of trees.

Resident.

Information sparse. Diet probably mostly insects, lizards, also spiders (Araneae) and snails. Forages mainly on ground; gleans invertebrates from leaves (both live and dead ones), and probes dead stubs.

Song loud , melodic, varied and complex, of whistles , warbles and trills, long sustained, may continue unbroken for several minutes; often sings at night; males sing in chorus at dawn, but singing less frequent during day. Call a loud “chuck” or “tchack”.

Peak periods in Jan–Mar and Jul–Sept. Monogamous. Nest built by female, a rather deep cup, two types distinguished, one tightly woven and compact, the other larger and tightly woven with bulky outer material; in each case constructed chiefly of dry vine stems, also dry grass blades, dry bark strips, spider webs, petioles and branchlets, external diameter 8·3–12·7 cm (mean 1·6 cm), height 5·7–17·7 cm (9 cm), internal diameter 4·6–8·6 cm (6·5 cm), cup depth 2·9–5·8 cm (4·5 cm); in most cases built in tree (mainly the introduced tangan-tangan) at height of 2·3–10 m; average size of seven territories 9338 m², ten times larger than territories of A. orientalis. Clutch 2–4 eggs (mean 2·5); no information on incubation and nestling periods. Adult male annual survival at least 82%.

CRITICALLY ENDANGERED. Restricted-range species: present in Mariana Islands EBA. Current population estimated at c. 3700 individuals, all of nominate race: 946 on Alamagan in 2010 External link and 2742 on Saipan in 2007 (6 Camp, R. J., T. K. Pratt, A. P. Marshall, F. Amidon, and L. L. Williams (2009). Recent status and trends of the land bird avifauna on Saipan, Mariana Islands, with emphasis on the endangered Nightingale Reed-warbler Acrocephalus luscinia. Bird Conservation International 19(4):323–337. Close ). Nominate race extirpated on Guam, where last known sighting, of a single individual, occurred in 1969. Race yamashinae became extinct on Pagan I, to which it was confined, before 1981 (7 Reichel, J.D., Wiles, G.J. and Glass, P.O. (1992). Island extinctions: the case of the endangered Nightingale Reed-Warbler. Wilson Bull.. 104(1): 44–54. Close ). Race nijoi almost certainly extinct on Aguijan: has not been observed since 1995, despite extensive surveys in 2000, 2001, 2008 and 2009 (6 Camp, R. J., T. K. Pratt, A. P. Marshall, F. Amidon, and L. L. Williams (2009). Recent status and trends of the land bird avifauna on Saipan, Mariana Islands, with emphasis on the endangered Nightingale Reed-warbler Acrocephalus luscinia. Bird Conservation International 19(4):323–337. Close , 8 Amidon, F., R. J. Camp, A. P. Marshall, T. K. Pratt, L. L. Williams, P. Radley, and J. B. Cruz (2014). Terrestrial bird population trends on Aguiguan (Goat Island), Mariana Islands. Bird Conservation International 24(4):505–517. Close ) External link . Surviving population declining rapidly: 59% decline in the three decades since 1982, and rate of decline is increasing External link . Cause is habitat loss (agriculture, home-building and tourist-related facilities), as well as predation by introduced brown tree snake (Boiga irregularis), monitor lizard (Varanus indicus), feral cats and rats (Rattus); also as a result of pesticide use and major fires. A recovery plan in progress includes programme for removal of goats (which destroy habitat) and snakes from the islands.