Fan-tailed Gerygone Gerygone flavolateralis Scientific name definitions

10 cm; 5·5–6·5 g. Typical small, rather drab gerygone. Male is olive-brown above, head more olive-gray, with indistinct narrow whitish fore supercilium and thin broken eyering; upperwing and tail olive-brown, subterminal white spots on outer tail feathers; throat whitish gray, flanks and belly lemon-yellow, rest of underparts pale grayish; iris red; bill black; legs black or dark gray. Female is paler than male. Juvenile has underparts entirely yellowish, with dusky band across breast and slightly more dusky-colored upperparts.

Gerygone flavolateralis is often treated as conspecific with Rennell Gerygone (Gerygone citrina) (e.g., 1 Dickinson, E. C., and L. Christidis, Editors (2014). The Howard and Moore Complete Checklist of the Birds of the World. Fourth Edition. Volume 2. Aves Press, Eastbourne, UK. Close ), but here is split on the basis of strong differences in plumage, eye color, morphology, and apparently song (though recordings of other taxa, particularly correiae from Banks Island and Vanuatu, are apparently lacking). In their assessment of the complex, del Hoyo and Collar (2 del Hoyo, J., and N. J. Collar (2016). HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions, Barcelona, Spain. Close ), employing the Tobias et al. (3 Tobias, J. A., N. Seddon, C. N. Spottiswoode, J. D. Pilgrim, L. D. C. Fishpool, and N. J. Collar (2010). Quantitative criteria for species delimitation. Ibis 152(4):724–746. Close ) criteria, from which the scores in brackets are derived, Gerygone citrina differs in its whitish-yellow versus dark reddish iris [3]; grayer head to throat sides [1]; brighter, more extensive yellow on belly [2]; whiter throat (ns[1]); greener upperparts (ns[1]); and longer bill [mean of 5 males 14.03 mm versus 12.42, 11.5, and 12.2 in 10 each of G. f. correiae, G. f. flavolateralis and G. f. lifuensis, respectively, and 12.4 in a single G. f. rouxi; allow 2].

Four subspecies recognized. Subspecies differ slightly in coloration, extent and prominence of supercilium, and biometrics.

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SUBSPECIES

Gerygone flavolateralis correiae Scientific name definitions

Distribution

Banks Islands and northern Vanuatu.

Identification Summary

Subspecies correiae is brighter than nominate with smaller white spots on outer four tail feathers.

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SUBSPECIES

Gerygone flavolateralis flavolateralis Scientific name definitions

Distribution

New Caledonia, Isle of Pines and southern Loyalty Islands (Maré).

Identification Summary

See Field Identification, above.

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SUBSPECIES

Gerygone flavolateralis rouxi Scientific name definitions

Distribution

Ouvéa, in northern Loyalty Islands.

Identification Summary

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SUBSPECIES

Gerygone flavolateralis lifuensis Scientific name definitions

Distribution

Lifou, in central Loyalty Islands.

Identification Summary

Subspecies lifuensis has smaller white tail spots than nominate.

Gerygone flavolateralis is presumably most closely related to Rennell Gerygone (Gerygone citrina), with which it was previously considered conspecific, though this taxon has not been included in any published molecular phylogeny. Outside of this close relationship, Gerygone flavolateralis has been found to be sister to a relatively large clade that includes Dusky Gerygone (Gerygone tenebrosa), Mangrove Gerygone (Gerygone levigaster), Gray Gerygone (Gerygone igata), and Brown-breasted Gerygone (Gerygone ruficollis), among others (4 Nyári, Á. S., and L. Joseph (2012). Evolution in Australasian mangrove forests: multilocus phylogenetic analysis of the Gerygone warblers (Aves: Acanthizidae). PLoS ONE 7(2):e31840. Close , 5 Marki, P. Z., K. A. Jønsson, M. Irestedt, J. M. T. Nguyen, C. Rahbek, and J. Fjeldså (2017). Supermatrix phylogeny and biogeography of the Australasian Meliphagides radiation (Aves: Passeriformes). Molecular Phylogenetics and Evolution 107:516–529. Close ).

New Caledonia, Loyalty Islands, and northern Vanuatu.

Forest and secondary growth, village gardens and scrub, from sea-level to hills; to at least 1600 m in Vanuatu, but on some islands there the species shuns heavily forested habitats at elevations above just 550 m.

Resident; capable of short movements, as it has apparently colonized various islands in Vanuatu from time to time.

Insectivorous; no details of prey items, but takes insect larvae and pupae, as well as imagos. Seen singly or in pairs or small family parties, joins mixed-species flocks with white-eyes (Zosterops), fantails (Rhipidura) and whistlers (Pachycephala). Forages from low levels up to canopy, mostly in middle stage. Gleans from foliage, twigs and branches; may also hover and sally after prey. Often quite tame.

Sings at any time of day, less in hottest period. Quiet, thin, piping repetitive tee poo tee tee poo tee series of up to seven notes, also a descending squeaky tee poo tee tee poo tee ti ti; in Vanuatu (subspecies correiae) has stronger, less piping and more run-together series, toodly toodly teedle tee too. Constant soft, quiet twittering as contact when foraging.

Season September–January/February in Vanuatu and September–December in New Caledonia, where most documented breeding attempts have been in October. Nest is a domed structure with a hooded side entrance near top and including a “tail” beneath, constructed from plant fibers, rootlets, soft bark and moss, bound with spider webs, lined with feathers and soft plants, usually suspended from vine stems 1–5 m above ground. Clutch 2–3 eggs, white or buff, marked with brown; no information available on incubation and fledging periods. Nests parasitized by Shining Bronze-Cuckoo (Chrysococcyx lucidus).

Not globally threatened (Least Concern). Restricted-range species: present in Vanuatu and Temotu Endemic Bird Area and New Caledonia Endemic Bird Area. Quite common on most islands. Survives well in secondary habitats, so long as some trees are present. Has apparently disappeared from some islands and colonized others in Vanuatu: e.g. species was unknown on Espíritu Santo until 1961 and also on Malo, but, conversely, may have disappeared from islands of Ambae, Ambrym, Epi, Emae, Gaua, Lopevi, Malakula, Pentecost and Vanua Lava since the 1926 Whitney Expedition.