Arctic Warbler: First Confirmed Record for Mainland Australia by C.J
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VOL. 17 (8) DECEMBER 1998 365 AUSTRALIAN BIRD WATCHER 1998, 17, 365-369 Arctic Warbler: First Confirmed Record for Mainland Australia by C.J. HASSELL, Broome Bird Observatory, P.O. Box 1313, Broome, W.A. 6725 Summary On 23 January 1998, an Arctic Warbler Phylloscopus borealis was seen and subsequently caught in a mist-net in the grounds of the Broome Bird Observatory, Western Australia. The bird was subsequently seen feeding on caterpillars in the same area until 25 January 1998. A description of the bird is given from observations in the field and from in the hand. Identification of Arctic Warblers and similar species is discussed. Although this is the first record for mainland Australia, there are previous records and specimens from islands off north-western Australia. Introduction The Arctic Warbler is a small insectivorous bird with olive-green upperparts, whitish underparts and with a conspicuous pale supercilium. All populations of Arctic W arb1ers are highly migratory: they breed in northern parts of Eurasia, northern China, Japan and western Alaska, and regularly migrate to spend the northern winter in South East Asia, from Burma and Thailand, east to the Philippines and south to the Indonesian Archipelago (Cramp 1992). At 0740 h on 23 January 1998, at the Broome Bird Observatory, Western Australia (17°59'S, 120°22'E), I saw with the naked eye a bird that I did not immediately recognise. On fetching binoculars and viewing the bird again, I noted it was obviously a Phylloscopus warbler. I watched the bird with Janet Sparrow, a fellow warden at the Observatory, through a window for approximately 2 minutes before it moved out of view. We quickly moved outside where we found the bird again, and were able to obtain good views, as well as hear it call. We contacted two other keen bird watchers, Mavis Russell and George Swann, and set up three four-shelf monofilament mist-nets in the area that the bird was using. We obtained good views of the bird. Although photographic equipment was set up, we were unable to photograph the bird due to poor light and weather conditions. Eventually the bird flew into the second shelf of one of the mist-nets. I extracted the bird at 1105 h, and it was fully processed and photographed within 2 hours, during which time the bird was given a 20-minute break, when it was held in a bird bag in a cool and shady position. On release, the bird flew into a nearby Acacia, shook itself and began to glean insects. Habitat and conditions The Broome Bird Observatory is a collection of nine buildings and a small camping ground, situated in coastal Pindan woodland dominated by Pindan Wattle Acacia eriopoda; other plants in this habitat include Kimberley Bauhinia Lysiphillum cunninghamii, Medicine Bark Ventilago viminalis, Hakea macrocarpa, Wild Pear Persooniafalcata and Native Willow Ehretia saligna. The red Pindan soil supports grasses and a variety oflow native shrubs and flowering plants. A Kimberley Bauhinia was the tree favoured by the Warbler, where it kept to the lower branches and the trunk. At the time of the observation, there was complete cloud-cover and intermittent rain. A low-pressure system, which subsequently intensified to form Tropical Cyclone Tiffany, was centred approximately 140 km north-west of Broome. AUSTRALIAN 366 HASSELL BIRD WATCHER Arctic Warbler at Broome, W.A., January 1998, showing conspicuous supercilium Plate 60 Photo: J. Sparrow Dorsal view of the Arctic Warbler at Broome, W.A. Plate 61 Photo: G. Swann VOL. 17 (8) Arctic Warbler - DECEMBER 1998 First Confirmed Record, Mainland Australia 367 Description This description is a combination of our field-identification notes (after having viewed the bird through Carl Zeiss J ena 10 X 50 and 8 X 40 binoculars), completed plumage-description sheets and characteristics of the bird when observed in the hand. First impressions My first impressions were of a long-bodied bird with a horizontal carriage (in contrast with Brown Honeyeaters Lichmera indistincta and Rufous-throated Honeyeaters Conopophila rufogularis, commonly seen around the area). With binoculars, the most striking feature was a long, narrow, pale-yellow supercilium, starting in front of the eye, near the bill, extending beyond the eye and curving down onto the side of the nape. Bare parts The eye was large and dark with a deep-brown outer iris and black orbital-ring. The large, robust bill had a black upper mandible with a tiny pale tip (not discernible in the field); the base of the lower mandible was yellow-orange, with the distal half dark hom, with a tiny yellow tip. The base of the bill was 5.9 mm wide. Tarsi were pale hom with a very pale yellow stripe along the back of each leg. The width of the tarsus was 2 mm, and the bird took a size 02 band. Head The bird had the distinctive supercilium and face pattern of a Phylloscopus warbler. The forehead and crown were dark olive, and the lores olive-grey. There was a very long, pale-yellow supercilium, which started from near the base of the bill, though, when viewed from above, the supercilia did not join above the upper mandible; it extended back above the eye and curved down onto the side of the nape. There was also an olive eye-stripe. The ear-coverts were pale yellow, mottled with olive (Plate 60). Upperparts and upperwing The nape, mantle, back, rump and upper tail-coverts were all dark olive, slightly brighter towards the rump and upper tail-coverts. The scapulars were also dark olive; in the field, the upperwing was similarly dark olive when folded. In the hand, the primaries were grey-brown with narrow yellow-olive outer edges. The fifth primary (p5) was non-emarginated (note: p1 was taken as the innermost primary). The secondaries were also grey-brown, but with broader yellow-olive outer edges. The tertials were olive. The primary coverts were similar in colour to the primaries. In the field, a short, very pale wing-bar was noted; in the hand, this was seen to be formed by pale-yellow tips on the four inner primary coverts and the first secondary covert. The median and lesser coverts were grey-brown with an olive wash, but two of the median coverts also had pale tips. The longest primary on the folded wing extended 14.8 mm beyond the tip of the longest tertia!, exposed tertials (that is, from the tip of the scapulars to the tip of the longest tertia!) were 20.2 mm. The wing formula showed p9 = p5. The uppertail was grey-brown with olive outer webs; the three outer feathers had pale tips and pale-edged inner webs; the fourth outer feather lacked a pale tip, but had a pale-edged inner web (Plate 61). Underparts and underwing The chin and throat were white with a yellow wash. The feathers on the upper breast were olive-grey with yellow tips and an overall yellow wash. This gave a AUSTRALIAN 368 HASSELL BIRD WATCHER distinctive streaking as seen in the field. The remainder of the underparts were white with a yellow wash. The undertail was gunmetal-grey with pale tips and edging, similar to that on the uppertail. The undersides of the primaries and secondaries were also gunmetal-grey, with narrow white inner edges. The axillaries were lemon-yellow, and the underwing-coverts were white with lemon tips. Call The bird called twice while we were watching it: it gave a harsh and relatively loud scolding double trrrrrick-trrrrrick or chrrrrrick-chrrrrrick, followed by a short pause and then repeated. The bird called both when in the tree and while in flight. Separation from similar Phylloscopus warblers Other Phylloscopus warblers, similar to the Arctic Warbler, which need to be eliminated to confirm our identification are: the Greenish Warbler P. trochiloides, a migratory species which breeds from northern Europe east to central Russia, and south to Kazakhstan, the Himalayas and south-western China, and spends the non breeding season from India, through Thailand to Indochina; the Large-billed Leaf Warbler P. magnirostris, a sedentary species, which ranges from India south to the Andaman Islands, and west to western and southern China; and the Eastern Crowned Leaf-Warbler P. coronatus, which breeds in eastern Siberia, northern and western China, Korea and Japan, and winters from eastern India east to Indochina and south to Java and Sumatra (King et al. 1989, Cramp 1992, Coates et al. 1997). I considered the Broome bird to be an Arctic Warbler because of the diagnostic combination of the following features: (1) Face pattern: This bird lacked the dark lateral crown-stripes and pale median crown-stripe diagnostic of the Eastern Crowned Leaf-Warbler (de Schauensee 1984, Flint et al. 1984, Lekagul & Round 1991). The long supercilium separated from the mandible, and strongly mottled ear-coverts indicated Arctic Warbler; the ear-coverts of the Greenish Warbler are usually less strongly marked (Dean 1985). (2) Underparts: The upper breast was streaked; Greenish Warblers usually have cleaner, virtually white underparts (Svensson 1984, Dean 1985, Cramp 1992). (3) Wing size, wing formula: Wing length was within the normal range for the Arctic Warbler, and too long for Greenish Warbler. The primary projection of the Broome bird showed the wing point = p8/p7; p7 is not the longest feather in the Greenish Warbler. In addition, the wing formula showed p9 = p5, whilst on the Greenish Warbler p9 = p1 (Williamson 1974, King et al. 1989, Cramp 1992). The fifth primary was not emarginated, in contrast with both the Greenish Warbler and the Large-billed Leaf-Warbler (Williamson 1974, King et al.