Weebill Smicrornis brevirostris Scientific name definitions

8–9·5 cm; 6 g. Tiny acanthizid resembling Acanthiza species, but with short stubby pale bill; often considered the smallest Australian passerine. Nominate race has top of head greyish, merging into greyish-olive on side of neck, most of lores white, diffuse dark brown loral spot, conspicuous off-white supercilium tapering behind eye, ear-coverts light brown; upperparts olive to greyish-olive (contrasting with crown), pale olive-yellow at base of uppertail-coverts; uppertail dark brownish-grey, broad black subterminal band; upperwing dark brown, narrow pale yellowish fringes on secondary coverts and tertials, finer yellowish edges on remiges; chin and throat off-white with variable fine short dusky streaking; breast creamy to very pale yellow (sometimes brownish at side), grading to richer yellow on belly and vent and brighter yellow on flanks ; undertail-coverts creamy, undertail dark grey with broad white tips; iris creamy or pale yellow; bill grey-brown to dark brown, often paler pinky-brown lower mandible; legs dark grey or pinkish-grey to dark brown. Sexes alike. Juvenile has duller head and upperbody with brownish cast, richer yellow fringes on tertials, underside paler, throat lacking streaks, iris dull grey or lime-green. Races differ mainly in colour tone: occidentalis is very like nominate, but top of head often slightly darker, has side or all of breast suffused with grey, breast centre usually streaked; flavescens is much paler and yellower than others, yellow-olive above (top of head contrasting less with upperparts), supercilium and lores off-white to pale yellow, no dusky loral spot, ear-coverts only faintly washed brown, chin, throat and undertail-coverts unstreaked pale yellow, merging into brighter yellow rest of underparts, bill very pale, flesh-brown or horn-coloured, lower mandible sometimes pale pink; ochrogaster is smaller, shorter-tailed and paler than others, a washed-out version of nominate, having pale olive upperparts contrasting less with top of head, loral spot and ear-coverts paler brown, chin to breast off-white with little or no yellow tinge and streaking faint or absent, bill slightly paler.

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Editor's Note: Additional distribution information for this taxon can be found in the 'Subspecies' article above. In the future we will develop a range-wide distribution article.

Wide range of wooded habitats, particularly eucalypt (Eucalyptus) woodlands, also dry sclerophyll woods, mallee and mulga habitats, sometimes in moist sclerophyll eucalypt forest and acacia (Acacia) shrublands; commoner in semi-arid than in arid zone, where mainly confined to drainage lines; typically avoids most types of rainforest and monsoon forest. Sometimes in riparian woods with pandanus (Pandanus), eucalypts, paperbarks (Melaleuca), casuarinas (Casuarina) and figs (Ficus). Occasionally found in farmland and suburban areas where suitable trees survive.

Resident; some local movements reported in N Queensland and S Western Australia. Around Canberra, individuals sometimes seen in marginal habitat or high up in Great Dividing Range, well outside usual range.

Arthropods, also some seeds. Prey items include spiders (Araneae), beetles (Coleoptera, including curculionids), flies (Diptera, including calliphorids), bugs (Hemiptera, including Lygaeidae), wasps (Hymenoptera, including chalcids), grasshoppers (Orthoptera), ants (Formicidae) and caterpillars (Lepidoptera), and various homopteran bugs including e.g. cicadellids, lanternflies (Fulgoridae), cercopids, lerp insects (Psyllidae), aphids (Aphididae). Usually seen singly, in presumed pairs or in small groups up to ten individuals; post-breeding flocks of 10–18 (and historically up to c. 30) recorded. Forages in canopy and subcanopy, sometimes descending to middle and lower levels, and occasionally on ground. Food obtained primarily by gleaning among foliage, sometimes on branches and trunks; occasional brief hover-sallying , or sally-striking after specific items. A core member of mixed feeding flocks, including those with Acanthiza species, Grey Fantail (Rhipidura albiscapa), Rufous Whistler (Pachycephala rufiventris), Spotted (Pardalotus punctatus) and Striated Pardalotes (Pardalotus striatus), and in Western Australia also Western Spinebill (Acanthorhynchus superciliosus). May be hard to see, as so small, active and high up; incessant calling a good first indicator of its presence.

Song given particularly on hot sunny days, a loud, liquid rich musical “pee-pee p’wee weep” (latter part sounding like “wee bill”), transcribed also as “weebit, weebee” or “willy weet, willy weee”; in duet, one individual (probably male) makes first part and probable female answers with second part. Trill calls (given more on overcast days, and early and late in day), act as contact and alarm, may be interspersed with song phrases. Also gives fast quite deep “tidid tidid”; continual “tiz tiz” when foraging, and soft “chip chip” often given in flight; high-pitched “trip”, often as prelude to trill.

Eggs recorded in all months but primarily Aug–Dec, timing of laying may vary according to rainfall (which is sporadic over much of range); suggestion that may breed more in austral autumn in N of range and more in spring in S. Usually solitary nester; usually two adults attend nest, but many reports of at least sporadic communal or co-operative breeding, with helpers at nest. Nest built by both sexes, sometimes with helpers, taking 6–15 days, domed and with hooded side entrance near top (reported also as purse-like or hooded cup with slit near top), made from grass, leaves, stems, wool, flowers, grass-heads, moss, fibre, bark, feathers, spider webs and egg sacs, also sometimes feathers and lichen, lined with feathers but wool or other soft material also used, external diameter c. 6·4 cm and length 7·6 cm (variable, up to 7·5 cm wide and 10 cm high); suspended from drooping branch or twigs, sometimes among upright bunches of twigs, usually in foliage of crown of tree, sapling or tall shrub, but sometimes in twigs or flowers and less often on lower branches, most in eucalypt (over 35 species recorded as used, and black box a favourite) but many other species occasionally utilized e.g. wattles, acacias, tea-trees (Leptospermum) and casuarinas; association with the communal spider Badumna candida noted in SW New South Wales and NW Victoria, where 12 of 17 nests were built against nests of this spider. Clutch 2–4 eggs, sometimes more (may be product of more than one female), clutch size reportedly increasing from N to S, mean in Queensland 2·2, in New South Wales 2·55, in Victoria 2·5, in Australian Capital Territory 2·7 and in South Australia 2·64; laying interval c. 48 hours, egg colour variable, creamy to pinkish-buff, brownish or stone-grey with tiny buff-brown to slate-grey freckles usually at larger end (sometimes over whole shell); incubation by both sexes, perhaps by female alone at some nests, from final or penultimate egg, period c. 18–21 days; all eggs hatch within 24-hour period, chicks fed by both sexes, nestling period 17–20 days; young may return to nest to roost for several days after fledging. Nests parasitized by Horsfield’s Bronze-cuckoo (Chalcites basalis) and Shining Bronze-cuckoo (Chalcites lucidus). Success rate moderate to poor: of 267 eggs in 109 nests , 93 (34·8%) hatched and 39 (14·6%) produced fledged young; in other samples, of 385 eggs from 154 nests 185 (48·1%) hatched, and of 213 nests 155 (c. 73%) failed and only 58 (c. 27%) fledged at least one young; of 40 nests in one study, 55·2% failed, causes of failure being equally predation and desertion (each 27·6%).

Not globally threatened. Common and widespread over much of Australia. Local declines have been noted (as with many other woodland birds), these being consequent upon habitat clearance and degradation; the resultant fragmentation encourages spread of feral predators such as cats, and makes it easier for avian predators such as currawongs (Strepera) to raid nests. Probably secure in the medium term, but numbers may have dwindled as, unlike in earlier years, there appear no longer to be reports of large flocks.