Next time you chance upon the pendant, teardrop-shaped nest of the Yellow-throated Scrubwren, be mindful of its significance within the ecosystem. Not only does it house this species but it is often tenanted, with some modification, (an excised chamber beneath the structure) by Golden-tipped Bats, a vulnerable species, seemingly unperceived by the birds. These micro mammals rely on these constructions as primary daytime roosts sometimes with multiple occupants. Large-billed Scrubwrens also often appropriate these nests, (occasionally even when recently completed), a practice not common in the bird world according to Alec Chisholm (1965), Bird Wonders of Australia. More on nests later.
“Silken bird with yellow throat” is the rather enchanting name translated from the Greek and Latin binomial given by Gould when he first described and painted this species in 1838. A member of the Australian Warbler family which includes scrubwrens, thornbills and gerygones, this bird, as conjectured, was recognised as distinct from other scrubwrens in 2018 with genetic research. The prefix ’neo’ was then added to the name.
These birds occur in eastern Australia in upland rainforest, wet sclerophyll forest and along watercourses in deep gullies. In Queensland there are two separate populations. In the north they are found from Cooktown to Townsville and their southern range extends from Bunya Mountains to Bega in NSW approximately.
A small, chubby bird (though larger than other scrubwrens), it has a canary-yellow throat, eyebrow and fine edging to the primaries. The male has a black mask and the female an identical one, but brown. The crown and upperparts are olive brown with underparts a subtle wash of olive-cream. The dark masked face bordered by yellow is a reliable distinguishing feature.
Active ground-dwelling insectivores, these appealing little birds tend to forage in pairs pecking with pencil-sharp beaks keeping within earshot of each other with a sharp one-note trill, jaunty songs and harsh chitters. They hop rapidly, seeming never to pause for a second on relatively long pale pink-tinted legs on the rainforest floor, over mossy logs, in moist timbered gullies, walking tracks and even road verges contiguous to these habitats. For a bird with such colouring it is surprisingly cryptic. Often observed foraging in the wake of leaf-scattering prospectors such as logrunners and lyrebirds, they glean invertebrates that have been disturbed and exposed.
These birds are known for their beautiful song and accomplished mimicry. Vocalisations are used in courtship songs, and it is thought, to declare territory. At Lamington National Park recently, I heard mimicry, in one bird’s repertoire, of Crimson Rosella, Grey Shrikethrush, and Eastern Yellow Robin but many more have been noted.
A half-built nest of the Yellow-throated Scrubwren resembles a bell, showing that there is no pre-built framework and that is constructed entirely from the top down. It is suspended usually from a lawyer vine in Queensland, and materials used include palm fibre, black rootlets, moss, ferns, lichen and leaf skeletons. The entrance hole is left as the pair proceed downward to complete and enclose the rounded base. A canopy over the entrance is added as well as a tunnel. (The nest is 19 cm x 30cm approximately). The birds then collect soft feathers for lining. Crimson Rosella and Wonga Pigeon are amongst the many recorded in Queensland. These nests begin with one chamber but others are added for subsequent broods. Streamers of vegetation hang below these structures and they are often built above water, close to, and resembling flood debris. It has been suggested that this may be a clever device to baffle predators. A clutch of 2-3 lustrous eggs, pale brownish-purple with variable blotching, is laid between July and February and the pair shares incubation over 21 days.
In the rainforest the nests are conspicuous, often close to tracks and sometimes around eye height of humans so there is a fair chance of encountering this feat of engineering at first hand, a visual reminder, I think, of the important part it plays amongst inter-dependent organisms.
References:
- Beruldsen, G (1980) A Field Guide to Nests and Egg of Australian Birds. Rigby, Brisbane
- Campbell AJ, Campbell’s Own Observations of the Yellow-throated Scrubwren (Museums Victoria Collection).
- Higgins, PJ, and Peter, JM, (2002) ‘Handbook of Australian, New Zealand and Antarctic Birds’ Vol 6: Pardalotes to Shrikethrushes. Oxford University Press, Melbourne.
- Madani, G, (2023) ‘Golden-tipped bat: gilded masters of camouflage living rent-free in the nests of oblivious birds’, Cosmos Magazine. (“pencil-sharp beaks” a term coined by Paul Evans, nature writer for The Guardian).
