Family: Large-billed Gerygone (Gerygone magnirostris) belongs to the family Acanthizidae in the order Passeriformes.
Habitat: Large-billed gerygone’s are small and inconspicuous in the outer foliage of trees where they live and feed. The various gerygones are pronounced jer-rig’-ony-pose an ecological question. How do they co-exist? Focusing on this question is the large-billed gerygone, for over its range it lives alongside three other gerygone in the closed forest: the fairy, green-backed, and mangrove. Subtle partitioning of habitat and foraging is probably the answer. Thus, the large-billed bird keeps mainly to the taller stands of Rhizophora mangroves where it meets the mangrove. And, with its stronger bill, it may take heavier, hard-shelled insects where it overlaps the green-backed gerygone and fairy gerygone in riverine rainforests and paperbark galleries along streams. The species is known as a floodbird because of its limited breeding area, where it hangs its messy nest low over the water and resembles flood debris.
Behavior: The large-billed gerygone is like other gerygones in behavior. It is sedentary, and singly or in dispersed pairs—rarely threes or fours—it gleans small leaf insects for much of the day in the upper strata of close forest. The male helps build nests but spends much of his time singing near by; it works hard but inconspicuously more on the inside than the exterior of vegetation, though it will hover to take insects on the wing. Nests are often built near the nests of hornets; probably only the female incubates, but both sexes feed the young, often rearing two broods a year. The nest and branchlets at the nest site seem to be the main place for mutual displays between paired birds, which perform slight bowing movements and fan the tail to expose the markings at its tip.
Identification: Both sexes are similar. The head and upper parts are warm-brown, with an indistinct white spot on either side of the forehead and an indistinct white eye ring in an otherwise plain face. The wings are back but the flight feathers are grayer. The tail is grey-brown with a brown-black bar near the tip and off-white spots at the top of the inner web of two to four pairs of feathers only. Underparts are cream-white, washed pale buff, or cinnamon-brown on the breast and flanks. Eye-rich red to red-brown Bill black. Feet grey. The immature bird (as an adult) has brown eyes and a brown bill.
Vocalizations: Large-billed Gerygone call is soft chattering in contact. The song is sweet, with short whistled notes, lively and jerky, rising and falling, uttered in rapid succession for short periods by both sexes. egg sacs, lined with feathers and down, slung from low, slender branchlets often overhanging or near water, 2–12 meters or more.
Eggs and Incubation: The bird lays two or three eggs, matt pale pink, freckled, spotted, and blotched with red and sometimes purple-grey, often in the indistinct zone at the larger end; oval, about 1 7 x 12 mm. The incubation period is about 13–14 days, probably by a female. Young fledge in about 10–12 days.
Nesting and Breeding: Large-billed Gerygone nesting and breeding occur in September–April. Nest a 500-700 mm long, straggling structure with egg chamber towards the base, a ragged tail, and short side-entrance hood made of shreds of bark, grass stems, rootlets, and leaf skeletons, often adorned with spiders’
Distribution: The bird is found in mangroves, riverine rainforest, and paperbark galleries, from western Kimberleys, WA, to Broad Sound, Queensland; broken at the Gulf of Carpentaria. Also found in Papua New Guinea and offshore islands.
Races: There are about 12 races, but only two occur in Australia. Some of the notable subspecies are listed below.
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m. rosseliana – Hartert, 1899
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m. conspicillata – (Gray, in 1859)
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m. cairnsensis – Mathews, in 1912
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m. affinis – Meyer, in 1874
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m. magnirostris – Gould, in 1843
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m. brunneipectus – (Sharpe in 1879)
Alternative Names: It is also known as a large-billed warbler, large-billed flyeater, floodbird, or brown-breasted flyeater.
Size: Large-billed Gerygone measures about 105–115 mm in length.
