White-tailed Iora Aegithina nigrolutea
Version: 2.0 — Published October 22, 2020
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Breeds annually, coinciding with the monsoon season in India. Lays mainly in June and July. Breeding season in Sri Lanka not well studied but nest with chicks observed in April, which is earlier than breeding season in western India.
Nesting starts with the monsoon rains in India, usually from June to August-September (3). The monsoon season results in growth of leaves on thorn scrub, and also an abundance of insects; it takes advantage of this to nest. Pairs are formed after courtship (see Sexual Behavior).
In Kachchh, nesting sometimes observed in mid-September (PG). Whether such late nesting is due to a poor monsoon season, or it is a second brood is not known. The nesting season in Kachchh is usually June-July, with eggs typically laid in the first week of July, and young observed in nests by August. In Kachchh in Gujarat, in observation of one nest, eggs hatched on 22 July (PG). By September, fledged juveniles are usually seen.
Nesting season not well studied in Sri Lanka but chicks present in the nest in the first week of April (29).
Nests in its preferred habitat of thorn scrub. Trees and shrubs are preferred, with nest observed in Acacia, Prosopis spicigera, Balsamodendron mukul, and rarely in young Ficus trees or neem (Azadirachta indica) trees in western India (PG). Nests are usually located in the midst of a patch of Acacia, with few trees surrounding the nesting tree. Nests in large trees are rare (PG).
In India, the height of the nest is usually at 2-3 m, sometimes down to 1 m from the ground, but not more than 5 m even if the nest is in a large tree (27). The nest is slung in the horizontal fork of an outlying twig, in an upright crotch (vertical fork), on a horizontal branch, laced in fork of Salvadora bush, directly onto bark surface of mimosa (Mimosa), or fig (Ficus) bough with vertical twigs (23). The vertical or supporting twig is often enclosed within the nest, probably as an additional support. In Sri Lanka, nest observed at a height of 8 m, in a tamarind tree (Tamarindus indica); the nest was well hidden and covered by leaves, protecting it from sunlight. The nest was in a vertical fork, surrounded by twigs (29).
In both India and Sri Lanka, nest of Common Iora (Aegithina tiphia) seen within 100 m of nest of White-tailed Iora.
The nest site selection as well as the nest construction is done by the female, with the role of the male in these tasks being negligible (27).
Structure and Composition
In India, the nest is cup-shaped, deep, neat, and well built (23). It is made up of fibers, grass, shreds of bark, and twigs, smeared with cobwebs on the outside. The outside of the cup is sometimes so thickly covered with cobwebs that it appears white. The inside on the cup is lined with fine soft fiber, and sparsely with hair and cobwebs. Nests are conspicuous initially due to white cobwebs, but the nest gradually becomes dirty brown due to the rains and nesting activities, making it more difficult to locate in the shrub or tree (27). The nest structure in Sri Lanka is similar; a neat cup, well covered with cobwebs (29).
In India, the nests measured about 65 mm in width (23).
The average egg size (n = 20) is 17.5 x 13.5 mm; the maximum size reported as 18.0 x 13.3 mm, and minimum sizes given as 17.0 x 12.8 mm and 17.2 x 12.6 mm (11).
The eggs are whitish, pinkish-white, or pale grayish, blotched with purplish brown, with a wide range of variations. The eggs are similar to those of Common Iora, and are probably indistinguishable from each other (11).
The clutch is normally 2-3 eggs. Clutch sizes of four noted, but this is exceptional; a clutch of a single egg also noted (11).
Details of egg laying not well known. There is no information regarding second brood in this species.
Incubation period not known but said to be similar to Common Iora (A. t. humei); incubation period in Common Iora is about 14 days (3). In observations in Kachchh in Gujarat (western India), incubation period observed to be around 17-18 days (PG).
Incubation is shared by both sexes, taking turns incubating throughout the day. At night, incubation is done by the female (27). Since incubation is shared between the sexes, the male does not bring food for the female when she is incubating. The pair is not very vocal during incubation and the male does not utter the long, drawn out calls.
No information available regarding hatching.
Condition at Hatching
At hatching, the young are altricial (needing parental care) and nidicolous (stay in nest; PG). Natal down is yellowish, with richer yellow streaking on head and mantle. The bill has a horn colored culmen, with a pink mouth. The emerging pin feathers on the wings are black, edged whitish. Young birds beg for food with bill open.
Growth and Development
In observations in Kachchh in Gujarat, young birds observed to stay in the nest for around 20-21 days (fledging period was about three weeks; PG). After around three weeks, young start moving out of nest and are capable of taking short flights, but are still tended to by the parents (PG).
Brooding is mainly done by the female (PG).
Both sexes bring food to the young. The male and female bring food separately or together to feed the young. The food is insects, mainly small green grubs and caterpillars; there are no details regarding feeding rates, but in one short observation, the male and female were observed to bring food approximately three times each in fifteen minutes of observation in Gujarat (western India; 27).
Great attention is paid to nest sanitation (23). After almost every time a chick is fed, the parent tickles the vent of the chick, producing a fecal sac. The fecal sac is initially eaten by the male and female. As the chicks get older, the fecal sac is taken away from the nest by both sexes. The young raise their posterior while the male or female take the fecal sac directly from the young. The fecal sac is deposited away from the nest.
Does not breed cooperatively. In one area in Gujarat in western India, where four pairs were nesting within a 1 km2 area, pairs maintained separate breeding territories and there was no observation of cooperative breeding (PG).
Brood Parasitism by Other Species
Though Common Iora is known to be a host for Banded Bay Cuckoo (Cacomantis sonneratii; 30), there are no observations of White-tailed Iora being a host for cuckoos, at least in western India (Gujarat; PG). There is also no information regarding brood parasitism from Sri Lanka. More information/study is required over its entire range to confirm whether the White-tailed Iora is a host for cuckoos.
Association with Parents or Other Young
After leaving the nest, young are tended to by both the parents. The male and female continue to feed the young, which do not move very far from the nest area (PG). A few days after leaving the nest, young are able to take short flights; they follow parents from tree to tree with weak fluttering flight. Both parents were seen following a recently fledged juvenile from one shrub to another in August in Gujarat in western India (PG). The period of dependency on the parents after leaving the nest is not known.
No information regarding fledgling stage from Sri Lanka.
Single juvenile/immature individuals, with tails growing and plumage like females, but paler, have been noted to feed and catch prey independently. The parents were not observed nearby (PG). After October-November, young are not separable from non-breeding adults in western India. The young are fledged by October-November in western India (Gujarat), and whether these immature individuals breed in the next breeding season (after about 7 or 8 months after leaving the nest) is not known. The molt in these birds is believed to be later than in adults (see Molts). There is no direct evidence of immature birds breeding in the following breeding season, but it is suspected that late breeding pairs could be immature birds breeding in the next season. However, further study required to confirm these hypotheses.
No information regarding immature birds from Sri Lanka.