SPECIES

White-tailed Iora Aegithina nigrolutea

Prasad Ganpule
Version: 2.0 — Published October 22, 2020

Appearance

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Identification

The White-tailed Iora is a small-sized (12–12.8 cm) songbird. Overall, it is a brightly colored species; boldly patterned in black and yellow. In India, breeding (Alternate) plumage in the male is acquired by a complete spring molt; the face, underparts, and collar are rich yellow, while the collar has a small amount of black fringing. The cap and upper body, except the rump, are solidly black; the rump is whitish. The wing coverts, inner secondaries, and tertials are broadly tipped in white, with the coverts forming two distinct wingbars [ ]. The tail is black, variably tipped white; a few tail feathers may be entirely white in some individuals, while in others, only a single tail feather may show white on inner or outer web, or on the tip; rarely, white in the tail may be entirely absent when freshly molted [ ]. The male in post-breeding or non-breeding (Basic) plumage (in India) resembles the female, with a pale yellow crown, pale yellowish-green mantle, yellow underparts, and extensive white in wings and tail [ ], and the two are not safely separable in the field. Females in breeding plumage [ ] are brighter than those in non-breeding plumage [ ].

Similar Species

Over most of its range, White-tailed Iora overlaps with Common Iora (Aegithina tiphia), and the two species are very similar. Male White-tailed Ioras in breeding plumage can be distinguished from Common Ioras by the white in the tail, more white in wings, a distinct yellow collar, a finer and shorter bill, and a shorter tail. Common Iora of the humei subspecies has a black cap with a black and gold collar in breeding plumage, rather like White-tailed Iora, but the finer bill, shorter tail, and variable amount of white in the tail of White-tailed Ioras are reliable characteristics for separation (1). Rarely, White-tailed Iora lacks white in tail (in freshly molted breeding plumage): in such situations, separation from Common Iora is possible only by hearing its song or call and on structural differences. Female White-tailed Ioras are separated from Common Iora in all plumages by the black or silver-gray tail with a variable amount of white, where female Common Ioras have a green tail without any white.

In Juvenile Plumage, White-tailed Iora shows some white in a blackish or silvery-gray tail; this feature is not shown by juvenile Common Iora, which has a greenish tail. White-tailed Ioras never show green in their tail at any age.

Plumages

Natal Down

In northern and western India, the first natal down (neoptile) is yellow, with richer yellow streaking on the head and nape. Plumage gradually becomes yellow on head, mantle, and underparts. Emerging pin-feathers on wings black and white, with edges whitish. Emerging tail feathers black with variable amount of yellow and white. The mantle is yellowish.

Juvenile Plumage

Like the adult female but paler, with pale yellow head and underparts; the mantle is pale yellowish or pale greenish-yellow with grayish fringing; they usually have two conspicuous wing-bars, white-fringed tertials, and secondaries with yellowish edges. The tail is blackish or pale grayish with a variable amount of white. Tail feathers are more pointed and narrower in juveniles, but always show some amount of white; even when the tail is growing in juveniles, it is black with much white. Overall, juveniles are duller than non-breeding plumaged adults with underparts also pale yellow (plumage looks faded). After tail feathers are fully grown, then they are very similar to non-breeding adults but flight is initially weaker.

No information about juvenile plumaged individuals from Sri Lanka.

Definitive Basic Plumage

Female. The non-breeding plumage is similar to the breeding plumage in females, except that the plumage is brighter in the breeding season. The amount of white in the tail is especially extensive during the non-breeding season, with the entire tail looking whitish (black sometimes reduced to only rachis or edges).

Male. Very similar to the female, and sexes are not separable in the field during the non-breeding season. In India, transitional plumage is seen in males during March-May and in September-October. In this plumage, a mix of black and yellow feathers on cap and mantle are visible. This plumage is seen before males acquire full breeding plumage (March-May) and when they are molting from breeding into non-breeding plumage (September-October). The males in transitional plumage are readily separable from females by the variable amount of black on head. The males in transitional plumage look untidy, with a mix of new and old feathers.

Definitive Alternate Plumage

Female. The face, nape, and underparts are pale yellow; the mantle is pale greenish yellow, showing little contrast with underpart color. The wings are black, with two prominent wing bars; the tertials and secondaries are prominently edged with white; the secondaries may also be edged pale yellowish (or pale greenish). The vent and undertail coverts are pale yellowish. The tail is blackish and shows an extensive amount of white.

Male. The cap, mantle, and wings are black; the face and underparts are rich yellow; the yellow neck collar is fairly distinct, but also has a small amount of black fringing; the tertials and inner secondaries are broadly fringed with white, with the tertials also broadly tipped white (white tips wear off on both tertials and secondaries, making wings look black [ ]. There are usually two conspicuous wing bars, formed by white median upperwing coverts and tips of greater coverts; the lower wing bar may be indistinct or lacking in some individuals; the rump is whitish. The tail is black with variable white tips; the white in tail very variable, ranging from only faint white tips on one or two feathers, to a few feathers wholly white. Some breeding plumaged males in southern India and Sri Lanka have a reduced black cap and a greenish mantle but are otherwise similar to males in northern and western India.

Molts

General

Birds have two molt cycles every year – a complete molt in early spring (breeding plumage) and a partial molt in autumn (non-breeding). In western India, males molt into breeding plumage in March-May. The full breeding plumage is acquired by the end of May or June. After breeding, males undergo a partial molt to non-breeding plumage. Females acquire breeding plumage (richer yellow underparts) in the spring and look paler in winter (dull, paler yellow underparts); whether this is due to worn feathers or a partial molt after breeding is not known.

There are some differences in the descriptions of molt cycles. Marien (2) describes White-tailed Iora as having a complete post-nuptial molt, restoring the birds to off-season (non-breeding) plumage; the breeding plumage is said to be acquired by an incomplete molt, which does not involve tail molt (2). However, in western India (Gujarat), breeding plumage is acquired in adults by complete molt in March-May and non-breeding plumage is acquired by partial molt in September-October (1). See molt strategy for more explanation.

Whether the molt strategy is different in populations in Sri Lanka is not known.

Molt Strategy

In western India (Gujarat), a few males, which have been seen in complete molt in September-October, with new feathers growing on tail and wing, are suspected to be sub-adult males undergoing a full molt into first adult plumage; such September-October birds undergoing a complete molt are rare and have been noted only a few times (PG). In these birds, there are a few blackish feathers on the head, but the cap is not fully black at this time. It would suggest that these males undergo a complete molt into their first adult plumage in September-October. This molt strategy is different from adults, which have a partial molt into non-breeding plumage in this period. First-year birds do not acquire full breeding plumage in spring, undergoing an incomplete molt which replaces body feathers but these birds do not show black cap (2). However, this requires further study.

Thus, there appear to be differences in timing of complete molt. Specimens collected by W. Koelz in northern and southern India were in heavy molt in September; specimens from western India (Gujarat) collected in January were not in molt. While adult males undergo a complete molt before breeding, it is also seen that a few males undergo a complete molt later in the year, after breeding. The reasons for these differences are not known and this needs further study.

Prealternate Molts

In western and northern India, breeding plumage in male is acquired by a complete molt in March-May. The complete molt usually begins by March or early April, when black feathers start appearing on the head [ ]. In April, it is in active molt; the black cap appears, and wing and tail feathers are also replaced [ ]. Birds in active molt look untidy, with new feathers visible in the wings and new tail feathers growing. Black feathers on the mantle and a full black cap are acquired by late May or early June, when molt is completed. In southern India, molt timing is similar; birds begin to molt into breeding plumage in March-May [ ]. In Sri Lanka, birds with black caps (or with black on head) are seen all round the year, even in the winter months of November-February [ ]. In northern and western India, males with black cap are never observed in the winter months from November-February.

Molt timing and strategy in Sri Lanka is not known.

Prebasic Molts

In India, adult males undergo a partial molt into non-breeding plumage by September-October. The black feathers on head and mantle are replaced and the rich yellow underparts become paler yellow. In this transitional plumage, a mix of retained black feathers and newly molted yellow feathers on head and mantle is usually seen [ ]. The wing and tail feathers are retained during this molt. The molt into non-breeding plumage is completed by end of October or early November. As noted above, the males of the Sri Lankan population seem to retain the black cap on head even in the non-breeding season. The molt in individuals in Sri Lanka has not been studied in detail. The timing of molt to non-breeding plumage in males in Sri Lanka needs further study.

Bare Parts

Bill

Bill is a plumbeous-horn color, with a darker culmen in adults (3). In Basic plumage, bill is more silvery gray [ ]. Chicks have pale grayish culmen with thick pale pink gape.

Iris and Facial Skin

Iris is pale yellow to dark brown. Eyes are darker in juvenile birds.

Tarsi and Toes

Plumbeous, dark gray, or silver gray.

Measurements

Linear Measurements

See tables under Tables and Appendices.

Mass

Males: 11-14 g (n = 8), females: 10-14 g (n = 9; 3).

Recommended Citation

Ganpule, P. (2020). White-tailed Iora (Aegithina nigrolutea), version 2.0. In Birds of the World (S. M. Billerman and B. K. Keeney, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.whtior1.02