Why the Purple Sunbird changes colour in spring

The Purple Sunbird

The Purple Sunbird   | Photo Credit: Wikimedia Commons/Imran Shah

Listen for the Purple Sunbird, one of the most common and most beautiful birds in Delhi’s urban gardens

Maya Angelou, an American poet, singer, and civil rights activist once said, “ A bird doesn't sing because it has an answer, it sings because it has a song.”

I am sure you’ve often heard a sweet, loud and strident t-k-t-k-t-k che-wing, che-wing che-wing mostly accompanied by a crackling rattle around your house. When you stepped out onto your balcony perhaps you couldn’t see who was making the sound. That’s because the Purple Sunbird is tiny. Many confuse this with a hummingbird, which doesn’t exist in India.

The Purple Sunbird (Cinnyris asiaticus) flits about all around the year, not as clearly visible as its song identifiable. Come spring, March or April, breeding season begins, and you’ll see the plumage of the males transform into a beautiful dark purple with a metallic purplish-to green-blue head, mantle, and breast — which can sometimes have a maroon shine. It’ll turn back to its original colour approximately by June, once the breeding season ends, with blackish-blue upperparts and yellow underparts, a metallic blue shoulder patch with a glossy bluish-black central band running down from the throat all the way till the abdominal area.

A female drinking nectar from a yellow oleander flower

A female drinking nectar from a yellow oleander flower   | Photo Credit: Wikimedia Commons/Achat

The females, however, remain dull brownish-grey to olive-brown above with an indistinct long supercilium (mostly behind the eye) with a pale rump and washed out yellow underparts. This quality of distinct features in sexes is called sexual dimorphism.

They are mostly found singly or in pairs and sometimes in small groups around flowering trees like the Yellow Oleander, Flame of the Forest (Butea monosperma), and Hamelia patens (a common avenue hedge or small tree in our city). They also feed on the berries of the Peelu (Salvadora persica) tree.

They have a fast and direct flight and thus are capable of hovering around flowers like hummingbirds do, to sip on their nectar, helpful in pollinating these trees. They’ll usually perch themselves near the base of the flower. Their diet is nectar-rich, but they may swoop down to pick up insects in flight, and feed on spiders, often stealing their web silk to build their own nests. Although the birds are small, their size does not deter them from joining other bird species in raucously mobbing predators.

In order to woo the females, the males flutter their wings and sing. The bond between the male and female is strong and males do assist in feeding the chicks but the females have a more extensive involvement as only they incubate the eggs.

The nests are usually suspended from branches of thorny plants (a defence mechanism to safeguard the nest), but considering the commonness of this bird in urban settlements, we see them making optimum use of wires and other manmade things for nesting quite frequently. They may even choose an indoor space, in places that are not frequented.

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Printable version | Jul 11, 2020 7:58:25 PM | https://www.thehindu.com/sci-tech/energy-and-environment/the-purple-sunbird-is-a-bird-that-turns-colour-in-spring/article31413380.ece

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