Symbiosis: How ornithophile flowers lure animals for pollination

Our newspapers and electronic media often publish gaudy pictures of mynas, starlings, orioles, bulbuls, leafbirds, parakeets, cuckoos, drongos, shamas, robins, sunbirds, and several other avian species drinking nectar from very large and showy red or orange-red flowers of shimul, mandar, palash, joba, and so on.

Many insects too, such as butterflies and bees, relish nectar produced by the tiniest of flowers to the large showy ones. Mammals like squirrels, langurs, monkeys, civets, mongooses, all fruit bats, and even jackals, love to drink nectar — a sugary chemical and a carbohydrate-rich liquid — from flowers.

Flowers of nectar-producing plants have special adaptations to attract invertebrates, almost entirely insects, and vertebrates, mainly birds and bats.

But what adaptations help lure the pollen carriers?

When I am in Dhaka during the flowering season of rudra palash, most of my free time is spent on the roof of the Kurvi Neer watching and photographing many species of birds, visiting the flowers of this plant from dawn to dusk. Watching the nectarivore birds and squirrels over the rudra palash flowers is very enchanting, soothing, and engaging.

Luring with sweets

To complete the process of cross-pollination, animals also must have evolved accordingly. Their aptly evolved bills, hairs or bristly facial feathers, tongues, proboscis, mouth parts designed for sucking, etc., help in sucking nectar or eating and carrying pollen.

Thus, in the process of visiting many flowers, cross fertilisation becomes possible. They transfer pollen from the first flower to the second, cross-fertilising them in the process.

To do this, plant adaptations include various types of nectar with or without flavour to attract insects or vertebrates.

Parts like the branch that bear the flowers, corolla or sepals-petals, stamen, pistil and stigma of an individual flower must be of such colour, size and shape that animals visiting it can get a foothold on or near a flower and then drink nectar or collect pollen.

Let's consider the purple sunbird, a common small Asian sunbird, just a little larger than the smallest flowerpecker. At the Green Mubazzarah Park in Al Ain, UAE, I observed both the male and female very busy collecting nectar from very large and showy red flowers of pahari parul or desert teak — the largest flower of any natural plant in the UAE.

During its bloom, dozens of sunbirds, bulbuls, a few migratory whitethroats, hordes of honey bees and wasps feast on its nectar and pollen.

The interesting fact is that the sunbird's bills are too small, less than an inch, for it to drink nectar from the top of the large flower. They do it from some flowers that are drooping downwards or parallel to the branches on which the sunbird could perch and insert the bills inside flowers.

But most of the time, it was uncomfortable for them to suck nectar from the open part of the super-large flower. So, they have developed a strategy in which they stand below or close to the flower at a vantage point on a branch. Then they insert the curved bill through the base of the flower and suck on the nectar.

Sunbird's bills and brush-tipped tongue form a tube by pressing the long tongue against the wall of the upper bills. Then it can suck nectar from the flower as we do when we are having a soft drink with a straw.

The rudra palash bloom

The African tulip or rudra palash was introduced in the Indian subcontinent by the British in the 1900s. The National Botanical Garden at Mirpur is just on the other side of the boundary of my residence at Dhaka, the Kurvi Neer (meaning bird's nest). There were at least five trees within five to 10 metres. From the rooftop, I could see the flowers just three to four metres away from me.

African tulips can get large, seven to 10 metres, with an umbrella-shaped crown. It flowers during February-April when each tree gets several hundred to over a thousand red, large, showy, 15 cm long and bulky flowers covering the whole crown. Each tree offers a spectacular appearance merging with the skyline by our Kurvi Neer.

Birds, bees and squirrels line up to drink nectar from rudra palash flowers. I have a series of pictures showing oriole, jungle myna, Asian pied starling, red-vented bulbul, purple sunbird, Irrawaddy squirrel and five-striped palm squirrel drinking nectar following different means of inserting bills or snouts through the open flower, piercing the corolla tube, or cutting the tube.

In the process, the birds and squirrels carry the pollen and transfer those to the flower visited afterwards.

Birds and other animals that drink nectar and collect pollen to supplement their food. In turn, they must do something that would benefit the flowers, which are offering precious sugary drinks to the animals.

So, most animals help in cross-pollination of flowers, or they transport a heavy gene pool from one flower to the other. Thus, both plants and animals have maintained a symbiotic relationship for the past millions of years.

When I am in Dhaka during the flowering season of rudra palash, most of my free time is spent on the roof of the Kurvi Neer watching and photographing many species of birds visiting the flowers of this plant from dawn to dusk.

Watching the nectarivore birds and squirrels over the rudra palash flowers is very enchanting, soothing, and engaging. The whole interaction keeps my mind super fresh.