The black-headed ibis is the avian analogue of the guy who would eat with chopsticks in a fancy restaurant and the next day, would be all fingers and slobbering over a plate at a greasy spoon.

With that idea in mind, zoom in on the section of the Perumbakkam wetland that is within sniffing distance of the fuel fumes swirling over the busy Perumbakkam Main Road (which stretches from Sholinganallur to Medavakkam).

A conspicuous number of black-headed ibises have been foraging for food on this side. Are these birds checking into a clean eatery or a grease pit?

(On April 8, with CMRL workers setting up boards and starting an activity, the black-headed ibises were not lingering on as long as they had in the preceding days. In the following days, though more CMRL boards have come up along this side of the wetland, foraging birds, including the black-headed ibises, have continued to show up).

As the black-headed ibis is versatile in terms of habitat choices, the species’ presence is hardly a reliable barometer of a habitat’s condition. The presence of water hyacinth however provides a more definite pointer to a particular condition.

On this side where the black-headed ibises are showing up oftener than before, the spread of water hyacinth seems wider than usual — a thought echoed by many regulars to the wetland — and this plant species thrives in water heavily laced with sewage.

“There are more nutrients available in the sewage — organic waste — that comes in, and that may cause a proliferation of water hyacinth, which in turn may provide food items for certain invertebrates,” says ornithologist V Santharam. “Black-headed ibis has a wide range of diet, including insects (arthropods) and other invertebrates.”

On most sides of the Perumbakkam wetland, the water betrays varying degrees of murkiness. As water hyacinths can float following the natural course of the water, concentration of water hyacinth in one area need not necessarily mean that section suffers from greater pollution levels. The presence of water hyacinth in one section of a waterbody/ marsh usually underlines that it has to be freed of sewage as a whole. Sewage may be flowing in from anywhere, and these inlets need to be identified and plugged.

A regular visitor to the Perumbakkam wetland — who wants to remain unnamed — calls to mind how following the catastrophic flooding in Perumbakkam, at least three channels were laid underneath the road leading to Global Hospitals to drain rainwater from a few Perumbakkam neighbourhoods into the wetland, from where, the it should flow into other channels that carry water all the way to Okkiyam Maduvu.

Though essentially speculative, this line of thinking is not distanced from reality, as misuse of rainwater channels is a recurrent issue in various parts of the city. Ridding the wetland of water hyacinth may be a predictably automatic response, but the intervention cannot stop there. The birder in question remarks how the Okiyyam Maduvu is not permanently healed despite regular efforts to remove the water hyacinth. After each exercise, the invasive species returns with a vengeance. The source of the problem — sewage inlets — has to be addressed. This birder also notes that the vegetation including the water hyacinth holds nests of jacanas and purple moorhens, and any intervention should not ignore this.

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