What comes to your mind when I say islands?
White sand, crystal blue water, swaying coconut trees with a gentle wind whistling through the leaves. Andaman, Maldives or maybe even Hawaii.
Fair enough. Oceanic islands are the ones that frequent the popular imagination. But they are not the only ones – river islands and lake islands!
Bangalore, dotted with its numerous water bodies, is no stranger to lake islands.
From 1110 acres to 892 to 446 and downwards, Bangalore lakes are of considerable size but varying nevertheless. Given the diverse lake dimensions, some lakes can be smaller compared to the larger ones such as Ulsoor Lake, Bellandur or Hesaraghatta Lake. However, both large and small lakes have islands built within their aquatic space.
Lake islands can be understood as primary roost sites for many birds – local and migratory ones. Birds need to feel safe in order to nest and breed. Human disturbance needs to be nil and Bangalore’s situation with regards to that factor needs no explanation. It cannot get worse.
Size matters – mound shaped and split ring lake islands
In such dire situations, having lake islands is crucial in ensuring safe resting and roosting areas for our avian friends. The larger the lake is, the more the island numbers could be. They could be of two different shapes – either a small, mound shaped one or it could have a split ring structure with water in the middle. Both are built by piling mud onto the earth’s surface as removing and relocating mud can be impossible as the soft lake bed will give away when any tractors ply on it.
While both kinds can be built in large lakes, the smaller ones cannot have the split ringed ones as their shape demands larger areas of water. Hebbal Lake, Madiwala Lake and Agara Lake can be found to have the split ring shape.
Hebbal Lake island split ring structure
Source: lakesofindia
Therefore, smaller lakes such as Kudlu Lake can afford to have mound-like structures of small size without jeopardizing the birds’ safety and protection.
Kudlu Lake island shaped like a mound.
Source: BBMP
You may still have a niggling doubt and wonder, if the lake is considerably smaller, how significant a role can the island play in ensuring safety to the birds since the lake shore will be much closer to the island itself? While that might be an important point to note, it is essential to realize that the lake islands serve one more crucial purpose.
Lake islands offer the necessary gentle slope margin
The lake islands offer a slope margin for the birds to wade into the lakes which is soon vanishing with the building of stone embankments that seal away the muddy area encircling the lake. As pointed out in an earlier article on the lake portal that talked about incorporating avian needs like the slope margin during lake rejuvenation process, birds have certain specific needs which can be ensured by the lake islands.
The slope of the margin needs to be gentle and not steep like those found at lakes with soup bowl designs. The soup bowl shape is given to lakes in order to secure proper containment of the water and is often accompanied with steep stone embankments. Such a design keeps out birds that require shallow waters. Different birds require different sloping margins, some shallow, while some with longer legs go for deeper areas. If we plot the slope margin requirements of different birds that enter the lakes, we get a beautifully spaced out, often overlapping areas where each bird prefers to stand.
By erasing the gentle sloping of the lake shore, we cut the avian wildlife by half (or more) as shore birds with shallow water requirements are discouraged from visiting the lakes.
Notwithstanding the steep lake shore embankment, the lake islands ensure that the descending sides of both the earth mounds and the split ring islands offer the gentle slope margin thus accommodating all avian life.
Such subtle interactions between our lakes and wildlife need to be recognized for fostering a healthier biodiversity-rich lake ecosystem.
Join us on our journey Wake the lake project as we set out to learn about our Bengaluru lake ecosystems and further revive our city’s dying lakes.
We gratefully acknowledge the various inputs and insights provided by Dr. MB Krishna towards the formulation of this article. He is an ecologist, ornithologist and a lake conservationist.
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