Wildbuzz | Mantling against pirates

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Birds of prey or raptors have colourful terminology to describe their behaviour. The vocabulary for raptors is rich due to the use of such birds for falconry and hawking – Shakespeare adapted many terms from falconry to suggest the human situation in his plays.

One such term is ‘mantling’, when the hawk or falcon or eagle has killed and seeks to hide and protect the food from other raptors or from foxes and dogs. In fact, raptors are opportunistic and snatch food procured through sheer hard hunts by other raptors or non-raptor bird species, depending upon larger size or number strengths, and that is termed as ‘piracy’ or pirating food.

In the classic mantling posture, the raptor uses its wings and tail to form a kind of umbrella over the kill or cloak it, and can resemble a female hunched over protectively while incubating eggs. According to bird behaviour expert, Melissa Mayntz, a raptor’s “wings are mostly spread and drooped to the ground, exposing the bird’s upper back, also called the mantle, which gives the action its name. The head is usually bent down to feed, and the tail is often spread and drooped to provide additional cover and counterbalance…While they are feeding on ground, particularly in open fields, rocky ground, or similar areas with less shelter or cover to provide natural concealment, the birds are more exposed.”

A posture of mantling by a migratory Booted eagle on a Gadwall duck kill was observed at the Gajoldoba wetland, West Bengal. The eagle could not carry the kill away to a safer perch and ate the duck in the open, exposed on the banks. “In this case, I also suspect that apart from the mantling posture, the eagle was trying to dry its wings by spreading them as it had splashed into water while swooping down on the duck to capture it. Without the wings dry, the eagle would have found it difficult to fly,” Dr Nisarga, the photographer, and chief cardiac surgeon at KIMS Hospitals, Hyderabad, told this writer.

A three-banded emerald jewel damselfly (Aristocypha trifasciata) at Palampur, HP. (PHOTO: PARVESH SINGH RANA)
A three-banded emerald jewel damselfly (Aristocypha trifasciata) at Palampur, HP. (PHOTO: PARVESH SINGH RANA)

Pollution inspector

If you see this creature nosing and buzzing silently around a wetland in good numbers, you don’t need the pollution control board to send an inspector to ascertain aqua purity or the extent to which human activities affect a freshwater resource.

The world over, aquatic insects like damselflies and dragonflies are relied upon by scientists as bio-indicators to arrive at a preliminary assessment of water quality. To assess water quality through these natural indices serves scientists well as it is low-cost research, obviating dependence on analytical studies of aqua health, which are costly and time consuming.

The creature in focus is the damselfly, which is lesser known, looks quite like the dragonfly but is subtly different from the latter. An estimated 498 species of damselflies and dragonflies falling under the insect order, Odonata, occur in India, of which 186 species are to be found only in India.

“The damselfly lays eggs in clear water and its nymphs (young ones) develop in water. The nymphs feed on mosquito larvae, lending the damselfly the agency of a biological pest control agent. If the water is not clear, damselfly numbers will decline due to impaired breeding success. Under the aegis of the National Mission for Clean Ganga, we carried out a research study over an 85-km stretch of the Upper Ganga (a Ramsar site) to assess aquatic insect biodiversity and biomonitoring of water quality. Our study found that insects such as damselflies showed declines over the river stretches that were polluted,” professor VP Uniyal, an entomologist from the Wildlife Institute of India, Debradun told this writer.

vjswild1@gmail.com

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