Every year, during the monsoon season, the Dheerpur Wetland Project (DWP) site undergoes a drastic transformation in its appearance. Torrential rains and stormwater flowing into the wetland from surrounding areas lead to flooding in most parts of the wetland. During this time, the DWP site also serves as a habitat for a variety of wetland bird species, many of which are seen only during the monsoon season. How do we know this? The Centre for Urban Ecology and Sustainability (CUES) carries out periodic bird surveys at the DWP site. The CUES birding team, consisting of three Researchers, use binoculars, spotting scopes, rangefinders, and bird books to spot, identify and count birds in the wetland. These periodic bird surveys have yielded valuable insights into bird ecology, and the data obtained serves as a yardstick to measure the progress of restoration efforts at the DWP site.
The sampling protocol for bird surveys was designed by CUES keeping in mind the area and habitat features of the DWP site. Further, since most birds are known to be diurnal, our sampling protocol requires all bird observations to be gathered during the day, and the data gathered so far is reflective of this. However, our curiosity got the better of us and we wanted to see if there was any bird activity in the DWP site at night. And so, we decided to try a novel method to observe birds at night. The method involved identifying specific spots in the wetland around which there was maximum bird activity during the day and setting up camera traps at those spots. The camera traps used were infra-red flash cameras with heat-in-motion sensors, which trigger every time an object with a temperature different from the ambient temperature creates any sort of movement in front of the camera. We identified 3 such spots, with all three being located in the DWP site’s largest water body.
What seemed like a straightforward and uncomplicated task, was not so straightforward after all. Wearing knee-length rubber boots and an additional water-proof plastic layer inside our boots should the water seep in, we ventured into the waterbody. After a few wobbly steps, we soon realized that the water was a lot deeper than we had expected. Sure enough, within a matter of seconds, our boots swallowed litres of water! As we made our way through the waterbody, we were weighed down not only by our water-filled boots but also our feet met with a lot of resistance from a dense web of water plants that had grown in the waterbody. It almost felt like these plants were hell-bent on not allowing us to progress on our mission. However, after some effort, we were able to reach the three designated spots to fix the cameras. We drove wooden poles into the ground, and with the help of nylon belts, fastened the cameras to the poles at a desirable height. Our camera trap stations were set up and the mission had begun.
After nearly 10 days of camera trapping in the DWP site, our results were very fascinating. Of the three camera trap stations, one of them showed evidence of bird activity at night. At this trap station, two species – Red Wattled Lapwing (Vanellus indicus) and Black Crowned Night Heron (Nycticorax nycticorax) – were seen at various times through the night. While Black Crowned Night Heron sightings were infrequent and mostly of solitary individuals, Red Wattled Lapwing sightings were frequent and often consisted of more than one individual. However, it is worth mentioning that this camera trap station was set up on a small sand embankment in the water body. At the other two camera trap stations, which were in the midst of the waterbody, bird activity was almost negligible during the night. Our camera trap images from these two trap stations showed that birds were inactive for roughly 13.5 hours from about 1700 hours to 0630 hours.
Besides this night data, we were able to gather valuable insights into other species that are seen during the day. Some of the other species we were able to capture on the camera traps were Common Moorhen (Gallinula chloropus), Gray-headed Swamphen (Porphyrio poliocephalus), Black-winged Stilt (Himantopus himantopus), Cattle Egret (Bubulcus ibis), Indian Pond Heron (Ardeola grayii), Asian Pied Starling (Gracupica contra), Bank Myna (Acridotheres ginginianus), Common Myna (Acridotheres tristis), Lesser-whistling Duck (Dendrocygna javanica), Bronze-winged Jacana (Metopidius indicus), Rock Pigeon (Columba livia), Eurasian Collared Dove (Streptopelia decaocto) and Black Headed Ibis (Threskiornis melanocephalus).
I would like to thank my colleagues Vipin Kumar and Shashank Bhardwaj for being an asset during field work. Their enthusiasm and knowledge of the wetland motivated me to venture into the waterbody to undertake the camera trapping exercise with them.