M Sc Dissertation(WII)

Eight species of kingfishers, Common, Collared, White-throated, Pied, Stork-billed, Black-capped, Brown-winged and Rudy, - coexist in the mangrove forests of Bhitarkanika along the east coast of India. Sympatric species with similar resource requirements need to have niche partitioning as a strategy to avoid competition in order to coexist together. To understand the mechanisms underlying such species coexistence, it is vital to know about the food requirements, foraging habitat preference, and how the resources are shared between these sympatric species. The present study attempted to understand the potential mechanisms that might play a role in food-niche differentiation and examined the occupancy patterns of four sympatric kingfishers i.e. Common, Collared, Black-capped and Brown-winged kingfisher in Bhitarkanika mangroves. I conducted field study from January to May, 2011 in Bhitarkanika mangroves. The creeks were catgorized as primary, secondary and tertiary creeks based on the branching pattern. A total of 16, one km trails were selected in the intensive study area. Each 1 km trail was further divided into 10, 100 m segments for Sub-sampling. During the survey only seven among the 10 segments of each 1 km trail were surveyed which were selected randomly with replacement. A total of 160 creek segments of 100 m length were surveyed for six times during the study period and relevant habitat variables were recorded. For foraging behaviour observation, point count method was used i.e., an individual bird was followed till it captured a prey and relevant foraging variables were recorded. A total of 53 independent prey captures were recorded for the four species of kingfishers. Focal animal sampling method was used and observations were made opportunistically for time budget observation. Detection histories were constructed for each segment for bird survey and all relevant covariates. The two model parameters i.e., the probability that a segment is occupied by the species ('I') and the detection probability (P) were estimated and analysed in the occupancy framework. For foraging behaviour and time budget analysis, different parametric and nonparametric tests were used. Occupancy analysis confined that Collared and Black-capped Kingfisher occur seasonally in Bhitarkanika mangroves; Collared being more abundant in summer and Black-capped in winter. For all the four sympatric species river/creek width had a negative association with detection probability. Habitat type also affected the detection probability of all the species except Collared Kingfisher. The detection probability of Common and Black-capped Kingfisher decreased with the increase in depth whereas it did not affect the detection probability of Collared and Brown-winged Kingfishers. Water current and turbidity were negatively associated with the occupancy of Common and Brown-winged Kingfisher. However for Collared and Black-capped Kingfisher, it differed with vegetation layer. Perch height and foraging distance differed significantly among the four species of kingfishers. All the prey characteristics i.e., prey type, prey size and foraging substrate differed significantly among the four species of kingfishers. This study reveals that each of the four species of kingfishers in Bhitarkanika mangroves occupy foraging niches corresponding to their respective body sizes. The occupancy pattern and foraging behaviour of the smallest species, i.e., Common Kingfisher and the largest species, i.e., Brown-winged Kingfisher is more similar. As, both mostly forage in water to catch fish, their occupancy is also determined by water current. They segregate in terms of prey size, which is reflected by the respective body sizes. On the other hand, the foraging behaviour of Collared and Blackcapped Kingfisher is similar in terms of prey characteristics.

This study investigated the diurnal and seasonal activity pattern of water monitor, Varanus salvator in Bhitarkanika Wildlife Sanctuary, India. The study was conducted in an intensive study area of 17 sq.km selected after a pre sampling survey in the Sanctuary. The methodology involved to record the activity pattern of water monitor was monitoring of two permanent standard paths every three hours on diurnal basis. Sightings of water monitors were recorded while walking on the standard path. Behaviour of water monitor was divided into four categories such as basking, foraging, resting and non-foraging. Microhabitat of water monitor was recorded on each sighting. Ambient and substrate temperatures and ambient relative humidity were recorded along with diurnal activity pattern of water monitors. Results show a shift in diurnal activity pattern with season. The activity pattern of water monitor was unimodal in winter and uniform in summer. Basking was the major activity of water monitor in winter, whereas all the activities were evenly spread out in summer.The lizards used different microhabitats for different activities. Maximum lizards were recorded active at cooler substrate temperatures (29°C). The relation of ambient and substrate temperatures with activity was curvilinear. At low ambient temperature basking was prevalent. With increase in temperature other activities, such as foraging and resting were recorded. At high ambient temperature lizards selected cooler substrates. Ambient temperature and ambient relative humidity varied inversely. The activity was low at high levels of humidity It is concluded that behavioural thermoregulation plays a major role in water monitor’s activity.

M Sc Dissertation(WII)

Browse

Filters

Settings

Sort By

Results per page

Search Results