Effects of water level changes and wading bird abundance on the foraging behaviour of blacknecked storksEphippiorhynchus asiaticus in Dudwa National Park, India

Abstract

The effect of water level changes and wading birds' abundance on the foraging behaviour of the blacknecked stork (BNS) Ephippiorhynchus asiaticus was studied from January 1995 to June 1997 in Dudwa National Park, Uttar Pradesh. Our observations indicate that BNS territoriality increased as food levels became depleted, resulting in increased rates of aggression towards intruders. Chasing or aggression was more intense during the early period (February and March) than the late period (April, May and June). Most of (> 50%) the aggressive encounters were observed between 0600 and 1000 h of the day. Seventeen species (including BNS) were observed interacting with BNS, throughout the study period. Most interactions were with the spoonbill, Platalea leucorodia (67.4%), followed by the whitenecked stork, Ciconia episcopus (16.6%). The distance (while foraging) between BNS and other wading birds varied significantly (P < 0.001) between years indicating that BNS and other water birds foraged at different water depths and thereby explored the wetlands fully. Spoonbills were chased often; the number varied from 1 to 43 birds. BNS occasionally accepted the presence of other wading birds, including spoonbills and started foraging amidst them. This led to successful foraging of BNS (solitary feeder). Other fish-eating bird species and their numbers also limited the food consumption of foraging BNS as they had to spend time chasing away the intruders. Availability of the preferred prey fish species, Heteropnestus fossilis, forced BNS to stay throughout the year in their respective territories. High (> 60 cm) water levels were not suitable for BNS even though the patch had high prey abundance.

Time-activity budget of the Black-necked Stork Ephippiorhynchus asiaticus during non-breeding season in India

“…It is reckoned that food availability is the most important limiting factor for storks in almost all aspects of their ecology, including distribution, longevity, breeding success and population numbers (del Hayo et al, 1992). In Dudwa, foraging bouts of the Black-necked Storks were greatly affected by the presence of other fish-eating birds (Maheswaran & Rahmani, 2001). Prey abundance in most of the wetlands attracted other fisheating birds.…”

“…Knowledge about the daily activity pattern of the Black-necked Stork is very essential in order to conserve the species as it declined drastically in the whole of the SouthEast Asia, and especially in India (Maheswaran et al, 2004). In India, ecological studies on Black-necked Stork have been conducted at Keoladeo National Park in Rajasthan (Ishtiaq, 1998), Dudwa National Park in Uttar Pradesh (Maheswaran, 1998;Maheswaran & Rahmani, 2001, 2002& 2005 and in Etawa and Mainpuri districts in Uttar Pradesh (Sundar, 2003).…”

Status and Diversity of Birds of Ramna Park, Dhaka, Bangladesh

“…For the avian fauna of Tilyar lake, Rohtak (Haryana, India), Singh and Laura (2013) reported the highest values of diversity indices in the month of December and lowest in the month of July. Another study found that high species diversity in December may be presence of migratory birds for food, proper foraging and breeding sites (Maheswaran andRahmani 2001, Albores andSiguenza 2011). On the other hand, high temperature, low food availability and local migration of migratory avian fauna to nearby agriculture fields for food may be the reason for low species diversity in the month of July (Maheswaran and Rahmani 2001).…”

Effect of water level fluctuations on temporal-spatial patterns of foraging activities by the wintering Hooded Crane (Grus monacha)

“…Simultaneously, mudflats have become the main stopover for cranes foraging [32]. As water level rose again, food resources could not be obtained and waterbirds opted for other habitats for foraging [7]. The Hooded Cranes turned to meadows, increasing the foraging time to get sufficient energy.…”

“…For many waterbirds, fluctuations in water levels change birdperched micro-habitats [5] and directly affect the length of exposure to and availability of food in these habitats [6,7]. Their foraging activities are also affected by human disturbance [8,9].…”