Friday, August 10, 2007

PS 72-3: Does gregarious foraging impacts on a feeding efficacy of the Indian black ibis?

Vinod C. Soni and Sachin N. Vyas. Saurashtra University

Introduction and Objective: Our preliminary observations revealed that the Microhabitat “garbage heaps” (GH) was exploited extensively over other foraging grounds by The Indian Black Ibis Pseudibis Papillosa (Ibis). We studied Ibis under normal environment to assess the impact of gregarious foraging on the feeding efficacy. Methods: Adult flock foragers were observed applying focal animal sampling method during 06:00 and 18:00 hours in 1988. Data were recorded following a sampling period and interval of 5 minutes each. Observations began with the feeding strike of the focal bird. All foraging activities were recorded with the help of 12x50 a pair of Super Zenith binoculars and Sanyo 1012 mini recorder. Time spent on each defined behavior was recorded with the help of 1/100th second accuracy Siko stopwatch. We assessed food density, flock size, efforts made in search of feeding spot, and interactions at GH. Results: Probing, a non-visual tactile method was the chief foraging technique applied with the rate of 90% time. Monthly flock size was 237 ± 124.23 in a square mile area of GH. 51.5 ± 43.07 food matter (insects/larvae) recorded in a square meter quadrant. Significant relationship (r=0.72) between the food density and number of Ibis was found. 11 ± 2.12 feeding attempts/min with the success rate of 78 % were made. 3 ± 1.31steps/min were made in search of food. A total of 01.69 % foraging time was budgeted in interactions. Crowding had a positive correlation with the occurrence of interactions (r=0.88), whereas a poor correlation was found between interactions and feeding attempts (r=0.05, df=116). Conclusions: Ibis is a communal tactile forager. Prey abundance sustains large flock size and keeps low prey search efforts. Agonistic behavior was common as supplanting each-other, but our study suggests no significant influence of gregarious foraging on the feeding efficacy.

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