International Journal of Biodiversity and Conservation Vol. 4(1), pp. 15-21, January 2012 Available online http://www.academicjournals.org/IJBC DOI: 10.5897/IJBC10.097 ISSN 2141-243X ©2012 Academic Journals Full Length Research Paper Population sizes of cotton pygmy-goose Nettapus coromandelianus coromandelianus Gmelin in some places of Assam (India) Upadhyaya S.* and Saikia P. K. Department of Zoology, T. H. B. College, Karchantola, Sonitpur (Assam), PIN-784189, India. Accepted 29 November, 2011 The breeding season is of paramount importance to the population size of waterfowl. All of the increase in population size occurs, as does much of the mortality during that season, which is often but a fraction of the entire year. Population of a species is indicative of the environmental factors of that area which strictly influences the species. The study includes the population size of the Cotton Pygmy- goose Nettapus coromandelianus coromandelianus Gmelin, a least concern anatid of South-east Asia and near relatives of Pygmy-goose of New South Wales which is under threatened condition. The study also includes the parameters influencing the population sizes. Two hundred and three (203) Cotton Pygmy-geese were observed during breeding season in 2006 and 2009 in study sites of Assam. Adult survival rates were found high 0.99 to 0.94 (SE < 0.005), but duckling survival was much lower, varying from approximately 0.1 to 0.3 during 2007 to 2009. No naturally died specimens have been collected during the study period, but 7 specimens have been reported to be killed by hunters among a total of 22 gooses were killed during 2006 to 2008. The present paper deals with the population dynamics of Cotton Pygmy-goose with special mention of the factors affecting their survival. Key words: Breeding, environmental, mortality, population, waterfowl. INTRODUCTION The Cotton Pygmy-goose (CPG) is a non-migratory neighboring countries to the east, but to be rare in dabbling duck (Anseriformes: Anatidae: Anatini) endemic Malabar, the Bombay Presidency, and Kathiawar to South-east Asia. Compared with the other dabbling (Abdulali 1962). The N. coromandelianus ducks, the species has fairly high power of flight and coromandelianus Gmelin is distributed with a breeding other terrestrial adaptations. It is fairly common during the habitat in South Asia, East and South-east Asia with a cold weather until the end of April and was observed in population of 125,000 to 1,100,000 (Delany and Scott, the inland tanks, with overgrown water plants in 2002). The South Asian sub-species have 1% level at Tinnevelly district of South India (Fleming, 1898). 1,000 (Li and Mundkur, 2007). The Australian species of Parrington (1903) and Gibson (1908) observed the Nettapus that is to say, N. albipennis is solely distributed distribution of CPG in Sind. Bacon (1908) has observed within the Australian rage with breeding capabilities and three CPGs in the Konkan (Western India). Mitchell has a population of 7,500 with 1% level at 75. The African (1914) observed the CPG in a region so far removed Pygmy goose, N. auritus is distributed in West Africa, from his usual habitat and detected two CPGs in Southern and Eastern Africa and Madagascar. Its Kashmir. In Blandford’s Fauna (1898) the CPG was said population in Southern and Eastern Africa is estimated to to occur throughout the greater part of India, and be in between 100,000 to 250, 000 with 1% at 1,750. In Madagascar, N. auritus has a population range of 5,000 to 10,000 with 75 at 1% level. The Green Pygmy-goose, N. pulchellus is distributed all over the Northern Australia *Corresponding author. E-mail: [email protected]. and Southern New Guinea (Perennou et al., 1994). 16 Int. J. Biodvers. Conserv. The CPG has a large population estimated to be 59,000 - binoculars (20 × 50) and tally counter was used as per requirement. 1,100,000 individuals with an estimated global extent of 1,000,000 - 10,000,000 km2. Global population trends Brood monitoring have not been quantified, but the species is not believed to approach the thresholds for the population decline During the breeding seasons in 2006, 2007 and 2008, broods were criterion of IUCN Red List. For these reasons, this checked daily around the Kadamani wetland using a telescope species is considered as Least Concern (Birdlife (Tasco 25 × 30) and binoculars (20 × 50). In 2006, brood sightings International 2004). The sub-species N. coromandelianus were recorded incidentally, approximately four times per week. Adults were identified and all ducklings were counted and assigned coromandelianus Gmelin occurs in South-East Asia with to an age class based on plumage characteristics as per Gallop no record of occurrence in Australia. It is resident but and Marshall (1954). Age categories included: stage-I) the downy local, practically throughout the Indian Union, both stage from 1 to 3 days; stage-II) ducklings in full patchy black and Pakistan’s, Nepal terai, Ceylon, Straggler to Andaman white feather covered; and stage-III) the fully, more or less grey and Maldives Island. It is distributed from plains to c.300 feathered post-fledglings. meters altitude. Though commonest in Pakistan, Punjab and Rajasthan but not recorded from Kerala till 1983 (Ali Mortality factors and Ripley, 1983). The CPG is widely distributed within its range, with 8 All ducklings and adult carcasses incidentally found on the studied sites meeting the 1% criterion in India. A large area were collected and preserved in 10% formalin for further concentration of birds was reported at Chilika Lake in study. Carcasses were measured, given external examinations and India with peak count of 30,534 during 2002. During 2003 later covered by earth. and 2004 the peak count was made with 2,088 and 4,000 at Denua in Orissa and Kallur Tank in Karnataka (Li and Data analysis Mundkur, 2007). Its population is going to be more or less vulnerable to be as threatened from the chance events Data collected during the study period (pre-breeding period, such as severe weather, diseases and other natural as breeding period and post breeding period) were used in the analysis. Survival and detection probability can be estimated for well as, anthropogenic activities as predator. Nesting multiple periods within a year. Adult survival (φ) probabilities were success and duckling survival also are difficult population estimated over three months time periods as per White and parameters to estimate. Nests are well concealed in the Burnham (1999). The estimate of survival is actually non-apparent tree holes, and the duckling in the feeding condition is survival, because Cotton Pygmy-goose emigrates from the wetland very difficult to detect as they frequently dive under the to the nearest trees or wetlands nearby. water. The protocol for monitoring Cotton Pygmy-goose has not been quantified in the studied wetland prior to this study, except the The study of the population extent of the CPG from the records made during 2004 to 2006 (Upadhyaya, 2006). Population North-Eastern region of India is quite irregular since the estimates were made based on detection probability obtained from past. Maximum count during 2001 to 2005 was found at census data collected by point count method as per Bibby et al. Kokilamukh (Jorhat district) of Assam and was 72 in the (1992) and Javed and Kaul (2002). Multiple surveys were year 2004 (Rahmani and Islam, 2008). The present paper conducted within a time period from 2006 to 2009 to estimate discusses the present population sizes of CPG in relation population size by calculating the average number of goose seen for a given period, divided by the mean detection probability for that to the mortality factors affecting their survival in the study period, with the variance of a ratio (Seber, 1982): area during 2007 to 2009. Ni = ni /dmi METHODOLOGY Where ni is the total of known birds observed and dmi is the detection probability. Assumption was made that detection Study sites probability, which relates to Cotton Pygmy-goose’s breeding phenology, remains constant per period since no data was Sixteen wetlands of Assam were selected for the study of recorded in the past from the studied wetland. Although this population of Cotton Pygmy-goose during 2006 to 2009. Mid-winter assumption may be violated some years due to variation in counts were made in Ajala suti, Belsiri, Boalmari, Borsola, Dhandi, breeding conditions, it does not provide estimates that suggest Gajalmari, Kankati, Ouguri, Rikamari, Sahala, Samarajan and population trends. Satajan. Seasonal counts were made at Bordoibam Bilmukh, The old-aged trees irrespective of species but with distinct Dighali wetland, Kadamani wetland and Kuwari fish culture pond. hollows or holes (natural or made by wood peckers) were visited during the breeding period in 2007 and 2008 to locate nests and determine nest success. Hatching success was determined by Population monitoring counting the number of egg shell membranes and unhatched eggs remaining. Eggs were counted at some active nests, but were not Surveys removed or handled to reduce the risk of damage or attracting the predators. Because of these constraints, ‘apparent nest success’ Three days continuous survey were made since 2007 by walking was reported instead of Mayfield’s daily survival rates for nests around the wetlands and counted all the goose visible around each (Sargeant and Raveling, 1992). Again apparent nest success rates wetland, beginning early in the morning one hour before sunrise till were often inflated, because many nests were destroyed before completing the round of each wetland. Birds were counted using they were found. Calculation of daily survival rates of nests Upadhyaya and Saikia 17 Figure 1. Population estimates of Cotton Pygmy-goose in selected sites of Assam, 2007 – 2009.