White- Headed Duck Population Dynamics Modeling (Case Study: The Wetlands of Golestan Province, Iran)

The white- headed duck (Oxyura leucocephala) is a globally endangered diving and migratory duck. Fluctuations of bird populations in wetlands occur because of hunting, climate, quality and quantity of habitat, disease, and security. Stella software was used to model the population dynamic of this species over a period of 18 years. The exponential growth rate of this species based on a regression equation was obtained. First, the exponential growth rate of O. leucocephala was used based on a regression equation in which climatic parameters played important part. Then, the model was run by different hunting rates, and the population was modeled for the next 50 years. The results show when hunting rate is constant in each year, rates higher than 0.7 cause the lowest annual population size, and the rate 0.9 causes population obliteration after 38 years. In the basic model, the rate 0.72 could be suggested for hunting to have a minimum constant population size, but in the second model, the standard deviation of six climatic parameters, and a random number was used. Therefore, the rate higher than 0.7 causes decline in the population below 10% (10 individuals) over a 6 years period. Thus, a mortality and hunting rate of below 0.7 for this bird is needed for this bird based on the second model that is more close to reality. However, because of the lack of environmental parameters that directly affect the survival of the bird to be used in the population modeling, we suggest that this species should be urgently put in the highly protected list of the Department of the Environment.