Lotus paddies play an important role as habitats of wintering waterbirds in Japan. However, feeding damages of lotus roots by ducks and coots brought about conflict with farmers. The purpose of this study is to examine the effect of bird-nets protecting lotus roots from waterbirds feeding damages using the numbers of individuals in the fields as an index.

We set 80 survey fields, 48 fields with bird-nets and 32 fields with no net, in Ibaraki prefecture, central Japan. Counting surveys were conducted 12 times at night (20:00-25:00) in February to March and October to December of 2011. Zero-inflated Poisson models were built to analyze environmental determinants of the numbers of waterbirds. Response variables were numbers of waterbirds (total and each species), explanatory variables were net setting and other environmental factors. Bayesian estimations were calculated by the MCMC method.

Ninety-five % confidence intervals of zip parameters overlapped between net categories, therefore bird-nets had little effect on prevention waterbirds from entering lotus paddies. Large mesh-size for medium-sized birds and spaces between net and the field would be the main causes of the result. In poster session, we will discuss the appropriate management for waterbirds feeding damage.