Recent Avian Poisonings Suggest a Secondary Poisoning Crisis of Black Kites During the 1980s in Taiwan

Abstract

The Black Kite (Milvus migrans) has a limited distribution within Taiwan due to a dramatic population decrease during the late 20th century. Prompted by some poisoning incidents of Black Kites and other farmland birds, we hypothesized that poisoning may be an underreported yet important threat. Thus, we created a citizen-science Facebook group in October 2014 in order to receive more information about possible poisoning incidents. By September 2016, we had received reports of 4753 dead birds in 213 separate poisoning incidents in agricultural areas. The types of fields most often associated with poisoning incidents were direct-seeded rice (Oryza sativa), rice that was soon to be harvested, and red beans (Vigna angularis). We tested tissues from 29 dead small birds for pesticide residues. Twenty-eight birds contained carbofuran, and one bird contained terbufos, both highly toxic pesticides. Furthermore, of seven dead Black Kites tested from 2010 to 2016, four contained carbofuran, and three contained second-generation anticoagulant rodenticides. After interviewing farmers and reviewing older agricultural literature, we concluded that most of these incidents represented intentional poisonings by farmers attempting to control avian pests and rats (mostly Bandicota indica and Rattus spp.). We suggest that the Black Kites were likely the victims of inadvertent secondary poisoning incidents. The dramatic decrease of the Black Kite in the 1980s coincided with the rapid increase in the area planted with direct-seeded rice and the widespread use of carbofuran and rodenticides. The recent decreased use of these pesticides due to restrictions has coincided with the recent slow recovery of the Black Kite population. Therefore we initiated public awareness campaigns, and the Taiwanese government has adjusted some pesticide-use policies.