Effects of Parental and Direct Methylmercury Exposure on Flight Activity in Young Homing Pigeons (Columba livia)

Abstract

Mercury is one of the most common metals found in contaminated ecosystems. It occurs naturally, but high levels found in contaminated areas derive from human use practices. Among the most vulnerable species to exposure are birds that live, nest, or feed in or near these contaminated ecosystems. Because of the known neurological effects of mercury on birds, it is hypothesized that effects upon migratory ability would be evident after exposure to low levels of this metal, and effects may be exacerbated in young birds. Difficulties in following mercury exposed birds once they migrate away from contaminated areas have left investigators with insufficient data to establish exposure levels causing injury of migratory species due to migration disruption. Breeding pigeons were exposed to ~1.0 mg/kg/day methylmercury via the drinking water, and first round offspring were trained to home after fledging, while also continually exposed to methylmercury. The young pigeons were released individually for three flights, and flight times were assessed and compared to control young pigeon flight times from 3.5, 9, 21, 53, 65, and 98 air miles as well as two individual flights at ~50 air miles from multiple directions. Results indicate that methylmercury exposed birds exhibit slower flight times than controls during the initial flight, and generally improve on successive flights at each distance and direction. This may suggest orientation impairment and allude to migration disruption in migratory species.