Developing the homing pigeon (Columba livia) to assess the effects of xenobiotics on avian species

The exposure of birds to chemicals from anthropogenic sources can sometimes be lethal. However, relatively few studies have been conducted on the effects of sub-lethal, environmentally relevant exposures on individual birds and bird populations. Homing pigeons were developed as a test species in several experiments to assess the effects of environmentally relevant, sub-lethal exposures to xenobiotics on flight, reproduction and development with implications at the population level. Time of flight analyses were performed with mitochondrial inhibiting chemicals that can be found in mine wastes including cyanide and arsenic. The results for both sets of experiments showed a dose-dependent increase in flight time in pigeons exposed at doses of 0--2 mg/kg. Subsequent to arsenate exposure the pigeons were utilized for trials on reproductive effects looking at fertility measurements, embryonic development with counter-stain and reverse-transcriptase-polymerase chain reaction techniques, and post-hatch weight measurements. Findings included a late expression of skeletal alpha-actin, a developmental marker, and a significantly lower 1-day post-hatch weight in chicks from arsenate exposed birds. A final study was conducted comparing the effects of carbofuran, a cholinesterase inhibiting carbamate, and diazinon, a cholinesterase inhibiting organophosphate, on time of flight. The results indicated a dose-dependent increase in flight time associated with carbofuran exposure at 0--2 mg/kg subtle or no effect with diazinon at 0--2 mg/kg. In conclusion, homing pigeons were good subjects for making observations and providing data consistent with what would be expected from current toxicological knowledge.