Irish raptors have shown dramatic decline over the past half century, of which agricultural pesticides may be a major cause.
Placement of poisoned ‘meat baits’ on farms, as a means of killing foxes, is legal in Ireland, though poses a threat to many raptor species. The widespread use of poisons in rodenticides may be consumed in large quantities by species such as Barn owls, which have declined by over 50% in the past 25 years. A recent analysis of a Golden eagle corpse, which have recently been reintroduced to Ireland, showed toxin poisoning to be the cause of death. It is believed the bird fed on a nearby lamb carcass, laced with the toxin Nitroxynil.
Toxins threaten raptors in two ways: through direct consumption of unprotected meat baits, and through biomagnification, as pesticides accumulate over time in the body from eating numerous infected prey. Pressures such as habitat destruction and severe winters have further exasperated these problems.
Similar problems have caused drastic decline in species such as the Californian Condor, Brown Pelican, Bald Eagle and Peregrine Falcon. DDT (Dichlorodiphenyltrichoroethane) was a heavily used insecticide in the early nineteen hundreds, since banned in many countries due to it’s devastating effects on wildlife. Egg-shell thinning resulted in reduced reproductive success, and populations of several raptor species plummeted. The Californian Condor surviving only through a captive breeding programme, and pesticide use has since been increasingly regulated.
Though toxins such as those used in rodenticides are highly lucrative within the agricultural business, their effects must be intensely researched if we are to prevent harm to wildlife. To date, the Californian Condor project has costed over $35million, and whilst populations are increasing, they are still low. Barn Owls, Kestrels and Long-eared Owls are all noted as being particularly vulnerable to rodenticides, whilst ‘meat bait’ and general pesticide use further threatens raptor populations in Ireland. At present BirdWatch Ireland is at the centre of such issues, monitoring to identify further population decline, with continued conservation programmes helping many declining species.