Many people who use rodent poisons such as anticoagulant rodenticides (ARs) for pest control, either are not aware of, or do not consider the secondary effect it can have on other wildlife.
Newer ARs (SGARs) are so powerful, one single feed can be lethal. However, there is a time delay between the rodent consuming the bait, and it actually taking effect. It is during this time that predators such as owls and birds of prey can easily consume multiple poisoned rodents, in turn becoming poisoned themselves.
SGARs don't break down quickly - it can stay in tissues and organs for years, making it easier for these bigger animals to also ingest lethal doses. Birds that regularly eat mice and rats are at particularly high risk of SGAR poisoning. Even at less than lethal doses, toxins will still make birds clumsy and slower to respond to threats, less efficient at hunting and more likely to be hit by a car.
Globally, SGARs have been responsible for declines in many carnivorous mammals and birds - not just owls.
What can you do to help?
Check the label for active constituents in the rodent bait.
Less harmful first generation compounds include: Warfarin / Coumatetralyl.
More harmful second generation compounds include: Brodifacoum / Bromadiolone / Difenacoum / Difethialone / Flocoumafen - leave these on the shelf!
Encourage native predators. A couple of ways to do this is to install an owl nest box, or to plant native trees.
Make your garden less attractive and friendly for rodents. A few ways you can do this is by clearing away waste, pick up fallen fruit, do not leave pet food out and seal any cavities or potential entrances to your property.
Consider more friendly pest control, such as snap traps.
Check what products and methods your local pest controllers use, if you employ one.
Spread the word about bird-friendly rodent control!