There are many Black Rats (Rattus rattus) around this year (2022), and quite a few are being found outdoors and moribund. That is typically because they are dying from anti-coagulant rodenticides. If you see a rat out in daytime, some action is desirable.
The readily available 'second generation' anti-coagulants such as Brodifacoum and Bromadiolone (also Difenacoum and Difethialone) make the rats and their carcasses dangerous to birds. Many owls and other predatory birds have been killed. You can do two things to reduce this impact.
- Dispose of the rat where birds cannot get the carcass (killing the ones that are still alive will reduce their suffering);
- Use, and encourage others to use, less damaging rodent control methods. Other methods include exclusion barriers (eg rat-proof your compost bin and chook yard/feeder), setting traps, or using baits containing safer chemical agents. First generation anti-coagulants such as Warfarin (also maybe Chlorophacinone or Diphacinone), are usually available from the same outlets that sell second generation compounds. In some cases, non-anticoagulant toxins may be in use, i.e. bromethalin, cholecalciferol and zinc phosphide but these are rarely available for household use.