Unfortunately, it is still too easy to buy toxic baits that can cause much secondary poisoning of wildlife, pets, and even people. Many studies have documented that the anti-coagulants in these baits result in the painful death of native predators including raptors, small and medium sized carnivores and more. Sadly, these are the very species that have evolved to react to increasing rodent populations.
The rain will help increase the population because rodents—and especially roof rats—will have a lot more food in the form of fruit. And the denser vegetation cover (e.g., ivy) will offer refuge. Mice and rats easily adapt to drought, so increased availability of water shouldn’t make much of a difference.
Unfortunately, rodenticide in bait boxes is a convenient way pest management professionals treat rodent infestations in an areawide way. We’d be better off encouraging raptor establishment! It's not too late to take steps to protect our native wildlife from unnecessary poisoning and a painful death.
Fortunately, there are non-toxic alternatives and one of the main things that can be done is to educate people to avoid rodenticides and promote healthy wildlife populations and habitat.
A very reliable web site, Raptors are the Solution includes an alternatives and tips page with very good information. Find some alternatives that best fit your situation and share them with others. Encourage local gardening and other businesses to remove toxic baits in favor of education and other alternatives to more efficiently deal with pest damage.
CDFW Rodenticides and Wildlife Website