If you are out here in California and they are out in force, then they are probably western toads. It happens every spring. As long as you have a fishing license, you can collect them. You have a bag limit of 4 a day. As far as killing them goes, they are very helpful to farmers and to the ecosystem, and make great pets too. There is really no need to thin the population. They're not pests. They eat pests. Anyways, it's spring, and all the tadpoles just finished growing. By summer their natural predators will have done the job just fine and everything will be balanced again. Peace out.

P.S. Do they look like this?