I have some further information about the owl that died of rat-poison. The chemicals were Brodifacoum and Bromadiolone, both of which are anti-coagulants.
These are “second generation” poisons, and cause death by internal bleeding. They’re both very potent, and are dangerous not only to rats, but to all mammals: cats, dogs, and small kids. And, as we’ve seen – birds, especially owls and hawks.
The antidote is Vitamin K, but it can take a 4-week course of treatment to cure a pet or a child.
The common brand names:
Brodicfacoum: FINAL, JAGUAR, PP-581, WBA 8119, d-con, Havoc, Ratak, Talon
Bromadiolone: Boot Hill, Bromone, Contrac, Maki, Rat-XB, Super-Caid, Super-Rozol
[Edited to Add: More information about the pesticides.]
In San Francisco, the SF Department of Environment permits the use of Bromadiolone on city-owned properties in the form of “Contrac All-weather Blox” — but only in a very restricted way:
For use only in City-owned sewer lines, San Francisco International Airport Terminal Areas, or for commercial lessees on city properties that are not adjacent to natural areas. In commercial establishments, use of product shall be a last resort after other, less-toxic measures have been implemented, including sanitation and trapping, and only where a significant public health hazard is recognized. In all cases, monitoring shall be used whenever feasible to minimize rodenticide use.
The other chemical, Brodifacoum, is not approved for use on city-owned properties.
The problem is that these chemicals are legal. San Francisco has a “Don’t Take the Bait” program in which they’re trying to get retailers and consumers to co-operate in not using the most dangerous formats for these poisons – but they’re still widely available.
Some of these poisons deliberately have delayed action, so that rats – who are pretty smart – will not realize that the bait is poisonous. That means that they go off after eating the bait, and then die over a period of days. They could die inside walls or under floors – or by being eaten by a hawk or owl or coyote or cat or dog when their weakness makes them easy prey. Then the bird or animal that eats them is at risk for poisoning. This happens a lot.
Sometimes, baits are set out in open trays, where any animal (or kid) who samples it can be poisoned.