Depends on the type of rodenticide. Most OTC bait is anticoagulant and lethal dose depends on body weight. If they don't consume the necessary amount they just end up with an upset stomach. There is no "slow kill" There are however stronger baits with different modes of action. What brand bait did you put out and what was the active ingredient?

The New England Wildlife Center says 25% % of the birds of prey admitted to their hospital have been poisoned by rodenticide.

From their page: this surprised me****

Hello friends, yesterday we admitted an American Bald Eagle in critical condition. I am so sad to tell you, that while this eagle had severe injuries, rodenticide (rat) poisoning was likely the underlying cause of his death. There are only 70 nesting pairs of Bald Eagles in Massachusetts. This terrible tragedy was entirely preventable. Many environmentally safe rodent control alternatives are on the market today that do not adversely affect the birds of prey or large mammals that feed on them. Please help us get the word out. Rodenticide kills hawks, owls… and the American Bald Eagle. It also harms and is fatal for dogs and cats.

When the American Bald Eagle was admitted, a full veterinary work up was done, our veterinary team found several life- threatening injuries, one of which caused a large amount of blood loss. Further diagnostics revealed a delayed blood clotting time which indicates exposure to anticoagulant rodenticides, aka rat poison. Unfortunately, due to the extent of his injuries our vet team made the difficult decision with the Massachusetts Division of Fisheries and wildlife to humanely euthanize him and end his suffering.

Unfortunately, rodenticide poisoning has become a very common problem in many species of wildlife, including birds of prey. We see it hundreds of times a year in our hospitals. Anticoagulant rodenticide toxicosis occurs when animals either eat rat bait, such as “D-Con”, directly or eat a rodent that has ingested the bait.

Secondary poisoning is the most common cause in birds of prey since poisoned rodents become easy targets.

The poison works by inhibiting the normal clotting process, which leads to uncontrollable blood loss from even minor wounds. The extreme blood loss can make the animal weak and susceptible to further injury and if left untreated ultimately death.

This year if you have to address a rodent control problem in your home or business, please do your homework and make sure you choose a method that does not harm wildlife. Thank you.