Please don't give that wormer to your pigeon as it's highly toxic to some birds, pigeons being one of them. I know of several people that have lost pigeons from using it. I nearly lost one too but caught it in time and befroe giving the second dose. Most vets don't realize it's toxic to pigeons and doves.
A much safer wormer is ivermectin which is given once and then repeated in 10 days. Modectin plus, for example is safe and treats all worms.
There is plenty writtien about it, the follow as an example.
Fenbendazole From Wikipedia, the free encyclopedia
Fenbendazole (Hoechst brand names Panacur and Safe-Guard, Intervet Panacur and Panacur Rabbit) is a broad spectrum benzimidazole anthelmintic used against gastrointestinal parasites including roundworms, hookworms, whipworms, the taenia species of tapeworms, pinworms, aelurostrongylus, paragonimiasis, strongyles and strongyloides and can be administered to sheep, cattle, horses, fish, dogs, cats, rabbits and seals. Drug interactions may occur if using bromsalan flukicides such as dibromsalan and tribromsalan. Abortions in cattle and death in sheep have been reported after using these medications together.
ToxicityDespite being widely used as a dewormer in many species, toxicity has been reported. Birds (storks, pink pelicans, vultures, pigeons and doves) and reptiles (vipers, turtles and tortoises) have shown toxicity associated with bone marrow suppression, intestinal crypt cell necrosis and distal villi sloughing. Abortions in domestic ruminants have been associated with concurrent use of anti-trematode therapeutic agents.
Fenbendazole is poorly absorbed from the gastrointestinal tract in most species. The LD50 in laboratory animals exceeds 10 g/kg when administered orally.