Hello and welcome to PT
There's always an advantage in getting fecal floatation of your birds' droppings done if you suspect internal parasites cuz' then you can use specific drug to target specific worms. But if that's not your choice then Moxidectin Plus is the dewormer of choice. Not all dewormers are safe for pigeons and doves even if they're safe for other birds. Moxidection PLUS is the one which is safest and is broad spectrum dewormer which kills all internal parasites. It also helps to kill external parasites too. Rotating it with some other safe dewormer is needed so that wroms don't develop resistance. Deworming is advised once in six months.
For external parasites,you can dust the birds with carbyl or permethrin dust...sevin dust be easily available brand. It will kill all external parasites within 15-20mins. You can also regularly add ivermectin in birds' bathing water and it will keep parasites away.
To your other question, avoid using any supplement which has alchohol in it. Pigeons and doves are different from all other birds. You can buy supplements made specially for pigeons available on pigeon supply places like Jedds, New England, Foys and several others to name. Google them
Thanks for the help! Another question, i found a few red bugs on one of my pigeons that resemble fleas but are long and thin. I believe they are the bird's version of ticks or fleas. What kind of powdered medication can I use to kill them or treat them? Also, I think more of my birds might have caught them. So id like to treat them all if possible (8 Rock Pigeons). Thanks
Sounds like Louse, are found on flight/tail feathers... For all the external parasites you can dust your birds with insecticide dust and all will fall off. For pigeons carbryl or permethrin dust can be used on the body below neck so that it doesn't get into eyes,ears and nostrils.
When you dust or deworm, treat all the birds at the same time.