Kaytee Exact is a brand of formula made for parrots but works really well for pigeon babies too. It's not as good as some homemade formulas but I always have it on hand. I've raised dozens of rescued pigeons and doves with it
Never used formula with a chicken though, I've tubed fluids but that's it. Not sure if there is even a formula that is recommended for chickens? Chickens are able to eat better then pigeons with crossed beaks in my experience! Just make sure there is access to a water sorce that is easy to drink from by dipping their beak in. The nipple-style seems like it would be very difficult.
