Chicken is said to be the favorite meat of choice for Deadly Nadder, who appear to benefit from a strict diet of poultry. It has been proven in Riders of Berk, that when fed chicken, a Deadly Nadder's speed and stamina can increase significantly, even to the point that one can come close to the speed of a Night Fury that is fed a diet consisting only of fish. Strangely, various sources state that Deadly Nadders will eat only poultry, and not anything else, although the film has proven this to be false, as before they were fed chicken, they ate fish, much like all the other dragons on the island. Chickens are known to be bred for their meat and eggs. However, Vikings believe that chickens are brainless birds. Chickens have shown to be protective and motherly, as in Animal House, they attempted to incubate Terrible Terror eggs.
In episode 10, Stormfly was shown to have increased her speed, to the point that she was even able to compete with the speed of Toothless. Astrid explains that she has been experimenting with her diet, and apparently it was working. Later in the episode, it is revealed that Stormfly has become faster because Astrid has been feeding her baskets full of chicken everyday, rather than fish. This indicates that chicken gives Deadly Nadders increased stamina and speed. Astrid still continues to give chicken to Stormfly, as it was shown in episode 13-"When Lightning Strikes".
Dragons: Race to the Edge
Tuffnut owns a chicken and they share a close relationship. After being bitten by a "lycanwing" (a play on the werewolf myth) Tuffnut believes he is turning into a dragon and to protect his friends he locks himself up in a chicken pen.