The "jungle cock" is the male version of the "jungle fowl", a bird which as its name suggests, lives in the jungle, particularly jungles in South Asia and Southeast Asia, and is the original ancestor species of the domesticated chicken.
Much like the peacock and the peahen among the peafowl (to which the jungle fowl is closely related), the jungle cock is extremely colorful, and has an extravagant fanning tail, whereas the jungle hen is plain and brown.
The tail feathers of the jungle cock are particularly valued by fly fishermen, for the purpose of making fly fishing lures. The "eyes" on these feathers are much smaller than the eyes on peacock feathers, and thus jungle cock feathers seem particularly easy for fish to confuse with the tasty baitfish.
Due to the dramatic shrinkage of its jungle habitat in recent decades, the jungle fowl is actually an endangered species, so killing a jungle cock or trading them across international borders is illegal. However, flocks of domesticated jungle fowl are raised commercially, particularly in England, to supply coveted jungle cock feathers to the fly fishing industry.
Feathers are usually taken from live birds without harming the animal, although birds are also sometimes slaughtered to sell their entire skin and feathers as jungle cock "capes".
A single jungle cock feather (a "spear") with high-quality "eyes" can sell for as much as $15, and a complete jungle cock "cape" can sell for as much as $200.