Beastmaster's Hunt: The Crane

Drop rates for these are ridiculously low at the start of 5.1, which they will hopefully fix.

Pristine golden crownfeathers are found at the Cradle of Chi-ji (where the August Celestials Red Crane dailies are: 31, 63).
Pristine jet crownfeathers can be found at the spires close to the Anglers dailies (64, 47 and 73, 44).

The drop rate is SO low I had to come to Wowhead to find out if I was doing something wrong... unfortunately it seems I'm not.

The droprate on these feathers are extremely low. It took me about ~100 crane kills to get all 5 of them, and on top of that, the cranes keep evading mid combat.

Luckily, you can only get the 200 extra rep from doing just one of the trap quests every day. That means you have the option to choose between Tiger, Crane and Crab. Thus you can choose either of the other traps, and still get your daily reputation without ever having to farm cranes.

I've done all 3 of them, and personally I prefer doing the Crab one. You kill monkeys that drop fish with a very high drop chance. Sure you need 30 of them, but it only takes 5 minutes compared to the 30 mins for the crane one.

Beastmaster's Hunt: The Crab

Now the easiest way to get your rep, is to simply not farm anything. Instead you camp the cages and kill the bosses other people have farmed for. You still get quest credit for killing the boss, even if you didn't tag it.

Another solution is have a rotation with friends and guildies. One person farms 1 trap every day, sharing the kill, and you rotate on a schedule.