Your not missing much in the way of drippings on a smoker cooking whole chickens or turkeys so long as your using enough heat (300*) or more.
Unlike the traditional oven and pan method that leaves the faucet running under the bird , the entire bird is getting heat and air flowing around it crisping up the outside. This is why so many people enjoy a whole bird deep fried, crispy outside all the way around and lots of tender juicy meat inside.
I did a 20 pound turkey yesterday, the catch can had maybe 3 ounces of juice in it when the bird finished this was cooked on a PG 500 at 315* for 3.5 hours and I let them rest a minimum of an hour before slicing another half hour is even better so you don't have juices running out when served they stay plenty hot under foil and towels.
Bottom side was just as crispy and sealed as the top: