After years of working in different conservation/hunting organizations, I've come to the conclusion Bowhunters are independent loners...perhaps due to the fact they hunt one-on-one. The Iowa Bowhunters Assoc. does a good job of organizing archery folks, but it's an uphill battle.
Special interest groups that have a narrow focus always have a tough time recruiting members. We have groups that specialize in Turkeys, Quail, Pheasants, Ducks, Deer, Elk, Sheep, Bears, Archery, Traditional Archery, Blackpowder, and bird watching. A few groups have broader interests and higher membership numbers, (ie: Izaak Walton League, and NRA).
Largest and oldest conservation/hunting/gun group in Iowa is the NRA (60,000 members). NRA's political arm for legislative action is the Iowa Sportsmans Federation.
In most organizations less than 2-3% of the membership get activly involved. The rest either don't have time or would rather send a check to help.