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Topic
- Wildlife refuges 65
- Birds--Conservation 40
- Lectures and lecturing 20
- Rivers--Oregon 8
- Waterfowl 7
- Hunting 6
- Agriculture 5
- Water--Pollution 5
- Wildlife management 5
- Conservation of natural resources 4
- Lakes--Oregon 4
- Salmon 4
- Dams 3
- Fishing 3
- Lakes--California 3
- Wildlife conservation 3
- Burning of land 2
- Ducks 2
- Fishes--Conservation 2
- Forests and forestry 2