I honestly feel like the officials here are just malingering to try to get drones banned because they don't like them. No way one tiny drone flying somewhere in the forest means no helicopters can do their job in the entire vicinity. It's no different than a large bird being around.
Aircraft dropping water on fires are:
1. flying very low,
2. over fires that will be causing a lot of turbulence,
3. in aircraft that are heavy loaded, making them less nimble than normal, and making maneuvering put more stress on the aircraft than normal,
4. in conditions with poor visibility.
This makes it a very stressful, dangerous kind of flight, where if anything goes wrong the chances of the pilot recovering in time are greatly reduced. Encountering a drone could easily lead to a crash in these circumstances.
And yes, it is very different from a large bird, because large birds will be avoiding the fire.
"Air tanker drops in wildfires are often just for show" https://www.latimes.com/local/la-me-wildfires29-2008jul29-st...
"To professional firefighters, though, it was a prime example of a “political air show,” the high-profile use of expensive aircraft to appease elected officials."
“CNN drops.”
There is a key difference between birds and drones. Birds tend to fly away from fires. Drone operators are getting close to the action. The forest may be big, but the chances are high that a drone pilot and helicopter pilot are aiming for the same spots.
Fire services do operate their own drones. But they do it in coordination and under the guidance with the air traffic controllers so the location is known at all times.