Disturbing the Swallows

I started monitoring the quality of the Rum River this spring for the Minnesota Pollution Control Agency. On Monday evenings, I park my car on the Pleasant Avenue bridge. First I rate the river quality on aesthetics (would I swim in it, etc). Then I throw an empty bucket tied to a rope over the railing and haul up a bucket of river water. I pour the water into a secchi tube that holds 60 centimeters of water. I see if I can distinguish the black and white pattern at the bottom of the tube. If I can't see it, I slowly let water out until I can see it and measure how deep the water is in the tube. Then I look for the screw in the bottom of the tube. If I can't see that, I slowly let water out until the screw becomes visible. I measure the temperature of the water in the bucket. And finally I take a large tape measure with a plumb bob taped to the bottom of it and measure how far down the river is from a specific spot on the bridge. While I'm doing all these things, I have drawn some attention. Several people have asked me if I needed help. I suppose they thought my car broke down and that is why I'm parked on the bridge. Several teen aged boys have asked me what I'm doing. I tell them the boring story and they bike away without asking too many questions. Once an angler in a boat said he was going to pull on that bucket to surprise me. I didn't see him because he was anchored out of my sight under the bridge. I guess I surprised him first. There is one group that becomes positively irate and agitated when I monitor the river quality. The cliff swallows fly into a rage every week, squawking and moving at me aggressively. The rope and the bucket must be threatening to them. Tonight the water was clearer than last week. Maybe the rain in the past week cleared it up.