Yesterday evening I kayaked out to the martin roost off Mandeville. I knew that it was about two miles offshore, but had a hard time targeting the spot while heading over from Sunset Point until, shortly before dusk, I was enveloped in a river of birds headed that direction- a flow that seemed to buoy me along. As dusk gathered,the flow gradually grew to about 50 birds passing by per second, chattering as they went. I then reached the bridge; birds were swarming noisily underneath, flying up to perch on the understructure. I ended up kayaking 1.3 miles of roosting birds; each bridge segment had about 1900 birds, which grew to 2400 before I turned around. This comes to 125,000 in the portion I covered; because I know it stretches twice that far, it seems that 250,000 is an appropriate estimate.
Being immersed by this huge mass of birds, together with lightning in the distance and the lapping lake swells, ranks this among my peak birding experiences.