Well it's a topic of endless debate, particularly on birdless mornings during Spring migration. I have heard many conflicting theories. The easiest to explain is what makes a great day, a "fallout". Perfect for birding, but not necessarily the birds, is when the weather turns bad during the night. That forces them to land, and if the weather strikes while they are over the lake, they'll come down as soon as they see shore.
The birdless days aren't as simple to explain, but the basic idea is that if the weather is good, they won't stop at the lakeshore, but just carry on until dawn and be much more dispersed. I guess it depends on the weather on the preceding days too, and where the birds are setting out from. I'd think in good weather, there would still be lots of birds looking for land after crossing the lake, but it often doesn't seem to work that way.
BB
Sent from my birdroid using Tapatalk.
