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Very, very, very broadly, and depending on all sorts of variables, mid-morning and mid-afternoon. That's because the big numbers are Broad-Wings, which basically vacate the continent en mass over a very short period of time in early fall. In Mass., something like 90 percent of the BWS seen over the entire 30 years of data have been seen between Sept. 10th and 20th. BWs use thermals to get height, then glide as far as they can before picking up another thermal. Their "goal" is to get as far as possible towards central America as fast as possible while expending as little energy as possible-- so soaring and gliding rather than flapping. The result of that is that when weather conditions are good -- those crisp fall days with lots of sun -- very strong thermals are created that take the birds in the middle of the day so high that they're often out of view. The "mid-day lull" is a well-known cliche in hawk-watching. In mid-morning and mid-afternoon, the sun angle is lower and the thermals not as strong, so they don't get as much height and that keeps them at a lower height. But again, that's not a rule, just a statistic. You can have huge flights visible at any time of day. One of the truly addictive things about hawkwatching during BW season is you can have an empty sky for hours, and then they start coming in and just pour through so you get hundreds or thousands over the course of a couple of hours, and then the spigot shuts off completely and the sky is empty again for the rest of the day. I once experienced an estimated 8,000-bird flight compressed into an hour and a half, and no more than 100 birds of various species spread over the rest of the day. Jane (Shoreham) On 9/19/2013 9:41 AM, Willem Leenstra wrote: > Is there a time of day when the numbers are higher than others? Broadly > speaking, that is, morning vs. evening? > > > On 9/19/2013 1:34 AM, Jane Stein wrote: >> Mt. Wachusett >