|This discusses overnight between Oct 8 and 9.
Oct 8 19:15. No obvious aggregations. Saw 4 under typical roost trees. All appeared to be males. Wind continued to blow to SE until around 22:00 then dropped.
Temperatures below are from truck built-in thermometer which has tested as accurate.
Oct 9. 7:30-8:00. air 55 degrees. At this date the sun rises from behind a nearby ridge to our east, and occurred from 07:25 to 08:05 varying due to terrain. Distinct shadow cut-off moves from west to east on ground and from top of trees to bottom. I saw a handful of monarchs under two typical roost trees. No aggregations. None on flowers. South wind started to increase at sunrise.
Oct 9. 8:45 - 9:15. Air 57-8 degrees. Light south wind. As I left house in truck, I saw Monarchs flying, mostly 10-25 feet from ground, from a number of large Live Oaks and Ashe Junipers. As I crossed the large meadow on the way to our largest tree grove, I saw a few Monarchs either flying low or on liatris. None were there at 7:45. When I reached the grove, I saw Monarchs leaving as described above, and also within it flying and perching. I had visited it an hour before and saw no monarchs. So they must have been well concealed, widely distributed, and probably well up in trees. That would make sense since the sun hits the tops first. Many were perched on green foliage in sun 15-20 above ground. Some that I disturbed from lower twigs in shadow flew up to perch in sunlight. Monarchs were also drifting out of the grove steadily.
I have been asked to comment on plants. This grove is mostly large Ashe Juniper, plus Gum Bumilia, Live Oak,
Sugarberry, Pecan, with Greenbriar, Grapevine and several other vines.
Understory shrubs Elbow Bush, Prickly Ash, American Beautyberry, Sumac,
others, plus forbs and grasses.
While returning to house across the same meadow, I saw more monarchs
than on the way out, flying and perched feeding. No obvious directional
flight and all were less than 5 feet from ground.
So it seems that the monarchs were here overnight, roosting cryptically
and not aggregated.
I did not attempt a careful number estimate. I will do that later in
Image is of one of the easier to see Monarchs in the sun on the second
trip to the grove. On Ashe Juniper limb.