Date: 09/04/2018

Number: 3900

Monarchs massing near Woodstock, Sept. 4

Over the past week, I've been watching a build-up of Monarchs just behind my place, about 2 km west of Woodstock [known locally as Dorland]. The area is on the steep, south slope of the Thames River valley and seems to work as a migration conduit for flying things - it does attract migrant raptors as well.

Today, I sampled two alfalfa fields and adjacent cultural meadow thick with blooming goldenrod. The alfalfa fields contained est. 3500 individual Monarchs, with an additional 400 to be found in the goldenrod areas. I've never, in 40 years living here, noted such numbers of Monarchs, especially contained in such as small area. There is a long, adjacent treeline that is also attracting hundreds of individuals each night as a roost site. Almost all roosting individuals choose the north side of the treeline and seem to favour bare branches as roost perches.

The alfalfa fields still host thousands of Clouded and Orange Sulphur as well as Cabbage White. A nearby meadow has also hosted great numbers of Green Darner, with a max. of 2000 yesterday, with much smaller numbers of Shadow and Lance-tipped Darner.

Woodstock, ON

Latitude: 43.1 Longitude: -80.7

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