Swift River Cruisers at Grand River at Scarfe Ave, Brantford - New for Hamilton Study Area

[Bill Lamond]

Hi,

While looking at loafing gulls (and American White Pelicans) at the Grand River at Scarfe Ave in Brantford, I saw a dragonfly cruise by that I thought looked like a River Cruiser. Knowing they do not occur here, I thought it must have been a Stream Cruiser, a species that also does not occur at this location but does occur downriver several kilometres. Soon after the dragonfly passed by again and with binoculars I could see that it indeed looked like a Swift River Cruiser - very dark, with a prominent club and prominent dorsal yellow spot towards the rear of the abdomen. Soon after there were two and they were "tangling" as male dragonflies do. The water here is quite shallow so I thought it best to put on my rubber boots and grab my net from the car and try to catch one of them for a confirming photo.

My first swing was a miss and I didn't see another for at least 10 minutes but one did appear again and on the 3^rd pass I netted it. A spectacular dragonfly to say the least. I was thinking this was the first record the Hamilton Study Area and likely for the Grand River watershed. However, on iNat there is a 2024 record from the Nith River (a Grand tributary) about 2km ENE of Drumbo, Oxford County by Jon Pleizier (outside of the HSA by several km). Still, a first for the HSA.

So it appears that this species has just colonized the Grand watershed in very recent times. It will be interesting to see how widespread this species becomes on the Grand watershed (if this happens). What is most interesting to me is why it was not already here? Was it here historically and subsequently eliminated by pollution and/or poor water quality? Even its current distribution in south-western Ontario is unusual. It does occur in the Lower Thames but not upriver in London where habitat seems suitable. Why? Pretty easy to fly upriver.

So much we do not know about dragonflies and their distribution.

Bill