Bruce Pit: Tiger Beetles and a Rare Dragonfly

Striped Hairstreak

Bruce Pit is under-valued as a great spot to see a variety of insects at the peak of summer. Though I’ve spent a lot of time looking for dragonflies there, it wasn’t until recently that I realized it could be good for other types of insects as well. In 2020 I found a species of tiger beetle there that I had never seen before, Punctured Tiger Beetle, and last year I observed it again, as well as another type of tiger beetle: the colourful Festive Tiger Beetle. Tiger beetles have long flight seasons, but are not active during the entire summer; they become inactive or aestivate (the summer equivalent of “hibernate”) during the hottest part of the year, so it is easier to find them towards the beginning and end of summer. I started visiting on June 17th this year, hoping to find some good odes, butterflies, and a few different tiger beetles for my life list.

After the Equinox

Black-capped Chickadee

While it is true that fall migration proceeds at a much more leisurely pace than migration in the spring, each species moves according to its own internal calendar. In late August and early September you might find warblers, Rose-breasted Grosbeaks, flycatchers, vireos, orioles, Cedar Waxwings, and Scarlet Tanagers foraging together in a single patch of woods. A month later the same patch of forest might hold sparrows, kinglets, Winter Wrens, Rusty Blackbirds, nuthatches, Hermit Thrushes, and boreal finches, while waterfowl on rivers and ponds increase in numbers and diversity. I usually notice the switch around the fall equinox, when the sparrows start to outnumber the warblers and I realize that it’s been a while since I last saw a flock of Cedar Waxwings. Now is the time to look for American Pipits in open scrubby areas or along rocky shorelines, scoters and grebes along the river, hawks and Turkey Vultures soaring toward southern climes, and any lingering warblers in the hope it is something other than a Yellow-rumped.

The Odes of Late Summer

Green-striped Darner (male)

By mid-August most dragonfly species are on the wane. A few families are still quite abundant, particularly the darners and meadowhawks, while small numbers of other skimmers and a few clubtails often linger into September. Forktails, bluets, and some spreadwings are also still common in the appropriate habitats in August and September. This makes it worth going out to good dragonfly habitats such as large rivers, lakes and marshes to see a decent variety of species.

Large dragonflies this time of year are particularly interesting; while Common Green Darners are the most frequently encountered large dragonflies of late summer, you might come across a Black-shouldered Spinyleg basking on the rocks along the river, a Wandering Glider zipping over a meadow, a Twelve-spotted Skimmer flying above a pond, or a group of mosaic darners swarming through the air late in the afternoon. The mosaic darners are a particular favourite of mine; they are large brownish-black dragonflies with mottled spots of blue, green or yellow depending on the sex. While they spend most of their time flying through the air hunting for small insects, I often come across them perching vertically on thick stalks of vegetation below knee-height in open grassy areas early in the morning. We have several different species in Ottawa, and trying to find something other than the ubiquitous Canada and Lance-tipped Darners is a fun exercise.