After the early start to spring, migration stalled with the arrival of a long-lasting weather system that funneled the dreaded north winds back down into the Ottawa Valley again. The past week has been filled with gray, overcast days, a bit of rain, a bit of snow, and several days of gusty winds. I’ve added a few new birds to my year list, but they are mostly species that have been present for a while now that I never got around to seeing earlier: Gadwall, Barn Swallow, and Yellow-rumped Warbler at the Richmond Sewage Lagoons, Red-necked Grebe at Shirley’s Bay, American Bittern and White-crowned Sparrow in Stony Swamp, Eastern Meadowlark and Osprey on Rifle Road, and the return of the neighbourhood Chipping Sparrows back on April 15th. The birds that returned early this spring and tripped the eBird filters a few weeks ago are all birds that overwinter close by in the southern US; while they took advantage of the warm southern winds to return to their breeding grounds early, birds that winter in Central and South America are still thousands of kilometers away and will return on their normal schedule.
Saturday was the nicest day of the past week, with the temperature getting back up to 20°C. It was calmer than it had been for a while, and mainly sunny in the early afternoon, which made it a perfect day to look for butterflies. After lunch I headed out to the Rideau Trail on Old Richmond Road, wondering if the Henry’s Elfin I had seen on April 9th was still there, and if any new butterflies were flying.
There weren’t very many birds around – a Pileated Woodpecker on a stump right next to the trail was my best one – but some Yellow Trout Lilies growing along the trail were great to see. These spring ephemerals grow in colonies which send up thousands of mottled green and brown leaves every year, although only those plants which produce two leaves will bear flowers. Older plants, and those with deeper corms (the underground “bulb”), are more likely to produce flowers than younger plants, but even so only a few flowers bloom per colony. I found a spot inside a fenced-off area where several flowers were growing; perhaps the fence helps prevent deer or other mammals from eating them, which in turn allows them to mature?
I returned to the same area I visited before, a relatively small, open deciduous area surrounded by pines. A single Mourning Cloak was fluttering through the shafts of sunlight high overhead (its shadow on the ground alerted me to its presence), and a few moments later a single bright blue butterfly the size of my thumbnail flew rapidly through the woods much closer the ground. This was a Northern Spring Azure, also called Northern or Lucia Azure (Celastrina lucia), one of the gossamer-winged butterflies that emerges early in the spring and brightens the dreary brown and gray woodland with its beautiful sky-blue colour. In our area it flies during the summer as well; although this later generation was once considered to be a separate species called the Summer Azure (Celastrina neglecta), recent research indicates that all the azure generations found in Ottawa are in fact one species.
When I returned to the trail I found a pair of butterflies spiralling together in a battle for supremacy; they were small and dark, and when they landed I realized they were both Henry’s Elfins. After watching them for a while a third butterfly interfered with their battle, until one flew off and engaged with a fourth. It was great to see so many of these small brown butterflies in one area.
Like the Northern Spring Azure and other elfins, the Henry’s Elfin overwinters in the chrysalis stage. This means that adults are ready to emerge from the chrysalis as soon as the weather warms up. In Ottawa emergence usually happens in the last few days of April, according to the Ontario Butterfly Atlas compiled by the Toronto Entomologists’ Association – between 2006 and 2019 (the last year for which records exist; it appears that 2020 records have not been added yet), Henry’s Elfins were first reported between April 26 and May 1st in 9 out of 14 years. Three of the remaining records are for dates after May 1st, and the remaining two dates are from early April: April 3, 2010 and April 8, 2012. So my sighting on April 9, 2021 was not the earliest sighting in Ottawa county, but it looks to be the third earliest checking all earlier records. I chose 2006 as a starting point since this is the year in which the number of local contributors and observations increased significantly; it is likely that this was when the first online group local dedicated to butterfly sightings was set up, either through the now-defunct Yahoo butterfly group that I joined sometime around 2010, or as an earlier email iteration. Prior to that, only a few naturalists dedicated to the study of butterflies contributed to our local records.
Henry’s Elfins fly for about a month, mostly throughout the month of May, with few records from the first week of June and virtually no records after that week. I have seen them in many of Ottawa’s forested conservation areas including most of the Stony Swamp trails, Mud Lake, Deevy Pines Park, and Roger’s Pond.
This elfin lives in variety of wooded habitats, including dry forest openings, urban woodlots, and woodsy swamp edges. They prefer shady deciduous forests with pine trees, and I often find them alongside Eastern Pine Elfins. Although they are said to visit flowers, I’ve never seen one do so; however, males often gather along damp trails and roads to sip moisture from the ground. Like the hairstreaks (another member of the gossamer-winged butterfly family), male elfins are territorial and sit on perches to watch for females and male intruders passing through their territory. They can usually be seen sitting on a prominent perch at or below eye level, although on my visit I found them perching on the leaves on the forest floor as well as on a low rock, an upright tree branch, and even a tuft of grass.
Caterpillar host plants include Redbud, huckleberries, blueberries, holly and viburnum. The caterpillars have also been discovered to use the non-native Glossy Buckthorn, an invasive plant in our region. Henry’s Elfins used to be considered “uncommon and local” in the Ottawa area until about 40 years ago when they began showing up in habitats previously considered to be unsuitable, such as openings and clearings in Glossy Buckthorn thickets or second growth woodland: habitats that had come into being with the naturalization of farmland that had been abandoned between 10 and 70 years ago. Naturalists hypothesized in the 1980s and 1990s that the new colonies – which represented an increase in the number of sightings in these habitats by a factor of 7 – were the result of these butterflies feeding on the buckthorn. To prove this hypothesis, larvae were successfully reared to adulthood using this plant. It was further predicted that this species’ ability to use such abandoned farmland, coupled with the continuing spread of the buckthorn, would result in it becoming a much more common butterfly in Ontario within the next few decades. This prediction has since come to pass, as these beautiful butterflies are now widespread throughout the region.
There are only two butterfly species in our area with which it could potentially be confused: the Brown Elfin and Hoary Elfin, both of which lack the white markings on the hindwing and the tail of the Henry’s Elfin. The Hoary Elfin prefers more open habitats such as forest openings, rocky or sandy barrens, and bogs where its host plant, bearberry, is found. The Brown Elfin inhabits bogs and wooded areas with acidic substrates where heaths are prevalent. As such, the Henry’s Elfin is the most likely elfin to be seen within the city itself, while the other two elfin species are found in more specialized habitats such as Mer Bleue, Constance Bay, and the Burnt Lands.
I don’t think I’ve ever seen more than two or three of these butterflies in one spot before, so it was certainly a thrill to see four trying to claim the same territory! At various times I would see two perching on the ground while two others battled together; then one of the perching butterflies would join in, while the fourth took a time out. I certainly enjoyed watching them on such a fine spring day, and gaining a glimpse into their secret lives.