Mocha Emeralds at Harrisburg

[Bill Lamond]

Hi,

I've posted before about this population of Mocha Emeralds east of Harrisburg along an abandoned rail line and at Fairchild Creek in Hamilton-Wentworth. Today (29 July) I was surprised to find at least three males (possibly more) patrolling along a small section of the creek. It was fascinating to watch the male emeralds hover along the creek bank at knee height, moving slowly with wings beating furiously. I wasn't aware that they would use such marginal habitat for breeding as the creek currently has zero flow. It was reduced to small pools, longish sections with water, and other areas with just mud. I used to think this intermittent nature of the creek only happened in dry years but I think it is normal for this creek to have zero flow in the height of summer except in wet years. I've included three photos of the habitat. You can see in the one photo that the streambed is just mud and branches to my right. I had no idea that Mocha Emeralds would use such habitats but indeed they do as confirmed by Paulson (2011) - "small streams with mud and leaf litter a few yards in width in forests. In late summer may decrease to a series of pools". This is a perfect description of this habitat. It almost looks repugnant as it is quite cloudy with the clay soils. And there is not much life in these small pools save for a few juvenile Green Frogs, crayfish and water striders. Odes are virtually absent here save for the emeralds. In the 40 minutes I was there I only saw one Common Whitetail fly through. No damselflies were seen. Perhaps the Mocha Emeralds use this habitat as there is little to no competition for their larva from other ode species?

This species must be more common in Ontario than currently known based on the habitats it will use. On the otherhand, perhaps "poor quality" streams such as Fairchild Creek are not that common.

Bill