March 29th – A Ribbon of Warmth

Snow-free west bank of the Grand River

The Grand River, which flows right by the front of the Ruthven Mansion, plays an incredibly important role when we’re experiencing the sort of weather of the past week. The Spring migration was in full swing when the snow storm hit and everything quickly ground to a halt. The snow was followed by a week of cold temperatures (down to -13 on some nights), exacerbated by northerly winds. How do these early-moving birds survive? They quickly spread out and hunt for whatever niches they can find that will offer food, some shelter from the weather and a little heat. Here’s where the river comes into play. The water temperature may be only a few degrees above freezing but….it is still above freezing and this is important when it’s -13 (or more with the windchill). And this comparatively warm condition is all that is needed for early emerging insects and spiders to come forth…snow or no snow. Consequently for the next week there have been birds all along the river, usually, when feeding at least, within 10-20 m of it. Walks along the River Trail at Ruthven or along the Rotary Club Trail that runs between York and Caledonia turned up lots of birds – mostly Common Grackles, Red-winged Blackbirds, American Robins and Song Sparrows. But there were also some ‘interesting’ birds as well: Rusty Blackbirds and an Eastern Phoebe (which stayed in the same spot for a week – a small exposed flat section of vegetation extending into the river; a good spot, it seems, for insects.

Some of the most important insects in terms of early bird survival are the non-biting midges or chironomids. Some species emerge from the river shorthly after breakup and form large swirling groups in the protective lee of trees and shrubs. They are an important food source for a number of bird species but especially for swallows. This was the case today. I saw the first 4 Tree Swallows of the year flying low over the surface of the river hunting for emerging insects that they appeared to be picking off the surface. It was interesting how they used this niche. They stayed close to the west side of the river and kept low. The west side gets a lot of sun in the course of the day and, consequently, is bare of snow on the steep banks. The bare earth begins to heat up as soon as the sun clears the horizon and I would venture that the air temperature close to that side is higher than in the middle of the river or on the east (mansion) side – especially low down sheltered from the wind.


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