The power of eBird is proving useful once again. You can visit their site and see where any species of bird has been reported.
For several years we have been intrigued by the presence of Carolina Wrens in our garden and neighbourhood. This is at the very northernmost extent of their range – it isn’t so much the cold that knocks them back as the availability or not of food sources. There is a paper in the literature that reveals they are quite hardy but when the snow is deep and crusted they are dependent on well-stocked garden feeders to hold onto their territorial gains.
We know they have spread into our area from the south and so it is interesting to see that the birds appear to have arrived up the Richelieu and perhaps Chateuguay valleys and also along the St-Lawrence forming a small resident population along the southern shore of Lac St-Louis spreading from Beauharnois to Parc de Rapides.
Those birds would seem to have then crossed the river at two places where it is narrowest – Point-des-Cascades and Parc-des-rapides.
The former group have left “outposts” from Pincourt, across Ile-Perrot to our cluster on the tip of the west island and thence northwards via Pierrefonds, into Laval and onwards to St-Thérese and Rosemere while the Parc-de-Rapides crossing has seeded birds onto the mountain. In each case the birds have taken the narrowest water crossing available, which makes sense. I suspect that over the next couple of years we should receive reports from Dorval, Lasalle etc as the WI birds raise more young and they push along the lakeshore looking for territory of their own. Maybe also a thrust north towards St-Jerome?
I have placed a copy of the eBird map below with my suppositional expansion routes marked. I would be interested in anyone else’s thoughts on this.
I have also plotted the sightings for three year periods from 1995 which seem to support the hypothesis that the Richelieu valley was their route into the Montreal region – this is in a short pdf file that you can view form the following link: Carolina Wren movements