Warblers are feasting on fall sweets

The weather here in Northwestern Ontario has been incredibly hot for this time of year. We have had daytime temps of 28 C which is in the 80s F. That anomaly is probably why we are still seeing warblers. In fact our yard here in Nolalu is abuzz with the little guys shown above. 

If you are a birder you know how difficult it is to distinguish warbler species in the fall. My bird book has an appropriately-titled page called "Confusing Fall Warblers." I frankly quit trying years ago but the ones we are seeing all over the lawn are pretty easy. The clue is the birds' rear ends. Yellow-Rumped Warbler. 

The other dead give away comes from where these warblers are feeding -- the ground. To my knowledge, they are the only warbler in these parts anyway that catch their prey on the ground. It would be nice to think they are eating the cluster flies that are just everywhere at this time of year but as I was manning the barbecue the other day I could see that at least some of them were picking off the white-coloured fruit flies that are very difficult for humans to detect. It usually takes bright sunlight with a dark background to see these minute flies.

Up at camp we saw ring-billed gulls catching the same tiny flies in mid-September. 

The fruit flies are found wherever there are asters which are  late-summer flowers that grow almost everywhere. They must be super nutritious for big birds like gulls to bother catching them out of the air. I would imagine the Yellow-Rumped Warblers are using the flies to fatten up before they head to Central or South America for the winter.