Weekly Reports

It has been an interesting week. With the exception of one absolutely gorgeous day it has been mostly cold, frosty and windy. Despite rather miserable weather bird activity has remained steady. Myrtle warblers are still pouring out of the northern forests by the thousands and mixed in with them are lots of orange-crowned warblers, blackpoll warblers, white-crowned sparrows and many others. Greater white fronted geese and sandhill cranes have also joined the migration train south. One rather surprising migrant has been the black-capped chickadee. Consistently for the past week and a half we have been observing as many as 50-60 chickadees a day moving through the observatory. This is interesting because chickadees are not typically migrants; they are a resident species. Normally a family group of chickadees (average 6-12 individuals) will occupy a medium to large territory that they move around within, rarely straying outside it. I did some reading into why chickadees would be migrating and from what I learned it seems that there are two main reasons for large irruptions of chickadees. The first is that they had a very successful breeding year coupled with a high survival rate from the previous year resulting in more juvenile birds than the habitat can hold, forcing the young birds to migrate elsewhere. The other reason – which I am strongly hoping it is not – is as a response to extreme winter conditions. Many wildlife species (not just the questionable groundhog) have an uncanny ability to ‘predict’ the weather and let’s hope the chickadees aren’t forecasting a winter too harsh for even them. It would have to be a very harsh winter indeed, chickadees are remarkably well adapted to survive our climate. For starters they have strong family bonds and benefit greatly from the safety that group-life offers, they help each other find food, avoid predators and can huddle together for warmth. Physically they have over-developed breast muscles that they can vibrate (think shivering) to generate heat that stays trapped beneath their thick, downy feathers. In very cold conditions they are also able to go into torpor, a state of reduced body function, to preserve energy. Torpor is essentially like a brief hibernation; during torpor a chickadee’s body temperature can drop as many as 10-12 degrees Celsius. Their other survival trick is storing food; a chickadee can remember as many as a thousand hidden food caches. With all the chickadees moving through it is inevitable that several have been caught in the nets. This is great for bolstering our totals, but bad for our sanity at times…. Chickadees can be trying to say the least. They bite, scream, scratch, growl and flap relentlessly, to put it simply they are 11 grams of whoop-ass. But you would have to be if you were a tiny bird living here year-round that had to deal with owls and goshawks. In addition to the chickadees, this week as had a few other interesting captures. We have started catching grey-cheeked thrush – the most northern breeding thrush in Canada, I caught my very first Le Conte’s sparrow, and we caught not one but two yellow-shafted flickers – a bird almost as ornery as the black-capped chickadee but over ten times the size.