Tuesday, April 7, 2009

Avian Erractics

Sometimes, you come across a boulder that seems out of place - not only might it be the only 3 foot wide boulder in the observable vicinity, but it also does not resemble any other stone formations in the area. Some of these rocks are "glacial erratics." Many are larger than 3 feet across, and many more are much much smaller. Glacial outwash formations like eskers are composed of millions of tiny glacial erratics in the form of sand.

But it is the big ones that capture the imagination. The object survived millenia of tumbling, freezing, thawing and colliding to end up posing as the Three Maidens at Pipestone, MN or being writ upon by Vikings in the case of the Kensington Runestone.

Over the past week, the pine siskins (which have been so numerous and persistently present that even my cat takes them for granted) have begun acting differently. Rather than just gorging at the thistle sock feeder, which is made from a synthetic netting, they have begun filtching fibers from the thing. And one fellow was observed with a clump of down at the other feeder, a tube feeder with broad seed tray beneath. He would pick up the down, look around, set it down and eat a bit, then repeat the sequence repeatedly. We suspect that this is nesting behavior and that at least one couple will be nesting in the nearby woods. But pine siskins don't nest here - they nest far North, in Canada.

There is speculation that the large numbers of pine siskins and white-winged crossbills that spent time in the Eastern US this winter were forced to do do by a seed crop failure in the Canadian boreal forest (the boreal forest is being massively harvested and mined - an act that will have effects comparable to the depletion of the Brazilian rain forest). While global climate change may be pushing some species further North, here we see others being displaced to the South by human activity.

So there are now bird erratics - Canadian birds out of place in Minnesota.

1 comment:

MarkN said...

Pine Siskins actually do nest in the piney areas of northern Minnesota; we were fortunate enough a few years back to have them nesting near our Nisswa cabin, and exhibiting similar behavior to that which you describe.

Especially with all the pines planted and thriving in this area (despite our "Big Woods" past), it would not surprise me to have them nesting here this year. Long-term trends (e.g. House Finch, Northern Cardinal and Red-bellied Woodpecker) are hard to predict per species. I'm not sure what the major swings are in the birch/aspen/pine seed cycle are, but it could be an extremely interesting graph (being a math geek).

Keep an eye on those birds, especially with the Breeding Bird Atlas project going on!