Tuesday, 1 March 2011

Remembering A Warmer Day

Winter is a wonderful and beautiful time of year but -30°C seems slightly ridiculous for March 1st!  Walking to school this morning, even the magpies were quiet, sitting like black and white puffballs on the branches.  While I’m still waiting for warmer weather and the early migrants it will bring, I thought I would “flashback” to a great trip to see departing migrants back in early November.
Snow Geese, Chen caerulescens
With my son and his grandparents in tow, I drove down to Lethbridge to meet up with Lloyd and the Lethbridge Naturalists at Stirling Lake for their annual Snow Geese trip.  The expected flocks were not present at the lake, although there was a large number of ducks (mostly Mallards) and some Tundra Swans.  Nevertheless, we could certainly see the geese high above. 

The adaptations of geese for high altitude flying are remarkable: the system of air sacs in all birds that ensures continuous flow of oxygen rich air across the lung surface1, the incredible aerodynamic efficiency granted by a large wing to body size ratio and V-formation flying, and in some species modified haemoglobin that increases oxygen uptake2,3.  Snow Geese have been observed flying at 20,000 feet and the Bar-headed Goose, which some sources place in the same genus as the Snow Goose, has been observed at well over 30,000 feet, migrating over the top of the Himalayas.

View Snow Geese Trip in a larger map

We moved on to Tyrrell Lake, a little further south, where we found several thousand birds in a field, foraging among the stubble.  At this point we were able to pick out a couple of Ross’s Geese among the multitude.  After watching from a distance the geese eventually took flight in several large groups and headed down to the lake, where they formed a giant raft.

Driving down beside the lake we found more migrants at the shallow south end of the lake.  These included several species of gull (Herring, California - not seen by me :( - Bonaparte’s and Ring-Billed), and many more ducks, including this lifer Northern Shoveler – what a beak!

All in all it was a great day and a wonderful reminder of the great community of birders in this province.  It’s a big boost for aspiring novices such as myself to have knowledgeable people helping me to see great bird events.

1 http://www.cs.mcgill.ca/~wliu65/media/biol111/19.pdf (great illustration of avian lungs about 2/3 of the way through the slides)

No comments:

Post a Comment