Friday, February 26, 2016

American Dipper

American Dipper - Cinclus mexicanus

Dippers are a winter visitor to the Elbow River behind my home. After breeding season, the birds often migrate north and to higher elevations to find and feed on aquatic invertebrates. They will winter in locations where the water remains ice-free.

These aquatic birds feed on insects, insect larvae, invertebrates, small fish, and fish eggs.

Dippers can walk and feed underwater. Young dippers can dive and swim before they can fly. The oxygen capacity of the blood in a dipper is higher than non-aquatic songbirds, which allows them to remain submerged for up to 30 seconds while foraging. Dippers have up to twice as many contour feathers compared to songbirds of a similar size and a thick coat of down. These birds need to preen for longer than average to maintain the waterproof and insulation properties of their feathers. The iris sphincter muscles in a dipper are adapted to change the curvature of the lens to facilitate vision both above and below water. 

The dipper has a loud ringing song that can be heard over the low-frequency background noise of streams and waterfalls. 

The photo above shows the white-feathered eyelids of the dipper. 

1. Baircich PJ & Harrison CJO. Nests, Eggs, and Nestlings of North American Birds. Princeton UP, New Jersey. 2005.
2. Sibley DA. The Sibley Guide to Bird Life and Behavior. Alfred A Knopf, New York. 2001.

Friday, February 19, 2016

Three-toed Woodpecker

Three-toed Woodpecker - Picoides tridactylus

These woodpeckers lack inner rear toes.

The stocky short bill is adapted to flake off bark rather than to excavate the wood.

The hole in the tree below is the start of a nesting cavity. 
Sibley David A. The Sibley Guide to Birds. Alfred A. Knopf, New York. 2000.

Friday, February 12, 2016

Pileated Woodpecker Holes

Pileated Woodpecker - Dryocopus pileatus

Pileated Woodpeckers are the largest woodpecker in North America.

In a search for insects, usually ants, the Pileated Woodpecker excavates large often rectangular holes in trees. The larger stout beak chisels off big chunks of wood. The holes are usually in living wood and are often within a few feet of the ground.
The holes in the photo below created a "face" with two eyes and a mouth. 

Elbroch M and Marks E. Bird Tracks and Sign. Stackpole Books. PA. 2001. 

Friday, February 05, 2016

Tracking Bobcat

Bobcat - Lynx rufus 

The track below shows both the larger front foot and the hind foot. The front feet are larger and have five toes but only four register. The fifth is higher up and only used with climbing. The hind feet have only four toes. The nails are usually retracted but the photo shows a possible claw print on the third toe of the front foot. Claws are not usually seen with ordinary walking but might be deployed with running depending on the terrain. The tracks below were not from a running Bobcat and a nail print is unexpected. The rear margin of the front and hind palm pads is trilobed. 
Snowshoe hare are the primary prey in this region and I often find the snow tracks of both animals in close proximity. Bobcats are sprinters.They generally do not attack unless they are within 10 meters of the quarry. Unless the prey can be captured within 3 to 18 meters, a Bobcat will usually abandon the hunt.

The Bobcat tracks below were in deeper snow and illustrate a normal walking gait.
Canada Lynx - Lynx canadensis is a similar species that is slightly larger, with longer ear tufts and a shorter tail with a full black tip. The fur is thicker, especially on the feet, adaptations that make sense for the more northern and mountainous range. I found the Lynx paw below during a hike around Banff. There were no other remains nearby. I presume that the paw was discarded from a Lynx that was trapped and killed for the pelt. 
The Bobcat below was in Glenmore Park. Notice the shorter "bobbed" tail, which is the reason for the name. 

Naughton, Donna. The Natural History of Canadian Mammals. U of T Press. 2012.