Duck Feet

PEI’s bird tracks come in five different forms. So far this winter we’ve looked at two: game bird (featuring Ruffed Grouse and Ring-necked Pheasant) and classic (aka ‘anisodactyl’, illustrated by a Bald Eagle). Today we look at the third type: webbed (aka ‘palmate’), with ducks as our example.

The basic structure of webbed tracks resembles that of game birds, with three long toes pointing forward and one short toe pointing back. However, in this case, the three front toes are connected by membranes (called webbing) and the short toe is really short and sometimes elevated – it doesn’t always show up in the track.

Webbing is a fantastic adaptation for swimming: it spreads out to increase surface area and act like a flipper when the bird pushes its foot back underwater and folds up to reduce resistance when the bird pulls its foot forward. When you see a webbed track, you can narrow down your suspects to waterbirds, with geese, ducks, gulls, and terns being the most common on PEI.

The keys to webbed track identification are size, length of the middle toe, and whether the small hind toe leaves an imprint or not. Black Duck and Mallard tracks (shown here) are two to three inches long and the small hind toe shows in some of the tracks (inset photo). Canada Goose tracks are much larger, (about four to five inches), while Gull tracks rarely show the small hind toe, and Tern tracks usually have the middle toe extending beyond the webbing.

Webbing isn’t waterfowl’s only adaptation: their legs and feet have a remarkable circulatory system to prevent heat loss in winter. If you put your hand in ice water, it will feel very cold – painfully so – within minutes. That’s because the large difference in temperature between your warm hand and the cold water causes heat to be lost very quickly. 

In waterfowl, veins carrying warm blood out from the heart are intertwined with arteries carrying cool blood back from the feet. This does two things. First, it cools the blood heading to the feet so the temperature difference between foot and environment is minimized. Less difference in temperature means slower heat loss and reduced risk of freezing. Second, the heat removed from the blood heading to the feet warms the blood returning to the heart. This helps the bird maintain its core temperature by not bringing that very cool blood on board. 

So, while we warm-footed humans would be dangerously uncomfortable standing on ice or snow, cool-footed waterfowl barely notice it.  In freezing temperatures, only 5% of the body heat lost by a duck is through its feet.

March marks the traditional return of migratory waterfowl, increasing your chances of finding their tracks around PEI Untamed!