Saturday, April 16, 2011

Spring Arrivals

One of my volunteers recently commented on the lack of spring migrants arriving in the area. So I took him out to the pond and showed him a couple of migratory ducks that have indeed arrived. He was quite struck with the beauty of these birds, at least one of which he had never seen before.

American Wigeon (male and female) with a male Mallard
 
This little exchange got me thinking about these ducks. While I can easily identify them, I have to admit I know very little about them. So I pulled out my Sibley Guide to Bird Life and Behavior to get myself a little learning.

I'm a little ashamed to say that while I have noticed bird's feet, I have never really given them much thought, except for birds of prey, who rely heavily on their feet for catching and killing their prey. But duck feet - nope, other than to acknowledge they are webbed, I haven't given them much thought at all.

Male American Wigeon
 
The most common method of movement for birds is of course flight, but birds also hop, walk, run, dive, and swim. Most waterbirds, such as ducks, use their feet to move through or under the water. For some water birds, the ability to swim or dive well  is far more important than it is for others. This can be seen in the placement of their feet.  Birds that spend a lot of time in water have a "design conflict" to overcome. For example, the best placement for the feet of a swimming bird is towards the back of the body, where paddling best moves them through the water. But this arrangement is very awkward for movement on land.  For this the feet are best placed near a bird's center of gravity, under the middle of the body.

The feet of an American Wigeon are placed...well, can you tell from this picture?

American Wigeon on land foraging for yummies
 
So wigeons walk much more easily on land than say, a loon, but are poorer swimmers. See, this intrigues me. Partly because I've never really thought about it. But now that I think about it, I realize that at my pond I often see wigeons on the land (along with mallard and teal), but almost never do I see ring-necked ducks on land (or Buffleheads or Redheads)- which are much more powerful swimmers and divers.

There's something to say about the way they swim as well, or more specifically their swimming posture, which is directly related to the way they forage. Maybe I'll get into that another day.  But for now, here's something to think about: water birds "sit" differently on the water, some ride high on the water, some ride very low, and others are intermediate in their water posture (options to consider: diving ducks, dabbling ducks and swans/geese). Any idea who does what?

5 comments:

Jenny said...

Who knew? My cool duck lesson for the day, Thanks!

Wren said...

That's fascinating - you've been far more observant than I have, but I'll pay more attention in the future.

It all makes perfect sense in some ways and none at all in others.

Patricia Lichen said...

Hmmm. I'm picturing swans and geese in the water, and am thinking that they ride high. I'd guess that diving ducks ride low and dabblers are intermediate. Am I right???

At any rate, I hadn't thought about the position of the legs and how that affects their actions on land/in water. Thanks for sharing this tidbit!

--Patricia Lichen, www.patriciaklichen.com

Wendy said...

Patricia, you are of course totally correct. :)

Oak in the Seed said...

I knew about loons but never extended the understanding of leg limb placement to the others. Makes me wonder more about evolution and which direction these birds are headed~to the water or away from it?
Good post!