Spinning and shoveling

Birds feed intensively at a migratory stop-over to build up fat reserves for their next long flight, and this was certainly evident in the ducks I watched at the MN Valley National Wildlife Refuge the other day.  Huge rafts of ducks floated far out in the river.

Ducks were much too far away to photograph, or even to identify with my binoculars.

Ducks were much too far away to photograph, or even to identify with my binoculars.

A few smaller flocks of Northern Shoveler were feeding in the shallow marshes near shore and allowed me to creep up closer to photograph them.

Most were feeding in small groups of 4-6 birds, consisting primarily of females with the occasional male among them.

Most were feeding in small groups of 4-6 birds, consisting primarily of females with the occasional male among them.

Feeding either singly or in small groups, the birds spun in tight circles, keeping their heads and bills immersed in the water and raising up only momentarily (to breathe, I assume).

You can see the results of the spinning feeding motion in the circles of water around the bird as it feeds.

You can see the results of the spinning feeding motion in the circles of water around the bird as it feeds.

Small groups of Shovelers feeding together form a "pinwheel" as they spin around.

Small groups of Shovelers often feed together, forming a “pinwheel” as they spin around. This kind of cooperative behavior probably helps suspend more food particles in the water.

The effect of the spinning motion, and especially of their feet raking the marsh bottom, brings up all sorts of food items, which are sieved by their grooved ridges (lamellae) along the edges of their elongated bill.  Water and food particles are drawn in the tip of the bill and pushed through the lamellae with the tongue to exit at the base of the bill, leaving the residue of food particles to be swallowed.  To maximize their contact with the particles suspended in the water, shovelers move the bill from side to side as they sit, spin, and suck in the medium.

Shovelers look a lot like Mallards, with the mottled brown and tan plumage of the hens and the glossy green heads of the drakes.

Mallards were feeding just as intensively as the Shovelers, but concentrating on the duckweed in the stagnant parts of the marsh.

Mallards were feeding just as intensively as the Shovelers, but were concentrating on the duckweed in the stagnant parts of the marsh.

But the size of that bill is distinctly different, and thus makes it easy to tell the two species apart.

But the size of the Shoveler’s bill is distinctly different from that of the Mallard’s, and that makes it easy to tell the two species apart.

Not only is the Shoveler bill a lot longer and broader than that of a Mallard, but the specialized lamellae on its edges and the Shoveler’s feeding behavior, mean that the two species have entirely different diets.

By Lord Mountbatten (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

By Lord Mountbatten (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)%5D, via Wikimedia Commons

Northern Shovelers eat a high proportion of animal food (especially snails), in addition to seeds and vegetation that is raked up from the bottom.  Mallards eat more plant matter (seeds and vegetation), except during the breeding season, when they too prefer an aquatic animal diet.

The Shovelers will probably leave when the marshy shallows of the lakes and rivers freeze over, and some of them will migrate as far south as northern South America for the winter.

Northern Shoveler drake

5 thoughts on “Spinning and shoveling

  1. I really liked your comparison between the shovelers and the mallards. I had never before considered the difference in diets between the two, though I had observed that their feeding behavior was different. I remember well my shock when I first saw the bill of a Northern Shoveler–I couldn’t believe my eyes. I especially enjoyed your pinwheel shot and will have to keep my eyes open to see if I can spot similar behavior.

    • It’s interesting that these ducks all feeding in roughly the same spots do select different types of food, I suppose to avoid competing with each other. Some websites said that Shoveler diet was as high as 90%, while others said 60%, but all agreed that it was much higher in animal content than the Mallard’s diet.

  2. Thank you for a nice explanation on the spinning Shovelers. Doing a search on-line, I was surprised it was difficult to find a good explanation of the behavior. I watched a large group of Shovelers spinning at the Arcata Marsh yesterday, in Arcata, California.

    • Oh good, glad the information helped. I ask a lot of why questions when I am out walking around and then come home to research them. That’s what the blog is all about. Thanks for writing.

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