The Daily Bucket is a regular feature of the Backyard Science group. It is a place to note any observations you have made of the world around you. Rain, sun, wind...insects, birds, flowers...meteorites, rocks...seasonal changes...all are worthy additions to the bucket. Please let us know what is going on around you in a comment. Include, as close as is comfortable for you, where you are located. Each note is a record that we can refer to in the future as we try to understand the patterns that are quietly unwinding around us.
March 31, 2015
Salish Sea, PNW
Two pairs of Gadwalls have returned to my nearby bay. I saw them most days last summer, and then they were gone all winter until a week ago, opposite the pattern for most ducks here. Their presence will be welcome in a comparatively empty bay over the summer after the flocks of winter ducks - like the buffleheads, wigeons, mergansers - go north and inland to breed.
The Gadwalls usually hang out around one part of the beach, by the outflow culvert that drains the wetland across the road. They feed on the ample sea lettuce that proliferates here, and like to drink the fresh water.
(All photos by me. In Lightbox...click to enlarge)
With few exceptions, most ducks here frequent both fresh and saltwater, making use of the variety of foods found in these very different habitats. We all know drinking saltwater is a bad way to quench our thirst: our kidneys can't produce a salty enough urine to excrete so much salt and will draw on our body fluids to dilute it, dehydrating us. Aquatic birds remove the excess salt in seawater by concentrating it in salt glands in their forehead, letting the supersalty fluid drip out of their nostrils. Amazing adaptation! They are even able to change the size of their salt gland to some degree depending on how salty their habitat's drinking water is. Cool huh?
Then why do birds congregate around a freshwater runoff stream, like the Gadwalls and these Glaucous-winged gulls?
The fact is, it takes energy to actively remove salt. That metabolic stress can be lessened by drinking less salty water whenever possible. So a stream of water running off a wetland is a very attractive piece of real estate on the beach. While I sat nearby and watched on this occasion, a pair of GWGs took possession of it, driving the Gadwalls away. The ducks milled around nearby.
A yearling gull dropped in to have a sip, and one of the adults chased it away.
Another young gull glided in with a crab, intending to dine in style. One of these adults attacked it savagely! But it flew off in seconds (though the crab was left behind).
And don't come back!
March is the last hurrah for gulls in the bay. They've been pairing up since winter, and for the last few weeks heading offshore, staking out nesting sites on the outer islands. Except for an occasional gull passing through, the lively raucous crowd is gone for the season.
This pair bathed and drank in the luxurious splendor of this freshwater runoff stream.
Why do birds prefer to bathe in fresher water if they can? I don't know. From my own experience, I get a lot more clean using fresh water than ocean water, and clothes stay stiff and damp forever when washed in seawater. Perhaps there's some similar effect on feathers. They certainly can and do bathe in the ocean. They also relish rain showers and rivers.
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Time for your observations of nature from your backyard. What's new?
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