23 June, 2002
Woke up, climbed out of the tent and onto a couple inches of snow that had fallen (and was still falling)! We put off searching until 12:30, then I headed back out to East Twin Lake (the bonanza King Eider site) and searched for more. When I left, it was still really cloudy, but warming up a little and little of the snow left on the ground. While walking back six hours later, the sun came out and I enjoyed one of the best evening walks of my life! After finding 3 more nests, feeling cold and spending time thinking about the work past biologists have accomplished, the evening walk was an true gift! Although I have much to talk about from today, I promised a science talk on Tundra Swans. More nature talk tomorrow! Happy science reading . . .
The Tundra Swan, Cygnus columbianus, or "qugruk" (Inupiak) is a large, magnificent bird seen flying and swimming in this area. It is the largest bird of the arctic, with a wingspan of 72-88" (6-7 feet) and a weight of 10-22 pounds. The tundra swan is interesting for many reasons. First, its size and pure whiteness makes it very visible, or conspicuous within the brown and green of the tundra vegetation, and upon the water after ice has disappeared. Second, not a lot of research has been done to provide a clear understanding of their behavior or breeding biology. Finally, to me personally, their reproductive strategy of monogamy (one partner for life) and association with this partner through their 20 year lifespan seems amazing for a wild animal.
The tundra swan spends the winter from the Chesapeake Bay area south to the Carolinas along the Atlantic coastline. In the spring, they begin the 3,500-4,200 mile migration up here to the arctic tundra. Once they arrive, they (1 male and 1 female) begin searching for a suitable nesting site and then building their nest. The nests are usually built on islands, made of dead sedge grasses and other rotting vegetation. They are built up to stand about 6-12" above the ground - very visible once you know what you are looking for. (We find ourselves using the nests for navigation as they stick up higher than most "hills"!!!)
As an aside, tundra swans and king eiders make totally different choices when building nests. The tundra swan usually builds its nest in a high spot that makes it visible to possible predators, but also gives them a better view of the approaching danger while sitting on the nest. On the other hand, King Eider's usually build their nests in low-lying areas between hummocks to better conceal them from possible predators. A possible reason for this difference is that the tundra swan, with its large size, is much better at protecting its eggs from predators, so an advanced warning with increased visibility is helpful. The smaller King Eider is not much of a threat against a predator, so concealment appears to be the better strategy.
Either way, once the tundra swan has its nest built, it begins laying eggs. Past research indicates that swans nesting in the arctic regions lay 3-4 eggs/nest. With the 12 nests we've found so far, there has been an average of 3.45 eggs/nest. The eggs, like the birds and nests, are very large. We have found them to have an average length of 107 mm (4.45"), width of 69 mm (2.87") and a mass of 273 g (.6 lb). To visualize the size of this egg, when I am holding it, it completely fills my hand!
After egg-laying, incubation begins. Incubation lasts an average of 31-33 days, with the female performing 70% of the work, but the male helping 30% of the time. After hatching, the young birds are ready for flight within 70-75 days. If one looks at the length of summer in the Arctic, it doesn't take long to understand that any delay in egg-laying would mean the young would not reach flight maturity in time to depart before temperatures drop and food becomes scarce in the fall. Because of these time constraints, if a tundra swan nest is depredated early, they will usually not lay any more eggs in hopes of reproductive success.
(most information from Wilderness Society in Birds of North America, No. 89.
As for behavior, I've had the opportunity to notice some beautiful activities. First, tundra swans spend the majority of their time with just their mate, so most often you will find just 2 swans on a lake or pond. Both the male and female have similar appearances, so it is difficult to know which is on the nest, but both stay close together. I had previously read some about swan courtship displays, and have now had the opportunity to watch in person. Interestingly, even after the nest is built and eggs are layed, the pair will still perform courtship dances . . . Almost like they have stayed in love!!!! When they display, they will rear back in the water to reach their necks high, spread their enormous wings, twist their necks - quite beautiful! Another observation I've made is their flight take-off from water. With their large feet, and the quietness of the uninhabited tundra, it is quite entertaining to hear their large feet slap the water as they run on its surface ! - the flap, flap, flap gets faster and faster until they are finally airborne and their impressive bodies are floating above you. Quite a breathtaking site!
More tomorrow on a variety of bird behaviors I've been able to observe, as well as a little about how the day goes.
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