Tundra Swan, Cygnus columbianus
Note: this post, while published, is a work in progress, as are all posts in this series, My Photo Life List. My goal is to photograph every species of bird that is seen on a regular basis here in Michigan, working from a list compiled by the Michigan chapter of the Audubon Society. This will be a lifelong project, that I began in January of 2013, and as I shoot better photos of this, or any other species, I will update the post for that species with better photos when I can. While this series is not intended to be a field guide per se, my minimum standard for the photos in this series is that one has to be able to make a positive identification of the species in my photos. The information posted here is from either my observations or the Wikipedia, the online free encyclopedia, however, I have personally shot all the photos appearing in this series.
This post represents a milestone, I am now half-way through the list from the Audubon Society that I am working from as I add species of birds to my life list. So, I thought that this post deserved to highlight a species with the “stature” befitting such a post. Therefore, I have chosen the tundra swan to mark the occasion.
Tundra Swan, Cygnus columbianus
The tundra swan is a small Holarctic swan. The two taxa within it are usually regarded as conspecific, but are also sometimes split into two species, Cygnus bewickii (Bewick’s swan) of the Palaearctic and the whistling swan, C. columbianus proper, of the Nearctic. For the purposes of this post, I’m going to lump the two sub-species together, as that’s the way that they appear on the list that I’m working from.
C. columbianus is the smallest of the Holarctic swans, at 115–150 cm (45–59 in) in length, 168–211 cm (66–83 in) in wingspan and a weight range of 3.4–9.6 kg (7.5–21.2 lb). In adult birds, the plumage of both subspecies is entirely white, with black feet, and a bill that is mostly black, with a thin salmon-pink streak running along the mouthline and, depending on the subspecies, more or less yellow in the proximal part. The iris is dark brown. In birds living in waters that contains large amounts of iron ions (e.g. bog lakes), the head and neck plumage acquires a golden or rusty hue. Pens (females) are slightly smaller than cobs (males), but do not differ in appearance otherwise.
Immatures of both subspecies are white mixed with some dull grey feathering, mainly on the head and upper neck, which are often entirely light grey; their first-summer plumage is quite white already, and in their second winter they moult into the adult plumage. Their bills are black with a large dirty-pink patch taking up most of the proximal half and often black nostrils, and their feet are dark grey with a pinkish hue. Downy young are silvery grey above and white below.
Tundra swans have high-pitched honking calls and sound similar to a black goose (Branta). They are particularly vocal when foraging in flocks on their wintering grounds; any conspecific arriving or leaving will elicit a bout of loud excited calling from its fellows. Contrary to its common name, the ground calls of the whistling swan are not a whistle and neither notably different from that of Bewick’s swan. The flight call of the latter is a low and soft ringing bark, bow-wow…; the whistling swan gives a markedly high-pitched trisyllabic bark like wow-wow-wow in flight. By contrast, the whooper and trumpeter swans’ names accurately describe their calls, a deep hooting and a higher-pitched French horn-like honk, respectively. Flying birds of these species are shorter-necked and have a quicker wing beat than their relatives, but they are often impossible to tell apart except by their calls.
As their common name implies, the tundra swan breeds in the Arctic and subarctic tundra, where they inhabit shallow pools, lakes and rivers. These birds, unlike mute swans, but like the other Arctic swans, are migratory birds. The winter habitat of both subspecies is grassland and marshland, often near the coast; they like to visit fields after harvest to feed on discarded grains and while on migration may stop over on mountain lakes. According to National Geographic, when migrating these birds can fly at altitudes of 8 km (nearly 27,000 ft). Tundra swan flocks usually fly in V formation.
In summer, their diet consists mainly of aquatic vegetation, e.g. mannagrass, Potamogeton pondweeds and marine eelgrass, acquired by sticking the head underwater or upending while swimming; they also eat some grass growing on dry land. At other times of year, leftover grains and other crops such as potatoes, picked up in open fields after harvest, make up much of their diet. Tundra swans forage mainly by day. In the breeding season, they tend to be territorial and are aggressive to many animals who pass by, outside the breeding season they are rather gregarious birds.
Healthy adult birds have few natural predators. Arctic foxes may threaten breeding females and particular the eggs and hatchlings. Adults typically can stand their ground and displace foxes but occasionally the foxes are successful. Another surprisingly serious nest predator for tundra swans are brown bears, which were apparently the primary cause of nesting failure in both the Arctic National Wildlife Refuge and Izembek National Wildlife Refuge. Other potential nest predators include red fox, golden eagles, parasitic jaegers, and glaucous gull. Brown bear, golden eagles and, rarely, gray wolves may on occasion succeed at capturing and killing an adult. Small or avian predators usually illicit either an aggressive response or the behavior of sitting tight on nests while larger mammals, perhaps more dangerous to adults, usually illicit the response of leading the cygnets into deep waters and standing still until they pass. About 15% of the adults die each year from various causes, and thus the average lifespan in the wild is about 10 years. The oldest recorded tundra swan was over 24 years old.
The tundra swans mate in the late spring, usually after they have returned to the nesting grounds, as usual for swans, they pair monogamously until one partner dies. Should one partner die long before the other, the surviving bird often will not mate again for some years, or even for its entire life. The nesting season starts at the end of May. The pair build the large mound-shaped nest from plant material at an elevated site near open water, and defend a large territory around it. The pen (female) lays and incubates a clutch of 2–7 (usually 3–5) eggs, watching for danger while sitting on the nest. The cob (male) keeps a steady lookout for potential predators heading towards his mate and offspring. When either of them spots a threat, they give a warning sound to let their partner know that danger is approaching. Sometimes the cob will use his wings to run faster and appear larger in order to scare away a predator.
The time from laying to hatching is 29–30 days for Bewick’s swan and 30–32 days for the whistling swan. Since they nest in cold regions, tundra swan cygnets grow faster than those of swans breeding in warmer climates, those of the whistling swan take about 60–75 days to fledge, twice as fast as those of the mute swan for example, while those of Bewick’s swan, about which little breeding data is known, may fledge a record 40–45 days after hatching already. The fledglings stay with their parents for the first winter migration. The family is sometimes even joined by their offspring from previous breeding seasons while on the wintering grounds. Tundra swans do not reach sexual maturity until 3 or 4 years of age.
On to my photos:
This is number 175 in my photo life list, only 175 to go! Half-way through, woo-woo!
That’s it for this one, thanks for stopping by!