Common Loon

Full Species Account

 

Some Native American cultures revered Common Loons as a link to world creation, or with pride and bravery (as seen in their territorial defenses) (1). We admire them for their beautiful breeding plumages, their grace, and their ethereal calls.

 

The Common Loon has four distinct calls used to communicate with their families and other loons: The tremolo, the wail, the yodel and the hoot. The tremolo is also known as the "crazy laugh." It is used to signal alarm, and, at night to advertise and defend its territory. Loons in flight sometimes give a slightly modified version of the tremolo. Loons are most vocal from mid-May to mid-June. (2) 

 

The Common Loon (Gavia immer) was previously known as the Great Northern Diver. The loons belong to a small family (Gaviidae) of diving birds and are sufficiently different from all other birds to form an entire order (Gaviiformes) by themselves. Separated evolutionarily by nearly 50 million years from the closest relatives, their ancestors may have been the same as those of penguins, albatrosses, and charadriiformes (gulls, shorebirds, gannets, cormorants, and puffins) (2, 3). Ornithologists first thought that loons were close relatives to the grebes (Order Podicipediformes) (1) but recent genetic studies do not support this relationship.  Instead, they confirm that the loons are related to the above water birds, and also the tropicbirds (4, 5).

 

Loons are large and bulky birds, with our Common Loon sporting a weight of 9 pounds, a wingspan of 46” and body length of 32” – that is, nearly 4 feet wide and 3 feet long (But remember the Northern Gannet with a similar body length has a 72” wingspan – almost 6 feet wide). The loon body is designed for diving as their previous name, divers, implies. Their legs are relatively short, but strong, and placed toward the rear of the bird - designed for propulsion underwater. The leg bone (tarsus) is compressed from side to side for less water resistance, and the three webbed front toes are oriented to provide for more surface area and increased propulsion. On occasion the wings are used for maneuvering underwater. Have you noticed while watching a loon dive, that it will surface great distances from its original plunge? They can dive to depths of 75 meters, but normal dives average 2-10 meters, and they can be submerged for as long as 8 minutes. (1)

 

The motion of the loon’s dive is graceful – it lowers its head and thrusts its body forward, all in one silent motion, as compared to grebes and cormorants that appear to hop or jump into a dive (1). See if you can see the differences in the diving characteristics of our cormorants, grebes, and loons off the Backshore.

 

During their dives, loons take small- to medium-sized fish in their freshwater breeding locations and during the winter off our coasts. However they will feed on invertebrates, frogs, and aquatic insects – even plant material at nesting sites. Prey is mostly swallowed while under water unless it is too lively or large, and the loons will then bring it to the surface to disable it. (1)

 

Plumage care is extensive as with all water birds. Loons have a characteristic manner in which they preen – while on the water they roll over on their side to expose the immaculate white bellies, lifting their large leg in the process. Watch closely and you can see the leg ‘waving’.  Their bathing is just as spectacular: wing-shaking, rolling, diving, and somersaulting – what spectacular entertainment for Backshore observers. (1)

 

The Common Loon’s winter plumage is similar to immature loons: A white face and fore neck with a brownish grey back; dark crown and nape; and white below. Their beaks are a light grey. Immature loons may show buffy scaly feathers on the upper parts of the body.  Adults shed their flight feathers all at once in the late winter/early spring, making them flightless for a few weeks. Body feathers are molted twice a year – in the autumn (grey non-distinct plumage) and early spring (to their breeding plumage). The spectacular breeding plumage is the same for both sexes – a black velvety head and upper neck with a purplish-green sheen, with short white vertical neck stripes. As in all species the under parts are white with a black tail, in both winter and breeding plumages. Their beak is heavy and mostly straight. (1, 6)

 

The Common Loon usually prefers large deep lakes, with islets (nest sites) for breeding and a long expanse of water for taking off and landing. In flight their necks are outstretched and below body level in such a way that they look hump-backed when in flight. They fly swiftly and with ‘purpose’, with feet extended beyond the tail (1). Although the positioning of the legs far back on the body is great for superb diving, it causes loons to be clumsy on land. They are found on land only when building and setting on their nests (2). Loons cannot even stand upright more than a few seconds. So the loons put weight on their breast and kick their legs out backwards (1). For this reason, they prefer to place their nest close to water such as on islets.

 

Common Loons are monogamous - pairing for life. After spending winters together they fly inland at spring thaw and return to the same territory each year. Because they are bonded as a pair during the winter (as compared to Northern Gannets that winter alone at sea and have extensive re-uniting rituals at their breeding sites), the loon pair’s nesting rituals are minimal. However, the display is elegant and it consists of several synchronized movements: Bill-dipping, Splash-diving and Rushing-underwater. The male selects and prepares the nest site - mosses and waterweeds. He will defend the nest with the above mentioned mating displays, and he will also use the Circle-dance followed by Water-chases and flapping-wings. Fights are infrequent but if they do occur, it is violent struggle using their wings and beaks as ‘weapons’. It may result in death – by drowning or spearing. (1, 2)

 

The Common Loon produces 1-3 eggs that are a large glossy olive brown and incubated by the male and female. Loons do not have brood patches (bare skin on breast), but instead there are blood vessels under the breast feathers that keep eggs warm. Incubation is for ~ 25 days. Hatchlings emerge in dark brown downy plumage and they are brooded ashore for the first 1-3 days. After leaving the nest the juveniles spend 2-3 weeks swimming or resting on the parents’ backs. (1) Michelle found “loons to be excellent parents who would put on quite a vocal and behavioral display if she got too close - to view and count their chicks (which she tried not to do of course). They were also very good at keeping their chicks out of harm's way by ushering them into the reeds or on their back at any sign of danger”.

 

Even after the young fledge (~77 days) they rely on food from parents until fully-grown, and sometimes into the winter. The Common Loon moves southward from Canada, Alaska and northern US after breeding, mostly to both coasts, including the Gulf of Mexico. In the early autumn Patty observed several loons in close proximity to each other in Whitehead Passage, frequently giving brief calls to locate each other. Are they family units? Were the parents feeding the juveniles?

 

Common Loons that winter on Western European waters most likely return to breeding areas of Iceland and Greenland. The Common Loon breed at 2-3 years of age and may live only up to 8 years, as compared to ~20 years for other loon species. (1)

 

Michelle was fortunate to have had a summer job observing their breeding behavior in the Adirondacks. Here is her fascinating account:  During the summer of 2012, I worked for The Adirondack Center for Loon Conservation. My job was to follow the progress and success rate of several pairs of loons. I observed the hatching and raising of their chicks on nine different Adirondack lakes. The Adirondack’s lake systems receive quite a bit of mercury fallout from mid-western industrial areas. This contaminant may affect the fish-eating loons' ability to produce viable eggs, and to raise their young.  As part of the study, the adult loons that I observed were captured, and blood and feathers were then collected. These samples were analyzed for mercury concentrations. These data were then used to determine if there was a correlation between mercury pollution and their nesting success. Over ten years of data showed that 21% of male loons and 8% of females are at risk for behavioral and reproductive impacts based on elevated levels of mercury in their blood. Additionally, it was found that loons breeding on acidic lakes had higher mercury levels and produced fewer chicks than loons breeding on non-acidic lakes (for more information on this research, please see the Adirondack Center for Loon Conservation at: http://www.briloon.org/adkloon). 

 

Has anyone observed a Common Loon completely submerged except for its head? They can vary their buoyancy in the water allowing for partial submergence.  What advantage is there to this behavior? Michelle observed this behavior in the Adirondacks. Here is her account of this behavior and her answer: Common Loons are very secretive birds and they don't like a lot of interaction with other creatures. Thus, when a Common Loon feels threatened, it will lay low in the water with only its head visible – just enough so it can breathe. While in my kayak, if I approached a loon too closely, it would lower its body below the surface, giving me the signal ‘to back off’. When I moved off a distance, they would then come back up to the surface - full body. This behavior was a good indicator for me where their ‘safe space’ was.  As the summer progressed I got better at knowing where that ‘safe space’ was allowing for better observation of their behavior, without any influence from my presence.

 

What great stories, Michelle.

 

Written by: Patty Wainright and Michelle Brown

Reviewed by: Sam Wainright

 

References

1.  del Hoyo, J., Elliott, A., and Sargatal, J. eds. (1992). Handbook of the Birds of the World. Vol. 1. Lynx Edicions, Barcelona (pages: 161-172).

2.  McIntyre, Judith W. (1988). The Common Loon.  Spirit of Northern Lakes. University of Minnesota Press, Minnesota. 

3.  Del Hoyo, J., and N.J. Collar. 2104. Handbook of the Birds of the World and Birdlife International Illustrated Checklist of Birds of the World. Lynx Edicions, Barcelona (page: 366).

4.  Hackett, S. et al. 2008. A phylogenetic study of the birds reveals their evolutionary history. Science 320(5884):1763-1768.

5.  Jarvis, E. D. et al. 2015. Whole-genome analyses resolve early branches in the tree of life of modern birds. Science. Vol 346(6215):1320-1331.

6. Sibley, D.A.  (2000). National Audubon Society: The Sibley Guide to Birds.  Alfred A. Knopf, Inc. NY (page: 25).

      

Links:

Adirondack Center for Loon Conservation

 

Common Loon Research in our area

Paruk, Dr. James. Biodiversity Research Institute, Gorham, Maine.

 

The Loon Preservation Committee

 

Common Loon winter plumage photos

 

All About Birds – Cornell Lab of Ornithology: Common Loon range map