Loon
| Divers/Loons | |
|---|---|
| |
| Great Northern Diver or Common Loon (Gavia immer). | |
| Scientific classification | |
| Kingdom: | |
| Phylum: | |
| Class: | |
| Order: | Gaviiformes |
| Family: | Gaviidae J.A. Allen, 1897
|
| Genus: | Gavia Forster, 1788
|
| Species | |
| File:Gaviidae Distribuzione.jpg | |
| Global distribution of Gaviidae (breeding and winter ranges combined) | |
The Loons (N.Am.) or Divers (UK/Ireland) are a group of aquatic birds found in many parts of North America and northern Europe. A loon is the size of a large duck or small goose, which it somewhat resembles in shape when swimming, but they are completely unrelated to waterfowl. Their plumage is largely black-and-white, with grey on the head and neck in some species, and a white belly, and they have a spear-shaped bill. All living species of loons are members of one genus (Gavia) in a family (Gaviidae), and order (Gaviiformes) all of their own.
ź== Ecology == Loons are excellent swimmers, using their feet to propel themselves above and under water and the wings for assistance. Because their feet are far back on the body, loons are badly adapted to moving on land. They usually avoid coming ashore, except for nesting.
All loons are decent fliers though the larger species have some difficulty taking off, needing a run into the wind to pick up enough velocity to get airborne. Only the Red-throated Diver can take off from land. Once airborne, their considerable stamina allows them to migrate long distances southwards in winter, where they reside in coastal waters. Loons can live as long as 30 years.
Diet
Loons eat fish, amphibians, and crustaceans, which they hunt for under water, finding their prey by sight. This includes crayfish, frogs, snails, salamanders and leeches. They prefer clear lakes because it is easier to see prey. The loon's pointy bill is used to stab or grasp prey. Vertebrate prey is eaten head first to facilitate swallowing.
To help digestion, loons swallow small pebbles from the bottom of a lake[citation needed]. Similar to grit eaten by chicken, these gastroliths may assist the loon's gizzard in crushing the hard parts of the loon's food (the exoskeletons of crustaceans and the bones of frogs and salamanders), as prey is swallowed whole.
=== Reproduction ===The Loons (N.Am.) or Divers (UK/Ireland) are a group of aquatic birds found in many parts of North America and northern Europe. A loon is the size of a large duck or small goose, which it somewhat resembles in shape when swimming, but they are completely unrelated to waterfowl. Their plumage is largely black-and-white, with grey on the head and neck in some species, and a white belly, and they have a spear-shaped bill. All living species of loons are members of one genus (Gavia) in a family (Gaviidae), and order (Gaviiformes) all of their own.
Contents [hide] 1 Ecology 1.1 Diet 1.2 Reproduction 1.3 Migration 2 Systematics and evolution 2.1 Species 2.2 Relationships and evolution 3 Trivia 4 References 5 External links
[edit] Ecology Loons are excellent swimmers, using their feet to propel themselves above and under water and the wings for assistance. Because their feet are far back on the body, loons are badly adapted to moving on land. They usually avoid coming ashore, except for nesting.
All loons are decent fliers though the larger species have some difficulty taking off, needing a run into the wind to pick up enough velocity to get airborne. Only the Red-throated Diver can take off from land. Once airborne, their considerable stamina allows them to migrate long distances southwards in winter, where they reside in coastal waters. Loons can live as long as 30 years.
[edit] Diet
Loons eat fish, amphibians, and crustaceans, which they hunt for under water, finding their prey by sight. This includes crayfish, frogs, snails, salamanders and leeches. They prefer clear lakes because it is easier to see prey. The loon's pointy bill is used to stab or grasp prey. Vertebrate prey is eaten head first to facilitate swallowing.
To help digestion, loons swallow small pebbles from the bottom of a lake[citation needed]. Similar to grit eaten by chicken, these gastroliths may assist the loon's gizzard in crushing the hard parts of the loon's food (the exoskeletons of crustaceans and the bones of frogs and salamanders), as prey is swallowed whole.
[edit] Reproduction
During the summer, loons nest on fresh water lakes and/or large ponds. Smaller bodies of water (up to 0.5 km²) will usually only have one pair. Larger lakes will have more than one pair, with each pair occupying a bay or section of the lake.
Loons build their nests close to the water, preferring sites that are completely surrounded by water. They may use the same site from year to year. Loons will use a variety of materials found nearby to build their nests — pine tree needles, leaves, grass, moss, and sometimes clumps of mud. Both the male and female help with nest building and with incubation, which usually lasts 26-31 days. If the eggs are lost, the pair may re-nest, often in the same general location.
Usually one or two eggs are laid in June. Loon chicks are precocial, able to swim right away, but are often seen riding on their parents' back. This behavior allows the chicks to rest, conserve heat, and avoid predators such as large carnivorous fish, snapping turtles, gulls, eagles and crows. After a day or two, chicks do not return to the nest anymore.
Chicks are fed exclusively by their parents for the first few weeks of life, and up until eight weeks of age, stay with their parents most of the time. After eight weeks, chicks will begin to dive for some of their own food. By 11 or 12 weeks of age, chicks are able to gather almost all of their own food and may be able to fly.
A pair may mate for life, although recent banding studies have shown that loons will sometimes switch mates after a failed nesting attempt and even between nesting attempts in the same season[citation needed].
[edit] Migration
Common Loons generally migrate to oceans for the winter because their poor walking ability and need for a "runway" of open water to fly leave them in danger if their lakes freeze. In February 2007, scientists found 17 dead loons at Lake Winnipesaukee in New Hampshire and speculated that the uncommonly warm early winter had confused the loons, leaving them vulnerable when the lake finally froze weeks later than normal. [1]
[edit] Systematics and evolution
Arctic Loon/Black-throated Diver [edit] Species All living divers are classed in the genus Gavia.
Red-throated Diver or Red-throated Loon, Gavia stellata. Black-throated Diver or Arctic Loon, Gavia arctica. Pacific Diver or Pacific Loon, Gavia pacifica - sometimes included in G. arctica Great Northern Diver or Common Loon, Gavia immer. White-billed Diver or Yellow-billed Loon, Gavia adamsii
[edit] Relationships and evolution The loons were formerly often considered to be the most ancient of the northern hemisphere bird families; this idea grew basically out of the perceived similarity of shape and (probably) habits between loons and the entirely unrelated extinct Cretaceous order Hesperornithiformes. However, the two groups are merely the product of convergent evolution and adapted in a similar way to a similar ecological niche.
More recently, it has recently become clear that the Anseriformes (waterfowl) and the Galliformes are the most ancient groups of modern birds, while loons belong to a more modern radiation. What is also generally accepted as a fact is that loons and grebes are not closely related at all, but rather one of the most stunning examples of convergence in the known birds. The Sibley-Ahlquist taxonomy still allied the loons with the grebes in its paraphyletic "Ciconiiformes", and it is almost certain that the relationships of loons lie with some of the orders united therein. Alternatively, loons have tentatively been considered to share a rather close relationship with waders, penguins or procellariiform seabirds (Olson, 1985; Mayr, 2004).
The conflicting molecular data is not much resolved by the fossil record. Modern loons are only known with certainty since the Eocene , but by that time almost all modern bird orders are known or strongly suspected to have existed anyway. The Late Eocene to Early Miocene genus Colymboides was widespread in Western and Central Europe; it is usually placed in the Gaviidae already, but may actually be more primitive; it is quite distinct from modern loons and could well be paraphyletic. From the genus Gavia, about a dozen fossil species have been discovered to date, which are known from the Early Miocene onwards and had a more southerly distribution (Brodkorb, 1953), like today's California, Florida and Italy. The following have been scientifically described:
Gavia egeriana (Early Miocene of Czechoslovakia) Gavia brodkorbi (Late Miocene of Orange County, USA) Gavia concinna Wetmore, 1940 (Early - Middle Pliocene of W and SE USA) - may be same as G. portisi Gavia howardae Brodkorb, 1953 (Middle Pliocene of San Diego, USA) Gavia palaeodytes Wetmore, 1943 (Middle Pliocene of Pierce, USA) Gavia portisi Regalia, 1902 (Late Pliocene of Italy) Gavia fortis Gavia moldavica Gavia paradoxa Gavia schultzi Undescribed fossils (Olson, 1985) are known from the eastern USA (Middle Miocene), Maryland (possibly Calvert Formation which is also Middle Miocene in age), and the Yorktown Formation (Early Pliocene at Lee Creek Mine, South Carolina where 3 unknown species are represented.
In addition, there are some much older forms that are sometimes assigned to the Gaviiformes. From the Late Cretaceous, the genera Lonchodytes (Lance Creek Formation, Wyoming) and Neogaeornis (Quinriquina Formation, Chile) have been described; the latter is most probably a primitive loon, but may also be a hesperornithiform, and both have sometimes been allied with the orders which are considered related to loons. Doubtfully valid and surrounced by considerable dispute (Mayr, 2004) is the supposed Late Cretaceous loon Polarornis (Seymour Island, Antarctica). A piece of a carpometacarpus supposedly from Oligocene rocks near Lusk, Wyoming was described as Gaviella pusilla, but this also shows some similarities to the plotopterids (Olson, 1985).
[edit] Trivia
The Common Loon is the national bird of Canada and is depicted on the Canadian one-dollar coin, which has come to be known affectionately as the loonie. It is also the official provincial bird of Ontario and the official state bird of Minnesota.
The genus name Gavia is Latin for "Smew", even though loons are not related to smews.
The European name "diver" comes from the bird's habit of catching fish by swimming calmly along the surface and then abruptly plunging into the water. The North American name loon comes from the bird's haunting, yodeling cry, a symbol of the Canadian wilds.
Mercer, Wisconsin is identified as the "Loon Capital of the World."
The Great Lakes Loons are a Single A baseball team based in Midland, MI.
[edit] References Brodkorb, Pierce (1953): A Review of the Pliocene Loons. Condor 55: 211-214. PDF fulltext Mayr, Gerald (2004): A partial skeleton of a new fossil loon (Aves, Gaviiformes) from the early Oligocene of Germany with preserved stomach content. Journal of Ornithology 145: 281–286. DOI:10.1007/s10336-004-0050-9 (HTML abstract) PDf fulltext Olson, Storrs L. (1985): Section X.I. Gaviiformes. In: Farner, D.S.; King, J.R. & Parkes, Kenneth C. (eds.): Avian Biology 8: 212-214. Academic Press, New York. Suck my Balls
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During the summer, loons nest on fresh water lakes and/or large ponds. Smaller bodies of water (up to 0.5 km²) will usually only have one pair. Larger lakes will have more than one pair, with each pair occupying a bay or section of the lake.
Loons build their nests close to the water, preferring sites that are completely surrounded by water. They may use the same site from year to year. Loons will use a variety of materials found nearby to build their nests — pine tree needles, leaves, grass, moss, and sometimes clumps of mud. Both the male and female help with nest building and with incubation, which usually lasts 26-31 days. If the eggs are lost, the pair may re-nest, often in the same general location.
Usually one or two eggs are laid in June. Loon chicks are precocial, able to swim right away, but are often seen riding on their parents' back. This behavior allows the chicks to rest, conserve heat, and avoid predators such as large carnivorous fish, snapping turtles, gulls, eagles and crows. After a day or two, chicks do not return to the nest anymore.
Chicks are fed exclusively by their parents for the first few weeks of life, and up until eight weeks of age, stay with their parents most of the time. After eight weeks, chicks will begin to dive for some of their own food. By 11 or 12 weeks of age, chicks are able to gather almost all of their own food and may be able to fly.
A pair may mate for life, although recent banding studies have shown that loons will sometimes switch mates after a failed nesting attempt and even between nesting attempts in the same season[citation needed].
Migration
Common Loons generally migrate to oceans for the winter because their poor walking ability and need for a "runway" of open water to fly leave them in danger if their lakes freeze. In February 2007, scientists found 17 dead loons at Lake Winnipesaukee in New Hampshire and speculated that the uncommonly warm early winter had confused the loons, leaving them vulnerable when the lake finally froze weeks later than normal. [1]
Systematics and evolution
Species
All living divers are classed in the genus Gavia.
- Red-throated Diver or Red-throated Loon, Gavia stellata.
- Black-throated Diver or Arctic Loon, Gavia arctica.
- Pacific Diver or Pacific Loon, Gavia pacifica - sometimes included in G. arctica
- Great Northern Diver or Common Loon, Gavia immer.
- White-billed Diver or Yellow-billed Loon, Gavia adamsii
Relationships and evolution
The loons were formerly often considered to be the most ancient of the northern hemisphere bird families; this idea grew basically out of the perceived similarity of shape and (probably) habits between loons and the entirely unrelated extinct Cretaceous order Hesperornithiformes. However, the two groups are merely the product of convergent evolution and adapted in a similar way to a similar ecological niche.
More recently, it has recently become clear that the Anseriformes (waterfowl) and the Galliformes are the most ancient groups of modern birds, while loons belong to a more modern radiation. What is also generally accepted as a fact is that loons and grebes are not closely related at all, but rather one of the most stunning examples of convergence in the known birds. The Sibley-Ahlquist taxonomy still allied the loons with the grebes in its paraphyletic "Ciconiiformes", and it is almost certain that the relationships of loons lie with some of the orders united therein. Alternatively, loons have tentatively been considered to share a rather close relationship with waders, penguins or procellariiform seabirds (Olson, 1985; Mayr, 2004).
The conflicting molecular data is not much resolved by the fossil record. Modern loons are only known with certainty since the Eocene , but by that time almost all modern bird orders are known or strongly suspected to have existed anyway. The Late Eocene to Early Miocene genus Colymboides was widespread in Western and Central Europe; it is usually placed in the Gaviidae already, but may actually be more primitive; it is quite distinct from modern loons and could well be paraphyletic. From the genus Gavia, about a dozen fossil species have been discovered to date, which are known from the Early Miocene onwards and had a more southerly distribution (Brodkorb, 1953), like today's California, Florida and Italy. The following have been scientifically described:
- Gavia egeriana (Early Miocene of Czechoslovakia)
- Gavia brodkorbi (Late Miocene of Orange County, USA)
- Gavia concinna Wetmore, 1940 (Early - Middle Pliocene of W and SE USA) - may be same as G. portisi
- Gavia howardae Brodkorb, 1953 (Middle Pliocene of San Diego, USA)
- Gavia palaeodytes Wetmore, 1943 (Middle Pliocene of Pierce, USA)
- Gavia portisi Regalia, 1902 (Late Pliocene of Italy)
- Gavia fortis
- Gavia moldavica
- Gavia paradoxa
- Gavia schultzi
Undescribed fossils (Olson, 1985) are known from the eastern USA (Middle Miocene), Maryland (possibly Calvert Formation which is also Middle Miocene in age), and the Yorktown Formation (Early Pliocene at Lee Creek Mine, South Carolina where 3 unknown species are represented.
In addition, there are some much older forms that are sometimes assigned to the Gaviiformes. From the Late Cretaceous, the genera Lonchodytes (Lance Creek Formation, Wyoming) and Neogaeornis (Quinriquina Formation, Chile) have been described; the latter is most probably a primitive loon, but may also be a hesperornithiform, and both have sometimes been allied with the orders which are considered related to loons. Doubtfully valid and surrounced by considerable dispute (Mayr, 2004) is the supposed Late Cretaceous loon Polarornis (Seymour Island, Antarctica). A piece of a carpometacarpus supposedly from Oligocene rocks near Lusk, Wyoming was described as Gaviella pusilla, but this also shows some similarities to the plotopterids (Olson, 1985).
Trivia
- The Common Loon is the national bird of Canada and is depicted on the Canadian one-dollar coin, which has come to be known affectionately as the loonie. It is also the official provincial bird of Ontario and the official state bird of Minnesota.
- The European name "diver" comes from the bird's habit of catching fish by swimming calmly along the surface and then abruptly plunging into the water. The North American name loon comes from the bird's haunting, yodeling cry, a symbol of the Canadian wilds.
- Mercer, Wisconsin is identified as the "Loon Capital of the World."
- The Great Lakes Loons are a Single A baseball team based in Midland, MI.
References
- Brodkorb, Pierce (1953): A Review of the Pliocene Loons. Condor 55: 211-214. PDF fulltext
- Mayr, Gerald (2004): A partial skeleton of a new fossil loon (Aves, Gaviiformes) from the early Oligocene of Germany with preserved stomach content. Journal of Ornithology 145: 281–286. doi:10.1007/s10336-004-0050-9 (HTML abstract) PDf fulltext
- Olson, Storrs L. (1985): Section X.I. Gaviiformes. In: Farner, D.S.; King, J.R. & Parkes, Kenneth C. (eds.): Avian Biology 8: 212-214. Academic Press, New York.
External links
- Photo of a loon
- Loon sounds
- Loon videos on the Internet Bird Collection
- http://www.saskschools.ca/~gregory/animals/loon/ln2.html
- Loon Preservation Committee
- The Flickr Loon group