Gaviidae Loons
Version: 1.0 — Published March 4, 2020
Introduction
Torpedo-like piscivores of cold northern waters, these sleek foot-propelled divers have feet with traditional webs, but flattened for a knife-like upstroke and placed far back on the body to generate a powerful downstroke. Loons are so adapted to their aquatic lifestyle that they cannot really walk on land, instead tobogganing their bodies to and from a nest that is at most a body’s length from water. Soon after hatching, the fluff-ball chicks join their parents on the open water, accompanying them as they forage for the family. The young will continue to be fed until they acquire the dense velvety plumage they will have as adults.
Habitat
Most loons nest on Arctic and subarctic ponds and lakes, with one species (Gavia immer) nesting on large lakes surrounded by boreal forest. They winter in coastal waters or on very large lakes.
Diet and Foraging
Adult loons feed primarily on fish with some amphibians and aquatic invertebrates. Newly hatched young are fed aquatic arthropods before small fish are introduced.
Breeding
Loons are socially monogamous with biparental care. Loon nests vary in form, not only among species but within as well. The two primary nest types consist of aquatic vegetation placed on dry land or a nesting platform in shallow water, built by piling mud and aquatic vegetation until it sits just above the water line. Female loons usually lay 2 eggs, and both parents share in nest construction, incubation, and provisioning of the young. After about a month of incubation, the precocial chicks hatch and remain in the nest for a few days, but soon join their parents in open lake waters, either swimming along or riding on the back of one of the parents while the other dives for food. By about three weeks of age, they begin feeding themselves, but they are still fed occasionally by their parents even after they can fly at about seven to nine weeks of age.
Conservation Status
Although loons have disappeared from some breeding lakes because of acid rain and pollution, only one species (20%) is at risk (1 NT). The population of the Yellow-billed Loon G. adamsii is declining from subsistence hunting, and the species is at risk in parts of its range from oil development, heavy-metal poisoning, and drowning in fishing nets.
Systematics History
Largely on the basis of skeletal anatomy, Gaviiformes had long been thought to be allied to Podicipediformes, Procellariiformes, or Sphenisciformes. Anatomical characters and interpretations of fossil evidence have suggested a sister relationship between Gaviiformes and Podicipediformes (Cracraft 1981). However, molecular phylogenetic studies suggest that the loons are not at all closely related to the grebes and that the morphological similarities of these families are due to convergence. The loons are instead more closely related to groups within a large “waterbird clade” that includes Procellariiformes and Sphenisciformes (van Tuinen et al. 2001, Ericson et al. 2006a, Hackett et al. 2008), or these two groups plus Pelecaniformes, Suliformes, and Ciconiiformes (Jarvis et al. 2014).
Conservation Status
Least Concern |
80%
|
---|---|
Near Threatened |
20%
|
Vulnerable |
0%
|
Endangered |
0%
|
Critically Endangered |
0%
|
Extinct in the Wild |
0%
|
Extinct |
0%
|
Not Evaluated |
0%
|
Data Deficient |
0%
|
Unknown |
0%
|
Data provided by IUCN (2023) Red List. More information