Loons

Loons

Loons are aquatic predators, so highly specialized for swimming and diving that they are unable to walk properly on land. Apart from penguins of the southern hemisphere, they are the most specialized diving birds. Propelled by foot, they are fast and maneuverable underwater where they readily capture fish. They regulate buoyancy by adjusting feathers, the volume of air in air sacs, and the amount of air in the lungs. They nest on inland, freshwater lakes in summer. The majority migrate to coastal waters for winter, although some over winter on large, ice-free lakes in the southern parts of their range.

Loons are mainly associated with clear, oxygen-laden (logographic) lakes of the northern hemisphere, in areas with a past history of extensive glacial coverage. These include thousands of lakes in the northern forests; taiga and open tundra scraped outfox rock by retreating glaciers. Although adult loons cannot walk inland, chicks can waddle upright and have been known on rare occasions to negotiate several hundred meters between tarns or lakes while parents prompted from air or water. Loons are characteristically lone nesters within a large defended territory but colonial nesting is the nature of the Red-throated loon and the Arctic loon. Territories range in size from 15-200 acres.

All loons exhibit a strong preference for foresting away from the mainland shore, whether on the island, bog islet, stone outcrop-ping, or log, although Arctic and Red-throated loons frequently nest in coves or promontories of small tundra lakes that lack islands. With flight feathers renewed, small groups (packs) of loons may join others and coalesce into flocks of several hundred uncertain large bodies of water prior to and during spring and fall migration. The arrival of the breeding ground is usually in singles, pairs (apparently more common in the Arctic loon), or small loosely associated groups. Territories are often reoccupied as soon as sufficient water is ice-free for landing. Loons return to the same territory and often reuse the same nest.

Milk is taken from the parents’ bill! Common loon chicks are weaned from parental feeding between their 8 and I Courtship appears to be a prominent ritualized display only in the Red-throated loon. Copulation is secretive, onshore in the nearer. Both parents may construct the nest to incubate and tend the young. Young loons are well developed (precisian) and leave thinnest within a day of hatching, weather permitting. They are brooded on their parents’ backs and under a wing if the weather is inclement or danger threatens. Loon chicks can dive within a day of Hutchinson their expertise rapidly increases! Although chicks peck at and eat small invertebrates such as mosquitoes, black fiend a variety of aquatic insects, they are fey both parents. Food is fresh-caught (not regurgitated) and comprised of invertebrates or fish (preferred when available in weeks, but they occasionally still take fish from parents until they migrate. Adult loons form small social groups on many lakes in summer although certain large lakes seasonally have groups of 80-250 loons. These social groups are frequently joined by the resident parent not tending chicks. Juveniles do not join these groups. In fact, they are readily attacked by strange adults.

Although loons can remain submerged for several minutes most dives last less thane minute. Underwater progress is casual while hunting but speed can sustain while pursuing prey or fleeing. Several hundred meters can readily be traversed underwater and although most foraging occurs in relatively shallow depths with good light, i.e. in the top I ohm (33ft), Common loons have become enmeshed in nets at depths greater than 8om (265ft).

Loons are visual hunters and capture fish crosswise in the bill. As with other predators of vertebrates, atypical behavior among prey is quickly singled outfox attack. Loons are opportunistic foragers; their prevalent prey is fish, of any species or size that can be captured and ingested, usually less than 15cm (7in) but reportedly even over 40 cm (16in). Crustaceans such as crayfish and shrimp, leeches, and frogs are also eaten. Loons appear to ingest vegetation only when ill. Digestion in their powerful gizzard is aided by pea-sized stones.

Loons are highly specialized final predators in an aquatic food web composed of complex, interdependent activities among prey and predator, from microscopic plants and animals through fishes to the loons. Hence any degradation of the environment adversely affects loons. In parts of their breeding grounds in North America and Europe, they have been reduced in numbers or eliminated because of loss of nesting habitat, disturbances of nesting and brood-in areas, excessive aquatic plant growth, unpredictable and extensive water-level fluctuations, and toxicity. Large numbers have occasionally succumbed to botulism and considerable numbers are destroyed boil slicks on coastal waters in winter. Acid rain is also destroying the food chain in thousands of lakes, particularly for the Common loon in eastern North America.

In spite of adversities, loons are reasonably numerous throughout much of their traditional range.

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