Archive for Sunday, August 9, 1998

THE BELTED KINGFISHER LIKES LIVING IN A HOLE IN THE GROUND.

August 9, 1998

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With relatives from around the world, the belted kingfisher is at home in Kansas.

The belted kingfisher is one of 86 species in the family of kingfishers, a group found nearly throughout the world, but mostly in the Old World tropics. All have big heads, short necks and short tails. They feed on small fishes, reptiles, mammals, crustaceans and large insects, and some even on earthworms, snails and crabs. The large kookaburras also take birds and snakes.

Our kingfisher is pretty well satisfied to take fishes and crayfish. But it is on record taking reptiles, juvenile birds, small mammals, and, in maritime settings, oysters and squid. Kingfishers tend to be sit-and-wait predators, but may also do a good bit of hovering before diving. Adults may teach their young how to catch fish by dropping dead prey into water beneath a perch, but it is unknown if this technique is used for lizards or other prey.

Small, medium and large

Kingfishers of the world may be small -- less than an ounce in weight -- or considerably larger, such as the kookaburras, large ones of which can weigh more than a pound. The belted kingfisher is of medium size by these standards, and most members of the group are smaller.

The belted kingfisher can be seen year round in Kansas. Numbers are greater in spring, summer and autumn. Winter records are likely to be from the southeastern or eastern sectors. The species nearly covers North America, shifting well north in summer and to Panama and the Greater Antilles in winter.

Belted kingfishers lay their eggs at the expanded end of a burrow that the pair excavates. Earthen banks of sandy soils are best for digging such burrows, and the cliffs along the Kansas River are used regularly by the birds. No nest is made; the egg chamber is from 3 to 6 feet from the entrance of the burrow, although much longer tunnels have been found. Burrows may be reused year to year. Some pairs excavate two or more burrows in a single bank, but only one is used for the eggs. The burrow site is the main focus of the birds' activities once excavations are begun. Digging is done with the heavy, blade-like bill, and the loosened material is ejected from the tunnel with the feet. A considerable plume of sandy clay may periodically be shuffled out of the entry hole.

Proud parents

Females lay an average of six very large eggs, the mass of which amounts to nearly half the body weight of the adult female. Incubation, by both sexes in bouts of up to 24 hours at a time, begins with the first egg. This means that the young hatch out serially. The last young to hatch compete with considerably older siblings for at least two weeks of the four-week nest life. This is usually considered to be a format for brood reduction if food scarcity occurs in the time the young are being fed by parents. And, if food is abundant, all the young may fledge.

Feeding of the young is a considerable undertaking in kingfishers, because adults continue parental care well after the brood has left the nest. This period is of about three weeks, and requires constant adult attention as well as periodic feeding, and perhaps instruction in how to catch a fish. Adults care for their young for as long as 50 days, from the egg to successful fledging.

Feeding clues

The diet of kingfishers can readily be determined by examining the pellets disgorged from their gizzards. Pellets are formed from indigestible parts of prey, such as bones, exoskeletons, scales, or fur. The birds usually take prey in proportion to availability. This is true for fishes and insects, but some species of crayfish seem to be avoided. Kingfishers tend to form pellets of entire fish skeletons plus scales. Sizes of prey fish are relatively small, and many fish may be required daily by each bird. A large fish is digested gradually, as it slowly moves headfirst down the esophagus and into the stomach. The pellet, however, is formed after digestion is complete and is disgorged as a unit.

Kingfishers have been thought to be significant predators at fish farms, fish hatcheries and along trout streams. And, if prey fish are small, many may be required daily by each bird. A nestling has been found to require 8.3 fish the size of coho salmon fingerlings per day for four weeks; that is 232 per kingfisher nestling or nearly 1400 for a brood of six. And, they eat more once they leave the nest.

Belted kingfishers have been seriously hunted as a result, although not always with convincing evidence that they are a cause of economic hardship, and despite the legal protection of the International Migratory Bird Treaty between the United States, Canada and Mexico. Fisheries managers have enough difficult problems that they almost welcome one that can be ``solved'' over the barrel of a gun.

But kingfisher populations are probably not affected much by shooting or other control methods used by humans, and populations are maintained nearly at equilibrium, from year to year.

An old bird

Regulation of population numbers is probably a reflection of the amount of suitable nesting habitat coupled with water of reasonably high quality. This mainly means water of some clarity, because kingfishers need to see into the water column in order to locate a meal.

Perhaps unexpectedly, pesticides seem not to be an important source of mortality for kingfishers. Apparently even adults take fishes of relatively young ages, which presumably have not had much time to concentrate toxins in their tissues before becoming bird food. This is not a recipe for human behavior, however, because kingfishers have a short individual lifespan compared to what humans normally expect.

As far as the species itself is considered, belted kingfishers have a fossil history extending back at least 600,000 years. In that respect and like many kinds of birds, they outdo us, because a half-million years ago our most recent ancestor, Homo erectus, had not yet finished its period of primacy, and modern humans were yet to come on the scene.

-- Richard F. Johnston, is professor emeritus at the Kansas University Natural History Museum and Biodiversity Research Center and a member of the Kansas Ornithological Society.

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