The Fisher King
Unlike most other birds, belted kingfishers depend upon the males for nesting success.
On the far side of the Connecticut River, a female belted kingfisher perches on the edge of a fish-filled dishpan. Yes, a dishpan! She seizes a fat minnow in her razor-sharp bill, stuns the flopping fish by whomping it against the plastic pot and swallows it headfirst, then and there.
"You might say this shows the female's superior wisdom," teases biologist Dan Albano, who is watching the event through a spotting scope. Her mate, he explains, dives into the dishpan from above in typical kingfisher fashion, then flies to a branch with his catch. "He's wasting a lot of effort," says Albano, a graduate student at the University of Massachusetts in nearby Amherst.
Spring has sprung in the broad valley of the Connecticut, New England's longest river: Red maples are budding, farmers are plowing, mourning doves are mourning and kingfishers are patrolling upriver anddown. Albano, meanwhile, is a familiar customer at the local bait shop where he buys fish for stocking in dishpans strategically placed near kingfisher nest burrows. "This is a low-budget project, and I've gone through 10 pounds of minnows this week," he grumbles. "One mated pair cleaned out a pot of 50 fish in a day. They munch them like we munch Doritos."
Albano has not concocted some bizarre twist to the bird-feeding game. He is supplementing the food supply of nesting kingfishers as part of a study designed to shed light on the species' breeding biology, especially the importance of the male in the pair-bond.
Conventional wisdom says that 90 percent of the world's 9,000 or so species of birds form monogamous pair-bonds during the breeding season. "However, with many monogamous birds the male's help is critical only during certain phases of the nesting cycle," Albano explains. "Often, the female bears most of the burden of parental care, and, given an adequate food supply, she probably can raise a brood to independence by herself." The male, meanwhile, may be busy spreading his genes elsewhere, Albano says, increasing his number of offspring but investing only minimal effort in caring for young.
"But belted kingfisher males appear to expend as much or more effort than females in every phase of the breeding cycle — in addition to feeding the females during the egg-laying period," says Albano. "I'm documenting the time spent by each sex at each stage, and I hope to learn what ecological and demographic conditions influence this atypical division of parental care."
The belted kingfisher (only the female sports a rust-colored belt across the belly) is one of North America's most widespread land birds. It breeds in every continental state and Canadian province and even nests above the Arctic Circle in Alaska and the Yukon Territory. Although the species is migratory, and some individuals fly as far south as Colombia and Guyana, male belted kingfishers will stay behind to protect their breeding territories during mild northern winters when rivers and streams remain ice-free. They are excitable and aggressive birds and express their displeasure at territorial intrusions with strident rattle calls not unlike the clatter of a New Year's Eve noisemaker.
While kingfishers seem to prefer nest sites near creeks and rivers, where fishing is usually best, almost any aquatic habitat — ponds and lakes, estuaries and ocean bays — can support nesting pairs if the food supply is adequate and the water clear and calm enough for the birds to spot prey within 2 feet of the surface. Belted kingfishers mostly consume fish 4 to 5 inches long, from fingerling trout to sticklebacks with sharp dorsal spines that break off in the pummeling. At times, though, the kingfisher diet includes such items as crayfish, salamanders, frogs, snakes, lizards, turtles, mice, small birds, berries, even butterflies caught on the wing. They also eat mollusks, so occasionally a kingfisher ends up in dire straits with its bill clamped shut by an oyster or mussel.
Aside from that prime fishing spot, the most important thing in a kingfisher's life is a close-by burrow site, preferably a sandy bank where the digging is easy. However, birders have discovered kingfisher nests in ditches, railroad embankments, sawdust piles, sand dunes, spoil banks, dead trees, rotting stumps and, perhaps strangest of all, a furrow in a newly plowed hillside. In Minnesota, sand- and gravel-mining operations recently created new nesting habitat in a landscape pocked with lakes, and local kingfisher populations boomed.
Male kingfishers, Albano reports, often dig several "demo holes" before the females arrive on the scene, perhaps as a way to advertise their territory to potential mates. And competition among females for a male with a choice location sometimes can get intense. In an earlier Ohio study by biologist William James Davis, a young female arrived early, mated with the resident male and laid a full clutch of eggs before an older female turned up. "Given the high stakes," Davis observes, "I expected the younger female to defend her territory successfullyagainst the hostile newcomer." In most animal societies, he points out, territory owners win such conflicts.
Davis watched the females scrap for two days while the male passively followed them about. "On the third day," Davis recorded, "the young bird had disappeared, in effect giving up her home to her adversary. The victor promptly dumped her rival's eggs and within a week had laid her first egg in an adjoining nest chamber. Presumably the male had no difficulty in accepting the newcomer as a mate."
Digging a nest burrow is a job that can take from two days to a week. Kingfisher literature suggests that the male spends twice as much time digging as the female, but 1,000 hours of nest watching has convinced Albano that the labor is more evenly divided. One bird hammers away with its bill for anywhere from a few seconds to three or four minutes, kicking out a shower of dirt, while its mate watches and calls from a nearby branch before they change places.
The tunnel entrance, which is the size and shape of a squashed tennis ball, usually is dug about 2 feet below the top of a riverbank. The best sites are several feet above the water so that eggs and nestlings will be reasonably safe from floods. A high opening also helps protect a kingfisher's nest from raids by swimming minks and snakes, but raccoons and skunks sometimes dig into the chamber from the top of the bank. Scientists have reported kingfisher tunnels as long as 15 feet, but the typical burrow extends 3 to 6 feet with a gentle upward slope that helps keep water out of the chamber. If a rock or tree root blocks the way, the birds jog around it. One ornithologist dug out a burrow that made a sharp U-turn so that the egg chamber was only a few inches from the cliff face.
The male's work has only just begun when the tunnel is finished. He is expected to feed his mate for a three-week period, beginning about 10 days before she lays the first egg and ending a day or so after the last egg is placed in the chamber. The male arrives on a perch with a fish positioned head-out, the female lands nearby, and the birds sidle along the branch, sometimes making 180-degree turns until they are side by side and the offering is accepted.
Ornithologists traditionally have viewed this elaborate behavior as cementing the pair-bond. Albano, however, believes that courtship feeding is critical to kingfisher nesting success because it augments the female's energy supply at a particularly taxing time, when the egg mass constitutes more than half of her body weight. Moreover, egg weight may be an important factor in nestling vitality. At nests where he supplemented the food supply with pots full of minnows, and males fed their mates until they were stuffed, the female kingfishers laid significantly heavier clutches than at unsupplemented nests. "Some of these eggs," he adds, "felt as heavy as bricks."
Albano also determined that during the 22-day incubation period, the male kingfisher spends as much time brooding the eggs as does his mate. And Albano's observations contradict the long-standing belief that only the female kingfisher broods at night. Male birds, he says, often stayed on the eggs all night and into the next afternoon before being relieved.
For the first four days of their lives, kingfisher hatchlings are fed tiny minnows barely a half-inch long. Over the next three weeks the parent birds make some 1,200 trips to the nest with progressively larger fish up to 6 inches long, with the male bringing twice as much food as the female.
"There is a delicate balance," Albano says, "between the energy demands of the growing nestlings and the ability of the pair to obtain enough fish." Kingfisher families are large — six to eight chicks is the usual size — and in his Ohio project, Davis estimated that parents with nearly grown young needed to catch 90 fish a day to feed themselves and their offspring. "Ownership of good fishing holes, however, does not guarantee an easy life," he reported in one journal. "Even a rich territory may provide few fish when the river becomes laden with silt and debris after a heavy rain." In bad weather, kingfisher nestlings can starve to death while waiting for deliveries from parents searching far and wide for food.
Three or four days before young kingfishers are due to leave their burrow, the parents curtail feedings. With fish in their bills, the adults call from a nearby perch, while the fledglings crowd the burrow entrance and beg. Finally, hunger forces them to make their maiden flights. Young kingfishers remain with their parents for about three more weeks, the time it takes them to learn to fish. Until their flight skills are honed, the young are easy prey for Cooper's hawks. The adults, on the other hand, deliberately mob any raptors in the neighborhood, and, if a hawk retaliates, evade pursuit with a last-second dive into the river.
Yet a pile of female kingfisher feathers below one of Dan Albano's Connecticut River nests attests to a sneak attack by a hawk or owl early in the season. In experiments where the biologist temporarily removed the male from a breeding pair, the female abandoned her nest. But this widowed male simply picked up a new mate from an incoming wave of migrating females and started over. Such observations suggest that, at least in the world of the belted kingfisher, a male is indispensible.
New York writer Les Line listens to belted kingfishers rattling along the creek running through his country retreat. Dwight Kuhn photographed these kingfishers near his home in Maine.