A flash of cobalt blue alongside a river or a stream is usually the first thing that alerts an observer to the presence of one of our most charismatic birds - the kingfisher. Although seldom seen, this shy little bird is readily recognised and much loved, and it has held a special place in our affections for centuries. Many legends surround its colour and its life. In Greek mythology the kingfisher is the Halcyon bird, which has the power to control the wind and waves, and builds a floating nest on the sea. Even today, the warm, calm days of the summer are called 'halcyon days'.
Distribution and habitat
There are 87 species of kingfisher worldwide, most of which are found in tropical and sub-tropical regions. The common kingfisher, Atcedo atthis, is the widest distributed of all the species and can be found in suitable habitats from the British Isles in the west to Japan in the east. It is the only species found in Europe. It is widespread in the British Isles, resident throughout England, Wales, Ireland and southern Scotland. Shortage of suitable habitat, as availability of both prey and suitable nesting sites, severely limits the UK population, which fluctuates around 3,600 and 6,000 breeding pairs.
Kingfishers inhabit slow-moving, shallow rivers or streams with clear water and with a fair amount of cover along the banks. Branches overhanging shallows make essential fishing perches. The water course must be clean enough to support abundant small fish, and contain a vertical bank for nesting. Fast-moving streams and polluted waters do not contain enough available fish. and hence do not contain kingfishers. Estuaries, harbours, and even garden ponds are sometimes visited, especially by Juvenile birds during autumn and winter months before they have established a suitable breeding territory on a river.
Kingfishers spend much of their time quietly surveying their surroundings from a perch low down at the water's edge. The kingfisher is a surprisingly small bird, and at 16-17 cm in length it is only a little larger that a house sparrow, although it has a far more solid appearance. It has a long, stout, dagger-like bill, short legs, a short tail, and a habit of perching upright. Its upper parts are iridescent 'kingfisher blue', with the brightest strip running down the back to the tip of the tail.
The wings and head are a slightly darker blue. Because the kingfisher's blue colour is created by iridescence (reflection and refraction of light within the feather) rather than by pigment, the colour appears to change in intensity, ranging from blue to green depending on the quality and angle of light that catches the plumage. The kingfisher has warm, chestnut-orange underparts, red legs, a white throat, and an orange and a white patch behind the eye. The male has a black beak, while the lower mandible of the female is partly or completely red. Juvenile birds have a black beak and legs for the first 3-4 months, and retain a white tip to their beak until the first winter.
Kingfishers eat mainly fish, chiefly minnows and sticklebacks, but they also take aquatic insects, freshwater shrimps and tadpoles etc. to top up their diet. Although they prefer fish averaging around 23 mm in length, they can handle comparatively large prey - anything up to 80 mm long.
An ideal fishing spot is a firm perch overlooking a clear, shallow pool of water. Once the bird has located a suitable prey and assessed its depth, it dives. At the entry into water, its beak is opened and its eyes closed by the third eyelid. The bird is effectively blindfolded as it catches the fish. On return to the perch, it repeatedly strikes the fish against the perch to kill it. Only then will the spines in the fins of some species such as sticklebacks relax to allow the bird swallow it, head first. Each bird must eat at least its own bodyweight of fish each day.
Territory is extremely important for kingfishers all year round. Any bird that is unable to secure a territory with an adequate food supply is likely to perish. This is particularly important before the onset of winter. The birds start to contest territories by mid-September. A breeding pair will often divide their summer territory between them. Freezing weather can sometimes force the birds out of their territories, which often takes them to less suitable habitats or into conflict with other resident kingfishers.
The size of the territory depends on the amount of food available, and on the bird population in the area. Territories tend to cover at least 1 km of river, but may extend over 3-5 km. Any nearby waterbody that provides good fishing will be included in the territory.
Kingfishers breed in their first year, and pair-formation usually starts in February. If the male and the female have neighbouring territories, these may merge for the breeding season.
Both birds excavate the nest burrow into the stone-free sandy soil of a low stream bank, usually about 0.5 m from the top. The birds choose a vertical bank clear of vegetation, since this provides a reasonable degree of protection from predators. The nest tunnel is usually 60-90 cm long, and the 6 cm diameter is only a little wider than the bird. The nest chamber at the end has a slight depression to prevent eggs rolling out, but no material is brought to the nest. 2-3 broods are raised in quick succession, normally in the same nest.
The first clutch of 6-7 eggs is laid late in March or early in April. Both adults incubate the eggs, and the chicks hatch 19-21 days later. Each chick can eat 12-18 fish a day, and they are fed in rotation - once a chick is fed, it moves to the back of the nest to digest its meal, causing the others to move forward. The chicks are normally ready to leave the nest when they are 24-25 days old, but if the fish supply is poor, they can take up to 37 days. Once out of the nest, the young are fed for only four days before the adults drive them out of the territory and start the next brood.
Survival, threats and dangers
Kingfishers are very short-lived. Many young will not have learned to fish by the time they are driven out of their parents' territory. It is thought that only a half of the fledglings survive more than a week or two. Although only a quarter survive to breed the following year, this is enough to maintain the population. Likewise, only a quarter of adult birds survive from one breeding season to the next. Very few birds live longer than one breeding season. The oldest bird on record was only 7.5 years.
Most kingfishers die of cold or lack of food - a severe winter can kill a very high percentage of the birds. Despite high breeding productivity, populations can take many years to recover from a bad winter. Weather conditions in the summer can also cause significant mortality. Cold weather or flooding in the summer can make fishing difficult, resulting in starvation of the brood, while flooding can also claim many nests. Traffic and window collisions are other known causes of death. The main predator is the domestic cat, but rats can also be a serious problem in places.
Kingfishers are high up in the food chain, and therefore extremely vulnerable to build-up of chemicals. Industrial pollution and contamination by agricultural run-off kills the fish the birds rely on, effectively excluding the birds from many stretches of river that would otherwise be suitable habitats. The long-term population declines since 1970 are generally attributed to river pollution.
Human disturbance of nesting birds is a serious problem, since the broods fail if something upsets the feeding routine. If human presence close to a nest prevents these shy birds from entering the nest for too long, the chicks may weaken enough (either from cold or hunger) to stop calling. This makes the parents wrongly assume that they are well fed and will not feed them. As a result, the chicks will perish.
Heavy machinery that grades the banks and drains the land destroys many nests each year on lowland rivers. Persecution to satisfy fashion trends and to provide feathers for fishing flies seems to be well in the past.