Feeding edit Male passing fish to female in spring courtship ritual Pellet of a common kingfisher
The common kingfisher searches for prey while perched 1-2 meters (3-7 feet) above the water on a branch, post, or riverbank, its bill pointing downward. When it detects food, it bobs its head to determine how far away it is, then descends sharply to grab its prey, which is typically no more than 25 cm (10 in) below the surface. Underwater, the wings spread, and the transparent third eyelid shields the open eyes. The bird takes off with its beak first and returns to its perch. The fish is adjusted at the perch until it is held close to its tail and repeatedly beaten against the perch. Once dead, the fish is positioned lengthways and swallowed head-first. A tiny, grayish pellet made of fish bones and other indigestible remnants is regurgitated a few times a day. [7].
The food is mainly fish up to 12. 5 cm (5 in) in length, although the typical size is 2 3 cm (7?8 in). [7] In Central Europe, 2097% of the food was discovered to consist of fish, with an average size of 206 cm. Fish ranged in size from 2% to 2010 cm. 5 cm (body mass range from <0. 1 g to >10 g, average 3 g). [17][18] Minnows, sticklebacks, small roach and trout are typical prey. Approximately 60% of the food items are fish, but this kingfisher also catches aquatic insects like water beetles and dragonfly larvae, as well as crustaceans like freshwater shrimp during the winter. [7] This species may also consume amphibians, such as the smooth newt (Lissotriton vulgaris). [19] In Central Europe, however, fish represented 99. Nine percent of the diet (information gathered from rivers, streams, and reservoirs between the years 201999% and 2013) [17] Common kingfishers have also been observed to catch lamprey. [20] According to one study, the food provisioning rate rose from 1498 g (505 fish for four nestlings) to 2968 g (894 fish for eight nestlings) as brood size increased. During the fledging period, each chick consumed an average of 334% of the fish they encountered, which led to an estimated daily food intake of 337 percent of the chicks’ body mass (averaged over the duration of the nestling period). The average daily energy intake was 73. 5 kJ per chick (i. e. , 1837 kJ per 25 days of the fledging period). [21].
The difference in refraction between water and air presents a challenge to any diving bird. Many birds have two foveae (the area of the retina with the highest density of light receptors), and when a kingfisher enters the water, it can switch from its primary, central fovea to its auxiliary fovea. A high-density retinal streak connecting the two foveae enables the bird to swing temporally as it descends upon its prey. [23] The bird’s ability to maintain visual acuity underwater is made possible by its egg-shaped lens, which points towards the auxiliary fovea. [22] The kingfisher has binocular vision in water and monocular vision in the air due to the locations of the foveae. Although underwater vision is not as sharp as it is above the water, the capacity to estimate the distance to moving prey is more crucial than visual acuity. [23].
A possible source of carotenoid pigments is an oil droplet found in each cone cell of a bird’s retina. These droplets enhance color vision and reduce glare. The reason why red droplets predominate in the oil droplets of aquatic kingfishers is unknown, but it’s possible that the droplets reduce glare or diffuse light from particulate matter in the water. [23].
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Geographical variation edit
Seven subspecies exist, with differences in the color of the upper parts and the intensity of the rufous color of the underparts; size varies among the subspecies by up to 10% in 2010. The races that live south of the Wallace Line have partially blue ear patches and the bluest upperparts. [7][9].
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