The kingfisher is a colorful small to medium bird generally found near to water. The Collared kingfisher is a very widespread species and has numerous subspecies, belonging to the Halcyoninae subfamily, the tree kingfishers. They occur on three continents, namely Australia, Asia, and Africa, occupying a wide range within those continents. The subspecies vary slightly in size but the plumage color is the main variation, with upperparts being greener or bluer, the underparts ranging from buff to white, and the size of the white loral spot differing. Males and females are similar, but the upperparts of males usually are slightly bluer than those of females. Juveniles have a duller color than adults, a black collar band and very small, black scaling over the breast.
The Collared kingfisher occurs from the Arabian Gulf and Red Sea throughout southern and south-eastern Asia, Indonesia, New Guinea, northern Australia, Vanuatu, Fiji, Tonga, Samoa and the Solomon Islands. It occupies a variety of coastal habitats, from sandy beaches and harbors to mangroves, tidal areas, and mudflats. In the west part of the range, it is mostly confined to mangroves, but may also occur in coconut plantations in Southeast Asia. It sometimes follows large rivers to reach open woodlands, gardens, parks and roadsides, often flying upstream as far as 40 km.
An able predator of fish, being a perch-and-wait type of predator, the Collared kingfisher sits on a branch near water, of one to three meters in height, swooping down to capture its prey on sand or mud. It sits and waits on its perch for a long time, and take its prey back to its perch, where it beats it to death. This species is solitary and highly territorial, locating a prime area according to the food available, desirability of trees for perching and safety of roosting sites. They search for food during mornings and evenings. In cooler weather they hunt for food during the middle of the day as well. Cleanliness is important to them, and they can be seen diving into the water in order to bathe, then flying to a perch where they preen themselves and let their feathers dry in the sunlight. Some even clean their heads with their wings. They use a branch for cleaning their impressive beaks, wiping them back and forth.
Collared kingfishers living in coastal regions and being opportunistic generalist carnivores feed mostly on shrimp, crabs and small fish. Those further inland eat land crabs, earthworms, spiders, insects, frogs, small snakes, and occasionally, mice, bird eggs, and chicks.
Little is known about the mating system of Collared kingfishers, however, most tree kingfishers exhibit a monogamous mating system. This means that males will mate with only one female and females will mate with only one male. The breeding season lasts from December to August, when the birds pursue each other during territorial courtship flights. Then the male offers a fish to the female, the pair bond cemented by both birds extending their wings. Breeding birds nest in solitary pairs, creating a nest in a termite nest, an old tree trunk, an old woodpecker hole or an earthen bank. The territory around the nest site is aggressively defended. Often two broods are raised in a year. 3-7 eggs are laid and incubation is for about 18 days. The chicks fledge at about 26-30 days old.
Although widespread, common and not currently threatened by extinction, in some parts of its range this species is threatened by loss of habitat, particularly due to the conversion of mangroves, such as in Australia, where they are destroyed for residential, infrastructure and tourist developments, which results in the Collared kingfisher’s nesting and foraging habitat being lost. These birds are also threatened by pollution in estuaries and the build-up of pesticides in the environment.
According to IUCN, Collared kingfisher is very widespread and common to abundant throughout its range but no overall population estimate is available. Currently this species is classified as Least Concern (LC), however, its numbers today are decreasing.