The blue-tailed bee-eater (Merops philippinus) is a near passerine bird in the bee-eater family Meropidae. It is widely distributed across South and Southeast Asia where many populations are strongly migratory, and seen seasonally in many parts but breeding colonially in small areas across their range, mostly in river valleys, where the nest by tunneling into loamy sand banks. They are seen mostly in open habitats close to water.
This species, like other bee-eaters, is a richly coloured, slender bird. It is predominantly green; its face has a narrow blue patch with a black eye stripe, and a yellow and brown throat; the tail is blue and the beak is black. The three outer toes are united around their bases. It can reach a length of 23–26 cm, including the two elongated central tail feathers which can jut two inches more than the remaining ten feathers. Sexes are alike. This species is usually found near water and like other bee-eaters it predominantly eats flying insects, especially bees (as large as the Xylocopa sp.), wasps and hornets, which are caught in the air by sorties from an open perch. They may also forage in flight over estuaries, backwaters and even over the sea but not far from the coast. This species probably takes bees and dragonflies in roughly equal numbers. The insects that are caught are beaten on the perch to kill and break the exoskeleton. This habit is seen in many other members of the order Coraciiformes. They call mainly in flight with a rolling chirping whistling teerp.
The only confusable species within its range is the blue-cheeked bee-eater which however tends to be found in drier areas. The blue-tailed differs in having the rump and tail blue rather than green and black. The undertail feathers are bluish rather than green in the blue-cheeked. The blue cheek patch is much smaller while the chestnut on the throat and breast darker and covering a larger area.
They breed in April to May in India nesting colonially with closely placed nest holes in a vertical mudbank or even burrowing into gently sloping land. They tend to choose sandy and sandy clay loams but avoid heavier clay loams. They also prefer clear mud banks without any vegetation cover. In Sri Lanka, they have been noted to breed in artificial sand dunes created by dredging of sea sand. The nest tunnel can run nearly 2 metres deep. About 5 to 7 near spherical eggs are laid. Both the male and the female take care of the eggs. The parents guard the nest to prevent intraspecific brood parasitism and extra pair copulation. These birds also feed and roost communally. One or two helpers may join the breeding pair after incubation begins. Although males and females appear similar to the human eye, males tend to have longer central tail feather extensions and UV reflectance studies demonstrate that healthy males had darker chestnut throats and brighter green body plumage while females showed brighter blue rumps and yellow chins.