Merops ornatus
rainbow bee-eater

All members of the Meropidae family (Bee-eaters) are considered “Old World” birds, inhabiting the Eastern hemisphere. Rainbow bee-eaters are the only species of bee-eaters that inhabits Australia. Most of the population breeds and inhabits mainland Australia but other populations of rainbow bee-eaters have been recorded in eastern Indonesia, New Guinea and a few in the Solomon Islands. Rainbow bee-eaters also have been recorded to fly as far north as the southern Ryuku islands of Japan, Saipan, Palau, and northern Mariana islands, though only as temporary visitors and not permanent residents to these regions. (Australian Government, Department of the Environment, Water, Heritage and the Arts, 2010; Del Hoyo, et al., 2001)

Rainbow bee-eaters inhabit a variety of habitats depending on what regional environments are available to them. These include sandy pastures, lightly wooded savannas, forests near fresh water creeks and lakes, and arable land in Australia. In the subtropical regions such as Indonesia, rainbow bee-eaters have settled in bamboo grooves, seedling palm plantations, and waterways along lowland rain forests. In areas closer to human civilization, they’ve been seen in parks, gardens, and clearings of logged forest. (Del Hoyo, et al., 2001)

Rainbow bee-eaters have many of the characteristics common to the family 'Meropidae' including brightly-colored plumage, medium to long wings, short legs, and long down-curved bills. Similar to many members of 'Meropidae', rainbow bee-eaters have tail streamers, which are elongated tail feathers that extend further than the other rectrices. Typically weighing 20 to 33 g, these birds grow up to 19 to 20 cm, not including the tail streamers which may add up to 7 cm to total length.

Rainbow bee-eaters have bright, distinguishing coloration. Their bodies are green with a bright aqua blue rump and burnished nape and crown. The wings of rainbow bee-eaters have reddish primary feathers bordered by green outer edges with dark gray colored tips. They have completely black tail feathers with streamers that vary by gender. Rainbow bee-eaters have a thin green area above their eyes (known as a supercilium) and a broad black eye stripe, bordered by a thin, light blue band underneath. They also have yellow on their chins and cheeks. Rainbow bee-eaters have rufous throats with a triangular black stripe (called a gorget) that narrows as it moves from the midline up to the shoulders.

Juvenile rainbow bee-eaters differ from the breeding adults’ coloration in several respects. The back and upper regions of the juveniles are an olive green, with pale yellow on their upper throat and chin. The lower throat is a reddish brown that blends into a vaguely streaked breast. Juvenile rainbow bee-eaters lack the streamers of the adults as well as the black gorget.

There is little sexual dimorphism in rainbow bee-eater however there are a few differences that can separate the sexes. Males have a red iris while females tend to have a more reddish-brown iris. The females are also duller than the males, with a less bronze color crown up top the head. Nearly a third of all adult males also have a thin hint of blue along the bottom of their black gorget. The key difference in characteristics between males and females are the tail streamers. Males have thin, long streamers with a speculated tip while females have a wider shorter version, averaging only 2 cm. (Del Hoyo, et al., 2001)

Rainbow bee-eaters breed in socially monogamous pairs and make use of cooperative breeding strategies, but as of yet, there is no information regarding courtship rituals in this species. It is also uncertain whether these couplings last a lifetime or whether the monogamous partnership lasts only for the season. While they are monogamous, Rainbow bee-eater pairs often have a single, male “helper” to assist with all aspects of rearing young. (Del Hoyo, et al., 2001)

Rainbow bee-eaters nest in ground cavities, constructed by both parents and the male helper. They excavate the burrows in level ground or ridges ruts and low banks. This species can nest colonially, with up to 50 burrows in the same area. The burrow is either straight or bent to one side, usually a meter to 3.3 meters long with a small chamber at the end. Rainbow bee-eaters do not make a nest but some may line the terminal chamber with grass, feathers, or wasp wings. The burrows of Rainbow bee-eaters generally are not reused each season; however, studies of banded pairs show the same nesting regions may be used repeatedly. (Australian Government, Department of the Environment, Water, Heritage and the Arts, 2010; Del Hoyo, et al., 2001)

The time at which the breeding season begins varies regionally. Typically this occurs around the Australian spring, September through November. In New Guinea, the eggs are laid in September, while Southern Australian populations lay in mid-November and December. Only one clutch of eggs is normally produced each season. Some studies have found that if a nest is lost early in the breeding season, the couple may attempt a second clutch. This second clutch, however, contains fewer eggs than the original. Females lay somewhere between 3 and 7 pearl colored eggs, (average usually being 4 or 5) laid over the course of 5 days. After the third egg is laid, incubation begins and after 22 to 31 days the eggs hatch, usually all on the same day. The young remain in the burrows for nearly a month before emerging outside and continue to be fed by the parents and the helper for another two to four weeks. (Australian Government, Department of the Environment, Water, Heritage and the Arts, 2010; Boland, 2004a; Boland, 2004b; Del Hoyo, et al., 2001)

Both parents and the helper excavate the burrows. Both parents and the helper also participate in all aspects of caring for the young, from incubation to post-fledging. After the chicks fledge, they continue to be fed by the parents and helper for another two to four weeks. (Boland, 2004a; Del Hoyo, et al., 2001)

Few studies have investigated the lifespan of rainbow bee-eaters. One study done in 1999, estimated that these birds live up to 24 months in the wild. This estimate was derived from maximum intervals between dates of banding and re-sightings. A possible explanation for the lack of research performed and the birds’ short lifespan could be the fact that these birds migrate over vast spans of open water. This migration pattern makes them difficult to track as well as having a high risk of death from exhaustion or starvation during the migration flight. In addition, there have been little studies of the age of maturity, though given the estimate of life expectancy and the once a year breeding season, rainbow bee-eaters must reach maturity rapidly in order to reproduce. (Australian Government, Department of the Environment, Water, Heritage and the Arts, 2010)

Rainbow bee-eaters are a migratory species that may travel in groups of up to 500 individuals. These birds may be solitary or social during the breeding season. In a given nesting area, there may be one to fifty nesting pairs. Most breeding pairs are assisted by a single, male "helper" which participates in all aspects of raising the young. In contrast to other species of bee-eaters, these helper males have not attempted to breed and failed; they devote the entire breeding season to tending the young of another pair. (Boland, 2004a)

Globally, rainbow bee-eaters occur over an estimated 6 million square kilometers. Exact territory size is unknown but for colonial breeders, pairs aggressively defend only the area surrounding the nest cavity. (Boland, 2004a)

Specific communication information for rainbow bee-eaters is not well known. Most members of the Meropidae family are vocal birds, calling loudly and often to other members of their species. Bee-eaters are known to practice reciprocal calling, one bird singing first with another bird responding, as well as calling collectively as a group at one time. Audible communication is generally important among members of Meropidae though little is known about the calls or the type of information conveyed within them. According to one field guide, rainbow bee-eaters’ call is described as being a high-pitched combination of chitter and chirps. Like all bird species, rainbow bee-eaters perceive their environment through visual, auditory, tactile, and chemical cues. (Del Hoyo, et al., 2001; Simpson and Day, 1996)

Examples of their vocalizations can be found at the links:

http://www.youtube.com/watch?v=vieWHXSF3Q0. http://www.birdsaustralia.com.au/education-resources/rainbow-bee-eater.html .

Rainbow bee-eaters eat predominately bees and wasps, both which are members of the family Hymenoptera. It has been documented that rainbow bee-eaters also fed on butterflies and moths (Lepidoptera), damselflies (Zygoptera), dragonflies (Anisoptera), beetles (Coleoptera) and most flying insects. Typically, this species captures their prey on the wing, flying from perches of power lines or leafless branches to the airborne insect. A few studies have noted that spiders may possibly be in the diet. (Del Hoyo, et al., 2001)

Though some studies have reported that the prey is eaten in flight, most rainbow bee-eaters return to a perch with their meal. Since the majority of rainbow bee-eaters’ prey have venomous stingers, the birds use a specialized behavior to deal with this problem. Upon catching the bee and returning to a perch, a bird will turn the bee in its beak by flipping it until the birds’ beak holds the insect just behind the thorax. From there, rainbow bee-eaters whack the bee’s head against the hard perch, rendering it incapacitated. This may take several attempts. After the bee is stunned, the bird grips the bee by the tip of the abdomen and while closing its eyes, crushes the stinger, releasing the venom and bowels of the bee. Rainbow bee-eaters then rub the bee’s eviscerated end along the perch five to six times, removing the stinger, before consuming. (Del Hoyo, et al., 2001)

An example of the behavior can be found at the following You-tube link: http://www.youtube.com/watch?v=45hucuxKa58

Dingos (Canis familiaris dingo), monitor lizards (Varanus varius), yellow-footed antechinus (Antechinus fiavipes), and cane toads (Rhinella marina) are the most significant predators for rainbow bee-eaters. These predators mainly prey on eggs and chicks. It has been suggested that introduced species (dingos and cane toads) have a higher predation rate than the native predators (monitor lizards and yellow-footed antechinus).

Rainbow bee-eaters exhibit mobbing behavior to deter predators. Also, it has been shown that nest predation decreases with increased colony size. (Boland, 2004b)

As an insectivorous species, rainbow bee-eaters likely have an impact on the local populations of wasps, bees, and other insects. Rainbow bee-eaters also serve as a food source for both introduced and native predators. As they do not re-use nesting cavities, the vacated burrows may serve as shelter for other species. (Boland, 2004a)

It is unknown if rainbow bee-eaters benefit the human economy.

Rainbow bee-eaters tend to settle or forage around beehives as a source of food. For honey harvesters and entomologists, the birds are known as pests and were often shot for bounty during the early 1900’s. Rainbow bee-eaters are now protected, but still may cause problems for honey harvesters across Australia. (Australian Government, Department of the Environment, Water, Heritage and the Arts, 2010)

Rainbow bee-eaters are protected under the Environmental Protection and Biodiversity Conservation Act of 1999. The population size of rainbow bee-eaters is estimated at over one million individuals spread across an estimated six million square kilometers. Due to the large population size and home range, the IUCN lists them as a species of least concern. ("IUCN", 2009; Australian Government, Department of the Environment, Water, Heritage and the Arts, 2010)