Bellbird
The bell miner (Manorina melanophrys ), commonly known as the bellbird, is a colonial honeyeater, endemic to southeastern Australia. The common name refers to their bell-like call. 'Miner' is an old alternative spelling of 'myna', and is shared with other members of the genus Manorina. The birds feed almost exclusively on the dome-like coverings, referred to as 'bell lerps', of certain psyllid bugs that feed on eucalyptus sap from the leaves. The psyllids make these bell lerps from their own honeydew secretions in order to protect themselves from predators and the environment.
Bell miners live in large, complex, social groups. Within each group, there are subgroups consisting of several breeding pairs, but also including a number of birds that are not currently breeding. The nonbreeders help in providing food for the young in all the nests within the subgroup, even though they are not necessarily closely related to them. The birds defend their colony area communally and aggressively, excluding most other passerine species. They do this in order to protect their territory from other insect-eating birds that would eat the bell lerps on which they feed. Whenever the local forests die back, due to increased lerp psyllid infestations, bell miners undergo a population boom.
The heritage listed mountain village of Bellbrook NSW was named after the distinctive sound of local bellbirds in 1882.
Bell miners are the smallest of their genus, and differ from the other three predominantly grey miner species in having olive-green plumage, darker on the wings and yellower on the belly.They are a medium bodied honeyeater, slightly smaller and stockier than a Lewin's honeyeater (Meliphaga lewinii ), weighing between 25g and 35g(average 29g).Bell miners are 17.5–20 cm in length (average 18.5 cm) with a 22–30 cm wingspan (average 26.5 cm).They have the characteristic yellow bill of the miners, which is slightly downturned. The legs are bright orange, and the bare patch behind the eye is red-orange.The crown and lores are black, while the feathers in front of the eye are yellow. A dark streak runs from the corner of the bill downwardgiving a slight frowning appearance. Eyes are brown and mouth is yellow.Both sexes look alike, though the males tend to be slightly larger.It is possible to determine the sex of the birds by analyzing wing length, tail length, and culmen depth, or by observing calls that are unique to females, but there is no easy way to reliably determine the sex in the field without careful observation of behaviour and calls.Juveniles are more brown-colored than the adults and overall less bright in color. Young birds do not have the bare skin patch behind the eye. The patch initially develops as pale grey, then transforms to pale yellow, and darkens to pale orange before taking on the adult bright red-orange color as the bird matures.Nestlings are born naked and develop light brown down about two days post hatching.
The birds are heard more than they are seen, as bell miners tend to forage high in the canopy, and their olive-green plumage blends into the surrounding leaves. However, they keep up their "ping" contact call as they forage throughout the day. In the Royal Botanic Gardens, Melbourne, bell miners come low enough to be easily seen and photographed.
Bell miners are distributed from around Gympie in Queensland, south along the coastal plain and ranges, to Victoria, around Melbourne.They prefer the margins of wet or dry sclerophyll forest and thick woodlands, often with a stream or other permanent water source nearby.This limits their range to higher rainfall areas near the coast, often bordering, but not inside, rainforest. Compared to the closely related noisy miner,bell miners prefer a denser habitat with a thick understory (<5 m), but a sparse midstory (5–15 m) and canopy (>15m).In an undisturbed setting, bell miners choose habitat with an understory of shrubs, ferns, sedges, and rainforest vines.They have been observed to expand their range in disturbed habitats that have a thick undergrowth of the invasive weed lantana.Bell miner population densities have been measured at 14-38 birds per hectare.They are particular about their preferred habitat and reasonably small disturbances to undergrowth, such as fire or lantana removal, can cause a colony to move to a new territory.
The complex social organization of bell miners was observed as early as the 1960s in New South Wales, and has been studied by several research groups in Victoria.Bell miners live in large colonies of 8-200+ birds, which consist of coteries or clans of generally related male birds and their offspring. Each coterie is made up of several monogamous breeding pairs with their nest helpers.As a colony, bell miners are aggressive and set up a permanent territory that they will defend together against all other honeyeaters and any other species, which they perceive are a threat to their preferred food source or themselves.Within the colonial territory, each breeding pair has its own foraging range. Helpers assist multiple breeding pairs, and move between the foraging range of several pairs. Coteries are groups that are interconnected and interact daily within the larger colony, due to a close genetic relationship.
Due to their aggressive nature, bell miners are known for excluding other birds from their territory, and larger avian species, like kookaburras, currawongs, and crows are mobbed by up to twelve miners from different coteries within the colony. Predators are repeatedly attacked, if they settle in another part of the colony's territory. Small birds that keep to the understory, like fairy-wrens, scrubwrens and blackbirds are often not driven out,but small birds that typically forage in the midstory or canopy or share similar foods, like pardalotes, are not allowed access within the territory. One of the few species that can sometimes displace bell miners is the similarly aggressive noisy miner, but in general noisy miners prefer areas with little understory.Bell miners are able to suppress the numbers of competing species in territory that they hold for years. However, bell miner colonies have clearly defined territorial boundaries, and beyond those boundaries the local bird assemblage resumes its normal diversity.
Bell miners specialize in consuming insects known as psyllids and their associated young nymphs, sweet lerps, and other psyllid secretions. Psyllid products may consist of up to 90% of the bell miner's diet. Bell miners forage primarily among leaves, branches, and loose bark in the canopy, generally at least 8 m in height, but they do descend to the dense understory. There is a theory that bell miners 'farm' psyllids by excluding other psyllid-eating bird species from a large enough territory, that the miners themselves do not require all the psyllids from in order to sustain the colony. One hypothesis under the farming theory is that the bell miners may selectively eat only older nymphs, or may often eat the lerps and leave the nymph unharmed. Evidence for this theory has been mixed. An early study of stomach contents did not find supporting evidence for this theory, as bell miner stomachs did not contain the higher lerp/nymph ratio that would have been expected. However, a later behavioral comparison between bell miners and noisy miners did observe that bell miners carefully used their tongue to remove lerps, which left the nymph intact. In contrast, noisy miners pried the lerp and nymph off with their beak and consumed both. When bell miners are removed, psyllid colonies are generally quickly decimated by the other forest bird species that move into the miners' former territory.
Although psyllids are the primary food source, like most honeyeaters, bell miners have also been recorded drinking nectar from eucalyptus, banksia, and mistletoe flowers, as well as eating various other insects, including spiders, beetles, weevils, moths, and wasps.
Bell miners are generally sedentary, and thus have a permanent all-purpose territory, which includes breeding. The primary breeding season is April/May to August/September in the northern part of their range and June/July to November/December in the southern range, but breeding has been observed in all months of the year, as females will often nest again after a failed nest or once the young have fledged. One female was recorded nesting five times in one season, though that many nest attempts is unusual. Bell miner pairs are monogamous, but the breeding tasks are divided between the sexes. Female bell miners build the nest over 8 days, incubate the 1-3 (but typically 2) eggs for 14.5 days, and brood the young for up to 12 days, depending on the weather. The nests are small, cup-shaped, and built with dry twigs, grasses, and bark woven together with spider web. Nests are generally hidden in the foliage of dense understory plants, 3-5m above the ground. The eggs are typically 24mm x 16mm, oval shaped, and pink in color. They have darker reddish-brown spots and blotches, primarily over the larger end. Pallid cuckoos have been recorded as nest parasites for bell miners.
While nests are all within the territory of the colony, they are not tightly packed as traditional colony breeders. Instead, nests are located within the breeding pairs' normal foraging range. They are generally within calling range of neighbour nests, but not too close. Female bell miners move nest locations after a nest failure, and were observed to move nests lower into the thick understory, likely reducing the risk of avian predators. However, they did not move nests far from the original location horizontally, possibly to stay within their home foraging range, and to retain their established set of helpers. Females will also alter brood sex ratios to meet conditions. When a colony is in a new location with an inferior food source, the ratio will be biased towards more females, which will disperse from the colony at sexual maturity. Once the food supply has been increased, the brood sex ratio is shifted towards future helping males.
