Bell Miners Manorina Melanophrys Research Articles

High densities of bell miners Manorina melanophrys associated with reduced diversity of other birds in wet eucalypt forest: Potential for adaptive management

High densities of bell miners ( Manorina melanophrys) are known to accelerate dieback in eucalypt forests presumably through their negative impact on other avian insectivores and predatory insects. Some areas of moist eucalypt forest that are managed for sustained timber production also support very high densities of bell miners. In this study, we quantified the relative population density of bell miners in forests, and investigated the relationship between bell miner population density, the relative population density of other birds and species richness. A study site of 900 ha was selected in Olney State Forest on the Central Coast of New South Wales (33°7′ S, 150°22′ E), an area that has been managed for timber production since the 1920s. Monthly census counts were carried out over a 16-month period to include diurnal and seasonal variation. Bell miner population density ranged from 14–38 birds/ha and was found to be negatively correlated with diversity of other species. A linear empirical relationship was found between bird species richness ( y) and bell miner relative population density ( x) by the equation y = −0.12 x + 7.78 ( R = 0.9638, n = 8, P < 0.0001), and an increase in bell miner abundance was found to decrease the abundance of other species as given by the equation y = −0.32 x + 16.83 ( R = −0.9646, n = 8, P < 0.0001). Experiments elsewhere in which bell miners were removed from eucalypt woodland plots have shown a return of avian biodiversity and enhanced tree growth, and this study provides an empirical relationship describing the impact on avian diversity for a given forest. We recommend a test of the hypothesis that manipulation of the understorey during burning and logging, could be used to reduce bell miner population levels in wet eucalypt forests, with corresponding benefits to avian biodiversity and tree growth. Work toward these ends has been initiated by the bell miner Associated Dieback Working Group in northern NSW at present and our findings support their strategy.

Eucalypt decline and dead trees: if it's not sexy few seem to care

Whether its Bell Miner Associated Dieback (BMAD), Eucalypt Decline or as the wording of the Key Threatening Process nomination states "Forest eucalypt dieback associated with over-abundant Bell Miners Manorina melanophrys, and psyllids, the phenomena of eucalypt decline on the east coast of Australia is serious. Approximately 781,000 hectares of east coast forests are currently predisposed to decline (Vic Jurskis unpub. data 2008). Among all the forms of dieback affecting east coast forest types, BMAD is one of the most serious and over $700,000 has been spent in the last few years trying to work out the what, why and where of managing this threat to forest ecosystems. Despite a 'task force' (the BMAD Working Group) having been set up to report on Bell Miner Associated Dieback, to the majority of Australian's, it either doesn't exist, they cannot agree on an acceptable term to describe it or it is not on their "peril radar". Substantial effort has been invested trying to unravel the mystery of BMAD and mitigating its impacts. Yet, to some decision makers, BMAD is not important and they see little association between this phenomena and drought, poor land management, weeds, fire and climate change; issues which do seem to capture their attention.

A critical analysis of ‘false-feeding’ behavior in a cooperatively breeding bird: disturbance effects, satiated nestlings or deception?

False feeding,' where helpers arrive at nests with food but fail to provision the young, has been reported in several cooperative species. This and other potentially 'deceptive' behavior has been interpreted as indicating that helping may operate as a signal within such social groups. We critically examine these phenomena in the provisioning behavior of the bell miner Manorina melanophrys. Exces- sively close observation distances can artificially elevate the rate of false feeding in this (and other) species, but once this had been accounted for, there was little evidence for any 'deceptive' behavior by helpers or breeders. Natural and experimentally induced variation in the presence of a potential conspecific audience at the nest did not have any consistent influence upon the rate of false feeds, which was low at 7.94% of 6,880 nest visits. Instead, encountering unexpectedly low levels of brood demand provided a more parsimonious explanation for those visits where helpers failed to feed nestlings or ate the food themselves. Failure to completely transfer a load to nestlings was more likely when the load contained a high proportion of sticky lerp, indicating a simple prey-transfer problem. Finally, individu- als that arrived at nests without prey were often members of neighboring breeding pairs, suggesting that these few non- feeding visits may instead involve an information-gathering function. We, therefore, suggest that future studies explicitly exclude the possibility of observer disturbance and all aspects of normal provisioning behavior before applying the terms 'false feeding' or 'deceptive' and inferring anything more than straightforward helping at the nest.

Provisioning calls of the cooperatively breeding bell miner Manorina melanophrys encode sufficient information for individual discrimination

Acoustically‐mediated individual discrimination has been the focus of much investigation in ornithology. For cooperatively breeding species, strong selection pressure favouring individual recognition during acts of altruism is predicted under many of the most interesting hypotheses proposed to account for helping behaviour. We investigated differences in 157 calls given by 12 different individuals as they provisioned nestlings, including both breeding and helper bell miners Manorina melanophrys (Meliphagidae), a cooperatively breeding honeyeater endemic to south‐eastern Australia. Individual differences were apparent in all 15 call parameters analysed, many with a high level of repeatability. Moreover, the information capacity of mew calls allows as many as 515 different signatures to exist in the system. As many parameters showed strong sex differences, separate discriminant functions were used to predict individual identity within each sex. Five parameters were used in a function that correctly identified over 90% of female calls in both a training (n=35) and test dataset (n=11) not used to generate the function. Among males, a separate function used six parameters to correctly assign individual identity in 89.3% (n=84; training) and 77.8% (n=27; test) of cases. Three original parameters, including spectral and spatial characteristics, were highly correlated with functions predicting identity in both sexes. The accuracy of functions was not influenced by a signaller's sex, breeding status, or by sampling period which was spread over as much as two breeding seasons within individuals. Significant potential therefore exists for bell miners to use these simple provisioning calls in individual discrimination. If this is the case, call information also has the potential to be used by receivers as predicted by signalling hypotheses proposed to account for cooperative helping behaviour, such as the pay‐to‐stay and social prestige hypotheses.

Male‐biased sex ratios in broods of the cooperatively breeding bell miner Manorina melanophrys

We examined the sex ratios of adults and nestlings in the cooperatively breeding bell miner Manorina melanophrys. Males were over‐represented among helpers (mean of 6.8 male helpers per nest compared to 0.3 female helpers). 58% of nestlings sampled were identified as male using a molecular genetic marker. This was a significant departure from parity, yet the magnitude of the bias varied between years. The beneficial and male‐biased nature of helping behaviour in this species and the similar size of male and female nestlings suggest the net cost of raising males is lower than the cost of raising females. Consequently, the male‐biased sex ratio of nestlings we observed is consistent with the predictions of the repayment hypothesis that females may bias the production of their young towards the more helpful sex. Difficulties of generating quantitative predictions from repayment models that can be tested in the field are discussed.

Removal of bell miners Manorina melanophrys from Eucalyptus radiata forest and its effect on avian diversity, psyllids and tree health

The removal of a colony of bell miners Manorina melanophrys from a Eucalyptus radiata forest in Victoria, Australia resulted in an immediate influx of other species of insectivorous birds and a short-term increase in avian diversity and abundance, similar to that reported by Loyn et al. (1983). Once bell miner numbers were greatly reduced on the experimental site, the remaining individuals ceased to exhibit interspecific territoriality and eventually abandoned the site. This suggests that a critical minimum number of individuals is needed to defend a territory. Once bell miners were removed an infestation of Glycaspis sp. psyllids at the site was devoured by the invading insectivorous birds. However, once bell miners recolonised the site, the Glycaspis sp. population returned to close to its former levels. The major reduction in the number of bell miners and psyllids at the site for a period of 10 months did not lead to an improvement in tree health during the 2 1/2 years following the cull. This contrasts with earlier findings by Loyn et al. (1983). Phytophthora cinnamomi (a pathogenic fungus) was present at both the experimental and control sites suffering dieback, and may have been the primary cause of the trees' ill-health and their lack of recovery, despite the reduction in psyllid numbers at the experimental site. Our results highlight the fact that removal of bell miners from a site suffering eucalypt dieback does not guarantee the recovery of the trees, especially if other factors may be contributing to the trees' decline.

Spatial Organisation of the Cooperatively Breeding Bell MinerManorina melanophrys

Bell Miners Manorina melanophrys are cooperative breeders and occur in discrete colonies. A colony comprised a number of breeding pairs occupying slightly overlapping foraging ranges that they shar...

Bell Miners: What Kind of ‘Farmers’ Are They?

SummaryThe hypothesis that Bell Miners Manorina melanophrys Meliphagidae when foraging on psyllids selectively consume the sugary cover of the insect (lerp) leaving the nymph behind (the ‘farming’ hypothesis) was tested, using data from the gizzard contents of 122 birds. The ‘farming’ hypothesis predicts that: (a) the gizzards of Bell Miners should contain relatively more lerps than psyllid nymphs; (b) they should have a larger lerps/nymphs ratio than gizzards of other, presumably ‘non-farming’, bird species; and (c) the highest values of lerps/nymphs should be found in adult male Bell Miners during the non-breeding season. None of the above predictions was supported. This preliminary work fails to produce strong evidence for the ‘farming’ hypothesis.

Feeding of the Female Breeder by Male Helpers in the Bell MinerManorina melanophrys

Observations of Bell Miner Manorina melanophrys female breeders being fed by one or more nest attendants while the former were incubating or brooding are reported. This behaviour might be the result of some male helpers trying to establish a mating relationship with the breeding female.

Methods for sexing and ageing the Bell Miner Manorina melanophrys

Methods for sexing and ageing the Bell Miner <i>Manorina melanophrys</i>

The Reproductive Behaviour of the Bell MinerManorina melanophrys

SummaryClarke, M.F. (1988). The reproductive behaviour of the Bell Miner Manorina melanophrys. Emu 88, 88–100.Bell Miners in three study colonies at Bundoora, Victoria, were monogamous. All breeding pairs were assisted in rearing of young by helpers. No extra-pair copulations were observed and it is unlikely that helpers contributed genetically to broods they aided. Breeding occurred in every month of the year and individual breeding pairs made successive attempts within a year. Individuals were capable of breeding nine months after fledging and did not appear to delay breeding to the same degree as many co-operative breeders. Breeding vacancies were filled rapidly. Male breeding vacancies were generally filled by individuals from within the colony whereas female breeding vacancies were filled by individuals from other colonies. Males were occasionally observed to feed their mates before copulation. Mate guarding by both sexes occurred when a new pairbond was being formed and during the period of nest construction. Nests were built by the female breeder. The mean time-interval between commencement of construction and the laying of the first egg was 7.8 ± 1.3 days. The average clutch size was 1.91 ± 0.07 eggs. Incubation was performed by the female over a mean total period of 14.4 ± 0.3 days. The mean number of days between the hatching of the last egg and the fledging of the last nestling was 11.7 ± 0.7 days. Dependent young continued to be fed at a decreasing rate by parents and numerous helpers (up to thirteen) up to an average of 10.6 ± 1.9 weeks after fledging. The mean number of young fledged per attempt was low (0.62 ± 0.22) and highly variable. The major cause of juvenile mortality was predation. Food did not appear to be limiting and there was no evidence of starvation. The large variability in the outcome of a reproductive attempt may have led to the degree of multi-broodedness in Bell Miners and male offspring being philopatric.

Co-operative breeding by the Australian Bell Miner Manorina melanophrys Latham: A test of kin selection theory

A population of Bell Miners Manorina melanophrys cosisted of two social units (“clans”), each consisting of one or more monogamous paris and numerous helpers. Individuals of a breeding pair occupied one home range, while non-breeding individuals occupied partially overlapping home ranges. Attendants (i.e. parents and helpers) showed clear preferences as to whom they aided (fed) and how much aid they provided. A significant correlation was found between the amount of aid given by an attendant and the genetic relationship between the attendant and the recipient. This provides strong quantitative evidence for the theory of kin selection. Only 14% of eggs laid produced juveniles which lived longer than 3 months. It is suggested that the extremely high juvenile mortality favours individuals which help relatives, even while such individuals have dependent offspring of their own.

Decline and extinction of the helmeted honeyeater at Cardinia Creek

Until recently the helmeted honeyeater Lichenostomus melanops cassidix was known from only two areas near the Dandenongs in Victoria. This paper records the probable extinction of populations in one of those areas, the Cardinia Creek system, and chronicles the gradual decline of the taxon in that area during this century. Some information on the ecology of birds in the colony is presented. It is suggested that the decline and extinction has resulted from changes in the drainage pattern of the creek which have affected susceptibility of Eucalyptus trees to attacks by psyllids. This has led in turn to expansion of range in another aggressive colonial species, the bell miner Manorina melanophrys, at the expense of the helmeted honeyeater.

Social Organization of Bell Miners

A preliminary account is given of a continuing study of an isolated sedentary population of colour-banded Bell Miners Manorina melanophrys at Bundoora, Victoria, started in March 1974. The population consisted of a loose aggregation of discrete and mobile groups based on the family unit. Groups held separate territories but combined with other groups in defence of the whole area. All avian intruders between the canopy and the top of the understorey are attacked. Twenty-six species were recorded as being attacked. Breeding was recorded in each month of the year. Nests were built by a single bird and were not re-used. One bird nested five times between August 1975 and May 1976. Breeding success was low. Only twenty-three per cent of eggs laid produced independent young. Mortality was greatest immediately after fledging. There was only one active nest in each group at any time and birds other than the parents fed the nestlings. Some visits were by birds of neighbouring groups.