Platycercus Elegans Research Articles

Fruitful use of bioacoustic alarm stimuli as a deterrent for Crimson Rosellas (Platycercus elegans)

Birds cause considerable damage to horticultural crops in Australia each year. The playback of species-specific bioacoustic alarm stimuli has been one of the most promising methods suggested to deal with bird-problems. However, no published studies have tested this method on species of parrots, one of the main avian pests of crops in Australia and globally. Furthermore the effectiveness of this method might be reduced if alarm calls were played back that came from a non-local population. The Crimson Rosella species complex (Platycercus elegans), a parrot with considerable acoustic variation throughout its range, is considered a pest species of several commercial fruit crops. This study tested whether alarm calls from Crimson Rosellas were effective in reducing the activity of Rosellas in apple orchards. Three groups of bioacoustic stimuli were compared: control stimuli, local alarm calls and non-local alarm calls. Our results indicate that the playback of alarm calls from Crimson Rosellas is effective in reducing the activity of Rosellas in orchards over the period of study, and we did not find any difference between the use of local and non-local alarm calls. Our study suggests that playback of alarm calls may be an effective deterrent of rosellas over a broad distribution, at least for short-to medium-term use.

Dispharynx nasuta (Nematoda: Acuariidae) Infection Causing Proventricular Lesions and Death in Three Captive Rosellas (Psittaciformes: Psittacidae)

Two adult male Crimson rosellas (Platycercus elegans) and an adult female eastern rosella (Platycercus eximius) were found dead in their cages in a private aviary in March 2009, April 2010, and February 2010, respectively, without premonitory signs. Their postmortem examination showed pectoral muscle atrophy and a distended proventriculus. The proventricular mucosal surface was covered with a gelatinous, whitish material, where a large number of nematode parasites identified as Dispharynx nasuta were present. A histologic examination revealed a hyperplastic mucosa, spirurid nematodes in the mucosal layer and inflammatory mononuclear cells in the lamina propria. This is the first report of a D. nasuta infection associated with proliferative proventriculitis and subsequent death in psittacine birds.

When more is less: Urban remnants support high bird abundance but diversity varies

Urban remnant vegetation, especially where it occurs in public parks, allows for relatively easy access for ongoing biodiversity monitoring. However, relatively little baseline information on bird species distribution and abundance across a range of identifiable urban remnants appears in the published literature. We surveyed the relative abundance and distribution of birds across urban and suburban remnant vegetation in Melbourne, Australia. One hundred and six species were recorded, of which 98 were indigenous. Red wattlebirds had the highest mean relative abundance with 2.94 birds/ ha, followed by rainbow lorikeets (2.51), noisy miners (1.93), brown thornbills (1.75) and spotted doves (0.96). There was no obvious trend between overall relative abundance and the size of the remnant, in contrast to species richness which was positively correlated with remnant size. The data revealed that some species were either totally restricted to, or more abundant in, larger remnants and generally absent from smaller remnants. Some of the more common birds (crimson rosella, superb fairy-wren, spotted pardalote and black-faced cuckoo-shrike) recorded during this study were detected at similar densities to those found in comparable vegetation to the east of Melbourne within a largely forested landscape. Other species occurred at much lower densities (e.g., white-browed scrubwren, brown thornbill, eastern yellow robin and grey fantail) or had habitat requirements or ecological characteristics that could place them at risk of further decline or local extinction in the urban area. We identify a suite of bird species of potential conservation concern within Melbourne’s urban landscape. The establishment of repeatable, fixed-point, and long-term monitoring sites will allow for repeat surveying over time and provide an early warning of population declines, or conversely an indication of population increase for other species.

Designing old forest for the future: Old trees as habitat for birds in forests of Mountain Ash Eucalyptus regnans

Old trees are one of many habitat attributes associated with old forests. They are known to be required by many wildlife species including cavity-dependent birds. Forest managers need to select strategies for retaining and regrowing old trees to maintain suitable numbers over time at appropriate configurations in the forest landscape. This paper presents data from wet forests in south-eastern Australia to help elucidate the effects of different strategies on forest birds as one element of biodiversity that needs to be conserved in these forests. Bird abundance was assessed by standard area search at 117 sites in forests of Mountain Ash Eucalyptus regnans in the Victorian Central Highlands, over the course of two spring-summer breeding seasons from 1996 to 1998. The sites contained 60-year regrowth from extensive wildfires in 1939, along with varying numbers of older trees that had survived the fire. Some of the old trees were dead and at varying stages of decay. Numbers of old trees were counted at each site and a range of other habitat measurements taken. Birds were considered by species or guilds of species (feeding and nesting guilds). Bird abundance data were regressed against numbers of old trees and other relevant habitat data. Cavity-nesting birds were positively related to numbers of old trees, and especially to those that remained alive. Bird species that nest in longitudinal cavities in small branches (spouts) were rare at sites that lacked old trees, and were related strongly to numbers of live old trees. Large cavity-nesters were related to numbers of live old trees or all old trees. Treecreepers correlated less strongly, perhaps because they use cavities in decaying snags and stumps as well as large old trees. Honeyeaters and Mistletoe birds were also positively associated with numbers of live old trees, although they do not need cavities. Total bird abundance was positively related to live, dead or all old trees. Several other relationships were found. For example, shrub foragers were related positively to abundance of tall shrubs but not low shrubs; wattle foragers were related positively to abundance of wattles (especially Silver Wattles Acacia dealbata); and Eastern Spinebills Acanthorhynchus tenuirostris were positively associated with abundance of Mountain Correa Correa lawrenciana (the flowers of which provide a major source of nectar). Non-linear relationships between bird abundance and densities of old trees were found for at least two cavity-nesting bird species. The relationship was convex for Striated Pardalote Pardalotus striatus (optimum density 5–12 live old trees/ha) and mildly concave for Crimson Rosella Platycercus elegans. This suggests that the former would benefit from strategies to disperse old trees among regrowth at suitable scales whereas the latter would benefit from strategies to produce clumped distributions of old trees. However, Striated Pardalotes showed a strong preference for live old trees, which cannot easily be kept alive among regrowth after logging or fire, suggesting clumped retention may be more practical for that species too. Three other species showed weak evidence of non-linear responses, but most species showed no significant evidence of departure from linearity. No species or guild showed strong evidence of a threshold level of old tree density (above ∼1 ha −1) below which those birds would not occur. Hence for most of the diurnal birds considered in this study, old trees appear to be useful in proportion to the overall number of suitable old trees that can be retained and regrown (rather than their spatial pattern), and especially the number that can be kept alive. Clumped retention strategies give the best chance of keeping many retained trees alive in retained patches. Otherwise, spacing patterns should be a secondary consideration, except where they are known to be important for species such as owls and arboreal mammals.

Does the ring species concept predict vocal variation in the crimson rosella, Platycercus elegans, complex?

Vocal variation may be important in population divergence. We studied geographical variation in contact calls of parrots of the crimson rosella, Platycercus elegans, complex, which is characterized by striking geographical plumage coloration variation. This complex has long been considered a rare example of a ring species (where two divergent forms coexist in sympatry but are connected by a chain of intermediate populations forming a geographical ring). We tested whether contact call variation is consistent with the ring species hypothesis. We recorded calls throughout the ring, including several sites from the three main population groups forming the ring and interfaces between them. We analysed duration, peak frequency, fundamental frequency and frequency modulation. We found significant differences, particularly in fundamental frequency and frequency modulation, at multiple biogeographical scales ranging from local populations to subspecies level. Discriminant function analyses showed some populations could be reliably discriminated from call structure. However, our results provided little support for three key predictions of the ring species hypothesis: (1) calls of the terminal, most divergent forms were not significantly different in three of the four acoustic variables, and differences did not appear to be maintained in sympatry, (2) phenotypically/geographically intermediate populations were not characterized by intermediate calls, and (3) call variation was not concordant with geographical sequence around the ring from one terminal form to the other. Our results underscore the emerging view that the evolutionary histories and phenotypic variability of many long-held ring species may be inadequately described by the ring species hypothesis and require alternative explanations.

Inducing whole‐assemblage change by experimental manipulation of habitat structure

1. Habitat structure long has been identified as a primary factor influencing local assemblage composition. Most evidence has been in the form of correlations of species occurrence and assemblage composition over a range of habitats, with experimental verification of relationships being relatively uncommon because of the difficulties of enacting precise manipulations of habitat structure. 2. Fallen timber (also known as coarse or large woody debris) is one of the few habitat-structural elements in forests and woodlands that can be manipulated with relatively high precision. We report on manipulations of wood-loads on 30 experimental 1-ha plots in floodplain forests of northern Victoria, Australia, over 4 years (one pre- and three post-manipulation). 3. We show that very high wood-loads (80 Mg ha(-1)) and intermediate wood-loads derived from tree crowns (40 Mg ha(-1)) increase species richness (all species and ground-foraging species) and numbers of birds (all species and ground-foraging species) relative to the control plots. 4. Three bird species consistently increased most following manipulations: white-plumed honeyeater Lichenostomus penicillatus (Gould 1837) (fam. Meliphagidae), brown treecreeper Climacteris picumnus (Temm. & Laug. 1824) (fam. Climacteridae) and yellow rosella Platycercus elegans flaveolus (Gould 1837) (fam. Psittacidae). The honeyeater is not considered as a ground or fallen timber dependent species, while the treecreeper and rosella both are regarded as being dependent on ground-layer structure. 5. Fallen timber management needs to be considered in a landscape and temporal context for improving conservation of avian biodiversity.

Theft of bower decorations among male Satin Bowerbirds (Ptilonorhynchus violaceus): why are some decorations more popular than others?

Male Satin Bowerbirds (Ptilonorhynchus violaceus) build stick structures known as bowers that serve as the focus for courtships and matings. Males decorate their bowers with numerous coloured decorations and are known to steal these decorations from one another. We investigated the stealing of bower decorations among males at the Bunya Mountains in Queensland, Australia. We aimed to (1) determine which classes of decorations were targets for theft in the studied population, and (2) examine whether the frequency at which individual decorations were stolen related to their intrinsic properties. To address our first aim, all decorations on the bowers of 21 adult males were labelled and their movements tracked throughout one mating season. To address our second aim, decorations stolen at least three times during the season were collected and their morphological and reflectance properties compared to those of decorations that were not stolen. In terms of the classes of decorations, tail feathers of Crimson Rosella (Platycercus elegans) were stolen more than any other class of decoration, but blue plastic bottletops were the most popular decorations relative to their availability on bowers. Frequently stolen individual decorations were similar to non-stolen items in their weights and surface areas, but were darker blue in colour than the decorations never stolen. Both bottletops and feathers reflected higher levels of ultraviolet (UV) light than did all other classes of bower decorations tested, thus suggesting that males may be using UV reflectance in sexual signalling. The darker blue, stolen decorations may increase contrast between the decoration collection and the platform, while the UV-reflecting subset of most frequently stolen decorations (bottletops and feathers) may increase contrast within the decoration collection. This in turn may increase the attractiveness of the display to females.

Does information of predators influence general wariness?

Antipredator behavior includes several qualitatively distinct activities, but few studies have determined the degree to which these activities are independent. If behaviors are not independent, then the nature of the relationship would illustrate potential performance constraints. We studied crimson rosellas (Platycercus elegans) and first focused on acoustic predator discrimination. We measured time allocation before and after playback of one of three experimental treatments (peregrine falcons—Falco peregrinus, wedge-tailed eagles—Aquila audax, and crimson rosellas) to determine whether or not rosellas discriminated predators from non-predators, and specifically whether or not they discriminated large from small predators. We then focused on the decision to flee. We experimentally approached subjects and measured the distance at which they oriented to us (alert distance) and the distance at which they fled (flight initiation distance; FID). We found that rosellas could distinguish among predators; however, there was no effect on general wariness as measured by FID. These two processes of antipredator behavior may, thus, be independent.

Effect of visibility on time allocation and escape decisions in crimson rosellas

Most studies of antipredator behaviour have focused on a single behaviour at a time, but ubiquitous factors may simultaneously influence a variety of activities. Habitat structure influences visibility, which influences both the ability of prey to detect and respond to their predators. We studied how habitat visibility influenced time allocation and escape decisions of crimson rosellas (Playcercus elegans). We examined the effect of visibility on time allocated to looking, locomotion and foraging. We measured escape decisions by experimentally approaching rosellas until they fled. We measured visibility by standing 12 m away from a 1-m2 white sheet containing 36 points and counting the number of points that were visible. As measured, visibility influenced time allocated to both foraging and locomotion. However, there was no effect of visibility on flight-initiation distance or two other related measures of escape (a measure of the latency to detect an approaching threat or the latency to flee once the threat was detected). Therefore, crimson rosellas modified their behaviour as a function of visibility, but this did not influence their decision to flee from an approaching human. We infer that they are sensitive to variation in visibility, but that this does not influence their overall perception of risk as we measured it. These two stages of antipredator behaviour may thus be largely independent; ubiquitous factors need not have ubiquitous effects on different aspects of antipredator behaviour.

Does intruder group size and orientation affect flight initiation distance in birds?

Wildlife managers use flight initiation distance (FID), the distance animals flee an approaching predator, to determine set back distances to minimize human impacts on wildlife. FID is typically estimated by a single person; this study examined the effects of intruder number and orientation on FID. Three different group size treatments (solitary person, two people side-by-side, two people one-behind-the-other) were applied to Pied Currawongs (Strepera graculina) and to Crimson Rosellas (Platycerus elegans). Rosellas flushed at significantly greater distances when approached by two people compared to a single person. This effect was not seen in currawongs. Intruder orientation did not influence the FID of either species. Results suggest that intruder number should be better integrated into estimates of set back distance to manage human visitation around sensitive species.

Laying date and laying sequence influence the sex ratio of crimson rosella broods

We examine the patterns of sex allocation in crimson rosellas Platycercus elegans, a socially monogamous Australian parrot. Overall, 41.8% of nestlings were male, a significant female bias. However underlying this population-level bias were non-random patterns of sex allocation within broods. Broods produced early in the season were female-biased, but the proportion of males in a brood increased as the breeding season progressed. Female rosellas may obtain greater fitness benefits from early-fledging daughters than sons because daughters can breed as 1-year-olds whereas sons do not breed until they are at least 2 years old. Laying date and laying sequence also interacted to influence the sex ratio of eggs. The sex of early-laid eggs strongly followed the brood level pattern, whereas the sex of middle- and late-laid eggs did not change significantly as the season progressed. Nevertheless, late-laid eggs were very unlikely to be male at the end of the season. We argue these differing seasonal patterns reflect the relative costs and benefits to producing early-hatched males and females at different times of the season. Female rosellas appear to maximise the probability that daughters are able to breed early but to minimise competitive asymmetries within the brood. In particular, late-hatched male chicks are disadvantaged if their oldest sibling is male, explaining the dearth of broods containing late-hatched males at the end of the breeding season.

Begging and food distribution in crimson rosella ( Platycercus elegans ) broods: why don't hungry chicks beg more?

Altricial nestlings solicit food by begging and engaging in scramble competition. Solicitation displays can thus signal both hunger and competitive ability. I examined nestling solicitation and parental responses in crimson rosellas (Platycercus elegans), a species in which parents engage in complex patterns of food allocation and appear to control the distribution of food. By manipulating the hunger of individual chicks and entire broods, I assessed how chick behaviours and parental food allocation varied with hatching rank, level of hunger, and intensity of nestling competition. Last-hatched chicks begged more than first-hatched chicks irrespective of individual hunger levels. The two parents combined fed individually hungry chicks more, but mothers and fathers varied in their responses to begging chicks: fathers fed last-hatched chicks in proportion to their begging intensity, whereas mothers fed chicks equally. Since fathers generally allocate more food to first-hatched chicks, fathers appear to use begging rates to adjust food allocation to non-preferred chicks within the brood. When I manipulated brood hunger levels, begging rates increased for first- and last-hatched chicks suggesting that chick begging rates are sensitive to the level of competition. This study shows that begging by rosella chicks does not correlate with hunger in a straightforward way and that the primary patterns of food allocation by parents are not influenced by chick begging. Thus the benefits of increased begging may be limited for nestlings in this species.

Food allocation in crimson rosella broods: parents differ in their responses to chick hunger

Food allocation in many asynchronously hatching bird species favours large, competitively superior chicks. In contrast, food is usually distributed equally within broods of crimson rosellas, Platycercus elegans, implying that parents do not simply feed the most competitive chick. We used two temporary removal experiments to manipulate hunger of: (1) individual first- or last-hatched chicks, or (2) the whole brood. When only a single chick was hungry, parents compensated fully and chicks gained the same mass over the day as during controls. Mothers and fathers, however, responded in different ways to chick hunger. Mothers did not strongly alter their food allocation when a single chick was hungry, and controlled the distribution of food by refusing to feed first-hatched chicks when they were hungry and by moving more during feeds. In contrast, fathers allocated more food to hungry last-hatched chicks. When the whole brood was hungry, parents were unable to compensate chicks and all chicks lost mass over the day. In these conditions, mothers preferentially fed first-hatched chicks, while fathers fed all chicks equally. Our results show that both mothers and fathers were able to discriminate and selectively feed chicks, but that parents responded differently to changes in chick hunger within the brood. Fathers responded more strongly to variation in chick hunger within the brood, suggesting they reallocate food based on short-term changes in hunger. Mothers distributed food preferentially to last-hatched chicks except when the whole brood was hungry, when they switched to favouring first-hatched chicks. This pattern is consistent with a strategy of adaptive brood reduction when food is scarce.

Last but not least: nestling growth and survival in asynchronously hatching crimson rosellas

1. Many species of altricial birds hatch their young asynchronously within broods. Although there are many potential benefits to parents, hatching asynchrony reduces the growth and often the survival of last‐hatched nestlings. The consequences of hatching asynchrony on the growth, size at fledging and survival of male and female nestlings of an Australian parrot, the crimson rosella (Platycercus elegans) were examined. 2. Crimson rosella broods hatched over 1·5–7 days, creating mass hierarchies where first‐hatched chicks were up to seven times larger than last‐hatched chicks. Hatching asynchrony and mass hierarchies increased over the breeding season, but were not strongly correlated with brood size. 3. Male chicks grew faster and were larger at fledging than females. Growth rates did not differ between hatching ranks. Chicks of all ranks were of equal sizes at fledging, but last‐hatched male chicks had lower fledging mass in pairwise analyses. Female mass at fledging did not decrease with hatching rank. Chick growth rates and size or mass at fledging were not related to hatching asynchrony, mass or size hierarchies in broods, brood size, laying date or year in mixed‐model analyses. 4. Last‐hatched chicks had the same post‐fledging survival as other chicks, however, they were more likely to die during the nestling period. Increased mortality of last‐hatched nestlings occurred only at hatching and chicks had equal mortality rates over the remainder of the nestling period. Early brood reduction was not associated with brood size or hatching asynchrony but increased over the breeding season, and in broods with high hatching success. 5. Hatching asynchrony in rosellas, unlike in most previous studies, did not lead to poor growth and subsequent survival of last‐hatched chicks. This suggests that the costs of hatching asynchrony are low in this species and that selective feeding by parents may increase the growth and survival of last‐hatched chicks. 6. Reduced growth and survival of later hatched chicks is not an inevitable consequence of asynchronous hatching; however, the costs to parents of overcoming competitive interactions between chicks may be higher than the benefits in most species.

Breeding biology of crimson rosellas (Platycercus elegans) on Black Mountain, Australian Capital Territory

The breeding behaviour of crimson rosellas (Platycercus elegans) in Canberra, Australia, was studied between 1993 and 1996. Female rosellas initiated breeding in late September or early October, laying a mean of 5.3 ± 0.1 (s.e.) eggs at 1–4-day intervals. Of all eggs laid, 50% fledged successfully. Rosellas had the highest breeding success in the wettest year (1995), when they bred earlier, laid larger clutches and fledged more young. Unexpectedly, breeding success was not lowest in the driest year (1994), although fewer birds attempted breeding and hatching success was low. In this study, poor environmental conditions for breeding were counterbalanced by decreased levels of conspecific interference through egg destruction. Overall, 55.8% of all clutches initiated were destroyed during laying, and more than half of this was attributed to rosellas. The reasons for egg destruction by rosellas were not clear. Boxes where clutches were destroyed were not quickly reoccupied and egg destruction was not highest when competition for nesting hollows was most intense. Clutch size and egg-laying intervals decreased over the breeding season, but the length of incubation did not. Large clutches did not produce more fledglings, because more eggs failed to hatch, especially early in the season. Eggs in a clutch hatched over a period of 0.5–7 days. Total hatching asynchrony increased over the breeding season and was not strongly correlated with clutch or brood size. This suggests that female rosellas initiated incubation at different times during laying. Clutches with longer hatching intervals took longer to incubate. If females in poor condition are inefficient incubators, female condition may affect the degree of hatching asynchrony.

Fruit removal of Coprosma quadrifida (Rubiaceae) by birds in south‐eastern Australia

Abstract Removal of the fleshy fruits of Coprosma quadrifida by birds was examined in relation to fruit crop size, neighbouring fruit crop size and time in the season in montane wet sclerophyll forest in south‐eastern Australia. On average, 84% of individual fruit crops were removed. Frugivores removed fruit in proportion to its abundance, indicating that they continually assess availability rather than respond to a critical abundance. The size of neighbouring fruit crops did not influence fruit removal rates, suggesting that there is little competition among neighbours for dispersers. The ripe fruits of C. quadrifida were eaten by 14 bird species, comprising 50% of the bird species trapped. Silvereyes (Zosterops lateralis) were the most abundant consumers of fruits. With the exception of the parrot, Platycercus elegans, all birds defecated seeds intact and had no influence on seed viability.

Evidence for Frugivory by Birds in Montane and Lowland Forests in South-east Australia

SummaryFrench, K. 1990. Evidence for frugivory by birds in montane and lowland forests in south-east Australia. Emu 90, 185–189. Fruit consumption by birds in forests near Healesville, Victoria was determined in 1987 and 1988 by analysing faecal samples of trapped birds. Evidence of frugivory was found in the faeces of 18 species of birds and a further three species were observed eating fruit. Five species of birds consumed large quantities of fruit during autumn while most birds appeared to supplement their basically insectivorous diet with small quantities of fruit. Of the nine common species of plants that produced fleshy fruits during the study, only six were evident in faeces. Some non-fleshy fruits were also eaten. Most species defaecated seeds intact; however, Crimson Rosellas were identified as the only seed predators.

Age-related Differences in Behaviour and Ecology of Crimson Rosellas, Platycercus elegans, during the Non-Breeding Season

Habitat use, diet and behaviour of adult and immature crimson rosellas were compared in the non-breeding season in a wet sclerophyll forest in southern Victoria. Immature birds occurred mainly at forest edges and were more patchily distributed than adults. They also differed quantitatively in their diet, spent more time feeding and less time resting, and occurred in larger flocks than adults. It is suggested that these dietary and behavioural differences probably result from either enforced use of inferior habitats and food resources, or less efficient foraging.

Use of Nest Boxes by Forest Vertebrates in Gippsland: Acceptance, Preference and Demand

Twelve species of vertebrates occupied nest boxes located in foothill forest trees in Gippsland, Vic., between 1977 and 1980. Boxes varied in entrance diameter, height above ground, and orientation. Over the study period 38% of boxes were found occupied and another 40% showed signs of having been visited. Occupancies were higher at the site with fewer natural hollows. Seasonal use of boxes varied between mammals and birds and between species. Boxes with small entrances were preferred, and low boxes were avoided by all species except the brown antechinus. Preference for the highest boxes was significant at one site only. Preference for diameter of entrance hole was significant for brown antechinus, sugar glider and crimson rosella; height was significant for sugar glider and brown antechinus; orientation was not significant for any species.

The Ingestion of Artifically Coloured Grain by Birds, and its Relevance to Verebrate Pest Control

In 23 field and aviary trials with several species of ground-feeding birds, the short-term uptake of grain coloured red, blue, green, yellow and black was compared with that of natural (uncoloured) grain. In all trials, one or more of the artificial colours caused a significant depression in the amount of food eaten. Although the preferences for grain of the five colours varied from trial to trial, the uptake of both blue and green grain was significantly lower than for untreated grain in all trials, and that of black, red and yellow grain was significantly lower than the control in 22, 19 and 15 trials respectively. Uptake of both blue and green grain was often significantly lower than that of the other three colours. Crimson rosellas, Platycercus elegans, which were fed on blue grain for 3 weeks before being presented with the full range of coloured and natural grain showed some association of the unnatural colour with food. They did not do so when pre-fed for less than 7 days. The possible use of coloured lethal baits to increase target specificity in the control of mammalian pests is discussed.