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    Sexual dimorphism of song and life history trade-offs in the New Zealand bellbird : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Albany, New Zealand
    (Massey University, 2018) Roper, Michelle Mary
    Birdsong and its function is well studied in terms of male-male competition and female-mate choice. This has generated a male bias in the song literature and the dilemma that little is known about female song. However, recent research posits that female song is not only common but is also the ancestral state of songbirds. Therefore, it is timely that I investigate the ontogeny, structure and production of female song within the context of the life history of female songbirds in order to increase our current understanding of the function and evolution of birdsong. In this thesis, I use a wild population of New Zealand bellbirds (Anthornis melanura) as a model species. The New Zealand bellbird is ideal for this research as they produce complex but sexually dimorphic song. With a cross-sectional approach, I found the songs of each sex diverged and became more consistent as the song developed from juveniles to adults, and that their sexually dimorphic songs developed over similar timeframes, suggesting potentially related functions. I also compared how the adult song repertoire of each sex varied over time, and found that males had larger repertoires at both the population and individual levels. The syllable repertoire of each sex changed at a similar rate due to shifts in relative abundance over time, suggesting both sexes may have analogous song functions and are potentially under similar selection pressures. Sexual variation in song could theoretically be explained by differences in the syrinx structure but there is a lack of comparative research in this field. I found that bellbirds had greater sexual dimorphism in the size of their bronchial half rings compared to species both with and without female song. This suggests syrinx size alone cannot explain sexual dimorphism in repertoire size, but may have a stronger influence on sex- and species-specific song frequencies. Long term studies provide insights to life history and my study population on Tiritiri Matangi Island has breeding data available as far back as 1977. The island’s history of ecological restoration has resulted in exponential growth of the bellbird population, and I found correlated reproductive trade-offs with a reduction in clutch size over time, likely owing to increasing competition for resources. My research demonstrates how female songbirds develop and change their song over time and that they have flexible life-history traits that enable them to cope with changing breeding conditions. My research is significant in that it is one of the first to study female song in a wild population and provides important insights into male and female song development, structure and role.
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    New horizons for female birdsong : evolution, culture and analysis tools : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Auckland, New Zealand
    (Massey University, 2020) Webb, Wesley
    As a result of male-centric, northern-hemisphere-biased sexual selection theory, elaborate female traits in songbirds have been largely overlooked as unusual or non-functional by-products of male evolution. However, recent research has revealed that female song is present in most surveyed songbirds and was in fact the ancestral condition to the clade. Additionally, a high proportion of songbird species have colourful females, and both song and showy colours have demonstrated female-specific functions in a growing number of species. We have much to learn about the evolution and functions of elaborate female traits in general, and female song in particular. This thesis extends the horizons of female birdsong research in three ways: (1) by revealing the broad-scale evolutionary relationship of female song and plumage elaboration across the songbirds, (2) by developing new accessible tools for the measurement and analysis of song complexity, and (3) by showing—through a detailed field study on a large natural metapopulation—how vocal culture operates differentially in males and females. First, to understand the drivers of elaborate female traits, I tested the evolutionary relationship between female song presence and plumage colouration across the songbirds. I found strong support for a positive evolutionary correlation between traits, with female song more prevalent amongst species with elaborated female plumage. These results suggest that contrary to the idea of trade-off between showy traits, female plumage colouration and female song likely evolved together under similar selection pressures and that their respective functions are reinforcing. Second, I introduce new bioacoustics software, Koe, designed to meet the need for detailed classification and analysis of song complexity. The program enables visualisation, segmentation, rapid classification and analysis of song structure. I demonstrate Koe with a case study of New Zealand bellbird Anthornis melanura song, showcasing the capabilities for large-scale bioacoustics research and its application to female song. Third, I conducted one of the first detailed field-based analyses of female song culture, studying an archipelago metapopulation of New Zealand bellbirds. Comparing between male and female sectors of each population, I found equal syllable diversity, largely separate repertoires, and contrasting patterns of sharing between sites—revealing female dialects and pronounced sex differences in cultural evolution. By combining broad-scale evolutionary approaches, novel song analysis tools, and a detailed field study, this thesis demonstrates that female song can be as much an elaborate signal as male song. I describe how future work can build on these findings to expand understanding of elaborate female traits.
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    The breeding ecology and mating system of the bellbird (Athornis melanura) on Tiritiri Matangi Island : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology at Massey University
    (Massey University, 2007) Cope, Taneal Mulock
    A large population of Bellbirds were individually banded and monitored on Tiritiri Matangi Island in 2005 and 2006. The main aim of this research was to provide baseline breeding data from a large, stable population of Bellbirds reminiscent of pre-colonisation New Zealand. Nesting observations indicated that Bellbirds preferentially nest in Cabbage Trees on the island. Nest success was similar to recent values detected for other open nesting passerines found on the island, and has not changed since the study by Anderson & Craig (2003) undertaken in 1979. This is interesting considering that predation pressures would have been significantly alleviated since the eradication of Kiore in 1993. Breeding was found to be highly asynchronous within neighbouring territories in both 2005 and 2006. The majority of social bonds were recorded as monogamous, similar to past findings; however this research reported one case of polygynandry. In addition, regular extra pair male visits to other nests were recorded, as well as the occurrence of extra pair copulations. Parental care was undertaken by both sexes; however was largely unequal in that the female invested more in nest attendance than the male. The inequality in parental care, as well as the observed extra pair social behaviours, led to doubts over the current certainty of monogamy as the mating system in this species. The genetic analysis of paternity revealed that both males and females engage in mixed mating strategies, with 81% of offspring a result of extra pair paternity. This represents one of the highest levels of promiscuity recorded in passerines to date. The high level of sexual dimorphism coupled with the high level of promiscuity indicates the importance of genetic evidence for conclusions regarding mating systems; especially in the honeyeater species that show sexual dimorphism and hence intense sexual selection.
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    Resource partitioning between two competitive species, the hihi (Notiomystis cincta) and bellbird (Anthornis melanura), during the non-breeding season on Tiritiri Matangi Island : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology at Massey University, Albany, New Zealand
    (Massey University, 2012) Roper, Michelle
    Understanding the level of competition and resource partitioning between New Zealand’s ecological honeyeaters is important for hihi (Notiomystis cincta) conservation management. Hihi management on Tiritiri Matangi Island has been thought to be hindered by competition with bellbirds (Anthornis melanura), particularly at the supplementary sugar water feeders. With some inconsistent results in differences between their foraging ecology at different locations and seasons, I collected data on the foraging ecology of both hihi and bellbirds on Tiritiri Matangi Island to compare with previous studies at other locations. Nectar was the main constituent of both species diet with fruit only being consumed in the autumn-winter months for both species. The main difference between the species was that hihi consumed more fruit than bellbirds and bellbirds consumed honeydew. Bellbirds foraged more in the higher vegetation layers and on higher nectar value flowers than hihi which corresponded with previous studies. This suggested that resource partitioning is likely to be in the form of bellbirds defending the best resources of higher nectar value in the higher vegetation layers with interference competition and hihi obtain resources with exploitation competition by utilising flowers which are often smaller, less abundant or produce less nectar in the lower vegetation layers. Male bellbirds and hihi were the most frequent visitors to the supplementary feeders. With few interspecific interactions it suggests that male bellbirds are unable to defend the feeders due to the feeders being overwhelmed with hihi and also showing how dependent hihi are on supplementary feeding. Female bellbirds were the least frequent visitors suggesting that intraspecific competition is greater at the feeders but only for bellbirds as there was little evidence of high competition between the hihi sexes. There may be some resource partitioning between habitat types as hihi were consistently found at higher densities in the mature forest habitat likely due to their dependence on the feeders and artificial nest boxes, whereas bellbird densities changed with resource availability and breeding season territoriality. The densities of both species were affected by the presence of feeders and nectar availability with positive correlation between the species in the non-breeding season, suggesting that hihi habitat preference was not affected by competitive exclusion from bellbirds. The removal of 100 bellbirds for a translocation had no evident impact on hihi and bellbird densities at capture sites.
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    Population genetics, biogeography and ecological interactions of the New Zealand bellbird (Anthornis melanura) and their avian malaria parasites : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (Ph.D.) in Zoology at Massey University, Albany, New Zealand
    (Massey University, 2011) Baillie, Shauna Maureen
    Habitat loss and redistribution of species has lead to population declines and loss of genetic diversity with serious implications to species survival on ecological and evolutionary scales. While there is no doubt that rapidly dwindling endangered populations require our immediate attention, studies on common species are equally important. The purpose of this thesis is to investigate the genetic connectivity, biogeographical relationships and host-parasite interactions of a common and widely distributed bird species, mainly because we want common species to remain common. Furthermore, I illustrate how studies such as this provide invaluable comparisons for sympatric endangered species. In this thesis, patterns of genetic variation of the New Zealand bellbird (Anthornis melanura) are delineated to assess their re-colonization potential among fragmented landscapes. Using a phylogeographic perspective I show how dispersal ability and secondary contact among isolated population fragments shape the evolutionary trajectory of a species. I also determine the biogeographical relationships between the bellbird host and its malaria parasites with key emphasis on host-parasite specificity. Finally, immunological trade-offs are investigated in disease epidemiology by examining host factors that influence malaria prevalence. I show that an immense capacity for dispersal has prevented divergence and shaped the high levels of genetic diversity and connectivity in bellbirds today. However, substantial genetic differentiation among subpopulations reflects recent habitat fragmentation. Based on these findings I conclude that continued habitat loss can lead to further reductions in gene flow, despite dispersal. Though restricted to northern populations, I provide evidence that the most abundant avian malaria lineage infecting bellbirds is likely an endemic Plasmodium (Novyella). This parasite exhibits bimodal seasonality and male-biased infections, but these relationships vary among subpopulations. Malaria prevalence appears to be governed by food availability and territory stability, thus habitat disturbance has repercussions to immune phenotype. With this thesis I advocate a re-thinking of conservation strategies toward spatial planning that enables ‘natural’ secondary contact among habitat fragments. Translocation is not necessary for all species. In addition to being the first study on seasonal and host factors affecting malaria patterns in the Southern Hemisphere, this thesis makes major contributions to science by elucidating some ecological relationships that underpin the evolution of immunity.