The ecology of the black-headed honeyeater Melithreptus affinis in Tasmania, Australia
Creators: name: Herman, K
Publisher: name: University Of Tasmania
Year: 2023

description: The island state of Tasmania supports an environment unlike anywhere else in the country. Historically the land has been exposed to glacial conditions, been both isolated and attached to the rest of the continent. This has resulted in a unique array of flora and fauna. Of the birds species found in the state, 12 are endemic, and it is one of these species that is the focus of this study. Melithreptus affinis is one of two members of this genus found in Tasmania, both of which are endemic. It was first described in 1835, and although known to science, little if any research has been undertaken on any aspect of this species ecology. This study rectifies this. In a context of the Tasmanian environment, the foraging and time budget of M affinis was constructed. Literature has already shown that there are significant morphological differences between M affinis and the mainland M lunatus, species believed to be allopatric counterparts. In fact, within the genus, both the Tasmanian species show much greater morphological divergence than the mainland species. Results showed that M affinis used a wider variety of habitats, or increased niche during this study, with foraging effort being distributed between gleaning and probing methods. These variations were influenced by seasonal factors and climatic conditions, showing the adaptability of the study species, and how closely it has evolved with the Tasmanian environment. Versatility was demonstrated when environmental conditions were less than optimal. Continuing this broadening of niche is the species use of a wider array of microhabitats than records show for Melithreptids on the mainland. Microhabitat use was distributed between upper, mid and lower canopies, whilst this genus is generally considered and upper canopy specialists. Again these changes may be a response to the climatic conditions at the time of the study. To date the literature on the breeding biology of insular species is limited to a small body pertaining to Northern Hemisphere species. Characteristics such as lower clutch sizes, later laying dates, prolonged nestling development and increased adult survival have been attributed to island populations. This study on M affinis was undertaken to determine if such trends were consistent in a Tasmanian context. Analysis of both field data and museum specimens showed that there were no discemable differences in most aspects of reproduction. The characteristics shown by M affinis are consistent with other members of the genus, as well as other members of the Meliphagidae family, except the duration of the incubation period in the species. This period is longer than would be predicted based on other members of the family. It is hypothesised that this increase may be the result of a longer history of this species in Tasmania and thus an adaptation to the colder conditions experienced during the glacial periods. It is not possible to compare this characteristic with the other endemic species, as this information is not available. The lack of variation in the reproductive traits of this endemic species allows for this species to considered equivalent to continental species, and raises the question as to the validity of insular or island effects on other aspects of the species ecology. This species has evolved in isolation, in an environment that has undergone substantial geological alteration, and has evolved in response to these environmental conditions.