Sea change for Australia's coastal raptors: the cost of urban living
The conversion of natural environments into land useful for human habitation has many effects on biodiversity and can alter the way terrestrial and aquatic ecosystems function. Urbanisation is particularly potent in coastal areas, where birds of prey have often been recognised as indicators of envir...
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| Format: | Text |
| Language: | English |
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Griffith University
2021
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| Online Access: | https://dx.doi.org/10.25904/1912/4331 https://research-repository.griffith.edu.au/handle/10072/408097 |
| Summary: | The conversion of natural environments into land useful for human habitation has many effects on biodiversity and can alter the way terrestrial and aquatic ecosystems function. Urbanisation is particularly potent in coastal areas, where birds of prey have often been recognised as indicators of environmental health. In Australia, four coastal raptor species are present: White-bellied Sea-Eagle (Haliaeetus leucogaster), Eastern Osprey (Pandion haliaetus cristatus), Brahminy Kite (Haliastur indus) and Whistling Kite (Haliastur sphenurus). Coastal raptors are important vectors of nutrient transport between marine and terrestrial systems and are key players in structuring biological communities. Most coastal raptor research has been in southern Australia where populations are in decline. However, little has been conducted in the urbanising region of South-East Queensland (SEQ). This thesis addressed urbanisation impacts on Australia’s coastal raptors in SEQ including breeding habits, physical impacts, rehabilitation outcomes and the importance of protected areas. Chapter 2 discussed Eastern Ospreys and their ability to adapt to urban areas and nest on artificial structures. This behaviour was investigated in two regions of SEQ: urbanised Moreton Bay Marine Park (MBMP) and rural Great Sandy Marine Park (GSMP). Most nests in MBMP were on artificial structures, while in GSMP most were on natural structures. This chapter showed that Eastern Ospreys have a high propensity for nesting on artificial structures when close to urban environments and that additional nesting platforms should be erected to avoid the risks associated with nesting on unsafe structures. Physical threats in urban landscapes are many and varied for Australia’s coastal raptors. These threats were investigated in Chapter 3, where admissions to Currumbin Wildlife Hospital Foundation (CWH) were analysed. Most birds were admitted from anthropogenic causes, most significantly from fishing equipment entanglement. Bird attack and vehicle strike were also significant. This is the first time fishing equipment entanglement has been quantified as a significant cause of injury to coastal raptors. This chapter highlights the importance of public education on the threats fishing equipment can cause to local wildlife. Although the majority of coastal raptors admitted to CWH were released, assessing rehabilitation success of raptors has been rarely attempted. Rehabilitation is intensive, expensive and the success rates post-release are rarely investigated. In Chapter 4, 28 banded coastal raptors and 2 White-bellied Sea-Eagles, fitted with GPS tracking devices, were monitored post-release. Band return was low but both tagged White-bellied Sea-Eagles survived beyond the crucial six week period, suggesting successful rehabilitation. Home ranges were much larger than previously reported for this species and illustrates how GPS tracking can enhance our knowledge of the ecology of these raptors. Chapter 5 explored trends in the presence of these species in SEQ using three datasets. Long-term data from Queensland Wader Study Group, habitat loss data from Global Forest Watch and nest location data were used to explore temporal trends in species sightings and cumulative habitat loss in Moreton Bay. White-bellied Sea-Eagle and Whistling Kite sightings decreased with increased cumulative tree cover loss while nest location data showed that coastal raptors were nesting in protected areas. These findings suggests that these areas are critical for their persistence in the region. This thesis showed that while many processes threaten the coastal raptors of SEQ, management is possible with education and innovative measures. Watercourses and protected areas were critically important for coastal raptors in urban areas, where fishing equipment entanglement is a key threat. Rehabilitation of coastal raptors by CWH is often successful and could be critical for the management of species populations and mitigation of threats. Furthermore, the benefits of GPS tracking in increasing our knowledge of the ecology of coastal raptors was clearly demonstrated. Although susceptible to many threats, the coastal raptors of SEQ showed resilience and adaptability, finding opportunities to breed in the protected areas of Moreton Bay. Eastern Ospreys have the ability to nest on various structures within the urban landscape and although risky, this behaviour shows that breeding platforms could be erected in urban areas to encourage ospreys to avoid dangerous nest sites and reduce competitive pressures for nesting space with the other species. The information presented in this thesis will contribute significantly to our knowledge on Eastern Ospreys, White-bellied Sea-Eagles, Whistling Kites and Brahminy Kites in coastal South-East Queensland. |
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