Beach-Nesting Birds Within Corner Inlet
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BEACH-NESTING BIRDS WITHIN CORNER INLET Monitoring of beach-nesting shorebird and seabird breeding success in Corner Inlet to assess the health of the RAMSAR site September 2019 – March 2020 By Amy Adams and Grainne Maguire, Beach-nesting Birds Program, BirdLife Australia Snake Island (Grainne Maguire). Executive Summary Beach-nesting birds (BNB) are a suite of birds including resident shorebirds and migratory seabirds, that are largely dependent on coastal habitats for breeding. Many beach-nesting bird species have experienced population declines, local extinctions and a contraction in range. Despite the highly threatened nature of beach-nesting birds and their habitat, little emphasis has been placed on their conservation and management in Australia. The Corner Inlet barrier islands offer a unique opportunity to monitor these beach-nesting shorebirds and seabirds during the breeding season where it is predicted that the local populations would experience higher rates of breeding success than the well-monitored but highly disturbed mainland sites. Three of the barrier islands (Snake, Clonmel, Boxbank) within Corner Inlet were surveyed on eight separate occasions between September 2019 and February 2020 with the aim to inform the Ramsar site’s Limit of Acceptable Change monitoring regime as well as to document the distribution and breeding success of beach-nesting bird species. Additionally, Dream Island was surveyed three times during the same survey period to search for evidence of nesting terns. Threat assessments were carried out at active nest sites and where appropriate, remote cameras were set to assist in identifying nest fates. In total, 283 Hooded Plover, 331 Red-capped Plover, 1,139 Pied Oystercatcher and 16 Sooty Oystercatchers were counted throughout the breeding season, with numbers varying each month. There were consistent sightings of pairs of breeding Hooded Plovers and Pied Oystercatchers on what we were able to estimate as 19 Hooded Plover and 59 Pied Oystercatcher territories across the three main barrier islands. There were no Hooded Plover fledglings produced across the three islands despite at least 42 nesting attempts by 19 pairs. Of the known 132 Pied Oystercatcher breeding attempts by 59 pairs, only one chick is known to have fledged. We detected five Caspian Tern and three Fairy Tern colonies on Clonmel Island. A small Fairy Tern colony and a single Little Tern nest were also detected on Dream Island. The Caspian Terns successfully hatched and fledged chicks although final numbers of fledglings are not clear due to the logistical challenge of capturing fledging of chicks of varying age within a narrow window of time. While there were challenges in accessing the islands, a wealth of data was collected to inform our understanding of the health of this system for breeding shorebirds and seabirds. Foxes were detected on Snake and Dream Islands, and evidence of fox predation was detected by remote cameras set on two Pied Oystercatcher nests on Snake Island. Ravens and Silver Gulls were the most common source of nest failure for a range of species on the islands, as well as tidal inundation of nests. Several recommendations are made regarding improving future monitoring and mitigating key threats to beach-nesting birds within the barrier islands to improve breeding success outcomes. Snake Island (Grainne Maguire). 2 Introduction Beach-nesting birds (BNB) are a suite of birds including resident shorebirds and migratory seabirds, that are largely dependent on coastal habitats for breeding. Shorebirds nesting along the southern coastline of Australia and Victoria in particular, include the Hooded Plover (Thinornis cucullatus), Australian Pied Oystercatcher (Haematopus longirostris), Sooty Oystercatcher (Haematopus fuliginosus) and Red-capped Plover (Charadrius ruficapillus). Beach-nesting seabirds that breed in Victoria, Australia, include Caspian Terns (Hydroprogne caspia), Crested Terns (Thalasseus bergii), Fairy Terns (Sternula nereis) and Little Terns (Sternula albifrons). Beach-nesting birds lay their eggs on beaches, in a simple scrape above the high-tide mark, sand spits, dunes or rocky shores, where sand, shell or rock provides an ideal substrate for their well camouflaged, stone coloured eggs. This camouflage serves to protect the eggs from native predators, and the colouration of their chicks also closely matches the coastal environment. Beach- nesting shorebirds are territorial, occupying discrete sections of coast with suitable nesting habitat and food to support the pair plus chicks. Red-capped Plovers can be less territorial, nesting semi- colonially in small groups. Beach-nesting shorebirds predominantly feed on invertebrates on the sand surface, under wrack, on rock platforms and in the soft wet sand. When their eggs hatch, the precocial (i.e. relatively mature and mobile from the moment of hatching) chicks move about with the parents, either being fed for the first few weeks as is the case for Oystercatchers, or foraging for themselves from the moment of hatching, as for the Plover species. Beach-nesting seabirds on the other hand, typically nest colonially, as they benefit from safety in numbers while one or both of the pair are out at sea foraging. Birds that nest on beaches experience one of the harshest struggles of any bird to successfully produce young (Maguire 2008). Prior to human settlement, high tides, storms and native predators, such as gulls, ravens and birds of prey, were the main threats shaping breeding success outcomes for these birds. Since European settlement, reproduction rates have been dramatically impacted by a range of new threats added to the coastal environment including: destruction and modification of habitat, introduced predators such as foxes and cats, increases in native predator populations (such as gulls and ravens) related to urbanisation, and human recreation (and their companion canines, horses and vehicles) on beaches that results in crushing of eggs and chicks, or lethal disturbance during incubation and chick rearing phases (Maguire 2008; Maguire et al. 2014). The features that adapt beach-nesting birds to their environment become detrimental to their breeding success where human recreation occurs: the location of nests, camouflage of the eggs and young, the long incubation and brood rearing phases, and the passive nature of nest and brood defence (with the exception of terns that swoop approaching people), all make them highly susceptible to breeding failure. Many beach-nesting bird species have experienced population declines, local extinctions and a contraction in range. Hooded Plovers and Fairy Terns are both listed as threatened species under the Federal Environment Protection and Biodiversity Conservation (EPBC) Act 1999. Despite the highly threatened nature of beach-nesting birds and their habitat, little emphasis has been placed on their conservation and management in Australia. There has been a bias in research and conservation efforts towards migratory shorebirds in comparison to resident species (Weston 3 2007), even though a greater number of resident species have a threatened status (Milton et al. 2005). Beach-nesting shorebirds and seabirds can be excellent indicators of coastal health, providing coastal managers with insight into the threats present within the coastal environment, and a measure of the effectiveness of investment in threat mitigation (Schlacher et al. 2014). They are therefore an important group of birds for coastal managers to focus their efforts. Study aims Nooramunga Marine & Coastal Park is one of four significant parks located within the Corner Inlet Ramsar Site. It covers approximately 30,000 ha between Port Welshpool and McLoughlins Beach and consists of a complex series of coastal habitats, islands, intertidal flats and subtidal marine environments. Of significance is a series of barrier sand islands that protect the inner islands from the open coast, namely Snake Island, Clonmel Island, Boxbank Island and Dream Island. The Hooded Plover, an iconic coastal species, has been the focus of BirdLife Australia’s Beach- nesting bird project since 2006. The species is listed as threatened both at the state and national level. Increasing the breeding success has been essential in halting the decline in Hooded Plover numbers experienced in Victoria. The Corner Inlet barrier islands contain important breeding areas for this threatened species as well as for other beach-nesting shorebirds including Red-capped Plovers and Pied Oystercatchers, and for seabirds including Crested Terns, Caspian Terns and occasionally Fairy Terns. Given the relatively pristine habitat within the Corner Inlet barrier islands, there is a unique opportunity to add to our knowledge of the breeding success rates of these species in habitats with low human visitation compared to the well-monitored, mainland beaches that experience moderate to high levels of human (dog, horse and even vehicle) visitation. The Corner Inlet barrier islands offer a unique opportunity to monitor these beach-nesting shorebirds and seabirds which would be predicted to experience higher rates of breeding success than the well-monitored mainland, due to the infrequent human use of the islands and thus presumably only natural, pre-European colonisation, threat levels. Little is known about the range and intensity of threats impacting beach-nesting shorebird and seabird breeding success within the barrier islands. Predators and weeds may be having greater influence on the