Environment Protection and Biodiversity Conservation (Wildlife Conservation Plan for Seabirds) Instrument 2022
136Wildlife Conservation Plan for Seabirds
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Gull-billed Tern (Gelochelidon nilotica)TABLE Species information for the Gull-billed Tern (Gelochelidon nilotica)
The Gull-billed Tern (Gelochelidon nilotica) and Australian Gull-billed Tern (G. macrotarsa) (del Hoyo and Collar 2014) were previously placed in the genus Sterna and lumped as S. nilotica following Sibley and Monroe (1990, 1993). Only the Gull-billed Tern is listed under the EPBC Act as a listed migratory and marine species. The Gull-billed Tern is a large gull-like tern with a diagnostic short thick gull-like bill, heavy rounded head and short thick neck. The species breeds at scattered sites in North and South America, Europe, Africa and Asia. It breeds in a variety of locations with bare or sparsely vegetated islands, banks, flats, or spits of dry mud and sand including barrier beaches (shoals), dunes, saltmarshes, saltpans, freshwater lagoons, estuaries, deltas, inland lakes, rivers, marshes and swamps (del Hoyo et al. 1996, Higgins and Davies 1996, Snow and Perrins 1998). During this season, it may also feed on emerging insects over lakes, agricultural fields, grasslands and even over semi-desert regions (del Hoyo et al. 1996). On passage the species typically forages over saltpans, coastal lagoons, mudflats, marshes and wet fields, overwintering on estuaries, saltpans, lagoons and saltmarshes, or in more inland sites such as large rivers, lakes, rice-fields, sewage ponds, reservoirs, saltpans and irrigation canals (del Hoyo et al. 1996, Higgins and Davies 1996, Snow and Perrins 1998). It is an opportunistic feeder and is largely insectivorous taking adult and larval terrestrial and aquatic insects as well as spiders, earthworms, small reptiles, frogs, small fish (6-9 cm long) (Richards 1990, del Hoyo et al. 1996).
The global population of Gull-billed Tern and Australian Gull-billed Tern combined is estimated to number between 150,000–420,000 individuals (Delany and Scott 2006), but the global population of G. nilotica has not been estimated separately following the taxonomic split. The Australian population estimate and trends are unknown. While recorded observer effort has been inconsistent over the years, there is considerable annual variation in Gull-billed Tern numbers in Victoria, probably with lowest numbers in wet years when there is extensive inland habitat, with more birds coming to Victoria in drought years (Victorian SAC pers. comm. 2020).
This species has been identified as particularly susceptible to abandonment of breeding sites due to human disturbance (Molina et al. 2014), although early dispersal from breeding sites appears to be a behavioural trait of the species that may mitigate the impact of disturbance. It is possible that, in the future, the effects of climate change could have an adverse impact on food sources and breeding habitat.
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Caspian Tern (Hydroprogne caspia)
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TABLE Species information for the Caspian Tern (Hydroprogne caspia)
The Caspian Tern (Hydroprogne caspia) is a large gull-like tern with a deep dagger-shaped red bill; it is the largest tern in the world. Its hoarse heron-like croaking call is distinctive. This species has a cosmopolitan but scattered distribution. Their breeding habitat is large lakes and ocean coasts in North America (including the Great Lakes), and locally in Europe (mainly around the Baltic Sea and Black Sea), Asia, Africa, and Australasia. North American birds migrate to southern coasts, the West Indies and northernmost South America. European and Asian birds winter in the tropics. African and Australasian birds are resident or disperse over short distances (del Hoyo et al. 1996).
The species shows a preference for nesting on sandy, shell-strewn or shingle beaches, sand-dunes, flat rock-surfaces, sheltered reefs or islands with sparse vegetation and flat or gently sloping margins surrounded by clear, shallow, undisturbed waters (Flint et al. 1984, Higgins and Davies 1996, del Hoyo et al. 1996, Snow and Perrins 1998). The species nests in large colonies or as single pairs or small groups amidst colonies of other species, neighbouring nests placed between 0.7 and 4 m apart (del Hoyo et al. 1996). The species may forage up to 60 km from the site of the breeding colony (del Hoyo et al. 1996). It also forms winter roosts on sandbars, mudflats and banks of shell (del Hoyo et al. 1996). Its diet consists predominantly of fish and minor amounts of the eggs and young of other birds, carrion, aquatic invertebrates (e.g. crayfish), flying insects and earthworms (Flint et al. 1984, Urban et al. 1986, del Hoyo et al. 1996, Shuford and Craig 2002).
The global population is estimated to number between 250,000–470,000 individuals (Wetlands International 2015). The overall population trend is increasing, although some populations are decreasing, stable, or have unknown trends (Delany & Scott 2006). This species has undergone a large and statistically significant increase over the last 40 years in North America (266 per cent increase over 40 years, equating to a 38.3 per cent increase per decade; Butcher and Niven 2007). Australian population estimates and trends are unknown.
Human disturbance represents a threat to this species. Caspian Tern colonies are especially vulnerable to disturbance during the early courtship and incubation stages, during which human visitation results in the flushing of the whole colony, potentially leading to nest or colony abandonment (Cuthbert and Wires 1999; Shuford and Craig 2002). The effect of disturbance during research activities has been well quantified, with activities such as banding and cannon-netting representing a large proportion of the reproductive failure in colonies studied (Shuford and Craig 2002). Disturbance due to recreational activities are less well quantified but likely also significant (Shuford and Craig 2002). Much of the loss of reproductive success due to human disturbance occurs through gull predation of chicks during the few seconds of panic flight in which the eggs and chicks of a nest are left exposed (Shuford and Craig 2002). Historically, exploitation has resulted in large population decreases through the collection of eggs and adults for food and feathers (Shuford and Craig 2002).
Monitor and manage, if required, the impact of Silver Gulls and other species on breeding colonies
Trail artificial nesting sites and social attraction techniques to establish new colonies
Photograph of a Caspian Tern in flight with a fresh catch
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Whiskered Tern (Chlidonias hybrida)
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TABLE Species information for the Whiskered Tern (Chlidonias hybrida)
The Whiskered Tern (Chlidonias hybrida) is a large marsh tern with a more dagger-shaped bill than congeners. This species is slightly bigger and bulkier than the White-winged Tern (C. leucopterus), with slightly longer and more uniformed broad wings and a slightly deeper fork-tail. The species utilises a variety of wetland habitats but shows a preference for freshwater marshlands with scattered pools, particularly where the surrounding vegetation is grazed by cattle or horses (Richards 1990). It frequents inland lakes, rivers, marshes, artificial fish-ponds and drainage-ponds (del Hoyo et al. 1996), swamps, river pools, reservoirs, large dams, sewage-ponds, flooded saltmarshes (Higgins and Davies 1996, del Hoyo et al. 1996) and rice-fields (del Hoyo et al. 1996). In Australia the species also occurs along the coast on estuaries, coastal lagoons, creeks in mangrove swamps (Snow and Perrins 1998) and tidal mudflats (del Hoyo et al. 1996). When breeding the nest is a heap of aquatic vegetation (Richards 1990, del Hoyo et al. 1996) or dry grass (del Hoyo et al. 1996), placed either on floating and emergent vegetation over water 60-80 cm deep or resting on the bottom of very shallow water (del Hoyo et al. 1996). The species nests in colonies, neighbouring pairs spaced between 1 and 5 m apart (del Hoyo et al. 1996), and may forage up to 9 km away from breeding sites (more usually within 1 km) (del Hoyo et al. 1996). Its diet consists of terrestrial and aquatic insects (del Hoyo et al. 1996) (e.g. Dytiscidae, adult and larval Odonata, Orthoptera, flying ants (del Hoyo et al. 1996) and mosquitoes (Richards 1990)), spiders, frogs, tadpoles, small crabs (del Hoyo et al. 1996), shrimps (Richards 1990) and small fish (del Hoyo et al. 1996).
The global population is estimated to number 300,000-1,500,000 individuals (Delany and Scott 2006). The overall population trend is fluctuating, although some populations are stable and others have unknown trends (Delany and Scott 2006). The Australian population estimate and trends are unknown.
The species suffers from the loss of natural wetlands to land reclamation, dry seasons and an increase in drainage schemes (Hagemeijer and Blair 1997), as well as the canalization of rivers (Tucker and Heath 1994). Human activities near breeding colonies can result in disturbance and the loss of nesting sites (Tucker and Heath 1994) and many nests are lost to adverse weather. Whiskered Terns are affected by water quality and pollution from insecticides and eutrophication (Martí and Moral 2004). The intensification of fisheries and bycatch in fishing nets are issues in part of its range (Golemansky 2011).
Manage freshwater wetland habitats to support the lifecycle of the species
Photograph of a Whiskered Tern in flight
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White-winged Black Tern (Chlidonias
leucopterus)
TABLE Species information for the White-winged Black Tern (Chlidonias leucopterus)
The White-winged Black Tern (Chlidonias leucopterus) is the smallest Chlidonias species, slightly smaller, slimmer and more compact than Whiskered Tern (C. hybrida). In breeding plumage, the adults are strikingly black and white, with diagnostic white forewing-coverts. The species breeds in Europe, Russia and China from April to August in small colonies of between 3 and 100 pairs (mostly 20-40 pairs) that may contain other species (del Hoyo et al. 1996). The species breeds inland on freshwater lakes (del Hoyo et al. 1996, Snow and Perrins 1998), swampy standing water, rivers (Snow and Perrins 1998) and shallow naturally flooded grassland (Richards 1990, Snow and Perrins 1998) with areas of open water bordered by stands of reeds, sedge and other aquatic vegetation (Snow and Perrins 1998). It generally avoids fish-ponds, rice-fields and ornamental waters (Richards 1990) but may feed over wet fields, dry farmland and steppe grassland (del Hoyo et al. 1996). Throughout the year the species feeds in flocks (Snow and Perrins 1998) and migrates and overwinters in large flocks (del Hoyo et al. 1996) of up to tens of thousands of individuals (Snow and Perrins 1998).
The global population is estimated to number 3,100,000-4,000,000 individuals (Delany and Scott 2006). The overall population trend is stable, although some populations have unknown trends (Delany and Scott 2006). The Australian population estimate and trends are unknown.
The main threats to this species are within its European range and have been identified as habitat destruction and water regulation in wetlands. In the west of its European range the reclamation of wetlands is causing declines and in Russia and the Ukraine dry breeding seasons and an increasing number of drainage schemes pose a threat (Hagemeijer and Blair 1997). It is also susceptible to avian influenza so may be threatened by future outbreaks of the virus (Melville and Shortridge 2006).
Manage freshwater wetland habitats to support the lifecycle of the species
Section 136 - Environment Protection and Biodiversity Conservation (Wildlife Conservation Plan for Seabirds) Instrument 2022 - Wildlife Conservation Plan for Seabirds | Zoe