|Species group report card
Supporting the marine bioregional plan
for the North Marine Region
prepared under the Environment Protection and Biodiversity Conservation Act 1999
© Commonwealth of Australia 2012
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Species group report card – seabirds
1. Seabirds of the North Marine Region
2. Vulnerabilities and pressures
3. Relevant protection measures
Attachment 1: Seabird species occurring in the North Marine Region
Species group report
card – seabirds
Supporting the marine bioregional plan for the North Marine Region prepared under the Environment Protection and Biodiversity Conservation Act 1999
The primary objective of the report cards is to provide accessible information on the conservation values found in Commonwealth marine regions. This information is maintained by the Department of Sustainability, Environment, Water, Population and Communities and is available online through the department’s website (www.environment.gov.au). A glossary of terms relevant to marine bioregional planning is located at www.environment.gov.au/marineplans.
Reflecting the categories of conservation values, there are three types of report cards:
species group report cards
marine environment report cards
protected places report cards.
While the focus of these report cards is the Commonwealth marine environment, in some instances pressures and ecological processes occurring in state waters are referred to where there is connectivity between pressures and ecological processes in state and Commonwealth waters.
Species group report cards
Species group report cards are prepared for large taxonomic groups that
include species identified as conservation values in a region; that is, species that are listed under Part 13 of the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) and live in the Commonwealth marine area for all or part of their lifecycle. All listed threatened, migratory and marine species and all cetaceans occurring in Commonwealth waters are protected under the EPBC Act and are identified in the relevant marine bioregional plans as conservation values.
Species group report cards focus on species for which the region is important
from a conservation perspective; for example, species of which a significant proportion of the population or an important life stage occurs in the region’s waters.
For these species, the report cards:
outline the conservation status of the species and the current state of knowledge about its ecology in the region
define biologically important areas; that is, areas where aggregations of individuals of a species display biologically important behaviours
assess the level of concern in relation to different pressures.
1. Seabirds of the North Marine Region
Northern Australia is extremely important for many species of seabird. The waters of the North Marine Region support large populations of seabirds, predominantly tern species. Offshore islands adjacent to the region host internationally and nationally significant breeding sites for significant numbers of colonially nesting terns; in particular the crested tern, bridled tern, roseate tern and black-naped tern (Chatto 2001). Individual breeding colonies may contain more than 60 000 adult seabirds from one to five species (Chatto 2001).
Fifty-one bird species listed under the EPBC Act are known to occur in the North Marine Region; another 49 listed bird species occur infrequently in the region (see Attachment 1). Of these listed bird species, this report card focuses on the 11 seabird species listed in Table 1. These species were selected following consideration of their conservation status, distribution and population structure within the North Marine Region, life history characteristics and the potential for the population(s) in the region to be genetically distinct from populations elsewhere. For the purposes of this report card, ‘seabirds’ refers to birds that feed primarily in marine waters by flying or swimming.
Taxonomic names used follow Christidis and Boles (2008).
The brown booby (Sula leucogaster) is listed as migratory and marine under the EPBC Act. It is the most common booby, occurring throughout all tropical oceans approximately bounded by latitudes 30° N and 30° S. The species forages in the North Marine Region and breeds in areas adjacent to the region.
The brown booby is a specialised plunge diver, and is thought to forage closer to land than other booby species, which are considered more pelagic (Marchant & Higgins 1990a). However, a study of the marine distribution of Christmas Island seabirds found that the brown booby foraged within 250 kilometres of the island (Dunlop et al. 2001). The brown booby feeds on a large range of fish species and some cephalopods.
The total breeding population in the Australian region in 1996–97 was 59 940–73 900 pairs (WBM Oceanics & Claridge 1997). The brown booby has been recorded in all months of the year around most of the Northern Territory coastline, except for the shallower, more turbid waters such as in the south-west, Van Diemen Gulf and the many mangrove-lined bays around the coast (Chatto 2001). There are no confirmed breeding sites for brown boobies in the Northern Territory (Chatto 2001). One almost inaccessible site on a large, high rock off the northern coast of Groote Eylandt may be a breeding site as it was reported to have 200–300 birds on it each year for about six weeks around August (C Davis pers. comm. in Chatto 2001). However, this site was ground-checked in October 1994 and there was no evidence of current or recent breeding (Chatto 2001). There are two large breeding colonies on the Wellesley Islands, Queensland (1400 nests on Manowar Island and 4500–6000 nests (20 000–30 000 birds) on Rocky Island in 1991; Walker 1992). The breeding season for brown boobies varies, with egg laying recorded throughout the year at many locations (Marchant & Higgins 1990a); however, young birds may disperse and/or migrate when not breeding.
The lesser frigatebird (Fregata ariel) is listed as migratory and marine under the EPBC Act. It is usually seen in tropical or warmer waters off northern Western Australia, Northern Territory, Queensland and northern New South Wales. The species forages in the North Marine Region and breeds in areas adjacent to the region.
The species is usually pelagic and often found far from land, but is also found over shelf waters, in inshore areas, and inland over continental coastlines (Marchant & Higgins 1990a). It resides further out to sea during the day and in inshore waters during rough weather or in the late evening (Chatto 2001). The lesser frigatebird feeds mostly on fish and sometimes on cephalopods. It forages by scooping up marine organisms from the surface of the water, taking flying fish from just above the surface, or by harassing other seabirds to force them to disgorge some of their meal (Marchant & Higgins 1990a). The lesser frigatebird appears to range relatively close to breeding colonies (Jaquemet et al. 2005) but some large movements have been recorded through band recoveries.
The lesser frigatebird breeds on the Wellesley Islands, Gulf of Carpentaria, Queensland (Chatto 2001). Manowar Island of the Wellesley Islands group supports up to 3800 breeding pairs (O’Neill & White 2003).The species has a protracted breeding season that varies slightly between different localities. In Australia egg laying occurs mostly about mid-year. At Manowar Island eggs, downy young and juveniles have all been seen in July (Garnett & Crowley 1987). The presence of fully feathered chicks together with eggs in mid-May at North Bountiful Island, Wellesley Islands, indicates a breeding occupation of at least April to June (Walker 1992). A frigatebird roost (non-breeding location) is recorded near Weipa, with up to 500 lesser frigatebirds observed (Mustoe 2008).
The streaked shearwater (Calonectris leucomelas) is listed as migratory and marine under the EPBC Act. It occurs frequently in northern Australia, with records from central Western Australia, around the north coast, and south to central New South Wales (Brooke 2004; Marchant & Higgins 1990b). The species forages in the North Marine Region.
The species occurs over pelagic and inshore waters. In northern Australia, the streaked shearwater is usually found in offshore waters more than 18 kilometres from the mainland coast (Marchant & Higgins 1990b). In the Gulf of Carpentaria the species mostly occurs further than 100 kilometres from land (Blaber & Milton 1994; Marchant & Higgins 1990b). The streaked shearwater eats mainly fish and squid caught by surface-seizing or by shallow plunges (del Hoyo et al. 1992; Marchant & Higgins 1990b). It has been recorded diving to a depth of 5 metres (Oka 1994a). The species also follows fishing boats and eats fish scraps thrown from boats (Oka 1994b). Off the Northern Territory coast, the species is common in the Arafura Sea during summer. Although the streaked shearwater does not breed in Australia, the species is recorded regularly in northern Australia from October to March, with some records as early as August and as late as May (Marchant & Higgins 1990b).
The black-naped tern (Sterna sumatrana) is listed as migratory and marine under the EPBC Act. It is found in the central and eastern Northern Territory, the Gulf of Carpentaria and the Torres Strait. The species forages in the North Marine Region and breeds in areas adjacent
to the region.
The species is generally recorded in the vicinity of its breeding colonies (Chatto 2001). The black-naped tern feeds solely on fish, with a mean length of prey of 35 millimetres, but it can also take fish up to 100 millimetres long (Higgins & Davies 1996). The estimated annual breeding population in the Northern Territory is 9000 birds, with colonies ranging in size from a few pairs to more than 1300 birds (Chatto 2001). In the Northern Territory, most black-naped tern breeding occurs off north-eastern Arnhem Land, on and around Groote Eylandt and in the Sir Edward Pellew Group of islands, with sparse at-sea records elsewhere off the northern Australian coast. Black-naped terns also breed on Bare Sand Island, west of Darwin, and off the Cobourg Peninsula and Croker Island. In Queensland, the species is common and widespread throughout the Gulf of Carpentaria. In the Northern Territory, the main breeding period is September–December, with some breeding also recorded in January and April–July.
The bridled tern (Onychoprion anaethetus) is listed as migratory and marine under the EPBC Act. It is widespread in the tropical and subtropical seas around Australia, breeding on islands, including vegetated coral cays, rocky continental islands and rock stacks (Chatto 2001; Higgins & Davies 1996). The species forages in the North Marine Region and breeds in areas adjacent to the region. The bridled tern feeds on a range of fish, crustaceans, cephalopods and insects (Higgins & Davies 1996).
Bridled terns are difficult to census accurately because of their cryptic breeding habits, with nests often under rocks or bushes in steep terrain with dense vegetation. The breeding population in the Northern Territory is estimated to be approximately 60 000 birds (Chatto 1998, 1999, 2001). Most colonies consist of 100–500 birds, and some contain 1000–5000 birds. The largest colony, on Three Hummocks Island, is estimated to have up to 30 000, but possibly more than 50 000, birds (Chatto 1998, 1999, 2001). On Low Rock, south-western Gulf of Carpentaria, more than 1000 birds were recorded in late September 1994 (Chatto 1998, 1999, 2001). If most of the birds recorded at the larger Northern Territory colonies actually breed at these sites, then it appears that this coast has nationally significant bridled tern breeding areas (Chatto 2001). On Higginson Islet the breeding season is protracted, with breeding recorded nearly all year, although mainly from April to June. On some islands, or in some years, breeding is concentrated in a short season, but on other islands breeding has been recorded in most months (Chatto 1998, 2001).
The caspian tern (Hydroprogne caspia) is listed as migratory and marine under the EPBC Act. It is mostly seen off the eastern and western coasts of the Northern Territory, except for the area between Maningrida and Elcho Island. The species is less often seen across much of the northern coast or in the far south-west (Chatto 2001). The species forages in the North Marine Region and breeds in areas adjacent to the region. The diet of the caspian tern includes fish, the eggs and young of other birds, carrion, aquatic invertebrates (e.g. crayfish) and flying insects (IUCN 2010).
It is thought that most caspian terns breed outside the Northern Territory (Chatto 2001). For example, in May 1986, 500 breeding pairs were recorded on Lake Gregory (Jaensch & Vervest 1990), Western Australia, near the Northern Territory border (Chatto 2001). Chatto (2001) suggested that the Lake Gregory breeding site may be the reason why there are reasonable numbers of caspian terns foraging in the Northern Territory even though there are low numbers breeding adjacent to the North Marine Region. In the Northern Territory, the caspian tern has been recorded breeding at four sites, each with a single nest, and all on small islands along the eastern coast (Chatto 2001). Two of the four sites had eggs in May while the other two had eggs in October. In surveys reported by Chatto (2001), non-breeding caspian tern numbers appeared fairly consistent throughout the year, except for slightly lower numbers in January and February, and higher numbers in July.
The crested tern (Thalasseus bergii) is listed as marine under the EPBC Act. It inhabits tropical and subtropical coastlines, and forages in the shallow waters of lagoons, coral reefs, bays, harbours, inlets and estuaries; along sandy, rocky, coral or muddy shores; on rocky outcrops in open sea; in mangrove swamps; and in offshore and pelagic waters (Higgins & Davies 1996). The species forages in the North Marine Region and breeds in areas adjacent to the region.
The crested tern usually feeds from the surface of the sea to less than 1 metre water depth but can forage well out to sea (Higgins & Davies 1996). Its diet consists predominantly of pelagic fish 10–50 millimetres long, although the species will also take cephalopods, crustaceans, insects and hatchling turtles opportunistically (IUCN 2010). Crested terns may also eat discards from trawl fisheries (Blaber et al. 1995).
The species shows a preference for nesting on offshore islands, low-lying coral reefs, sandy or rocky coastal islets, coastal spits and lagoon mudflats (IUCN 2010). The crested tern is widespread and numerous along the coastline of the Northern Territory, although it is less common around the southern part of Van Diemen Gulf and in the south-west (Chatto 2001). Chatto (2001) reported 20 crested tern breeding colonies off the Northern Territory, with many in excess of 5000 birds and two in excess of 50 000 birds. Breeding colonies are distributed from Melville Island in the north-west to the Sir Edward Pellew Islands in the south-east of the Northern Territory. Most breeding colonies are on small inshore islands except for the larger North-West Crocodile Island, which is well out to sea (Chatto 2001). Surveys in 1994 suggested that more than 60 000 crested terns were breeding off the Northern Territory coast. The combined total of the two largest colonies alone in 1999 was more than 100 000 birds, which could indicate that 1999 was a particularly successful breeding season, or that numbers of crested terns off the Northern Territory are increasing (Chatto 2001). Walker (1992) recorded 13 000–15 000 crested tern pairs on the Wellesley Islands off Queensland.
Around the Northern Territory coast, crested tern breeding occurs consistently between March and July regardless of the timing of other species nesting at their breeding sites. Birds in breeding plumage begin arriving in numbers in March and April, and most eggs are laid from late April to early June (Chatto 2001).
Lesser crested tern
The lesser crested tern (Thalasseus bengalensis formerly known as Sterna bengalensis) is listed as migratory and marine under the EPBC Act. The species inhabits tropical and subtropical sandy and coral coasts and estuaries. It breeds on low-lying offshore islands, coral flats, sandbanks and flat sandy beaches, and forages for small pelagic fish and shrimp in the surf and over offshore waters (IUCN 2010) in both areas of reef and deeper shelf waters (Surman & Nicholson 2008). The species forages in the North Marine Region and breeds in adjacent areas.
The lesser crested tern occurs around most of the Northern Territory coast but is absent or rare in the far south-west; around Van Diemen Gulf and the Tiwi Islands; and in parts of north-east Arnhem Land. The highest density of confirmed sightings is along the coast to the south-west of Darwin. Larger flocks of lesser crested terns are distributed in four locations: in the area between Darwin and North Perron Island; and in the north-west, the north-east and the south-east corners of the Top End (Chatto 2001).
The lesser crested tern may move nesting sites from one year to the next (Surman & Nicholson 2008). A single breeding colony of lesser crested terns, comprising approximately 440 birds with at least 150 nests, has been recorded in the Northern Territory on an island in the south-east (Chatto 2001). At the colony, the terns began breeding in late August – early September (Chatto 2001). However, this breeding site does not account for the numbers of lesser crested terns present in the Northern Territory.
The little tern (Sternula albifrons formerly known as Sterna albifrons) is listed as migratory and marine under the EPBC Act. It is widespread in Australia, with breeding sites distributed from north-west Western Australia, around the northern and eastern Australian coasts, to south-eastern Australia and Tasmania (Higgins & Davies 1996). The species forages in the North Marine Region and breeds in areas adjacent to the region.
The little tern is commonly seen in sandy coastal habitats and in mangrove-mudflat habitats along the coast, or in bays and estuaries, generally within 1 kilometre of the coast (Chatto 2001). However, in the Northern Territory, little terns are known to nest on the beaches of small offshore islands, within approximately 25 kilometres of the mainland or another large island or island chain (Chatto 2001). The extent of occurrence and area of occupancy for this species is increasing with the ongoing management of breeding sites (Garnett & Crowley 2000). The little tern usually forages close to breeding colonies (Higgins & Davies 1996). It feeds mainly on small fish (less than 10 centimetres in length), but also on crustaceans, insects, annelids and molluscs (Higgins & Davies 1996).
In the Northern Territory, breeding colonies of this species have been recorded on sandy beaches, often mixed with shells or coral rubble, just above the high-tide mark among the dunes, or on open blow-out areas among or behind the dunes. Breeding has been recorded in 44 colonies in the Northern Territory and is likely to occur at many more sites (Chatto 2001). Of the 44 recorded colonies, 20 comprised 11–100 birds and one colony had at least 150 pairs (Chatto 2001). The northern Australian breeding population has an extended breeding season covering most of the year. Breeding occurs from April to early January, with the main periods being late April–July and September – early January (Chatto 2001).
The roseate tern (Sterna dougallii) is listed as migratory and marine under the EPBC Act. It is found in the northern waters of Australia around offshore coral or continental islands, and near the mainland if breeding islands are nearby (Higgins & Davies 1996). The species forages in the North Marine Region and breeds in areas adjacent to the region.
The species often rests and forages in sheltered estuaries, creeks, inshore areas and waters up to several kilometres offshore (del Hoyo et al. 1996 in IUCN 2010). The roseate tern diet consists mostly of small pelagic fish (del Hoyo et al. 1996 in IUCN 2010; Urban et al. 1986), although it will also take insects and marine invertebrates such as crustaceans (del Hoyo et al. 1996 in IUCN 2010; Urban et al. 1986). Roseate terns in Australia are found to feed primarily in the open sea and at greater distances from the colony (on average) than other similar species of inshore tern (Hulsman 1989).
Northern populations of the roseate tern breed in summer and winter on offshore islands, cays and banks, mainly of sand, coral or rock (Higgins & Davies 1996). Around the Northern Territory coast, roseate tern breeding colonies vary in size from a few pairs in association with larger black-naped tern colonies to sites consisting of many thousands of nesting roseate terns (Chatto 2001). At some of the active breeding sites, high hundreds to low thousands of roseate terns in non-breeding plumage have also been recorded roosting (Chatto 2001). The number of breeding roseate terns off the Northern Territory coast has been roughly estimated at more than 26 000 (Chatto 2001). All confirmed roseate tern breeding sites are on islands, most of which are along the east coast from north-east Arnhem Land to the Sir Edward Pellew Islands (Chatto 2001). A small number of breeding colonies are also found around Cobourg Peninsula and the islands to the east of Croker Island; with another on Haul Round Island, near Maningrida on the central north coast. Roseate tern breeding occurs in two distinct periods of the year—a small number of colonies nest between April and June–July, while most nest between September and December–January (Chatto 2001). Large numbers of non-breeding Asian migrants may also be present in some areas during the summer months, as occurs on the Great Barrier Reef (O’Neill & Elder 2005; O’Neill et al. 2008).
The common noddy (Anous stolidus) is listed as migratory and marine under the EPBC Act. It is mainly found off Queensland and the Western Australian coast where island breeding colonies are of considerable size. All sightings of the common noddy off the Northern Territory have been at latitudes north of 14° (Chatto 2001). The species forages in the North Marine Region and breeds in adjacent areas.
Small numbers of non-breeding common noddies have been recorded in the North Marine Region between September and March (Chatto 2001). There is only one known breeding location off the Northern Territory coastline, on an island in north-east Arnhem Land, which hosts about 100–300 birds (Chatto 2001). This colony has been checked only twice, in different years. In one of these years birds were on eggs in early May and breeding had finished by mid-September (Chatto 2001).
The common noddy forages in inshore waters surrounding breeding islands, often along the line of breakers or in lagoons, and disperses up to 50 kilometres into the pelagic zone to forage (especially when not breeding). Out at sea it often rests on buoys, flotsam, ships and on the open water (IUCN 2010). Its diet consists mostly of small fish as well as squid, pelagic molluscs, medusae and insects (IUCN 2010).