Introduced mallards (Anas platyrhynchos) occur on many islands of the South Pacific, where they hybridise with the resident grey duck (A. superciliosa). In October 2007, we conducted systematic surveys of Lord Howe Island to estimate the abundance and distribution of grey ducks, mallards, and their hybrids. Hybrids were common in areas of high public use, particularly where there was mown or grazed grass. Phenotypic characteristics suggest that mallards are now dominant and have supplanted the native grey duck, with 81% of birds classified as mallard or mallard-like hybrids, 17% as intermediate hybrids and only 2% as grey duck-like hybrids. No pure grey duck were observed. These hybrids pose direct and indirect economic, social and environmental impacts to Lord Howe Island. A management program to remove mallards using trapping, shooting and opportunistic capture by hand was conducted in October 2007. Standardised indices of duck abundance before and after management indicates that the total population was reduced by 71.7%. Eradication of mallard and hybrids from Lord Howe Island is considered achievable with a program of education, monitoring, and continued control to prevent re-establishment.
A small black-and-white storm petrel seen off Whitianga, New Zealand, in Jan 2003 was tentatively identified as a New Zealand storm petrel (Pealeornis maoriana). A further sighting in the Hauraki Gulf in Nov 2003 of multiple birds identified as New Zealand storm petrels led to the realisation that the species was both extant and apparently locally common. Prior to these sightings this enigmatic seabird was known only from 3 specimens collected in the 1800s, and unreported since. This paper reviews these 2 sightings that constitute the rediscovery of an ‘extinct’ species not reported for more than 150 years. Possible reasons for the lack of sightings before 2003 are discussed and a review of black-and-white storm petrel records prior to 2003 around northern New Zealand is presented.
The nesting of variable oystercatchers (Haematopus unicolor) on the Kaikoura Peninsula was studied at 6 sites over 8 years. Only in 1 year were birds known to have laid eggs at all 6 sites and only at 2 sites was nesting observed every year. Loss of nests often resulted in re-nesting and at 1 site birds made 4 attempts in 1 season. Over the 8 years, 117 eggs were found in 53 nesting attempts between mid-Oct and late Jan. The average size of 114 eggs was 58.2 x 40.6 mm. Thirty of 53 nesting attempts were completed and averaged 2.4 eggs/clutch (range 1–3 eggs). Twenty three chicks hatched from observed nests: this comprised 20% of eggs laid, 32% of eggs from completed clutches, and 72% of eggs from successful nests. At least 7 more chicks hatched from nests not found. A total of 17 chicks fledged including 6 chicks from nests not found. The other 11 fledglings came from 13 nests with hatchlings (0.84 chicks/nest; 41% of the eggs laid), 30 completed nests (0.37 chicks/nest; 15% of the eggs from these nests) and 9.4% of all eggs laid. Including chicks from 3 nests not found increases fledging to 1.06 chicks/nest with hatchlings, 0.51 chicks/completed nest and about 14% of eggs laid. Newly fledged young were seen from 26 Dec until mid-Mar. High tides washed away several nests, seals squashed eggs in 1 nest, and 1 adult was probably killed by a cat. While people walk in the vicinity of nesting, there was no evidence that they caused egg or chick losses.
Thirty-four species of birds are recorded from the isolated Pacific island of Nauru. Six are treated as hypothetical pending corroboration; 3 others are introductions. Eighteen of the 25 indigenous species are non-breeding visitors (mainly migrating seabirds and shorebirds). The 7 confirmed or probable resident breeders include only 2 land birds, the Micronesian pigeon (Ducula oceanica) and the endemic Nauru reed-warbler (Acrocephalus rehsei). The Australian pelican (Pelecanus conspicillatus) and white-winged tern (Chlidonias leucopterus) are reported as first records for Nauru. Hunting pressure and habitat degradation have contributed to reduced numbers of the Micronesian pigeon and the once abundant black noddy (Anous minutus), but the Nauru reed-warbler occurs commonly in degraded and modified habitats. Second-stage mining to recover phosphate deposits will likely reduce available habitat further for all resident breeding species, although land restoration is also planned. Bird band recoveries indicate that many seabirds, especially black noddies, reach Nauru thousands of kilometres from where they were fledged, but to what extent they are recruited into the local breeding population is unknown.
During 1971-75 and 1991-95, surveys of Caspian tern (Sterna caspia) colonies throughout New Zealand were carried out. The breeding population in 1971-75 was 1266 pairs, in 16 colonies, predominately in the northern North Is. In 1991-95, there were 1190 breeding pairs found in 17 mainly northern colonies, suggesting the population had been relatively stable over the 20-year period. As census methodology may under-record the breeding of isolated pairs, we included an estimate of the number of isolated pairs to give a total national population of 1300-1400 breeding pairs. This is less than 3% of the global population. Colony size and location showed some change between survey periods; 6 colonies disappeared and 8 new colonies were formed. Addition surveys in 2011-2015 are recommended to compare recent population trends.
I conducted road counts on the North I and South I of New Zealand in Mar 2006 to evaluate relative abundance and distribution of Australasian harriers (Circus approximans). Over 1670 km were traveled on the North I with 98 harriers detected, yielding 1 harrier/17.0 km traveled. Over 2430 km were traveled on the South I with 145 harriers detected, yielding 1 harrier/16.8 km traveled, with no difference in number of harriers detected/km traveled between islands (P > 0.25). Three survey routes, 1 on southeastern North I and 2 on northeastern and east-central South I, were particularly productive yielding 1 harrier/7.1-11.1 km traveled. My results provide empirical support for the frequently cited description that the Australasian harrier is now New Zealand’s most abundant native diurnal raptor, and has largely benefited from the conversion of land from native forest and scrub to pasture at the likely expense of other native and endemic species.
In Jul and Aug 2005, 18 North Is kokako (Callaeas cinerea wilsoni) were released into a 450-ha area of New Zealand native forest subject to intensive control of introduced mammalian predators. The area, Ngapukeriki (near Omaio, Bay of Plenty, New Zealand), lies within a 13,000-ha matrix of native and exotic forest subject to lower and variable degrees of predator control. In contrast to most previous kokako translocations, this project employed 3 tactics to maximise the likelihood that kokako would remain in the target area: 1) many birds were released in a short period; 2) playback of kokako song was broadcast in the release area (potentially creating an “acoustic anchor”); and 3) a kokako pair was held at the release site in an aviary. Most birds approached to within 20 m of playback speakers, some approaching repeatedly. Several interactions between released birds were observed, including vocal interactions and instances of birds associating with one another temporarily. Visits to the aviary pair were rare. On 13 Apr 2006, all 8 trackable birds and 4 birds whose transmitters had failed remained in the core management area; locations of remaining birds (with lost or non-functional transmitters) were unknown. At least 5 territorial pairs had formed, and 1 chick was known to have fledged. To our knowledge, this was the 1st time song playback had been used as an attractant in a terrestrial bird reintroduction.
Natal dispersal of the New Zealand falcon (Falco novaeseelandiae) was documented using relocations of radio-tagged and colour banded falcons in Kaingaroa pine plantation. The age at which fledglings commenced natal dispersal was highly variable. The earliest fledglings dispersed 42 days after fledging, whilst others did not disperse out of their natal territories, remaining there to breed. After 91 days, 87% of fledglings had begun dispersal out of their natal territory. The mean time for the onset of dispersal was 76 days. Males generally dispersed earlier than females, but no significant difference was recorded. Both radio telemetry and colour band recoveries indicated that a large proportion of fledglings dispersed out of the study area. Mean natal dispersal distance within Kaingaroa Forest was 9.6 km. No significant difference was observed in natal dispersal distances between the sexes, although males generally roamed further afield than females. During this study, several females were recorded successfully breeding during their 1st year, a year earlier than usual. Males did not attempt to breed until they were 2 years old. We conclude that the high emigration rates and favourable breeding conditions in pine plantations make these habitats highly likely to act as source populations for neighbouring areas where populations of the New Zealand falcon may be in decline.
Breeding of pied shags (Phalacrocorax varius) at 2 colonies at Makara Beach, Wellington, was studied from Mar 1996, when breeding was 1st noted there, to May 2005. Pairs occupied and refurbished vacant nests rather than build new nests. The number of breeding attempts increased from 3 in 1996 to 46 in 2004, with 166 occurring during the study. New nests (n = 14) took about 3 weeks to build; most nests were used twice a year. Clutches were laid in all months, but there were 2 peaks: 61 nests (37%) in Feb–Mar and 53 nests (32%) in Aug–Sep. Overall, 76.6% were successful (fledged at least 1 nestling, n = 154 breeding attempts for which the outcomes were known), and the mean success was 1.4 fledglings nest-1. The proportion of successful breeding attempts and the mean number of fledglings produced nest-1 were similar for 1996-2000 (when the number of breeding attempts yr-1 increased from 3 to 11) compared with the 2001-2005 period (when breeding attempts increased from 15 to 46 yr-1). Of 14 breeding attempts for which clutch size was determined, mean clutch size was 3.4 (range 2-4 eggs), and mean brood size at fledging was 2.1 young (62% of eggs resulted in fledglings). The maximum number of shags counted at the colonies increased from 14 in 1996 to 68 in Dec 2003, after which numbers appeared to stabilize. However, since 2003, numbers of pied shags seen elsewhere in the Wellington region, particularly on Mana I and at Waikanae Estuary, have increased.