Publications Archive

Information on the relevant spatial scale for controlling pest birds causing significant crop damage is generally lacking. Here, we assess the potential of 2 radiotracking systems (hand-held vs. elevated twin-Yagi antennae) for monitoring pest bird ranging behaviour on and around an arable farm. Radio-transmitters were fitted to 19 European greenfinches (Carduelis chloris) in the summer and 25 house sparrows (Passer domesticus) in the winter. Greenfinches were most likely to be detected in or near Brassica seed crops, particularly on the study farm, but 12% travelled large distances (>3 km) between Brassica crops in the landscape. Even though house sparrow home ranges were widely dispersed across the landscape, most overlapped with the farm boundary and were positively associated with woody vegetation. Relative to hand-held antennae, the elevated twin-Yagi system increased the detection radius for tagged birds from 100 m to 2000 m and also the number of location data, albeit over a more restricted area.

Orange-fronted parakeets (Cyanoramphus malherbi) are New Zealand’s rarest parakeet species with a global population of less than 500 individuals on remnant mainland populations and reintroduced populations on offshore islands. Since there is limited information about habitat preferences by this species on offshore islands I characterised habitat use on Maud Island, where captive-bred parakeets were introduced in 2007. I compared the vegetation characteristics of 29 plots (each 25 m2) where parakeets were encountered and 23 plots randomly selected. Parakeets were observed foraging in 96.6% of the plots. Plots used by parakeets showed significantly higher density of stems under 20 cm dbh and a higher canopy than random plots. Used plots also tended to have greater canopy cover and lower understory and ground vegetation covers. These results indicate that orange-fronted parakeets use ecotones of broadleaf coastal forest-manuka scrub, and pine plantations-manuka scrub for foraging highlighting the potential value of islands with mixed patches of these vegetation types as future refuges for this critically endangered species.

The diet of the Australasian gannet (Morus serrator) at Farewell Spit, New Zealand, was studied by the analysis of 70 regurgitations collected from the 1995 to 2001 breeding seasons. Surface schooling pilchard (Sardinops neopilchardus) was the main prey, followed by anchovy (Engraulis australis). The composition of the diet was similar in most seasons examined except in 1996 in which anchovy was the main prey item. Such a change in diet could be linked with a pilchard mass mortality in New Zealand in August 1995. The estimated annual prey consumption by birds at the Farewell Spit gannetry was 852 tonnes. Although annual catches of pilchard and anchovy by commercial fisheries in the area are still relatively small, an increase may interfere with prey availability, and in turn, increase competition between marine predators and influence the breeding success. Our analyses of diet are consistent with previous studies showing that Australasian gannets as flexible foragers and they highlight their importance as bioindicators of fish stocks in New Zealand.

The New Zealand endemic red-billed gull (Larus novaehollandiae scopulinus) was designated as a ‘Nationally Vulnerable’ species in 2008 as a consequence of recent substantial population declines at large breeding colonies, particularly the one situated at Kaikoura, north-east South Island. In contrast, numbers increased further south along the Otago coastline, south-east South Island. Nest numbers from 7 surveys from Moeraki to Nugget Point increased from 565–1480 in 1992 to 4612–4652 in 2011 and corresponded to an average annual increase of 6–10% through 20 years. The recent decline at Kaikoura has been attributed mainly to a decline in prey availability linked to changes in oceanographic indicators, including sea surface temperature (SST). Fluctuations in SST at Otago and Kaikoura are negatively correlated and may explain the concomitant opposite trends in population sizes. Conservation management at Taiaroa Head and at other key mainland breeding locations is necessary to ensure the viability of red-billed gulls at Otago.

The Marlborough Sounds has a coastline of 1500 km and hosts the greatest diversity of marine shag species in New Zealand. A survey of all breeding shag species was conducted in spring 2006. Apart from New Zealand king shag, 3 species were counted: spotted shag (Strictocarbo punctatus), pied shag (Phalacrocorax varius) and little shag (Phalacrocorax melanoleucos). Two other species (black shag Phalacrocorax carbo and little black shag Phalacrocorax sulcirostris) also occur in the area but were not recorded breeding. A total of 1,254 pairs of spotted shag were recorded at 193 sites, with most colonies occurring in the outer Sounds and inner Queen Charlotte Sound. Average colony size was 6.5 pairs (range 1-76 pairs), with 85% of colonies containing ≤10 pairs. The distribution of spotted shag colonies appears to be influenced by the availability of suitable cliff habitat. Breeding pied shags were found at 48 colonies, with a total of 438 pairs. Colonies were widely distributed, and average colony size was 9.1 pairs (range 1-28), with 83% containing ≤15 pairs. A total of 226 little shag pairs were found at 24 colonies, with most colonies also including nesting pied shags. Colony size was on average 9.4 pairs (range 4-24), with 75% of colonies containing ≤10 pairs. Colonies of pied shags and little shags were found mostly in native vegetation. Colonial seabirds that occur at relatively few locations can be used as indicators to establish critical thresholds for marine management and marine conservation. It is proposed that this survey provide a good baseline for such an approach in the Marlborough Sounds.

Diagnostic prey remains of Auckland Island shags (Leucocarbo colensoi) were analysed from 23 regurgitated pellets collected in August 2010 at Enderby Island, Auckland Islands. Allometric equations from a reference collection were applied to prey remains to provide estimates of prey length and wet mass. A minimum total of 1058 prey items from 7 genera were represented in pellets, with an estimated total wet mass of 13.2 kg. The mean number of prey items per pellet was 46 (range 7-90), with mean total prey mass per pellet of 589 g (range 86–1037 g). Small octopus (Octopus sp.) was by far the most important prey item and was present in all regurgitated pellets. It accounted for 57% of prey by number and 68% of prey by wet mass. Only 2 other genera contributed ≥ 5% towards the total mass of prey—red cod (Pseudophycis bachus) and triplefin (Forsterygion sp.) The overwhelming importance of octopus in the diet is unprecedented among shags for which diet composition is known.

We investigate the phylogenetic affinites of the New Zealand blue duck (Hymenolaimus malacorhynchos), a riverine specialist of uncertain relationships, using 2613 bp of DNA sequence data from 3 mitochondrial genes. Hymenolaimus has variously been considered an aberrant Anas species, or an ancient taxa in the tribe Anatini. Presently, it is placed in a highly-derived clade (Tribe Merganettini) with the shelducks. Our findings show that Hymenolaimus forms a monophyletic clade, and does not fit within any of the other duck tribes around the world. Our study also confirms convergent evolution among duck species that inhabit fast flowing rivers.

Ruru or moreporks (Ninox novaeseelandiae) are an iconic native species that are relatively widespread in New Zealand, yet little is known about populations that reside within urban areas. Here we present results from a ruru survey conducted by volunteers within the city of Hamilton, New Zealand to: 1) collect baseline data for future comparative ruru surveys, and 2) to introduce and promote ornithology to a wider audience. In addition, these data may be used to quantify the success of urban restoration projects and pest control operations, as many of the desired outcomes of those projects (e.g., increased native vegetation and reduced mammalian predators) would have a positive impact on ruru numbers. Twenty sites were surveyed in areas such as amenity parks and gullys with established vegetation. Teams of observers recorded the time and approximate bearing of all ruru vocalisations at sites for 1 h each night for 5 consecutive nights between 2000-2230 hours in late October 2011. Ruru were detected at 80% (16/20) of sites at least once over the survey period; at 13 of these sites ruru were detected on >2 nights, while birds were detected every night at 5 sites. Multiple birds were detected at 11 sites, which suggested that some may have been resident pairs and breeding. We recommend that including members of the public in similar surveys is highly desirable as it raises awareness around conservation issues and introduces ornithology to a wider audience.