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Organochlorine residues in New Zealand birds of prey

Organochlorine residues in New Zealand birds of prey

Territory serial numbers refer to documented falcon pairs (Fox, 1977c). Where the RI was determined, the mean index of the six post-1962 eggs (Table 4, Nos. 3, 4, 8, 9, 10, 13), including an egg from captive birds, was 5.6% below the mean pre-1948 level. This was statistically significant (P < 0.05, Students t-test). Five eggs from pairs which had access to prey from cultivated ground (Table 4, Nos. 2, 3, 4, 6, 7) showed a mean decrease in thick- ness of 8.5% compared with the mean pre-1948 value, which is altered to 8.4 % if the egg from the captive birds is excluded. Both figures indicate significant thinning compared with pre-1948 eggshells (P < 0.001 and P < 0.01, respectively, Students t-test). The maximum thinning was 13.3 % in a North Canterbury egg (No.6) from a pair with a history of egg breakage. However, the total DDT level in this egg was only 1.50 mg/kg wet weight and in the four eggs in which shell thickness and DDT levels were both measured, there was no noticeable correlation between the two parameters. An egg (No. 13) from the Leatham River area, a rather remote part of inland Marlborough, contained only 0.86 mg total DDT/kg wet weight and was of 'normal' (pre-1948) shell thickness.

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Distributions of New Zealand Birds on Real and Virtual Islands

Distributions of New Zealand Birds on Real and Virtual Islands

Simberloff and Abele (1976) attacked this preference for large reserves on the basis of the following specious reasoning. They calculated from species/area relationships that one large reserve might contain more or fewer species than the equivalent area in small reserves, and that therefore island biogeography was neutral on the question of optimal reserve size. I am not aware of anyone having proposed total species number as the argument favoring large over multiple small reserves, until Simberloff and Abele set up the argument as a straw man. Several groups of authors (Terborgh, 1976, Whitcomb et al., 1976, Diamond, 1976b) immediately responded that the relevant criterion is number of species that a conservation program saves and that would otherwise be endangered. A New Zealand forest reserve that held 15 species like fantail, silvereye, and grey warbler, while losing two species like kokako and yellowhead, would rate as a disaster. Nevertheless, Simberloff and Abele (1982) continued in a subsequent paper to ignore this fact and to pretend that the relevant criterion is total species number.

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Behavioural plasticity of life history traits in the New Zealand avifauna

Behavioural plasticity of life history traits in the New Zealand avifauna

Moors (1983) compared predation rates of eggs and chicks between introduced and native New Zealand birds. His study found no difference between the predation rates, but using a larger data set I found that native birds generally experienced higher rates of nest predation than introduced species in areas with no predator control (chapter 2). Native birds may not be able to cope with high predation rates by introduced mammals compared to introduced species that evolved with mammals because of different life history traits. Trevelyan & Read (1989) tried to determine if New Zealand birds differ from their continental relatives in Australia (where birds did evolve with mammals) by comparing differences between the two populations in incubation and nestling periods. However, even though Australian birds were predicted to have different life history strategies compared to New Zealand birds, no significant differences were found. They suggested this could be due to the high selective pressure from the introduced mammals on New Zealand birds, which has caused the New Zealand birds to acquire life history strategies like Australian birds thereby increasing their chances of survival. These

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MHC genetic diversity and avian malaria prevalence in Mokoia Island saddlebacks

MHC genetic diversity and avian malaria prevalence in Mokoia Island saddlebacks

genetic structuring. We also cannot discount the possibility that there may be an association between MHC diversity and intensity of infection, which we were unable to test at this time. Assuming that phenotype-genotype associations exist, then a failure to detect associations could result from a number of factors aside from small sample sizes. As described above, highly susceptible individuals might be omitted during sampling if they are less active than healthy individuals, or if they die from their infections (Westerdhal et al. 2005). Second, as native New Zealand birds are probably not naïve to some avian malaria parasites or their mosquito vectors, it is possible that this co-evolutionary history imparts a measure of resilience against introduced lineages. In this scenario, historical selection pressures could have led to contemporary birds having similar, resistant genotypes. At least two Plasmodium lineages (BELL01 and KOKAK001) are thought to be endemic to New Zealand (Baillie & Brunton 2011; Ewen et al. 2012; Howe et al. 2012), and a native New Zealand mosquito, C. pervigilans, is a confirmed Plasmodium vector (Massey et al. 2007). Thus, birds that become infected with new strains of Plasmodium may not necessarily suffer severe infection. Third, most non-native Plasmodium species were likely co-introduced to New Zealand during colonial times (Ewen et al. 2012). Thus, even if a history of co-evolution with one Plasmodium lineage did not bestow resistance to a novel strain, enough time may have passed for some New Zealand species/populations to have experienced evolution in response to non-native Plasmodium, similar to what appears to be occurring in low elevation populations of the Hawaiian amakihi (Hemignathus virens) after introductions of P. relictum to the Hawaiian Islands in the early 1800s (Foster et al. 2007).

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Visual and taste cues for minimising native bird interactions with toxic 1080 baits –  a review of current practices

Visual and taste cues for minimising native bird interactions with toxic 1080 baits – a review of current practices

Conclusions about the relative efficacy of green and blue dye with and without the addition of cinnamon in reducing the risk of poisoning from cereal bait used for aerial control of possum and rats are hampered by several factors. First, many of the trials were conducted on small samples of captive birds, and so may not have been representative of the responses of free- living bird populations (Esther et al. 2011). Second, the trials on New Zealand birds tested efficacy of different colours only as deterrents to feeding, not as cues for avoidance learning. Third, most of the original reports on which the choice of additives is based provide little or no details on key aspects of methodology – identity of the dye (dyes may vary in spectral signature); concentration of dye used (which may affect bait palatability and/or contrast with background); how baits were presented (e.g. choice or no-choice trials); what background baits were presented on (potentially influencing bait visibility/novelty); source of cinnamon oil (leaf or bark); sample sizes; and how the responses of test birds or bait acceptability/rejection were measured. The background against which baits are presented may be of particular significance. Udy and Pracey (1981) noted that weka did not find or ignored baits dyed to approximately match the colour of grass when they were scattered on grass. Willson et al. (1990) and Allen et al. (1990) recorded differences in preferences of frugivorous birds for coloured foods when they were presented on different backgrounds, with baits on a similar coloured background selected less often.

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Do New Zealand invertebrates reflect the dominance of birds in their evolutionary history?

Do New Zealand invertebrates reflect the dominance of birds in their evolutionary history?

Atkinson and Millener (1991) reconstructed the feeding guilds of New Zealand birds based on the Holocene fossil record. Apart from the large ground herbivores (moa) that had no such extensive counterpart elsewhere, they also identified a ground-surface/subsurface feeding guild of ground insectivores which raked, dug, probed and gleaned for invertebrates on the forest floor, claiming that such a guild was not represented elsewhere. This group includes the kiwi species (Apterygiformes: Apteryx), flightless rails (e.g. weka (Gruiformes: Gallirallus), snipe (Charadriiformes: Coenocorypha), snipe-rail (Gruiformes: Capellirallus), owlet- nightjar (Caprimulgiformes: Aegotheles), acanthisittid wrens (Acanthisittidae) and robin (Petroicidae: Petroica), together with the laughing owl (Strigiformes: Sceloglaux) and the enigmatic Aptornis (Gruiformes: Aptornithidae), a total of seventeen species, nine of which are extinct. Thirteen were flightless or had reduced powers of flight, and at least eight were nocturnal or crepuscular. Apart from kiwi, which must be rated as unique in this context, some components of this guild may well have existed elsewhere, such as blackbird and thrush (Turdus spp.), but they would have been less nocturnal in their feeding impacts. On the other hand, the guild of 20 arboreal (and presumably diurnal) insectivores, although containing some unique examples like huia, was not exceptional in terms of foraging behaviour or sensory mechanisms. They point out that elsewhere, for example in Australia, the diurnal insectivores are also predominantly birds, but in contrast with New Zealand, there is a paucity of ground-feeding insectivorous birds, their place being taken by nocturnal insectivorous marsupials (Lein 1972). New Zealand’s ground-active lizard fauna, in the absence of mammalian competition and predation, might also have fulfilled the roles of some insectivorous mammals elsewhere.

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Using five-minute bird counts to study magpie (Gymnorhina tibicen) impacts on other birds in New Zealand

Using five-minute bird counts to study magpie (Gymnorhina tibicen) impacts on other birds in New Zealand

Abstract: We used five-minute bird counts to investigate whether introduced Australian magpies (Gymnorhina tibicen) influence the abundance of other birds in rural New Zealand. Over 3 years, magpies were removed from five c. 900-ha study blocks, one in each of Northland, Waikato, Bay of Plenty, Wellington and Southland. Birds were counted in both the treatment blocks and paired non-treatment blocks for the 3 years of removal and also 1 year before. To minimise problems raised elsewhere with index counts we (1) selected treatment blocks and count stations using randomisation procedures, (2) used trained observers who spent equal time in paired treatment and non-treatment blocks, and (3) counted all blocks at the same time of year and only in good weather. On average, 548 magpies were removed from each treatment block each year, with magpie counts reduced by 76% relative to non-treatment blocks. Our results suggest magpies may restrict the movements of some birds (including kererü and tüï) in rural areas, but are less important than pest mammals at limiting population abundance at a landscape scale. We submit that five-minute bird counts were appropriate for our objectives, but that more research to examine their relationship to absolute densities is needed.

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DNA barcoding the birds of New Zealand : a thesis presented in fulfillment of the requirements for the degree of Doctor of Philosophy in Molecular BioSciences at Massey University, Auckland, New Zealand

DNA barcoding the birds of New Zealand : a thesis presented in fulfillment of the requirements for the degree of Doctor of Philosophy in Molecular BioSciences at Massey University, Auckland, New Zealand

Within the barcoded sample data here presented, there appears to be a number of species that were over represented. The Spur-winged Plover (Venellus miles), a medium sized bird (350g) is a relatively recent migrant to New Zealand with the first breeding pair being noted in 1932 [36] but it is implicated in 28% of all morphologically described birdstrike events around the country [15] and its numbers are increasing. However, only 5% (BS3 & BS10) of the samples tested ( χ 2 df=1 p<0.05) were of this species. Christchurch and Wellington have below national average birdstrikes with V. miles but these figures may also be an artifact of sample size. In addition, since this species is so frequently implicated in birdstrike, airport staff may have become skilled at identifying remains from this species and, therefore, do not typically send it to be DNA barcoded as often as other less frequently observed species.

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Seabird bycatch in New Zealand trawl and longline fisheries, 1998 2004

Seabird bycatch in New Zealand trawl and longline fisheries, 1998 2004

Waugh, S.M., MacKenzie, D.I. & Fletcher, D. 2008 (31:x): Seabird bycarch in New Zealand trawl and longline fisheries, 1998-2004. Papers and Proceeding of the Royal Society of Tasmania 142(1): 45-66. https://doi.org/10.26749/rstpp.142.1.45 ISSN 0080-4703. Sextant Technology Ltd, 116 Wilton Rd, Wellington, New Zealand (SMW*), Proteus Wildlife Research Consultants, PO Box 5193, Dunedin, New Zealand (DIMacK, DF). * Author for correspondence. Email: s.waugh@sextam-technology.net

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Five-minute bird counts in New Zealand

Five-minute bird counts in New Zealand

There is considerable interest in replacing Dawson and Bull’s (1975) categories of seen and heard by a near/far split at a chosen break point. Both Dave Dawson (pers. comm.) and the author support this change as seen/heard has rarely been analysed, the task of determining and recording two distance categories seems comparable to the seen/heard category that is being replaced, and two categories would enhance the options for analysis (e.g. Moffat & Minot 1994) while preserving comparability with the large body of historical data. DOC is currently trialling a new 5-minute bird count method for the national Tier 1 Inventory and Monitoring programme which has three distance categories <25 m, <100 m and >100 m (MacLeod et al. 2012). The rationale is that the >100 m category replaces the original 200 m cut off and allows distant birds to be removed during the analysis, and the 25 m break replaces the original seen/heard split. It remains to be seen whether this new method is practical and whether it results in the same number of birds being recorded as the Dawson and Bull method; there is a risk that counters, preoccupied with the distance categories, fail to record some birds. As discussed, it is essential that any new method results in data comparable with historical data.

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Honeydew and Its Importance to Birds in Beech Forests of South Island, New Zealand

Honeydew and Its Importance to Birds in Beech Forests of South Island, New Zealand

Bellbirds were the only species observed often enough to analyse their time-budget monthly (Fig. 6). Combining data for all months, bellbirds spent 50% of their time foraging (range 36-70%). They spent significantly longer feeding on honeydew when its sugar concentration was low (r = -0.652, p <0.05), but their feeding was not affected by the number of droplets present (r = -0.564, 0.1 > p > 0.05). Bell- birds spent most time feeding on honeydew during February and March when the droplets were fur- thest apart and least concentrated. The increased time spent foraging for honeydew during these months therefore may reflect the greater amount of time needed to obtain the same amount of energy from this food.

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Foods and Foraging of Forest Birds in Temperate Rainforest, South Westland, New Zealand

Foods and Foraging of Forest Birds in Temperate Rainforest, South Westland, New Zealand

South Westland Nothofagus forests are not as depauperate in nectar and, particularly, in fruit supplies as has often been suggested. While it may be generally true that Nothofagus trees provide few resources for birds (Kikkawa, 1975; Craig et al., 1981; Wardle, 1984; Lee et al., 1991), in South Westland the silver beech associations have a significant shrub and epiphyte flora which provide a wide range of foods. Important nectar sources come from mistletoes, horopito, orchids (Dendrobium, Earina), Pseudopanax spp., and probably Astelia spp. Fruit bearing plants particularly horopito, Pseudopanax spp., Coprosma spp. and Myrsine spp., were common throughout, not just on stream edges as in other areas (Craig et al., 1981). Such diversity may result from high rainfall, as Nothofagus forests on the drier east coast of New Zealand have a much simpler structure (Wardle, 1984) or because possums, which selectively browse some of the fruit-bearing species (e.g., Wilson, 1984), are only recent colonists to southern South Westland and have yet to reduce plant diversity.

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Avian influenza and avian paramyxoviruses in the New Zealand bird population : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Virology at Massey University, Palmerston North, New Zealand

Avian influenza and avian paramyxoviruses in the New Zealand bird population : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Virology at Massey University, Palmerston North, New Zealand

AAHL, Geelong, Australia) diluted 1 : 1 000 i n 0.5M carbonate buffer (pH 9.6). Plates were incubated for 2 h at 37°C on a plate shaker at a speed of 400 rpm. After washing at least 4 times in washing buffer (0. 1 % Tween 20 in PBS), 25 f!l of NP-40 treated antigens (equal volumes of 1 J..lg/ml of H 1 N 1 95/29 1 8 human isolate (obtained from David Featherston, CDC, Porirua, New Zealand) and H4N6 duck isolate (Stanislawek 1 992» purified as described elsewhere (Meulemans et al . 1 987» were added. At the same time, 25 f!l of tested serum (diluted 1 : l O in washing buffer with 2% bovine serum albumin) was added to the same well and i ncubated for 60 min. Plates were washed again and 50 f!1 of purified monoclonal antibody (against influenza A nucleoprotei n obtained from hybridomas mAb anti-NP, ATCC No. HB65, H 1 6-Ll O-R5 using the procedures of CELLMAXTM QUAD Artificial Capillary Cell Culture System, Cell co Inc, MD, United States and Z2-SEPTM Pharmacia Biotech) was diluted 1 : 1 000 and incubated for 30 min, washed again, and a further 50 f!l of anti-mouse IgG HRP conjugated antibody (DACO AlS, Denmark) diluted 1 :3000 was added and incubated for a further 30 min as above. After the last washing 1 00 f!l of TMB substrate (Meulemans et al. 1 987) was added and after 1 0 nun the reaction was stopped by adding 50 J..lI of 1 M H2S04. The optical density (OD) was read at 450 nm using Multiscan, Flow, ELISA reader (Labsystems Multiskan® Multisoft) and the results were interpreted following the formula:

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Dietary diversity in fruit-eating birds: a biogeographic comparison between New Zealand and Canada

Dietary diversity in fruit-eating birds: a biogeographic comparison between New Zealand and Canada

Observations in New Zealand were made in Nelson Lakes National Park, which is located in the northern region of the South Island (41º48' S, 172º50' E; Fig. 1). The area experiences a mild climate with approximately 1000 mm annual precipitation and the same average temperature (c. 10°C) as the Canadian site. The prevailing vegetation type is Nothofagus forest (see Wardle 1984), which is dominated by three tree species, Nothofagus fusca, N. menziesii and N. solandri, all of which are wind- dispersed (nomenclature follows Allan (1961) and Connor & Edgar (1987)). Fleshy-fruited trees and shrubs are common beneath the forest canopy. Fourteen species were observed during the course of observations: Carpodetus serratus, Coprosma foetidissima, C. linariifolia, C. propinqua, C. rigida, Coriaria arborea, Elaeocarpus hookerianus, Griselinia littoralis, Halocarpus biformis, Leucopogon fasciculatus, Myrsine divaricata, Neomyrtus pedunculatus, Pittosporum divaricatum, Pseudopanax

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Investigating causes of population decline in New Zealand plants and animals: Introduction to symposium

Investigating causes of population decline in New Zealand plants and animals: Introduction to symposium

One symposium paper provides a textbook example of how putative agents of decline may be investigated in parallel and ranked in terms of the likelihood that they are the cause of the problem. Cabbage trees (Cordyline australis (Forst.f.) Endl.) were ubiquitous in urban and rural landscapes in New Zealand until quite recently, but skeletons of dead trees starkly mark a population decline. Beever et at. (1996) describe how they systematically ruled out aging, changes in vigour or flowering patterns and abiotic influences as causes of cabbage trees decline. They hypothesized that a pathogen was involved in cases of sudden decline, and after researching likely possibilites, could not rule out phytoplasmas as disease agents (Beever et at., 1996). The final, experimental test of their hypothesis may have to wait until phytoplasmas can be cultured.

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Impacts of introduced mammalian predators on indigenous birds of freshwater wetlands in New Zealand

Impacts of introduced mammalian predators on indigenous birds of freshwater wetlands in New Zealand

Indirect techniques of mediating predator numbers, such as water level management and safe habitat creation, may also have potential. Studies show that fewer mammalian predators are present on islands compared with the nearby mainland (Zoellick et al. 2005) and that smaller or more isolated islands are visited less frequently than larger or less-isolated ones (Heikkilä et al. 1994; Nordström & Korpimäki 2004; Zoellick et al. 2004). Man-made pontoons provide brown teal with safe roosting sites (BKC pers. obs.) but it is not known whether such devices enhance survival. Seasonal and human-induced- seasonal variations in water levels are likely to affect access and impact of predators on wetland birds (Duncan et al. 2008). Water level fluctuations in wetlands influence breeding success of birds directly via frequency of nest flooding (Desgranges et al. 2006), but water level fluctuations and drying of wetlands also influence potential access by ground-based predators (Anderson et al. 2000; Jobin et al. 2009). Polak (2007) found a significant positive relationship between water depth around the nest and breeding success in Eurasian bitterns (Botaurus stellaris). In this case, lower water levels allowed greater access by ground predators, but there may also have been a confounding relationship between depth of water and food availability (Gilbert et al. 2007).

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Williams, Gordon - an Appreciation of His Contribution to New Zealand Ecology

Williams, Gordon - an Appreciation of His Contribution to New Zealand Ecology

Gordon also served ecologists well in the field of voluntary administration. He was an officer of the Ornithological Society of New Zealand from 1957 to 1971 (successively as secretary, vice president and president) and presided over the successful amalgamation of the Society's national bird banding scheme with that of the Wildlife Service on game birds. He served as the New Zealand Ecological Society's editor from 1966 to 1970 and president from 1972 to 1974. During his time as president, the Ecological Society was urging moderation in the exploitation of beech forests and "an ecological approach to New Zealand's future" (Fordham and Ogden, 1974*). Some of the views expressed in this latter document were foreshadowed in Gordon's earlier papers on the role of the ecologist in national development (1970) and on the need for town planners to provide for the survival of natural communities (1971).

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Avian translocations to and from Tiritiri Matangi 1974–2013

Avian translocations to and from Tiritiri Matangi 1974–2013

issue) and wetapunga (Deinacrida heteracantha). Burrowing seabirds are an essential component of New Zealand ecosystems (Bellingham et al. 2010) and have an important impact through burrowing activity, vegetation modification and, critically, through the transfer of nutrients via guano deposition, regurgitations and adult, egg and chick mortality (Warham 1996; Mulder & Keall 2001). The link between terrestrial and marine ecosystems (Department of Lands and Survey 1982) and the role of seabirds as essential components of the ecosystem (Hawley 1997) was acknowledged in early Tiritiri Matangi management plans, but there was no discussion of seabird translocations. There are two main reasons for this. First, the 1997 plan (Hawley 1997) considered petrels and shearwaters (Procellariidae) would naturally re-establish on the island. Second, very few seabird translocations had been carried out in New Zealand up to 1997 (Miskelly et al. 2009), whereas considerable expertise for terrestrial translocations had existed since the 1960s. However, since 1997, there have been important advances in seabird translocation techniques (Miskelly et al. 2009) and several species are recommended for introduction in the new Tiritiri Matangi Biodiversity Plan (Supporters of Tiritiri Matangi 2013). So, there are clearly still exciting opportunities for avian translocations to Tiritiri Matangi, including seabirds and even ecological analogues (Parker et al. 2010), such as the New Zealand snipe (Coenocorypha spp.), to replace the extinct species that once existed in the Auckland region.

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Gastrointestinal parasites in endemic, native, and introduced New Zealand passerines with a special focus on coccidia :a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Science at Massey University, Palmer

Gastrointestinal parasites in endemic, native, and introduced New Zealand passerines with a special focus on coccidia :a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Science at Massey University, Palmerston North, New Zealand

The relationship between host and parasite is ancient and like any other birds in the world, New Zealand native passerine birds are hosts to a whole variety of gastrointestinal parasites, in particular coccidia. Coccidian parasites are generally host specific, obligate intracellular protozoan parasites and members of the phylum Apicomplexa. The phylogenetics of coccidian parasites are still in flux due to the advent of molecular techniques which produces different results to those of the more traditional morphometry-based taxonomy. Traditionally the most common Apicomplexans that affect passerine birds are members of the genus Isospora. Although coccidian gastrointestinal parasites are important pathogens, particularly for captive populations of native New Zealand songbird species, their prevalence, epidemiology, life cycles and taxonomic relationships are still widely unknown. Likewise, the number of coccidian parasite species infecting a native passerine bird and the possibility that these parasites might have been introduced by non- native passerines remains uncertain. Under natural conditions, these parasites seldom pose a threat, but stressors such as quarantine for translocation, overcrowding or habitat changes may cause an infection outbreak that can severely affect wild native passerines.

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Predation and other factors currently limiting New Zealand forest birds

Predation and other factors currently limiting New Zealand forest birds

Ongoing declines and resultant small populations also characterise the present forest avifauna. Many species are endangered, threatened or declining (BirdLife International 2000; Hitchmough et al. 2007; Robertson et al. 2007), also threatening ecological processes such as pollination and seed dispersal (Kelly et al. 2010). Predation continues to be an obvious factor to consider as a key cause of declines inside large native forest tracts because predatory introduced mammals are still widespread there, and evidence for predation is widespread (e.g. Lovegrove 1992; Powlesland et al. 1995; McLennan et al. 1996; O’Donnell et al. 1996; Brown 1997). However, the 14 widely distributed pest mammals may also limit food supply for birds, since they include omnivores (e.g. brushtail possum Trichosurus vulpecula and ship rat Rattus rattus), and herbivores (e.g. feral goat Capra hircus and red deer Cervus elaphus), as well as carnivores (e.g. stoat Mustela erminea and feral cat Felis catus) (Brockie 1992; Innes & Barker 1999; Atkinson 2001; King 2005; Forsyth et al. 2010). While evidence of predation may be clear in the form of a bird carcase, evidence for food shortage is mostly circumstantial (Newton 1998). Further, predation and food supply may interact, so in some cases both may contribute. For example, birds trade off predation risk against the need to feed (e.g. Beck & Watts 1997; Giesbrecht & Ankney 1998; Kullberg 1998); hungry birds take more risks than satiated ones (Koivula et al. 1995), and starving birds may be more vulnerable to infection by parasites and less able to avoid predators (Rohner & Hunter 1996; Klasing 1998). In this way, deaths caused proximally by predation or parasitism may in fact be due ultimately to food shortage (Rohner & Hunter 1996; Rolstad & Rolstad 2000).

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