Changes in biologically-active ultraviolet radiation reaching the Earth's surface.

The Montreal Protocol is working. Concentrations of major ozone-depleting substances in the atmosphere are now decreasing, and the decline in total column amounts seen in the 1980s and 1990s at mid-latitudes has not continued. In polar regions, there is much greater natural variability. Each spring, large ozone holes continue to occur in Antarctica and less severe regions of depleted ozone continue to occur in the Arctic. There is evidence that some of these changes are driven by changes in atmospheric circulation rather than being solely attributable to reductions in ozone-depleting substances, which may indicate a linkage to climate change. Global ozone is still lower than in the 1970s and a return to that state is not expected for several decades. As changes in ozone impinge directly on UV radiation, elevated UV radiation due to reduced ozone is expected to continue over that period. Long-term changes in UV-B due to ozone depletion are difficult to verify through direct measurement, but there is strong evidence that UV-B irradiance increased over the period of ozone depletion. At unpolluted sites in the southern hemisphere, there is some evidence that UV-B irradiance has diminished since the late 1990s. The availability and temporal extent of UV data have improved, and we are now able to evaluate the changes in recent times compared with those estimated since the late 1920s, when ozone measurements first became available. The increases in UV-B irradiance over the latter part of the 20th century have been larger than the natural variability. There is increased evidence that aerosols have a larger effect on surface UV-B radiation than previously thought. At some sites in the Northern Hemisphere, UV-B irradiance may continue to increase because of continuing reductions in aerosol extinctions since the 1990s. Interactions between ozone depletion and climate change are complex and can be mediated through changes in chemistry, radiation, and atmospheric circulation patterns. The changes can be in both directions: ozone changes can affect climate, and climate change can affect ozone. The observational evidence suggests that stratospheric ozone (and therefore UV-B) has responded relatively quickly to changes in ozone-depleting substances, implying that climate interactions have not delayed this process. Model calculations predict that at mid-latitudes a return of ozone to pre-1980 levels is expected by the mid 21st century. However, it may take a decade or two longer in polar regions. Climate change can also affect UV radiation through changes in cloudiness and albedo, without involving ozone and since temperature changes over the 21st century are likely to be about 5 times greater than in the past century. This is likely to have significant effects on future cloud, aerosol and surface reflectivity. Consequently, unless strong mitigation measures are undertaken with respect to climate change, profound effects on the biosphere and on the solar UV radiation received at the Earth's surface can be anticipated. The future remains uncertain. Ozone is expected to increase slowly over the decades ahead, but it is not known whether ozone will return to higher levels, or lower levels, than those present prior to the onset of ozone depletion in the 1970s. There is even greater uncertainty about future UV radiation, since it will be additionally influenced by changes in aerosols and clouds.     

Geographical differences in erythemally-weighted UV measured at mid-latitude USDA sites.

UV measurements from instruments maintained by USDA at 16 mid-latitude sites were analysed to investigate geographic differences. Fifteen of the sites are in North America, and one is in New Zealand. The instruments measure erythemally weighted UV radiation, and the results are presented in terms of UV Index (UVI). The focus of this work is on data from 2003, but the main results are also shown for years 2002 and 2004. In the North American sites, the peak UVI values increase by approximately 15% between latitudes 47 degrees N and 40 degrees N, and they show an increase with altitude of approximately 15% in the first kilometer, but much smaller rates of increase above that level. Peak UV intensities in the New Zealand site (45 degrees S, alt. 0.37 km) exceed those at comparable latitudes and altitudes in North America by 41 +/- 5%, and are more comparable with those over 1 km higher and 5 degrees closer to the equator. The number of observations on these days that exceeded various thresholds of UVI showed similar patterns. Furthermore, the number of days in which the peak values exceeded various thresholds also showed similar patterns, with the number of extreme values in New Zealand being anomalously high. For example, the only sites in North America where UVI exceeded 12 were at the high altitude sites in Colorado and Utah, for which there were 53 days, 6 days and 2 days respectively at the 3.2 km, 1.6 and 1.4 km sites. By contrast, the peak UVI at Lauder (0.37 km) exceeded 12 on 17 days. Lauder was the only site under 1 km altitude where the UVI exceeded 11 on a regular basis (48 days). The optical depths at Lauder were significantly lower than at all North American sites. These, together with the lower ozone amounts and the closer Earth-Sun separation in summer all contribute to the relatively high UV intensities at the New Zealand site. Other sites in New Zealand show similar increases compared with corresponding sites in North America, and the differences persist from year to year. The contrast in UV between New Zealand and North America is similar to that observed previously between New Zealand and Europe. During winter months, the UVI in New Zealand is not particularly high, giving a larger summer/winter contrast in UVI, which may be important from a health perspective.     

Persistence and stability of lotic invertebrate communities in New Zealand

1. Persistence and stability of lotic invertebrate communities were determined at an annual time scale over a 9‐year period (1990–98) at 26 river sites over the northern half of New Zealand. In addition, a number of water quality variables were measured monthly and flow information collected continuously over the same period at each site. 2. The aim of the study was to describe the levels of interannual variability in invertebrate communities, and relate community changes to variability in environmental conditions. The consequences of this temporal variability for the sensitivity of predictive models were also investigated. 3. Levels of change in environmental conditions varied significantly between years, but were relatively similar across sites. In contrast, community persistence (similarity between years in species assemblage composition), and stability (similarity between years with respect to relative abundance of species in the community) both varied significantly between sites, but changes between years were similar. Community stability was highest at sites with relatively harsh flow conditions (high coefficient of variation, high relative size of floods), and was also greater in communities dominated by Ephemeroptera. 4. Relationships between change in environmental conditions and changes in community composition and structure were relatively weak for most individual sites. However, when average levels of change for each of the 26 sites were used, communities showed greater persistence under conditions where flow conditions remained relatively constant. Water quality changes had no significant effect on community persistence when assessed for all 26 sites combined. 5. Results from this study suggest that lotic invertebrate communities fluctuate around a relatively stable state, at least over a 9‐year period. However, the extent of interannual variation in community composition and structure observed, along with the relatively low degree of cluster fidelity observed within a single region, suggests that predictive models based on reference site conditions extrapolated over several years should be applied with caution in New Zealand streams.     

Increasing Disadvantages in Cancer Survival in New Zealand Compared to Australia,between 2000-05 and 2006-10

New Zealand has lower cancer survival compared to its neighbour Australia. If this were due to long established differences between the two patient populations, it might be expected to be either constant in time, or decreasing, as improving health services deals with inequities. In this study we compared trends in relative cancer survival ratios in New Zealand and Australia between 2000–05 and 2006–10, using data from the New Zealand Cancer Registry and the Australian Institute for Health and Welfare. Over this period, Australia showed significant improvements (6.0% in men, 3.0% in women) in overall 5-year cancer survival, with substantial increases in survival from major cancer sites such as lung, bowel, prostate, and breast cancers. New Zealand had only a 1.8% increase in cancer survival in men and 1.3% in women, with non-significant changes in survival from lung and bowel cancers, although there were increases in survival from prostate and breast cancers. For all cancers combined, and for lung and bowel cancer, the improvements in survival and the greater improvements in Australia were mainly in 1-year survival, suggesting factors related to diagnosis and presentation. For breast cancer, the improvements were similar in each country and seen in survival after the first year. The findings underscore the need to accelerate the efforts to improve early diagnosis and optimum treatment for New Zealand cancer patients to catch up with the progress in Australia.     

Biology and Host Range of Phytomyza vitalbae and its Establishment for the Biological Control of Clematis vitalba in New Zealand

Phytomyza vitalbae Kaltenbach (Diptera: Agromyzidae) creates mines in leaves of Clematis vitalba , a significant environmental weed in New Zealand. Studies in Europe found that most leaves had one mine, but some had many; heavy mining deformed leaves and reduced photosynthetic area.; P. vitalbae was multi-voltine; fecundity averaged 521 eggs per female; and larval parasitism was high. Together, these biological characteristics suggested it had the capacity to produce large populations in the absence of parasitism. P. vitalbae has been recorded on other Clematis species in Europe, and experimental determination of host range confirmed this species was narrowly oligophagous, but posed no significant risk to New Zealand native plants. Results suggested mines might be produced in some exotic Clematis species growing in New Zealand, but only where flies fed on C. vitalba before ovipositing. P. vitalbae was released from quarantine in New Zealand in 1996. It is considered to be established at 20 of the 29 release sites, and populations have grown rapidly at those sites. The fly spread 5 km within 15 months at one site. Three parasitoids have been reared from P. vitalbae mines since its release in New Zealand, but it is uncertain whether parasitism will adversely affect leafminer populations.     

Investigation of Genetic Structure between Deep and Shallow Populations of the Southern Rock Lobster,Jasus edwardsii in Tasmania,Australia

The southern rock lobster, Jasus edwardsii, shows clear phenotypic differences between shallow water (red coloured) and deeper water (pale coloured) individuals. Translocations of individuals from deeper water to shallower waters are currently being trialled as a management strategy to facilitate a phenotypic change from lower value pale colouration, common in deeper waters, to the higher value red colouration found in shallow waters. Although panmixia across the J. edwardsii range has been long assumed, it is critical to assess the genetic variability of the species to ensure that the level of population connectivity is appropriately understood and translocations do not have unintended consequences. Eight microsatellite loci were used to investigate genetic differentiation between six sites (three shallow, three deep) across southern Tasmania, Australia, and one from New Zealand. Based on analyses the assumption of panmixia was rejected, revealing small levels of genetic differentiation across southern Tasmania, significant levels of differentiation between Tasmania and New Zealand, and high levels of asymmetric gene flow in an easterly direction from Tasmania into New Zealand. These results suggest that translocation among Tasmanian populations are not likely to be problematic, however, a re-consideration of panmictic stock structure for this species is necessary.     

Cloud frequency correlates to plant species composition in the high Andes of Ecuador

Two data sets representing atmospheric moisture are available for the high Andes of Ecuador, (i) cloud frequency obtained from weather satellites, and (ii) interpolated rainfall estimates obtained from global climate observations. We analyzed their correlation to vascular plant species composition at 18 Ecuadorian superpáramo study sites. Of particular interest was whether cloud frequency could be used as a proxy for precipitation. Cloud frequency had distinct seasonal and spatial variation among the sites. The spatial gradient of cloudiness was strongest during June–August and weakest around the equinoctials. Interpolated rainfall estimates also showed seasonal and spatial variation among the sites, but there was no correlation between them and cloudiness. Cloud frequency during June–August was the only significant variable in the canonical correspondence analysis (CCA) of the species composition, whereas rainfall estimates, geology, presence of glaciers, and size and altitudinal range of the superpáramos were not significant. When the spatial components were filtered out from the species composition data by employing partial CCA, cloud frequency during December–February became the only significant variable. Our results suggest that cloud frequency data may be a useful tool in mountain ecology research, serving as an indicator of habitat humidity when exact precipitation data are lacking.     

Estimating ultraviolet radiation at the earth's surface

Surface ultraviolet (UV) irradiance depends not only on stratospheric ozone amounts, but also varies with time and date, latitude, cloud amount and aerosol load. Any assessment of the effect of stratospheric ozone depletion on surface UV irradiance must take into consideration all of the above parameters. Measurements in the UV-B region may be accomplished using filter and detector combinations which mimic a biological response curve. However there are uncertainties such as in determining the exact filter response and in the cosine error of the detector. The UV-A region lacks a strong ozone absorption band and approaches which relate measured UV-A irradiance to measured global irradiance show promise. Theoretical models have been derived which calculate spectral UV irradiance in cloudless and cloudy conditions. Results show that cloud transmissivities increase as wavelength increases; however, there is a strong dependence on cloud type. In the absence of surface observations of clouds, satellite data may be used to map UV-A and UV-B irradiance in a region, and this approach is illustrated using two specific examples.     

Polytrichum commune Hedw. and Polytrichadelphus magellanicus (Hedw.) Mitt. used as decorative material on New Zealand Maori cloaks

Abstract

Confirmation of the occurrence of the moss Ptychomnion densifolium on the main islands of New Zealand is provided and the features which separate it from the more common P. aciculare are outlined. A brief account of the history of P. densifolium in New Zealand is given and its morphology there is discussed. A key to the two species in New Zealand is provided and habitat differences between them outlined. New Zealand material differs from type locality (Tristan d' Acunha) material in having longer and more twisted acumens, and in this respect is similar to New Zealand material of P. aciculare. New Zealand populations of P. densifolium are recognisable in having stem leaves reflexed from an oblong sheathing base, and well developed basal leaf plications. It is a relatively widespread species in New Zealand, occurring in mostly upper elevation, open sites.     

A European pest to control a new zealand weed: investigating the safety of heather beetle, Lochmaea suturalis (Coleoptera: Chrysomelidae) for biological control of heather, Calluna vulgaris

Heather, Calluna vulgaris (L.) Hull, is a serious invasive weed in the central North Island of New Zealand, especially in Tongariro National Park, a World Heritage Area. Heather beetle, Lochmaea suturalis (Thomson), is a foliage-feeding pest of Calluna in Europe, that was selected as the most promising biological control agent for introduction into New Zealand, because it causes high levels of damage to Calluna in Europe. Host-range tests indicated that L. suturalis poses a negligible threat to native New Zealand plants. Cultivars of Calluna grown as ornamentals are suitable food plants, but are unlikely to be severely affected because L. suturalis requires a damp understorey of moss or litter for successful oviposition and pupation, which is rarely present in gardens. However, mosses and litter occurring under Calluna stands in Tongariro National Park are suitable substrates for eggs and pupae. Lochmaea suturalis released in New Zealand has been freed of parasitoids and a microsporidian disease that attack the beetles in Europe.     

Comparative biogeography of New Zealand trees: species richness, height, leaf traits and range sizes

New Zealand forests grow under highly oceanic climates on an isolated southern archipelago. They experience a combination of historical and environmental factors matched nowhere else. This paper explores whether the New Zealand tree flora also differs systematically from those found in other temperate and island areas. A compilation of traits and distributions from standard floras is used to compare the New Zealand tree flora with those of Europe, North America, Chile, southern Australia, Fiji and Hawaii. New Zealand has a large number of trees (215 species ≥6 m in height). It is more tree-rich than temperate North America and Europe having up to 50% more species at a quadrat scale of 2.5? latitude x 2.5? longitude. However, this richness is due to a greater abundance of small trees (≤15 m in height) and we argue that it is a legacy of allopatric speciation and radiation during the late Neogene (2.5?10 million yrs ago) when the New Zealand landmass was repeatedly split into smaller island groups and mountain building occurred. The leaves of New Zealand trees, along with those of southeast Australia, are smaller and narrower than those of the temperate northern hemisphere. Dominance of the canopy by small-leaved evergreen conifers and angiosperms may have facilitated the persistence of small tree species in the lower canopy. The proportion of tree species with a deciduous or divaricating habit, and toothed-margin leaves, increases with latitude, suggesting a link with lower winter temperatures in the south. Tree species richness decreases with increasing latitude and, in conformity with Rapoport?s Rule, latitudinal range width increases. Wide-range trees are mainly bird-dispersed, fast-growing seral small trees, or long-lived, tall podocarps. Wide-range trees appear to have no greater tolerance of climate extremes than narrow-range trees, and their persistence at high latitudes derives from their enhanced colonization ability.     

Community reassembly: a test using limestone grassland in New Zealand

To examine community reassembly, we sampled grasslands on calcareous soil (4%–24% CaCO₃) in New Zealand that were largely composed of species introduced from Britain. We tested whether the British species had reassembled on New Zealand limestone into the same communities as they form on limestone in Britain. The vegetation of six New Zealand sites was sampled, each with ten 2 × 2 m quadrats that followed the standard methodology of the British National Vegetation Classification (NVC). Analysing species presence and cover using program TableFit with the full database of British species, the New Zealand species assemblages gave poor to moderate fits (40%–72%) to the communities of the NVC, and even then not to calcareous grassland, though one site did fit to a calcareous spring community. The poor fits can be partly attributed to the absence from New Zealand of many British calcareous-specialist species. On omitting from the NVC database all species not present in New Zealand, the fits increased somewhat to 48%–77%. Using this modified database, two sites fitted British calcareous grassland communities. These two sites are on thinner soil (<10 cm depth), under lower rainfall. Where fits were obtained to calcareous communities, the environment of the community in Britain matched very well that of the New Zealand site. It is concluded that environmental and perhaps biotic filtering has been strong enough in some sites to assort alien species into the same species assemblages as they form in their native range, indicating the Deterministic model of community structure. However, the absence of some species has prevented full reassembly.     

Body size – prey size relationships in European stoats Mustela erminea: a test case

From the close correlation between the body size of European stoats and the mean size of their vertebrate prey it ought to be possible to predict the body size of European stoats living on a prey fauna of a given size distribution. In New Zealand, stoats of European stock have lived for > 100 yr on a prey fauna containing fewer small and more large vertebrate prey than in Europe. They have become generally larger than their ancestors, as expected – especially the females. The vertebrate prey size index for New Zealand stoats extends the correlation predicted from European data. New Zealand stoats also eat large numbers of native insects. If these are included the local prey size indices are lower but still tend to vary with the substantial local variation in body size of stoats within New Zealand. Recent results from southern Ireland also fit the European correlation, but the few data so far available from Northern Ireland do not.     

Vegetative Production and Performance of

Aspects of the production and vegetative performance of Calluna vulgaris (heather) were examined in four areas of New Zealand between 1981 and 1983; Tongariro National Park in the North Island, together with Mount Cook National Park, the Wilderness Scientific Reserve, and Ben Callum peat bog in the South Island. The height and height/width quotient of Calluna bushes, the diameter increment of woody stems and the amount of flowers/stem all decreased with altitude. Other age-adjusted components of stem biomass were positively related to soil depth, soil moisture, soil organic content and soil pH. Biomass by direct harvest gave values between 300 g per m and 2200 g per m for plant communities with Calluna. These are similar Values to recorded from British and European heaths, although the contribution of Calluna to the total biomass was often less in New Zealand. Calluna from New Zealand has a higher proportion of wood relative to total biomass than is normally found in Britain and Europe and this is probably related to the management of British and European heaths by burning. Multiple regressions indicated that increased woodiness is associated with lower altitudes and deeper, moister soils. Woodiness tended to decrease on more organic and more acidic soils, with a corresponding increase in the proportion of green shoots. Flowering declined with increased altitude, while the proportion of green shoots relative to total biomass increased. It is suggested that the upward extension of Calluna within Tongariro National Park is limited mainly by constraints on flowering and sexual reproduction.     

Tracking environmental stress gradients using three biotic integrity indices: Advantages of a locally-developed traits-based approach

Estuarine and coastal ecosystems are productive and functionally diverse areas that provide a wide range of societal benefits. Along with human exploitative uses comes an array of anthropogenic disturbances that can affect ecological integrity, including changes to the composition and resilience of benthic macroinvertebrate communities. To understand the responses of ecological communities to anthropogenic disturbance and to manage and mitigate effects, indices for assessing the ecological integrity of estuarine and coastal waters have proliferated worldwide. Using data from 84 intertidal sites in Auckland, New Zealand, we evaluated the suitability of two widely used measures of ecological integrity that were developed in USA and Europe, respectively: the Benthic Index of Biotic Integrity (B-IBI) and the AZTI's Marine Biotic Index (AMBI). We then developed a local index based on macrofaunal traits and verified its utility using independent data from >100 additional sites. The local traits based index (TBI), constructed from the richness of macrofaunal taxa in seven functional groups, responded to changes in sediment mud percentage and heavy metal contaminant concentration gradients below international guidelines. The TBI performed better than the indices developed overseas, probably because they were designed to track organic enrichment and hypoxia, which are not the predominant stressors in New Zealand at present. The TBI successfully tracked the stressors that were the most relevant locally and indicated the relative levels of within-group taxonomic richness at various sites. As within-group richness is a component of functional redundancy and ecological resilience, the TBI offers a trifecta of simplicity, robustness and meaningfulness that will facilitate management.     

Light conditions and the evolution of heteroblasty (and the divaricate form) in New Zealand

Heteroblasty, changes in vegetative phenotype during ontogeny, is unusually common in the New Zealand flora. Some feature(s) unique to the New Zealand situation must have influenced the evolution of this strategy. Similarities were examined between the ontogenetic changes in phenotype and growth strategy in Elaeocarpus hookerianus, Carpodetus serratus and Pseudopanax crassifolius. Variation in hypothesised light capture efficiency of juvenile and adult forms can be related to changes in the light environment that these growth forms experience. Heteroblasty is hypothesised to have evolved as a result of the change from a low light intensity environment below the canopy of high altitude conifer/broad-leaved forests, to a high light intensity environment above the canopy. The differences in architecture between juvenile E. hookerianus and C. serratus on the one hand, and P. crassifolius on the other hand, are likely to be related to their adaptation to heterogeneous moderate light intensity and homogeneous low light intensity, respectively. The divaricate form characteristic of many New Zealand shrubs may have arisen following the development of heteroblastic trees with a divaricate juvenile, and the subsequent loss of the adult state. This paper provides hypotheses which future research can scientifically test.     

The importance of viticultural landscape features and ecosystem service enhancement for native butterflies in New Zealand vineyards

The fragmentation of habitats in intensively managed farming landscapes is often considered to be partly responsible for butterfly population decline in Europe and the USA. Although relatively little is known about New Zealand butterfly ecology, agricultural landscapes in lowland New Zealand are managed similarly to those in Europe and ecosystem services (ES) in these landscapes are generally at a low level. In the northern hemisphere, attempts are being made to address the problem through agri-environment schemes, but such farmer compensation is not available in New Zealand. Instead, landowner- and research-led initiatives are currently the only potential approaches. One such project in the Canterbury province, New Zealand, is the Greening Waipara project. This aims to return native plants to viticultural landscapes and enhance ES, and while research has sought to quantify economic benefits of the project, there has been no work to establish if the plantings are improving or are likely to improve non-target invertebrate biodiversity, for example arthropods that are not biocontrol agents. In the first study of its kind in New Zealand, butterfly surveys were conducted in vineyards and linear mixed modelling techniques were used to identify the most important vegetation and structural features which may influence butterfly distribution. While the native planting areas were not important for butterflies, remnant patches of native vegetation in unproductive areas were vital for sedentary species. These results are discussed in relation to the conservation of native species in New Zealand vineyards and in the context of conservation in and around farmland in general.     

Systematic and conservation implications of geographic variation in pipits (Anthus: Motacillidae) in New Zealand and some offshore islands

The New Zealand Pipit Anthus novaeseelandiae occurs as a single species in Europe (as Richard's Pipit), Asia, Africa, New Guinea, Australia and New Zealand. In the New Zealand region, subspecific status has been accorded to allopatric populations on the mainland (A. n. novaeseelandiae) , on the Auckland and Campbell Islands (A. n. aucklandicus) , on the Antipodes Islands (A. n. steindachneri) and on the Chatham Islands (A. n. chathamensis) . Analyses of 23 allozyme loci and morphometric variation of populations on mainland New Zealand and on the Auckland, Campbell, Antipodes and Chatham Islands showed an appreciable and significant divergence between mainland and island populations. The magnitude of the allozyme difference is sufficient to suggest full species designation for the island birds, a conclusion supported by morphometric analyses and in sharp contrast to current taxonomy. However, formal taxonomic change will not be undertaken until the two New Zealand groups have been compared with more distant populations of this wideranging genus. The cryptic variation found in this species has conservation management implications for the small offshore populations.     

The role of plant phenology in stomatal ozone flux modeling

Plant phenology plays a pivotal role in the climate system as it regulates the gas exchange between the biosphere and the atmosphere. The uptake of ozone by forest is estimated through several meteorological variables and a specific function describing the beginning and the termination of plant growing season; actually, in many risk assessment studies, this function is based on a simple latitude and topography model. In this study, using two satellite datasets, we apply and compare six methods to estimate the start and the end dates of the growing season across a large region covering all Europe for the year 2011. Results show a large variability between the green‐up and dormancy dates estimated using the six different methods, with differences greater than one month. However, interestingly, all the methods display a common spatial pattern in the uptake of ozone by forests with a marked change in the magnitude, up to 1.9 TgO₃/year, and corresponding to a difference of 25% in the amount of ozone that enters the leaves. Our results indicate that improved estimates of ozone fluxes require a better representation of plant phenology in the models used for O₃ risk assessment.     

Enhanced niche opportunities: can they explain the success of New Zealand's introduced bird species?

Aim  The niche hypothesis could explain why some species introduced to new locations reach higher densities than in their native range: it posits that the new environment provides more abundant or higher quality resources or habitat, a more suitable physical environment or both. We investigate whether 11 bird species occur at higher densities in their introduced range than in their native range and whether the differences can be explained by the availability of preferred habitat or the suitability of climatic conditions in their introduced range relative to their native range.
Location  South Island, New Zealand (the introduced range); UK (the native range).
Methods  We first develop a series of models that accurately predict the density of 11 bird species at 54 UK farmland sites, which are closely matched to our New Zealand sites, from habitat and climatic variables. We then use these models to predict the density of the 11 species at 54 New Zealand farmland sites and compare the predicted and observed values.
Results  Actual densities at New Zealand sites were on average (median) 22 times (range: 1–6361) higher than predicted from the UK models and similarly higher than actually observed at comparable UK sites. Habitat and climatic variables can accurately predict bird densities in the UK but grossly underestimate densities for all species except Turdus merula in New Zealand.
Main conclusions  These findings indicate that factors other than the measured habitat and climatic variables must differ between the two regions and explain the much higher densities of New Zealand birds. We suggest that introduced birds, other than T. merula , in New Zealand may still experience enhanced niche opportunities due to greater availability of higher quality resources within habitats, release from natural enemy regulation, less exposure to extreme weather events, particularly during winter, or some combination of these processes.