Birds as indicators of sustainable management practices on New Zealand kiwifruit orchards.
Coleman, Guinevere Jane
New Zealand relies heavily on its agricultural industry, and with 60% of land area utilised for production, over 40% of the countries export earnings come from the land. Dominated by Zespri International Ltd., kiwifruit production is New Zealand’s largest horticultural export. Concerns over the impact of production on environmental and consumer health led to the introduction of ‘Kiwigreen’, an Integrated Management (IM) scheme that aims to reduce the amount of sprays being applied to the orchard. The industry took little time to take up the Kiwigreen policy and now all non-organic growers are part of the Kiwigreen system. While in theory the industry is now more environmentally friendly, little research has been conducted to confirm this. Additionally, little research has been done to compare the environmental impacts of IM orchards compared to organic orchards, which are assumed to be more environmentally benign. This study is part of the Agriculture Research Group on Sustainability (ARGOS) which was started in 2003 with the aim of investigating the environmental, social, and economic sustainability of production landscapes in New Zealand. The kiwifruit component is dedicated to helping growers produce fruit in a healthy orchard environment. By researching the environmental, social, and economic aspects of the industry, it is hoped that a greater understanding of the way these factors influence each other and the industry as a whole can be found. The aim of this research is to look at birds in their role as important environmental indicators, and the factors affecting their survival. Birds are widely considered to be good indicators of environmental health, as they are often directly influenced by land use through predation, habitat quality, and food supply. To this end, this study looked at the density estimates of common orchard bird species, and at the possibility of using the fantail as an indicator of orchard environmental health, in relation to orchard management type (IM green (Hayward), IM gold (hort16A), and organic green (Hayward)) and season. In addition, this study looked at the attitude of growers towards birds and their potential as an indicator of environmental health being directed towards consumers. ARGOS study orchards are arranged in clusters, each containing an IM green orchard, IM gold orchard, and an organic green orchard. Distance sampling was conducted on three clusters (nine orchards in total) in the Bay of Plenty region. Sampling was repeated over seven circuits, with three in the summer (bird breeding/fruit growing) months, one in the autumn (orchard fruit picking), and two in the winter (orchard pruning) months. Transect lines were walked along the length of the orchard, fifty metres apart. Birds were counted and detection distances, behaviour and habitat data, and several field parameters were recorded. Organic and gold orchards had significantly higher species richness compared to green orchards, but there were no differences between orchards for overall species abundance. Densities for key bird species, blackbirds (Turdus merula), song thrushes (Turdus philomelos), house sparrows (Passer domesticus), silvereyes (Zosterops lateralis), and fantails (Rhipidura fuliginosa) were estimated using DISTANCE™ 6.0, release 2. Detection functions were found for both summer and winter seasons, and these were used to estimate densities for season, and for circuit. Blackbirds had the highest total counts, followed by sparrows, silvereyes, and song thrushes. However, density estimates for silvereyes were up to three times higher than blackbirds, with estimates of up to 59/ha on gold orchards. All five species showed some seasonal variation in estimated densities, suggesting previous studies looking at bird populations in the breeding/summer season only cannot infer that results reflect year-long trends. Green orchards appear to support higher numbers of sparrows. Organic orchards appear to support higher numbers of song thrushes in the winter, and higher numbers of fantails in the summer. Findings were comparable to available estimates in previous studies, with differences in conspicuousness and effects of behaviour and habitat variables accounting for differences between seasons and orchard type. This study has highlighted the importance of seasonal variation when investigating the impacts of land management practices. Fantail encounters and feeding effort were recorded on six clusters (eighteen orchards). Circuits and transect lines followed the same method as in Chapter one. Behavioural time budgets and feeding rate were used to determine feeding effort, and encounters were used to estimate relative abundance. Fantails were found to be in higher numbers on organic orchards through the breeding season, and had strong seasonal changes, with higher numbers present in all orchards in the winter months. Feeding effort, in both proportion of time spent feeding and attempted captures per second, was significantly higher in the winter months, but no difference between orchard types was found. The effect of orchard spray regimes may account for lower numbers in IM orchards compared to organic orchards, affecting prey availability. Population numbers may be affected by local migrations, the effects of flocking in the winter months, meta-population fluxes, and/or changes in feed resources. Based on this study, it is concluded that further research is needed to determine whether the fantail can be used as a reliable indicator of orchard health, as populations of fantails are not high enough, nor are factors affecting abundance well enough understood. The development of an eco-label for New Zealand kiwifruit, for demonstrating an aspect of the eco-friendly nature of production, is expected to have a market benefit for exported fruit. Twenty seven ARGOS growers were interviewed to gain a perspective on their opinions regarding the introduction of an eco-label for exported fruit; their perceptions on bird populations; and their management actions towards birds on their orchards, as well as mammalian predation. Growers were positive about the introduction of an ‘eco-friendly’ label but were wary about the consumer’s potential response towards a specific ‘birdfriendly’ label. Growers had limited knowledge of specific bird population numbers, and the majority neither encouraged nor discouraged birds on their property, but did remove empty nests from the vines. Some actively encouraged native species, and others actively removed ‘pest’ species such as sparrows and pukekos. Control of mammalian pests was common, including the removal of rabbits, rats, and possums. Results found here were compared to selected results of the 2008 National Farm Survey, conducted by ARGOS. This survey not only canvassed opinions from ARGOS growers, but also a random sample of kiwifruit growers from the wider industry. This wider selection of growers indicated low support for the introduction of an eco-label. This growers survey, together with results from a 2008 National Farm Survey suggest that ARGOS growers are more aware of environmental issues and more supportive of a proposed eco-label, compared to the random sample of growers who indicated environmental initiatives were not a priority. The attitude of consumers towards environmental issues surrounding kiwifruit production needs to be gauged in order to give growers an incentive to improve their orchards for bird populations. This study was a part of the wider research pool of the ARGOS project, complementing previous and ongoing research on kiwifruit orchards as well as in the dairy, sheep/beef, and highcountry sectors within the ARGOS framework. The results found in this study highlighted a number of future research areas that would further complement this study including: • The effect of the size of neighbouring bush patches, as well as the distance between patches and orchard habitats, on bird distribution patterns on the orchard. • The influence of other habitats within the orchard property (e.g. shelterbelts, gardens, and other crops) on bird distribution patterns. • Multi-year seasonal fluxes of fantail numbers, and whether strong seasonal patterns of summer/winter abundance is a typical pattern. • Local migration patterns of fantails on and off the orchard. • Survival rates of fantails over-winter, and breeding success of fantails within the orchard environment. • Investigation into the use of additional or alternative bird indicator species on kiwifruit orchards, for example non-native insectivorous birds, or other native birds such as the tui.
Advisor: Moller, Henrik; Macleod, Catriona
Degree Name: Master of Science
Degree Discipline: Zoology
Publisher: University of Otago
Keywords: birds; fantails; kiwifruit; distance sampling; integrated management; organic
Research Type: Thesis