State and trends in the diversity, abundance and distribution of birds in Upper Hutt City November 2015 1 State and trends in the diversity, abundance and distribution of birds in Upper Hutt City. Nikki McArthur1, Susanne Govella2, Jono Walter2 and Delia Small2 1Wildlife Management International Ltd 2C/- Greater Wellington Regional Council PO Box 607 Shed 39 Blenheim 7240 2 Fryatt Quay New Zealand Pipitea www.wmil.co.nz Wellington 6011 This report was prepared by Wildlife Management International Limited for Greater Wellington Regional Council as fulfilment of the Contract of Services dated 25th August 2015. 1st November 2015 Citation: This report should be cited as: McArthur, N.; Govella, S.; Walter, J. and Small, D. 2015. State and trends in the diversity, abundance and distribution of birds in Upper Hutt City. Client report prepared for Greater Wellington Regional Council. Wildlife Management International Ltd, Blenheim. All photographs in this report are copyright © WMIL unless otherwise credited, in which case the person or organization credited is the copyright holder. Cover Image: Juvenile New Zealand fantail (Rhipidura fuliginosa) photographed on the Hutt River adjacent to Trentham Memorial Park, Upper Hutt (November 2014). Image courtesy of N. McArthur. State and trends in the diversity, abundance and distribution of birds in Upper Hutt City ABSTRACT Five-minute bird counts have been carried out at 45 bird count stations situated in native forest habitat in six selected Upper Hutt City parks and reserves each year between 2011 and 2014. The aim of these surveys is to monitor trends in the diversity, abundance and distribution of native forest birds in Upper Hutt City’s reserve network, to provide a measure of local biodiversity management outcomes. Between 26 and 31 bird species were detected during these bird counts each year, with approximately half of these species being native species and half being introduced and naturalised species. There has been little change in the number of native forest bird species detected in Upper Hutt reserves between 2011 and 2014, suggesting that the environmental management of these reserves is succeeding in maintaining native species diversity. Both rifleman and kakariki (red-crowned parakeet) are only present in very small numbers in one or two of the reserves surveyed, so may not be present in sufficient numbers to maintain viable populations in the long term. Both Keith George Memorial Park and Wi Tako Reserve once again emerge as important reserves in Upper Hutt City, as each supports populations of the majority of native forest bird species detected during these counts. On average, a higher number of native forest bird species were recorded per bird count station in Upper Hutt City reserves compared to those surveyed in Wellington City. This is because around 25% of the native forest bird species recorded in Wellington City reserves had very localised distributions (typically centred on Zealandia), whereas almost all species detected in Upper Hutt reserves had fairly widespread distributions. Native bird species that feed predominantly on nectar or fruit have shown some significant year to year fluctuations in abundance between 2011 and 2014, likely due to annual variation in the local availability of food resources. In contrast, many of the insectivorous birds have shown relatively little change in abundance over the past four years. One exception is the fantail, which has undergone an 11-fold increase in abundance in Upper Hutt City reserves between 2011 and 2014. This is likely to represent a rapid local population recovery following a very heavy mortality event that occurred during the winter of 2011. Encounter rates for tomtit have been significantly higher in both 2013 and 2014 than during the preceding two years and this may be early evidence that local tomtit populations are responding to local mammalian predator control efforts. Both this new survey design and the incorporation of bird distribution data collected by local citizen scientists has allowed us to map the distribution of birds in Upper Hutt City in much greater detail than previously. These counts have revealed that the north-eastern portion of Keith George Memorial Park and the southern portion of Wi Tako Reserve both support higher numbers of tomtits, fantails, whiteheads and bellbirds than remaining portions of both reserves. This suggests that the north- eastern and southern portions of these two reserves provide particularly high quality habitat for these native species, likely due to the presence of mature stands of both black and hard beech. We recommend that these bird counts be continued on an annual basis to provide a consistent, repeatable measure of trends in bird diversity, abundance and distribution in Upper Hutt City. We also recommend that Upper Hut City considers investing additional resources towards further encouraging Upper Hutt City residents to report bird observations from suburban areas and other parks and reserves around the city using online biodiversity reporting tools. Keywords: Upper Hutt City, five-minute bird count, bird abundance, Wi Tako Reserve, Keith George Memorial Park, citizen science, eBird, NatureWatch. McArthur, N.; Govella, S.; Walter, J. and Small, D. 1 State and trends in the diversity, abundance and distribution of birds in Upper Hutt City 1 INTRODUCTION Annual bird monitoring is carried out in a number of parks and reserves in Upper Hutt City to monitor trends in the diversity, abundance and distribution of native birds in these reserves. Bird monitoring in Upper Hutt began in 2005 when five-minute bird count stations were established in Keith George Memorial Park as part of Greater Wellington Regional Council’s Key Native Ecosystem programme (Stephens et al, 2007). In 2006 and 2007, bird count stations were installed in a further six parks and reserves around Upper Hutt to provide a more detailed picture of city-wide trends in bird distribution and abundance (Figure 1.1). The results of the first six years of bird counts have been reported in Stephens et al, (2007), Fea & Moylan (2008) and Govella et al, (2011). These authors reported that native bird diversity and abundance tended to be greater in the larger reserves with better habitat connectivity to surrounding areas of native or exotic forest habitat. Fantail (Rhipidura fuliginosa), tui (Prosthemadera novaeseelandiae), grey warbler (Gerygone igata) and silvereye (Zosterops lateralis) were the five most frequently encountered native bird species. Keith George Memorial Park emerged as a particularly important site for native birds in Upper Hutt because it was the only reserve sampled that supported large populations of both whitehead (Mohoua albicilla) and tomtit (Petroica macrocephala). In 2011 this bird monitoring programme was replaced with a new survey designed to monitor changes in the apparent abundance of native forest birds across the entire network of selected reserves, rather than attempt to compare indices of abundance between individual reserves (McArthur et al, 2012). Tui were chosen as a focal species for this new survey design and a sample size of 90 five-minute bird counts was selected to ensure sufficient statistical power to detect a 25% or more change in the apparent abundance of tui from one year to the next. These new bird count stations were surveyed in both 2011 and 2012 and the results of these counts confirmed that larger and better connected reserves such as Wi Tako Reserve and Keith George Memorial Park supported the greatest diversity of native forest bird species. In addition, the average number of native bird species recorded per bird count station each year was significantly higher in Upper Hutt City reserves than in the Wellington City parks and reserves network. This result is due to differences in patterns of bird distribution between the two cities. Whereas around a third of the native bird species detected in Wellington City reserves had fairly localised distributions centred on Zealandia, a pest-free sanctuary situated in the Karori Reservoir Valley, the majority of native bird species recorded in Upper Hutt City reserves had much more widespread distributions (McArthur et al, 2012). Silvereye, grey warbler and tui were once again three of the most common bird species recorded in Upper Hutt reserves in both 2011 and 2012, although there was a significant reduction in both silvereye and tui abundance between years. Fantail abundance was extremely low in 2011, probably as a result of heavy mortality suffered during two unusually heavy snowfall events that occurred during winter 2011. Fantail abundance increased substantially between 2011 and 2012 however, suggesting that by the following year local fantail populations were already recovering from this severe weather event. Kakariki (Cyanoramphus sp.), bellbird (Anthornis melanura) and rifleman (Acanthisitta chloris) were all detected in Wi Tako Reserve for the first time in 2011, but this may have been a consequence of the improved search effort and coverage that was built into the new survey design, rather than evidence that recent re-colonisation events have occurred (McArthur et al, 2012). These bird counts were repeated again in both 2013 and 2014 and this report provides a summary of the results of these more recent bird counts. In addition, this report also attempts for the first time to incorporate local ‘citizen science’ bird distribution data to provide additional information on the McArthur, N.; Govella,