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Extract only - complete publication at www.jncc.gov.uk/worldwaterbirds

Waterbirds around the world
A global overview of the conservation, management and research of the world's waterbird flyways

Edited by G.C. Boere, C.A. Galbraith and D.A. Stroud Assisted by L.K. Bridge, I. Colquhoun, D.A. Scott, D.B.A. Thompson and L.G. Underhill

EDINBURGH, UK: THE STATIONERY OFFICE


Extract only - complete publication at www.jncc.gov.uk/worldwaterbirds

© Scottish Natural Heritage 2006

First published in 2006 by The Stationery Office Limited 71 Lothian Road, Edinburgh EH3 9AZ, UK. Applications for reproduction should be made to Scottish Natural Heritage, Great Glen House, Leachkin Road, Inverness IV3 8NW, UK. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 0 11 497333 4 Recommended citation: Boere, G.C., Galbraith, C.A. & Stroud, D.A. (eds). 2006. Waterbirds around the world. The Stationery Office, Edinburgh, UK. 960 pp.

Names used for geographical entities do not imply recognition, by the organisers of the Waterbirds around the world conference or other supporting organisations or governments, of the political status or boundaries of any particular territory. Names of territories used (and any alternatives) are included solely to help users of this publication apply information contained within this volume for waterbird conservation purposes. The views expressed in papers included within this volume do not necessarily represent views of the editors or the organisations and governments that supported the conference and this publication.

Cover photography:

Whooper Swans Cygnus cygnus arriving at Martin Mere, England. Photo: Paul Marshall. (www.paulmarshallphotography.com)

Copyright of all photographs used in this publication resides with the named photographers.


Waterbirds around the world

Breeding performance of tundra waders in response to rodent abundance and weather from Taimyr to Chukotka, Siberia
Mikhail Y. Soloviev1, Clive D.T. Minton2 & Pavel S. Tomkovich3 1Department of Vertebrate Zoology, Biological Faculty, Moscow Lomonosov State University, Moscow, 119992, Russia. (email: soloviev@soil.msu.ru) 2165 Dalgetty Road, Beaumaris, VIC 3193, Australia. (email: mintons@ozemail.com.au) 3Zoological Museum, Moscow Lomonosov State University, Boshaya Nikitskaya Street, 6, Moscow, 125009, Russia. (email: pst@zmmu.msu.ru) Soloviev, M.Y., Minton, C.D.T. & Tomkovich, P.S. 2006. Breeding performance of tundra waders in response to rodent abundance and weather from Taimyr to Chukotka, Siberia. Waterbirds around the world. Eds. G.C. Boere, C.A. Galbraith & D.A. Stroud. The Stationery Office, Edinburgh, UK. pp. 131-137. ABSTRACT Nesting success, rodent abundance and summer temperatures across the breeding ranges of four Arctic waders in eastern Siberia were analysed in conjunction with data on the proportions of juveniles on the non-breeding grounds in south-eastern Australia in 1979-2003 with a view to revealing the response of wader populations to varying environmental conditions during the breeding season. The effect of temperature on the proportion of juveniles was found to increase in the Sharp-tailed Sandpiper Calidris acuminata, Curlew Sandpiper C. ferruginea, Red-necked Stint C. ruficollis and Ruddy Turnstone Arenaria interpres, which to some extent corresponds to the increasing severity of their breeding environment. The proportion of juveniles on the non-breeding grounds increased with an increase in rodent abundance across the breeding range in the Sharp-tailed Sandpiper and Red-necked Stint, but not in the Ruddy Turnstone and Curlew Sandpiper. Nesting success measured within the breeding range depended on July temperatures only in the Ruddy Turnstone, and did not depend significantly on rodent abundance in any of the species under investigation. Thus, although the breeding performance of Arctic waders at the level of flyway populations depends on air temperature and rodent abundance during summer, the relative role of these environmental factors differs between species. Mean July temperatures were increasing from 1979 to 2003 across the breeding range of the Red-necked Stint. During this period, the proportion of juveniles was increasing both in this species and the Sharp-tailed Sandpiper. INTRODUCTION Recent research has demonstrated that many populations of waders are declining (International Wader Study Group 2003, Stroud et al. 2006). The reasons for these declines are rarely known with certainty, but global climate change is considered to be an important, or even the principal, factor in the declines in Arctic-breeding birds (e.g. ZÆckler & Lysenko 2000, Rehfisch & Crick 2003, ZÆckler et al. 2003). Arctic-breeding waders are known for the pronounced variation in their breeding success caused by variation in breeding conditions. Given that waders are generally long-lived birds with low adult mortality, variations in breeding success can make a critical contribution to population change. Thus, an understanding of the processes that are occurring on the breeding grounds and their effects on recruitment in wader populations is instrumental for the development of adequate conservation measures in the flyways. Prey-switching by predators has been suggested as an important factor determining the breeding success of tundra birds, first by Roselaar (1979) and then in a number of other studies. Summers & Underhill (1987) were the first authors to relate presumed predation pressure on the Taimyr Peninsula, Siberia, with the proportion of juveniles in wader populations in their non-breeding areas. However, this relationship has never been analysed over a wide geographical area. Climatic variables may also affect the breeding performance of Arctic waders at scales from local to global (the latter was shown for 1992 by Ganter & Boyd 2000), but their role has rarely been assessed from a longterm perspective (Boyd 1992, Boyd & Piersma 2001) and apparently never in conjunction with the impact of predation pressure. Thus, existing knowledge of the responses of wader populations to environmental factors on the breeding grounds has been limited in time and space, and has highlighted the role of a single factor. To a large extent, this has been due to a deficiency of large-scale and long-term data from the breeding grounds that would allow formal quantitative processing. Monitoring conducted over a period of 16 years from 1988 to 2003 within the framework of the Arctic Birds Breeding Conditions Survey (a project of the International Wader Study Group) has been able to fill this gap, and has provided data on nesting success and certain environmental factors, such as rodent abundance, within the breeding range of many waders. We have analysed these data in conjunction with the available weather data and data on the proportions of juvenile birds on the non-breeding grounds in south-eastern Australia. This study focuses on processes developing in the East Asian-Australasian Flyway, which until now has received much less attention from researchers than the intensively studied East Atlantic Flyway. The following specific questions were addressed: 1. How conditions on the breeding grounds relate to nesting success and productivity measured in the non-breeding areas? 2. How the above relations (if any) differ between species? 3. If there are any long-term trends in productivity, and how they relate to possible trends in environmental factors on the breeding grounds? METHODS Data on nesting success and rodent abundance Data on the nesting success of waders and rodent abundance on the breeding grounds were gathered during the course of the

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Arctic Birds Breeding Conditions Survey (ABBCS), and included estimates from various localities in eastern Siberia (all original data are available at http://www.arcticbirds.ru). The data, which in most cases were not quantitative, were brought to ordinal scale with ranks from 1-3, corresponding to low, average and high estimates of nesting success and rodent abundance. The considerable variation in the precision of the estimates between localities was addressed by ranking the quality of the estimates of nesting success and rodent abundance on a scale of 1-5. These rankings were used for weighting in statistical analyses. Criteria for assigning ranks to estimates of parameters and their quality are explained in Table 1. When quantitative information was lacking, the ranking was based on the mutual agreement of two experts (MYS and PST), who evaluated descriptive information available in the breeding conditions reports. These reports rarely discriminated between species when providing information on nesting success, and the estimates from some localities represented an evaluation of nesting success for the wader community as a whole. Nesting success in this survey was considered strictly as survival of nests, and did not take into account later components of breeding performance, such as the survival of chicks or juveniles. Relating the information on nesting success and rodent abundance with particular wader species was achieved by interpolating estimates from localities across the ranges of the wader populations under investigation, and averaging the interpolated values. A multiquadratic function with no smoothing (Buhmann 2003) was used for interpolation on a grid with a cell size of 50 km. Averaging the interpolated values resulted in estimates which were no longer ordinal, but still in the same range as the original estimates from point localities (ranks 1-3).

Four species of waders which migrate to south-eastern Australia for the northern winter, and for which good quality data were available for most years, both from the breeding grounds and from the wintering areas, were selected as study species: Ruddy Turnstone Arenaria interpres, Sharp-tailed Sandpiper Calidris acuminata, Curlew Sandpiper C. ferruginea and Red-necked Stint C. ruficollis. Delineation of the breeding ranges of the populations of Ruddy Turnstone and Curlew Sandpiper migrating to Australia involved an analysis of long-distance recoveries and flag-sightings, and information from the ABBCS database, Arctic Bird Library at the UNEP World Conservation Monitoring Centre, and Atlas of Breeding Waders of the Russian Arctic (Lappo et al. in prep.). The limits of the flyway population of Ruddy Turnstones in the Arctic were set at a point just west of the Lena River delta (120° E) and the Bering Strait (170° W); for the Curlew Sandpiper, the limits were set at Taimyr Lake (100° E) and northern Chukotka (177° E). The flyway populations of the Sharp-tailed Sandpiper and Red-necked Stint encompass the entire ranges of the species. Weather data Weather data were obtained from the web-site of the World Meteorological Organization (National Climatic Data Center, USA). In this study, analyses of weather variables were restricted to mean air temperatures in June and July, although other parameters (e.g. precipitation, timing of snowmelt) could also have been of major importance. However, temperatures were the only variables for which it was possible to obtain consistent, long-term data for an area of interest extending for over 3 500 km from west to east in eastern Siberia.

Table 1. Criteria for assigning ranks to estimates of nesting success and rodent abundance, and for assigning ranks to the quality of these estimates.
Ranks Nesting success Criteria for estimates of the parameter 1 <33.3%, if estimated directly as a proportion of hatched nests or using the Mayfield (1975) method; low when based on expert evaluation. 33.3-66.7%, if estimated directly; average when based on expert evaluation. >66.7%, if estimated directly; high when based on expert evaluation. 0-3 specimens per 100 trap-days; low when based on expert evaluation. Rodent abundance

2

4-10 rodents per 100 trap-days; average when based on expert evaluation. 11-30 animals per 100 trap-days; high when based on expert evaluation.

3

Criteria for estimates of parameter quality 1 Unsupported evaluation by respondent. Visual evaluation during a period of less than one month, or interview data, or unknown source. Visual evaluation during a period of less than one month and interview data. Direct counts for a period of less than one month, or visual evaluation for a period exceeding one month, or counts of nests under snow. Combination of two conditions of rank 3, or combination of any condition of rank 3 with any condition of rank 1. Direct counts for a period exceeding one month.

2 3

Evaluation based on abundance of wader broods. Direct estimates of nesting success with sample of 5-30 nests, or observations of larger numbers of nests terminated before hatching. Combination of two conditions of rank 3, or combination of any condition of rank 3 with condition of rank 2. Direct estimates of nesting success with sample exceeding 30 nests.

4

5

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We obtained the mean monthly temperatures for June and July for each weather station located to the north of 50° N for the period 1978-2003 (i.e. from the start of cannon-netting for waders in Australia), and then estimated the deviations of these means from the monthly averages over the period 1994-2003. The last 10 years were chosen as a reference period because the available weather data were the most consistent during this period. Deviation values obtained from the weather stations were then interpolated across the whole of the Arctic for each year from 1978 to 2003, and the interpolated values averaged across the flyway population ranges of the four wader species under investigation. The interpolation technique was the same as that used for nesting success and rodent abundance. These average values indicated whether conditions in the respective months across the species' ranges were warmer or colder than the average for the 10-year period 1994-2003. Data on proportion of juveniles The Victorian Wader Study Group has been collecting data on the proportion of juvenile waders in cannon-net catches in southeastern Australia since 1978. Data on the percentages of juveniles were gathered in 1978-2003 for the Red-necked Stint, in 19792003 for the Curlew Sandpiper and Sharp-tailed Sandpiper, and in 1989-2003 for the Ruddy Turnstone. In-depth analyses of the data sampling procedures, possible biases and considerations required during interpretation of data have been published elsewhere (Minton et al. 2000). Analyses of the proportions of juveniles in the catches have been made by Minton et al. (2001, 2002a, 2002b, 2003a, 2003b, 2004). All catches were made between mid-November and the end of February, except for a few catches of Red-necked Stint and Ruddy Turnstone which were made up to mid-March in some years. The annual samples of Red-necked Stint and Curlew Sandpiper ranged from several hundred to several thousand birds, while the average annual samples of Sharp-tailed Sandpiper and Ruddy Turnstone were only 180 and 122 birds, respectively. We accounted for the presence of small sample sizes in the latter two species by assigning quality ranks based on the number of birds in the total catches: 1 = <50 birds a year; 2 = 50-99 birds; 3 = 100 or more birds. This scale was chosen to provide the closest match to the previous analyses of juvenile percentage data from the Australian non-breeding grounds, which defined samples below 30 birds as inadequate, and distinguished "small" and "large" catches based on the threshold of 50 birds (e.g. Minton et al. 2004). Processing and analyses of data The statistical processing of data was based on fitting regression models, and incorporated weighting of observations with data quality ranks. Outliers were identified using studentized residuals, and excluded from samples when they represented apparently unrealistic values (e.g. 66.7% juveniles in a sample of 66 Sharp-tailed Sandpiper in 1989). The most general form of dependence of wader productivity on environmental factors was studied by extracting the principal components from two groups of variables: (1) four variables (one per species) corresponding to proportions of juveniles on the
1

wintering grounds; and (2) eight variables corresponding to July temperatures and rodent abundance within the breeding ranges of the four wader species. This analysis was restricted to the period 1989-2003 for which all data were available for all four species. Spatial analyses were made using Mapinfo GIS (MapInfo Corp. 1996), while statistical processing employed Systat 7.01 (SPSS Inc. 1997). RESULTS Effects of temperature and rodent abundance on the breeding performance of waders The principal results of the statistical testing are summarized in Table 2, while Fig. 1 shows the dependence of juvenile proportions on July temperatures and rodent abundance. An increase in summer air temperatures within the breeding range resulted in an increase in the proportion of juveniles in the non-breeding grounds in each of the four wader species under consideration. The estimated effect of this increase in temperature, expressed as percentage increase in the proportion of juveniles per one degree of increase in the average June and July temperatures across the range of the species, varied from 3.2 in the Sharp-tailed Sandpiper to 14.0 in the Ruddy Turnstone. The effect was most pronounced for mean July temperatures in all species except Sharp-tailed Sandpiper, in which the effect of July temperature, in isolation, was not significant at P<0.05. However, when the average June and July temperatures were combined for this species, the effect was significant. Summer air temperatures had a significant effect on nesting success across the breeding range only in the Ruddy Turnstone, although the marginally significant effect of July temperatures in the Sharp-tailed Sandpiper is noteworthy. The proportion of juveniles on the non-breeding grounds in south-eastern Australia increased significantly (P<0.05) with an increase in rodent abundance in the Sharp-tailed Sandpiper, but not in other species, although an examination of the graphs revealed that a good regression in the case of the Red-necked Stint was adversely affected by a single apparent outlier ­ the low proportion of juveniles in 2000 (Fig. 1). The relationship between nesting success and rodent abundance was, at best, marginally significant in the Ruddy Turnstone. Summer temperatures across the breeding ranges of the four species of waders were significantly correlated with each other (P<0.05, Spearman correlation of ranks=Sr below), as were the values for rodent abundance (P<0.05). However, juvenile proportions in Australia were significantly correlated with each other (P<0.05) only in a single pair of species, namely Ruddy Turnstone and Curlew Sandpiper, the only two high Arctic species under consideration. Extracting the Principal Components1 from the proportions of juveniles of the four species for the period 1989-2003 aimed at revealing common patterns of variation in the productivity of the different species using a data reduction approach. PC1 explained 54.5% of the total variance of the four variables, and was mostly related to variation in the proportions of juvenile Curlew Sandpiper, Ruddy Turnstone and Red-necked Stint (loadings ranging from 0.68 to 0.94), while correlation with the proportions of juvenile Sharp-tailed Sandpiper was much

A Principal Component Analysis is used to simplify a data set; more formally, it is a linear transformation that chooses a new co-ordinate system for the data set such that the greatest variance by any projection of the data set comes to lie on the first axis (then called the first principal component, PC1), the second greatest variance on the second axis (PC2), and so on.

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Table 2. Estimates of the effects of environmental parameters on the breeding productivity of waders (response variables), and evaluation of trends. The effects are expressed as percentage change in dependent variable per unit change in independent variable; e.g. in the Sharp-tailed Sandpiper, the proportion of juveniles increases by 7.35% when rodent abundance increases by one unit (from "low" to "average", or from "average" to "high"). P-values for the corresponding effects are given in brackets, and estimates of effects significant at P<0.05 are shown in bold.
Parameter Red-necked Stint June temperature July temperature Average of June & July temperatures Rodent abundance 2.21 (0.198) 6.36 (0.003) 4.65 (0.027) 10.68* (0.110) June temperature July temperature Average of June & July temperatures Rodent abundance 0.23 (0.220) 0.25 (0.125) 0.29 (0.130) 0.39 (0.256) Juvenile proportion Nesting success Rodent abundance June temperature (1950­2003) July temperature (1950­2003) 0.51 (0.024) 0.01 (0.667) 0.02 (0.322) 0.02 (0.015) 0.02 (0.026) Curlew Sandpiper 1.72 (0.117) 6.30 (0.001) 3.50 (0.024) 9.52 (0.168) 0.14 (0.194) 0.18 (0.155) 0.22 (0.099) 0.40 (0.211) 0.32 (0.088) 0.02 (0.500) 0.01 (0.650) 0.003 (0.778) 0.01 (0.183) Species Sharp-tailed Sandpiper 2.10 (0.14) 1.95 (0.066) 3.16 (0.032) 7.35 (0.016) 0.08 (0.534) 0.17 (0.086) 0.24 (0.099) 0.33 (0.369) 0.58 (0.019) 0.03 (0.503) 0.04 (0.195) 0.001 (0.939) 0.03 (0.020) Ruddy Turnstone 6.78 (0.40) 11.71 (0.018) 14.01 (0.045) 16.52 (0.170) 0.44 (0.182) 0.28 (0.038) 0.41 (0.041) 0.62 (0.073) -0.77 (0.562) 0.004 (0.916) 0.04 (0.092) 0.01 (0.120) 0.03 (0.001)

Response variable: juvenile proportion

Response variable: nesting success

Linear trends with year

*

The effect of rodent abundance on proportion of juveniles increased to 24.3 (P<0.003) after removal of a single apparent outlier in 2000 from the data set.

smaller (­0.34). Variation in the proportions of juveniles in the latter species was accounted for by PC2 which explained 26.6% of the total variance (loading 0.84 for the Sharp-tailed Sandpiper, and loadings in the range ­0.40 to +0.39 for the other three species). PC1 extracted from the eight environmental variables explained 62.8% of their total variance (loadings in the range 72.1 to 83.6). PC2 explained 24.4% of the total variance, and separated temperature variables (loadings >0.25) from variables of rodent abundance (loadings <­0.45). There is a fairly good linear relationship between PC1 extracted from data on juvenile proportions and corresponding to wader breeding performance, and PC1 extracted from environmental variables on the breeding grounds (Fig. 2), and this is also statistically significant (P<0.05, Sr=0.621).

Trends in environmental factors in Siberia and the proportions of juveniles in south-eastern Australia Mean July temperatures increased significantly during the period 1950-2003 at a rate of 0.017-0.029°C per year across the breeding ranges of all species except Curlew Sandpiper, while mean June temperatures increased significantly only in the range of the Red-necked Stint (Table 2). To allow comparison with the trends in breeding performance, we analyzed trends in July temperatures during the periods for which data on juvenile proportions were available for each of the four species. This analysis yielded a highly significant (P<0.003) increasing trend (at a rate of 0.053°C per year) across the breeding range of the Red-necked Stint, and a marginally significant (P=0.057) increasing trend (at a rate of 0.1°C per year) across the breeding range of the Ruddy Turnstone.

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Fig. 2. Environmental factors within the breeding ranges of four species of waders in eastern Siberia (PC(1)-environment) and the percentage of juveniles on the wintering grounds in south-eastern Australia (PC(1)-juveniles).

Fig. 1. Percentage of juveniles in four species of waders in south-eastern Australia in relation to deviations in July temperature and rodent abundance on the breeding grounds in eastern Siberia.

In south-eastern Australia, the proportion of juvenile Rednecked Stints and Sharp-tailed Sandpipers increased significantly (P<0.03) at an average rate of 0.51% and 0.58% per year, respectively. However, no significant trend was found in the period 1988-2003 either for rodent abundance or wader nesting success across the ranges of the four species, although in the case of the Ruddy Turnstone, the marginally significant value for the effect of year on rodent abundance suggested some tendency for increase. This was probably not confirmed because of the short time series and extremely high variation of the variable. DISCUSSION In this study, we have revealed the relationships between the breeding performance of four Arctic-breeding waders and

some environmental variables within their breeding ranges. The magnitude of the effect of June and July temperatures on breeding performance increased with an increase in the severity of environmental conditions. Thus, the Sharp-tailed Sandpiper (which shows an increase of only 3.2% in the proportion of juveniles per degree Centigrade rise in temperature) inhabits southern and typical tundra sub-zones (as defined by Chernov 1985), mires and floodplain habitats with abundant sedge vegetation. This corresponds to the least severe environment compared with that of the other three species. The effects of summer temperatures on the proportions of juvenile Rednecked Stint and Curlew Sandpiper were similar to one another (increasing by 6.4% and 6.3% per degree, respectively). The former species primarily inhabits upper slopes and watersheds in southern and typical tundra, while the latter inhabits slopes and watersheds in typical and Arctic tundra. The severity of the environment in the breeding habitat of these two species is probably, therefore, comparable. Finally, the Ruddy Turnstone inhabits typical and Arctic tundra, but in typical tundra, its breeding range is mostly restricted to the sea coast, where the possibility of adverse weather is considerably higher than in inland areas. The proportions of juvenile Red-necked Stint, Curlew Sandpiper and Ruddy Turnstone were more strongly correlated with July temperatures than June temperatures, while in the Sharp-tailed Sandpiper, the percentage of juveniles was correlated with June and July temperatures combined. A stronger effect of early summer (June) temperatures seems natural in a species with a southerly distribution. Given that chicks of Arctic waders hatch primarily in July, the greater influence of July temperatures on juvenile production in most species is probably explained by the higher sensitivity of the chicks to adverse weather conditions, especially recently hatched chicks, compared with clutches of eggs. The hypothesis that the

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primary impact of summer temperatures on breeding performance is via mortality of chicks is also supported by the virtual absence of any relationship between nesting success (up to hatching) and summer temperatures (the Ruddy Turnstone, which inhabits the most severe environment, being the only exception in this study). The absence of a significant relationship between wader nesting success across the breeding ranges and rodent abundance contradicts the predictions of the Roselaar-Summers preyswitching hypothesis. Our small sample size (16 seasons) and the low quality of data in many years, in particular the data on nesting success, could be a reason for this failure to demonstrate a statistical relationship between these two parameters. The relationship between proportions of juveniles and rodent abundance found in the Sharp-tailed Sandpiper and Red-necked Stint indicates that prey-switching is likely to affect productivity in at least some of the species under consideration, but the reasons why only these species showed a significant relationship are not as yet clear. The effects of rodent abundance on the nesting success of waders and production of juveniles are less pronounced than the effects of weather. We hypothesize that this is due to the abundance of alternative prey during the incubation period, while temperatures have most effect at the later stage of chick-rearing and thus have a more direct influence on the proportions of juveniles in the population. The correlation of environmental factors (temperatures and rodent abundance) within the ranges of different species of waders with each other is not surprising given the considerable overlap in the waders' ranges. The absence of a strong correlation in juvenile proportions among most species of waders indicates that the response of waders to similar environmental factors on their breeding grounds differs between species. In particular, the response of the Sharp-tailed Sandpiper to environmental factors differs from that of other species. This may be due to the smaller extent of the Sharp-tailed Sandpiper's breeding range and its more southerly distribution. Although there are differences between wader species in their response to the Arctic environment, there are also certain similarities. There were years (e.g. 1989 and 1992) in which the combined effects of low summer temperatures and low rodent abundance resulted in very poor breeding performance of all, or nearly all, species, while in other seasons (e.g. 1991) superb environmental conditions resulted in very high reproductive success in all species (Fig. 2). Deviations from this relationship require special consideration. Good environmental conditions in 2000 failed to ensure high breeding performance by waders (Fig. 2). This apparent anomaly was probably the result of an unusual pattern of July air temperatures in eastern Siberia in this year. The very high July temperatures responsible for the relatively high averages across eastern Siberia occurred mostly in eastern Yakutia and western Chukotka ­ an area which is not inhabited at high density by any of the species under consideration. Conversely, July was cold in western Yakutia, Taimyr and eastern Chukotka, and this probably resulted in the low breeding performance recorded in Australia. Thus, accounting for heterogeneity within the breeding range can greatly aid in the interpretation of results, but the required data have yet to be collated. In the four species under investigation, the most pronounced long-term increasing trend in juvenile proportions was in the

Red-necked Stint, and this corresponds to the most pronounced increasing trend in July temperatures, which occurred within the breeding range of this species. This tallies well with an increase in numbers of Red-necked Stints on the non-breeding grounds, as revealed by monitoring counts in Australia (Minton 2003), and gives persuading evidence of the long-term impact of processes developing on the breeding grounds on recruitment and numbers in wader populations. While all the evidence points to the positive effects of increasing summer temperatures on wader breeding performance, certain issues remain unclear and require further research to assess the possible impacts of changes in the environment on population productivity and numbers. The following research topics require further investigation: 1 Increasing summer temperatures might, at some point, reach a threshold after which their effect on wader breeding performance will no longer remain beneficial. For example, high summer temperatures could lead to increased dryness of habitats and an associated decrease in the availability of the soil invertebrates on which the waders feed. The consequences for populations of reaching this upper temperature threshold are not known, but could easily be dramatic. Trends in the breeding performance of the Curlew Sandpiper require thorough investigation. The Australian non-breeding population of this species has shown a major decline in numbers, with counts in some areas down to 25% of former levels (Minton 2003). Most of the decline has occurred since 1994 (Minton et al. 2002a). However, no evidence was discovered of any deterioration in environmental factors across the breeding range of the species during the present study, implying that stable values of the factors under investigation are not sufficient to support stable populations. It is likely, therefore, that other factors are responsible for the decline in the Curlew Sandpiper population, but what these factors are remains unknown. While summer temperatures affect productivity of all four species of waders to varying degrees, some species also respond to changes in rodent abundance. The reasons for the differences between species in their response to rodent abundance are unknown, as also are the effects of interactions of rodent abundance with temperature. It is also possible that the indirect effect of the lemming cycle on wader productivity differs in various parts of the Arctic, and may, for example, be especially pronounced on the Taimyr Peninsula (e.g. Underhill 1987, Underhill et al. 1989). This issue needs verification. The contribution of impacts away from the breeding grounds to changes in juvenile proportions are unknown. Staging sites of migrants in the East Asian-Australasian Flyway are subject to various threats due to intensive development in coastal areas. Studies of population processes in northern Siberia and Australia will hopefully help to interpret correctly those impacts to which birds are exposed on their migration routes.

2

3

4

ACKNOWLEDGEMENTS From 1988 to 1996, collection of data on the breeding grounds and data processing were carried out by the Working Group on Waders (Commonwealth of Independent States), while activi-

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ties in 1997-2004 were conducted within the framework of the ABBCS and with support from the International Wader Study Group, Working Group on Waders (CIS), the Government of The Netherlands, and Wetlands International. We would like to give our special thanks to the large number of people who contributed their data to the ABBCS over a period of 16 years, and all those who participated in the wader-catching activities of the Victorian Wader Study Group over a period of 26 years. Derek Scott provided valuable comments on the manuscript. REFERENCES Boyd, H. 1992. Arctic summer conditions and British Knot numbers: an exploratory analysis. Wader Study Group Bulletin 64 (Suppl.): 144-152. Boyd, H. & Piersma, T. 2001. Changing balance between survival and recruitment explains population trends in Red Knot Calidris canutus islandica wintering in Britain, 1969-1995. Ardea 89 (2): 301-317. Buhmann, M.D. 2003. Radial Basis Functions. Cambridge University Press, Cambridge. Chernov, Y.I. 1985. The Living Tundra. Cambridge University Press, Cambridge. Ganter, B. & Boyd, H. 2000. A tropical volcano, high predation pressure, and the breeding biology of Arctic Waterbirds: a circumpolar review of breeding failure in the summer of 1992. Arctic 53: 289-305. International Wader Study Group 2003. Waders are declining worldwide. Conclusions from the 2003 International Wader Study Group Conference, Cadiz, Spain. Wader Study Group Bulletin 101/102: 8-12. Lappo, E.G., Tomkovich, P.S. & Syroechkovski, E.E., Jr. In prep. The Atlas of the Breeding Waders of the Russian Arctic. MapInfo Corp. 1996. MapInfo Professional 4.12. (Computer software). Troy, New York. Mayfield, H.F. 1975. Suggestions for calculating nest success. Wilson Bulletin 87: 456-466. Minton, C. 2003. The importance of long-term monitoring of reproduction rates in waders. Wader Study Group Bulletin 100: 178-182. Minton, C., Jessop, R. & Hassell, C. 2000. 1999 Arctic breeding success from an Australian perspective. Arctic Birds: an international breeding conditions survey newsletter 2: 19-20. Minton, C., Jessop, R., Collins, P. & Hassell, C. 2001. Indications of year 2000 Arctic breeding success based on the percentage of first year birds in Australia in the 2000/01 austral summer. Arctic Birds: Newsletter of International Breeding Conditions Survey 3: 31-32. Minton, C., Jessop, R. & Collins, P. 2002a. Variations in apparent annual breeding success of Red-necked Stints and Curlew Sandpipers between 1991 and 2001. Arctic Birds: Newsletter of International Breeding Conditions Survey 4: 43-45. Minton, C., Jessop, R., Collins, P. & Hassell, C. 2002b. Year 2001 Arctic breeding success, as measured by the percentage of first year birds in wader populations in Australia in the 2001/02 austral summer. Arctic Birds: Newsletter of International Breeding Conditions Survey 4: 39-42.

Minton, C., Jessop, R. & Collins, P. 2003a. Sanderling and Ruddy Turnstone breeding success between 1989 and 2002 based on data from SE Australia. Arctic Birds: Newsletter of International Breeding Conditions Survey 5: 48-50. Minton, C., Jessop, R., Collins, P. & Hassell, C. 2003b. Arctic breeding success in 2002, based on the percentage of first year birds in wader populations in Australia in the 2002/03 austral summer. Arctic Birds: Newsletter of International Breeding Conditions Survey 5: 45-47. Minton, C., Jessop, R., Collins, P., Sitters, H. & Hassell, C. 2004. Arctic breeding success in 2003, based on juvenile ratios in waders in Australia in the 2003/2004 austral summer. Arctic Birds: Newsletter of the International Breeding Conditions Survey 6: 39-42. Rehfisch, M.M. & Crick, H.Q.P. 2003. Predicting the impact of climatic change on Arctic-breeding waders. Wader Study Group Bulletin 100: 86-95. Roselaar, C.S. 1979. Fluctuaties in aantallen krombekstrandlopers Calidris ferruginea. Watervogels 4: 202-210. SPSS Inc. 1997. SYSTAT 7.01 for Windows. (Computer software). Chicago, IL. Summers, R.W. & Underhill, L.G. 1987. Factors related to breeding production of Brent Geese Branta b. bernicla and waders (Charadrii) on the Taimyr Peninsular. Bird Study 34: 161-171. Stroud, D.A., Baker, A., Blanco, D.E., Davidson, N.C., Delany, S., Ganter, B., Gill, R., GonzÀlez, P., Haanstra, L., Morrison, R.I.G., Piersma, T., Scott, D.A., Thorup, O., West, R., Wilson, J. & ZÆckler, C. (on behalf of the International Wader Study Group). 2006. The conservation and population status of the world's waders at the turn of the millennium. Waterbirds around the world. G.C. Boere, C.A. Galbraith & D.A. Stroud (Eds.), The Stationery Office, Edinburgh, UK. 643-648. Underhill, L.G. 1987. Changes in the age structure of Curlew Sandpiper populations at Langebaan Lagoon, South Africa, in relation to lemming cycles in Siberia. Transactions of The Royal Society of South Africa 46(3): 209-214. Underhill, L.G., Waltner, M. & Summers, R.W. 1989. Threeyear cycles in breeding productivity of Knots Calidris canutus wintering in southern Africa suggest Taimyr Peninsula provenance. Bird Study 36: 83-87. ZÆckler, C. & Lysenko, I. 2000. Water Birds on the edge: First circumpolar assessment of Climate Change impact on Arctic water birds. WCMC Biodiversity Series No. 11. http://www.unepwcmc.or g/climate/w aterbirds/ WaterBirds_part1.pdf. ZÆckler, C., Delany, S. & Hagemeijer, W. 2003. Wader populations are declining ­ how will we elucidate the reasons? Wader Study Group Bulletin 100: 202-211. WEB-SITES ABBCS database: http://arctic.ss.msu.ru/birdspec/. Arctic Bird Library: UNEP World Conservation Monitoring Centre: http://www.unepwcmc.org/arctic/birds/ArcticBird Library.htm. World Meteorological Organization: National Climatic Data Center, USA: http://www.ncdc.noaa.gov/ol/climate/climatere sources.html.

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