original article an evaluation of ˜ve agricultural habitat

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Ornithol Sci 18: 3 – 16 (2019)

ORIGINAL ARTICLE

An evaluation of �ve agricultural habitat types for openland birds: abandoned farmland can have comparative values to undisturbed wetland

Munehiro KITAZAWA1,#, Yuichi YAMAURA2,3, Masayuki SENZAKI1,4, Kazuhiro KAWAMURA1, Masashi HANIOKA1 and Futoshi NAKAMURA1

1 Graduate School of Agriculture, Hokkaido University, Nishi 9, Kita 9, Kita-ku, Sapporo, Hokkaido 060–8589, Japan

2 Department of Forest Vegetation, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305–8687, Japan

3 Fenner School of Environment and Society, Australian National University, Canberra, ACT, 2601, Australia4 Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, 16–2,

Onogawa, Tsukuba, Ibaraki 305–8506, Japan

Abstract Populations of birds inhabiting wetlands and grasslands are decreasing globally due to farmland expansion and subsequent agricultural intensification. In addition to conserving natural habitats, managing cultivated farmland and abandoned farmland are likely to be important future conservation measures; however, their relative suitability as avian habitat remains understudied. In this study, we evaluated five habitat types (wetland, pasture, cropland, abandoned farmland, and solar power plant) for openland birds in an agricultural landscape in central Hokkaido, northern Japan. Abandoned farmlands had bird species richness and total bird abundance val-ues similar to those of wetlands. These values were generally higher in abandoned farmlands and wetlands than in croplands, pastures, and solar power plants. The per pair reproductive success of Stejneger’s Stonechat Saxicola stejnegeri and the amount of its prey (arthropods) did not differ among the five habitat types. Three species (Black-browed Reed Warbler Acrocephalus bistrigiceps, Common Reed Bunting Emberiza schoeniclus, and Japanese Bush Warbler Cettia diphone) arrived earlier in wetlands than in other habitat types. These results suggest that, although protecting the remaining wetlands is of prime importance for the conservation of openland birds in agricultural landscapes, valuing and managing abandoned farmlands would be a promising alternative.

Key words First arrival date, Food abundance, Hokkaido, Reproductive success, Stejneger’s Stonechat

ORNITHOLOGICALSCIENCE

© The Ornithological Society of Japan 2019

(Received 11 November 2017; Accepted 18 May 2018)# Corresponding author, E-mail: [email protected]

Conserving bird species that inhabit wetlands or grasslands (hereafter referred to as openland birds) is now widely regarded as an urgent issue, mainly due to the drastic replacement of their original habitats with farmland and subsequent agricultural intensification (Finlayson & Spiers 1999; Millennium Ecosystem Assessment 2003; Ceballos et al. 2010). Although preserving and restoring original avian habitats is clearly important for bird conservation, this approach inevitably requires considerable social and financial

investment (Main et al. 1999; Holzkämper & Seppelt 2007). Previous studies have shown that many open-land bird species use various habitat types including cultivated land. For example, pastures and croplands in European agricultural landscapes harbor diverse openland bird species (Robinson et al. 2001; Batáry et al. 2010). In Asia, rice paddies serve as important habitats for openland birds (Maeda 2001; Wood et al. 2010). Therefore, valuing and managing cultivated habitats in agricultural landscapes may be an option alongside conservation of original habitats.

Globally, farmlands are being rapidly abandoned (Ramankutty & Foley 1999; Alcantara et al. 2013),

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potentially reducing suitable habitat for many open-land birds (MacDonald et al. 2000; Sanderson et al. 2013). However, although many existing studies have emphasized the negative effects of farmland aban-donment (Queiroz et al. 2014), it is noted that some papers have reported the importance of abandoned farmlands as habitat for openland birds (Kamp et al. 2011; Katayama et al. 2015). For example, in east-ern Hokkaido, northern Japan, Hanioka et al. (2018) compared the habitat suitability of wetland and aban-doned farmland for birds. In abandoned farmland, many openland bird species had larger than 1/2 densities of wetlands. Globally, solar power plants are being increasingly constructed in agricultural landscapes. Little is known about the environmental impacts of these developments (Turney & Fthenakis 2011; Gibson et al. 2017). Habitat suitability for openland birds thus varies for each habitat type, and recent land use changes in agricultural landscapes may also affect the diversity of openland birds; nev-ertheless, the relative suitability of various habitat types in agricultural landscapes remains unclear.

Avian habitats in agricultural landscapes have been evaluated according to bird species richness and bird abundance (e.g., Bengtsson et al. 2005; Flohre et al. 2011). However, bird abundance does not always indicate reproductive success (van Horne 1983; Vickery et al. 1992), suggesting that habitat evalu-ation based solely on bird species richness or bird abundance may fail to identify habitats with high reproductive success (Purvis et al. 2000; Kristan 2003). This is particularly important in agricultural landscapes because human intervention can disrupt the links between traditional habitat selection cues and habitat quality (Schlaepfer et al. 2002; Bock & Jones 2004). Thus it is desirable to examine habitat suitability in agricultural landscapes not only based on bird species richness and bird abundance, but also using other metrics such as reproductive success.

The objective of this study was to evaluate five habitat types (wetland, abandoned farmland, pasture, cropland, and solar power plant) for openland birds in an agricultural landscape, in central Hokkaido, based on bird species richness, bird abundance, reproduc-tive success, first arrival date, and prey amount. First arrival date, which is the date when the first indi-vidual of a species is observed (Goodenough et al. 2014), is a reasonable metric of habitat suitability for migratory birds (Sergio & Newton 2003; Robertson & Hutto 2006) because individuals arriving early can occupy territories where reproduction was previously

successful (Cooper et al. 2011) and mates were easily found (Lozano et al. 1996). Prey amount is another important metric because it has substantial impacts on bird abundance and reproductive success (Newton 1998).

MATERIALS AND METHODS

1) Study areaWe conducted the field survey on the Yufutsu Plain,

located in central Hokkaido, northern Japan (42°38 ́N, 141°46 ́E). In the early 1900s, this region was cov-ered with approximately 8,000 ha of wetlands (GSI 2000). From the 1950s to the 1970s, approximately 80% of these wetlands were converted into farmland, urban, and industrial areas (GSI 2000). Only a few fragmented and isolated wetland patches remain (Fig. 1). Some croplands have been abandoned since 1969 (Wild Bird Society of Japan 2006), and abandoned farmlands now occupy approximately 700 ha of the Yufutsu Plain (Kitazawa Munehiro personal observa-tion). The area occupied by solar power plants in this region has been increasing since the 2010s and is cur-rently estimated at approximately 390 ha (Kitazawa Munehiro personal observation).

2) Habitats in the agricultural landscapeWe surveyed openland birds in wetlands, aban-

doned farmlands, pastures, croplands, and solar power plants within the study area. We defined a wetland as an area characterized by the Common Reed Phragmites australis and Bluejoint Reedgrass Calamagrostis langsdorffii, both of which are domi-nant wet grass species in this area. Abandoned farm-land was defined as land that had once been cropped and was abandoned more than 10 years ago. Japanese Silver Grass Miscanthus sinensis was the dominant species in abandoned farmland. In some plots, Com-mon Reed and Japanese Alder Alnus japonica growth was patchy. In pastures, grass was mown from late June to mid July. The main crops in the croplands were leaf vegetables, corn, and soybeans. Common Reed, Japanese Silver Grass, and Japanese Butterbur Petasites japonicus were the dominant species in the field margins of pastures and croplands. The width of the margins was 15.2±8.6 m (mean±SD). We defined solar power plants as land where solar panels were arranged in parallel rows at equal intervals. In the solar power plants that we surveyed, solar panels (1.6 m2 per panel) occupied 50–60% of the area, and the remainder was covered by grass vegetation

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Agricultural habitats for openland birds

(Poaceae or Cyperaceae), which was cut from early June to early July.

3) Establishment of census plotsWe established 25 census plots in the five focal

habitat types (five in wetlands and abandoned farm-lands, six in pastures and croplands, and three in solar power plants; Fig. 2). All census plots were established randomly on the condition that plots were spaced at least 500 m apart and within com-

Fig. 1. Spatial distribution of four habitat types (wetland, natural grassland, farmland, and forest) of part of the Yufutsu Plain in 1919 (a), 1953 (b), and 2006 (c). Classification and distribution of habitat types are based on 1:50,000–scale topographical maps provided by the Geographical Survey Institute of Japan (http://mapps.gsi.go.jp/maplibSearch.do#1). Farmland includes pasture, cropland, and rice paddy. Although abandoned farmland is not identified, but included in wetland or grassland, dynamics of habitat types and the appearance of abandoned farmland are shown. For example, in the enlarged map shown in black squares, wetlands were converted into farmland from 1919 to 1953, and then partly changed into natural grassland from 1953 to 2006, meaning that these farms were abandoned.

Fig. 2. Study area and distribution of the census plots. We established 25 census plots (open circles): wetlands (five plots), abandoned farmland (five plots), pasture (six plots), cropland (six plots), and solar power plants (three plots). One solar power plant plot is not shown, because the landowner requested anonymity. Census plots were spaced at least 500 m apart.

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partments (mean±SD: 59.9±68.4 ha) consisting of a single focal habitat type. Using this method, we prevented double counting of individual birds (Ralph et al. 1993) and avoided recording birds that breed in different habitat types near the census plots (i.e., spill-over effect: Barlow et al. 2007). Each census plot was 300 m long×100 m wide (3 ha). The survey line ran through the center of each plot. We estab-lished the plots using QGIS Desktop 2.16.3 (QGIS Development Team 2016).

4) Bird surveysFrom May 15 to July 16, 2016, we slowly walked

the survey lines nine times and recorded individual birds seen or heard, species, sex, and breeding behav-ior (e.g., singing, nest building, or carrying food to nestlings) within the plots (i.e., territory mapping: Bibby et al. 2000). Survey times were from dawn to 1000, and from 1700 to dusk, when activity and song output of birds was greatest (Bibby et al. 2000). Avoiding rain, fog, or heavy wind (>4 m/s), we walked each line at 7-day intervals during the sur-vey period. To avoid survey time bias, we visited each plot at different times. We drew the territories of birds that were recorded at least twice (Bibby et al. 2000) during this period within the range of their known territory sizes (e.g., Nakamura et al. 1968; Haneda & Okabe 1970; Cramp 1977–1994; Higuchi et al. 1997). We then obtained the number of ter-ritories and species within a census plot. We defined bird abundance as the number of territories. We also recorded the approximate locations of nests within a plot as frequently as possible. We recorded any fledg-lings found, and defined the number of fledglings as a metric of reproductive success.

To record the first arrival date of each species, we conducted a first arrival date survey 14 times from April 10 to May 28, 2016. We slowly walked the survey lines used for the territory mapping sur-vey from dawn until dusk. When a bird species was detected for the first time during this period, its date was treated as the first arrival date. We required three days to visit all census plots and defined this as the survey period (Appendix 1). When we did not finish surveys in all plots within three days, we extended the survey period to 4–8 days (adding 1–5 days). Throughout the period of the first arrival date survey, vegetation was not very dense in each habitat type (i.e., resultant detectability was sufficiently high; cf. Yamaura et al. 2016). The focal migrants through-out the first arrival date survey, Stejneger’s Stone-

chat Saxicola stejnegeri and Chestnut-eared Bunting Emberiza fucata, were easily detectable (Yamashina 1941), because they tended to sing or perch on top of shrubs. Therefore, we deemed bird detectability as stable regardless of time of day or habitat type.

5) Prey amount surveyAlmost all openland birds on the Yufutsu Plain

feed on arthropods during the breeding season (Yamashina 1941). Therefore, we surveyed the amount of arthropods (prey) present using sweep-net sampling. Sampling was performed six times at each plot at intervals of 12 to 16 days from May 15 to August 3, 2016, and was completed between 0800 and 1600 under good weather conditions (sunshine, wind speed<4 m/s). We randomly established two 20 m long survey lines within each census plot. In croplands, we surveyed in field margins to ensure that we did not disturb farm work. We performed one stroke per metre walked along each survey line. Arthropod samples were immediately conserved in ethyl acetate. We later identified arthropods to order (Aranea, Coleoptera, Diptera, Lepidoptera, Odonata, Orthoptera, Hemiptera, Hymenoptera, and Plecop-tera). Arthropods were dried in an oven for 24 h at 60°C and weighed with a precision balance to the nearest 0.001 g. We calculated the summed values of all arthropods separately for each plot from May 15 to August 3, by which time nearly all openland birds had arrived on the Yufutsu Plain. Hereafter, we used these summed values in our analyses.

6) ComparisonsamongthefivehabitatsWe compared bird species richness, bird abun-

dance (i.e., number of territories) for each species and for all species (total bird abundance), and repro-ductive success per plot and per pair using general-ized linear mixed models (GLMMs) with Poisson error and log link functions. Plot identity (ID) was treated as a random intercept. For bird abundance for each species, the models including habitat types where no individuals occurred did not converge; we thus excluded the data of these habitat types from the analyses. We used generalized linear models (GLMs) with Gaussian error for first arrival date and prey amount. For first arrival date, we only analyzed spe-cies for which we had confirmed breeding behavior (e.g., singing, nest building, or carrying food to nest-lings) in more than one plot for a given habitat type. For this analysis, we used the median of the survey period converted to Julian date. For example, the first

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arrival date recorded during 13–15 April was 104 (April 14). As the final species did not arrive until May 28 (e.g., Middendorff’s Grasshopper Warbler Locustella ochotensis), we also used the results of our territory mapping survey between May 29 and June 18 as the results of the first arrival date (Appendix 1). Consequently, we analyzed first arrival dates from April 10 to June 18. We analyzed prey amounts by comparing the dried prey amount (summed values) among habitat types. Five habitat types were used as a single categorical explanatory variable, which was coded using the cell means method (i.e., omitting the intercept: Kéry 2010). When the 95% confidence intervals did not overlap between two habitat catego-ries, we interpreted the differences as significant.

7) Comparison of effects of habitat types, preyamount,andfirstarrivaldate

Previous studies have shown that both habitat type and prey amount can limit the abundance and repro-ductive success of birds (Newton 1998). Moreover, first arrival date can be related to reproductive success (Smith & Moore 2003; Cooper et al. 2011). There-fore, we compared the effects of habitat type and prey amount on total bird abundance and bird spe-cies richness. We also compared the effects of habitat type and prey amount/first arrival date on reproduc-tive success per plot. For total bird abundance and bird species richness, we built a null model (with no explanatory variables except for the intercept) and two models using prey amount or habitat type as the explanatory variable. For reproductive success per plot, we built a null model and three models using prey amount, first arrival date, or habitat type as the explanatory variable. We again used Poisson GLMMs (with plot ID as the random intercept) for these analyses. We quantified the explanatory power of individual models using the proportion of devi-ance explained: ((null deviance) – (residual deviance of each model)) / (null deviance). Analyses were performed using the lme4 package, version 1.1–12 (Bates et al. 2015), in the R software, version 3.3.1 (R Development Core Team 2016).

RESULTS

During the bird surveys, we recorded 17 species and 287 bird territories for which we confirmed breeding behavior (e.g., singing, nest building, or carrying food to nestlings). All of the species that we recorded were openland species (i.e., no forest

species: Appendix 2). The four dominant species were Black-browed Reed Warbler Acrocephalus bis-trigiceps (73 territories), Stejneger’s Stonechat (40 territories), Chestnut-eared Bunting (37 territories), and Lanceolated Warbler Locustella lanceolata (32 territories). The abundance of the remaining species was lower than 30 each. For most species, territories were confirmed by completion of the sixth territory mapping survey, with the exception of the Black-browed Reed Warbler (seventh survey), Chestnut-eared Bunting (eighth survey), and Japanese Bush Warbler Cettia diphone (eighth survey).

1) Bird species richness and bird abundanceBird species richness was higher in abandoned

farmland than in pasture, cropland, or solar power plants (Fig. 3a). The differences among the other pairs were not significant. Total bird abundance in wetlands and abandoned farmland was greater than in cropland, and also tended to be (non-significantly) greater than in pasture and solar power plants (Fig. 3b). Although habitat type was a significant predic-tor of total bird abundance and bird species richness, prey amount had no significant effect on either of these metrics (Table 1).

We compared the abundance of 12 openland bird species recorded in multiple habitat types (Appendix 3). Lanceolated Warbler abundance was significantly higher in wetlands and abandoned farmland com-pared to pasture (Appendix 3h). Stejneger’s Stonechat abundance in abandoned farmland and Black-browed Reed Warbler abundance in wetlands tended to be higher compared to cropland (Appendix 3a, c). The abundance of Chestnut-eared Buntings in pastures tended to be higher than in wetlands (Appendix 3b). Among the remaining eight species, habitat type had no significant or distinct effect on their abundance among the habitat types they occupied, although five species did not occur in pastures or solar power plants, and seven species did not occur in croplands (Appendix 3). Besides the 12 species above, four spe-cies occurred only in abandoned farmland (Appendix 3m-p), while the Brown Shrike Lanius cristatus was recorded only in pastures (Appendix 3q).

2) Reproductive successStejneger’s Stonechat was the only species for

which we could record the number of fledglings in more than one habitat type. The reproductive success of Stejneger’s Stonechat per plot and per pair did not differ between the five habitat types (Fig. 3c, d),

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although per-plot reproductive success in cropland was comparatively lower than in the other habitat types. When comparing the effects of habitat types, prey amount, and first arrival date on the per-plot

reproductive success of this species, the model with first arrival date had the highest explanatory power and the lowest AIC of the three models (Table 1).

Fig. 3. Bird species richness (a), total bird abundance (b), reproductive success (RS) of Stejneger’s Stonechats per plot (c) per pair (d), prey amount (e). Black circles indicate model-predicted values of each metric; open circles indicate measured values; bars indicate 95% CIs (confidence intervals). W: wetlands; A: abandoned farmlands; P: pastures; C: croplands; S: solar power plants.

Table 1. Outputs of models with different hypotheses. For the analysis with total bird abundance or bird species richness as the response variable, we compared models with habitat type or prey amount as the single explanatory variable. For the analysis with the reproductive success of Stejneger’s Stonechats per plot as the response variable, we compared models with habitat type, first arrival date, or prey amount as the single explanatory variable.

Models Coefficient SE P Intercept AIC Deviance explained

Total bird abundance Habitat type model ― ― <0.001# ― 157.3 0.14 Prey amount model 0.30 0.38 0.44 1.97 173.5 0.004

Bird species richness Habitat type model ― ― 0.003# ― 111.4 0.14 Prey amount model –0.13 0.25 0.61 1.72 121.5 0.003

Reproductive success per plot Habitat type model ― ― 0.16# ― 111.9 0.06 First arrival date model –0.13 0.08 0.09 1.42 103.1 0.09 Prey amount model 1.00 0.66 0.12 –0.46 110.1 0.02

SE: Standard error; P: p-value; AIC: Akaike’s information criterion.―: Results not shown because habitat type models have five different coefficients/standard error values/intercepts.#: Results of likelihood ratio test between the null and habitat type models because habitat type models have five different coef-ficients.

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3) First arrival date and prey amountWe analyzed 14 species for which we confirmed

breeding behavior in more than one plot for a given habitat type (Appendix 2). We found differences in the first arrival dates among habitat types for three

species (Fig. 4). The Black-browed Reed Warbler arrived earlier in wetlands than in abandoned farm-land and cropland (Fig. 4c). The Common Reed Bun-ting Emberiza schoeniclus arrived earlier in wetlands and solar power plants than in cropland (Fig. 4d).

Fig. 4. First arrival dates. Black circles indicate model-predicted values of first arrival dates; open circles indicate measured values; bars indicate 95% CIs. W: wetlands; A: abandoned farmland; P: pasture; C: cropland; S: solar power plants. Model-predicted values and their 95% CIs were not estimated for habitat types where the species occurred in only one plot.

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The Japanese Bush Warbler arrived earlier in wet-lands than in abandoned farmland (Fig. 4i).

During the prey amount survey, we recorded a total of 19.3 g of arthropod biomass (Orthoptera: 0.56 g, Hemiptera: 4.6 g, Coleoptera: 3.2 g, Lepidoptera: 2.4 g, Diptera: 2.7 g, Hymenoptera: 3.4 g, Odonata: 0.1 g, and Aranea: 2.3 g) and found no differences in prey amount among habitat types (Fig. 3e).

DISCUSSION

1) Bird species richness and bird abundanceBird species richness was higher in abandoned

farmland than in pasture, cropland, or solar power plants (Fig. 3a). This result can be explained by the high tree coverage and the presence of species, such as the Grey-capped Greenfinch Chloris sinica, and the Long-tailed Rosefinch Uragus sibiricus (Kiyosu 1952, Appendix 3n, o), nesting in trees (Suárez-Seoane et al. 2002) in abandoned farmland. Addi-tionally, total bird abundance tended to be higher in wetlands and abandoned farmland than in the other habitat types (Fig. 3b). These results can be explained by the large coverage of wetland vegetation (e.g., Common Reed or sedges) and the dominance of several bird species nesting specifically on this type of vegetation (e.g., Black-browed Reed Warbler or Lanceolated Warbler; Kennerley & Pearson 2010) in these two habitat types (Appendix 3c, h). From the perspectives of bird species richness and total bird abundance, our results suggest that both natural wet-lands and abandoned farmland provide more suitable habitats for openland birds than do the other habitat types that we examined.

2) Evaluation by reproductive successAlthough we attempted to survey reproductive suc-

cess for all species, we were only able to obtain the necessary data for Stejneger’s Stonechat due to the difficulty of observing the breeding behavior of the other species. The number of fledglings per plot and per pair did not differ significantly among the five habitat types (Fig. 3c, d), although per-plot reproduc-tive success in cropland was relatively lower than that in other habitat types (Fig. 3c). This was because there were fewer breeding pairs of this species in cropland (Appendix 3a).

The reproductive success of grassland birds in pas-tures suffers from management intensification (e.g., earlier and more frequent mowing or increased appli-cation of fertilizers: Grüebler et al. 2008; Strebel et

al. 2015). However, in this study, we found no clear impacts of pasture mowing on the productivity of Stejneger’s Stonechat. We identified eight nests in pasture plots. Two of these were likely within mowed areas and the others were likely in field margins. Therefore, the time lag between mowing and fledg-ing may explain this result. In census plots, pastures were mown from the end of June to the middle of July (Kitazawa Munehiro personal observation). All Stejneger’s Stonechats in the census plots fledged between early June and early July, suggesting that mowing time rarely overlapped with fledging time, although the detrimental impacts of mowing may be clearer in other species or years (e.g., Santangeli et al. 2018).

3) EvaluationbyfirstarrivaldateTo our knowledge, no study has examined whether

first arrival date differs among species or habitat types in agricultural landscapes. We analyzed the first arrival dates of 14 species and showed that only three species arrived earlier in wetlands than in other habitat types. Because earlier arrival can represent higher productivity (Smith & Moore 2003; Cooper et al. 2011), these results suggest that wetlands may be superior habitats for these three species. The repro-ductive success of Stejneger’s Stonechat per plot also tended to be higher in plots where it arrived earlier (Table 1). The lack of difference in first arrival date among habitat types for the other 11 species may be attributable to our coarse survey interval (3–8 days). It may be possible to detect differences in the first arrival dates of these species if daily censuses were conducted, as has been done in previous studies (e.g., Lozano et al. 1996; Cooper et al. 2011).

4) Evaluation by prey amountAlong with agricultural intensification, declines

in the availability of prey such as invertebrates can limit avian abundance (Wilson et al. 1999) and repro-ductive success (Newton 1998) among birds living in agricultural landscapes. However, in this study, prey amount had no effect on bird species richness or total bird abundance (however, note that we surveyed only field margins in croplands), and did not differ among habitat types. Although we also compared the summed values of individual families among the five habitat types, in seven of eight families (with the exception of the Diptera), the amount of prey did not differ (results not shown). Thus, bird abundance in our study area is presumed to have been determined

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by other factors such as shelter, space, or the pres-ence of other species (Hildén 1965; Fuller 2012).

CONCLUSION

Overall, wetlands seemed to be the most impor-tant habitats for openland birds in terms of the five metrics we assessed, which suggests that protecting remnant wetlands is the highest priority for avian conservation in agricultural landscapes. However, the area occupied by abandoned farmland is expanding rapidly, both in Japan and globally. According to the five metrics we used in our evaluation, in terms of avian species richness and total bird abundance, the suitability of abandoned farmland was comparable to that of wetlands. However, the low number of repli-cates per habitat type in our study makes it difficult to generalize from our findings. Nevertheless, previ-ous studies in eastern Hokkaido have also suggested that abandoned farmland can serve as suitable habi-tat for openland bird species (Hanioka et al. 2018), which is consistent with our findings. Therefore, at least in Hokkaido, valuing and managing this rapidly expanding habitat type can also provide opportunities for the conservation of openland birds.

ACKNOWLEDGMENTS

We thank Tomatoh, Inc., anonymous solar power plant companies, the Tomakomai Experimental Forest (TOEF), and the citizens of Atsuma and Mukawa for their cooperation with our field survey. Thoughtful comments by J. Kamp and an anonymous reviewer helped to improve the manuscript. Finally, we thank the members of the Forest Ecosystem Management Laboratory of Hokkaido University for their helpful discussions. This study was supported by the Envi-ronmental Research and Technology Development Fund (4-1504 and 4-1805) of the Ministry of the Environment of Japan.

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Appendix 1. Survey periods and duration of first arrival date survey and territory mapping survey.

First arrival date survey Territory mapping surveyNote

Survey periods Duration Survey periods Duration

4/10–4/12 3

4/13–4/15 3

4/16–4/18 3

4/19–4/22 4 Extended by one day due to heavy rain

4/23–4/25 3

4/26–4/28 3

4/29–5/1 3

5/2–5/4 3

5/5–5/12 8 Extended by five days due to bad weather

5/13–5/15 3

5/16–5/18 35/15–5/21 7 Conducted both territory mapping survey and first arrival date survey*

5/19–5/21 3

5/22–5/24 35/22–5/28 7 Conducted both territory mapping survey and first arrival date survey*

and extended first arrival date survey period by one day due to rain5/25–5/28 4

5/29–6/4 7 Conducted territory mapping survey only; results were also used for the analysis of first arrival date



6/19–6/25 7 Excluded from the analysis of first arrival date#




*: Once we had conducted a territory mapping survey in a plot during this period, we did not survey the plot as part of the first arrival date survey. This is because we could obtain sufficient data to record first arrival date by the territory mapping survey. That is, in such a case, the results of the territory mapping survey were also treated as the results of the first arrival date survey.#: All openland birds considered to have arrived, hence we excluded this period.In total, the first arrival date survey was conducted 14 times, while the territory mapping survey was conducted nine times.

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Appendix 2. Species surveyed.

English names Scientific names First arrival date

Stejneger’s Stonechat Saxicola stejnegeri AnalyzedChestnut-eared Bunting Emberiza fucata AnalyzedBlack-browed Reed Warbler Acrocephalus bistrigiceps AnalyzedCommon Reed Bunting Emberiza schoeniclus AnalyzedBlack-faced Bunting Emberiza spodocephala AnalyzedSkylark Alauda arvensis AnalyzedMiddendorff’s Grasshopper Warbler Locustella ochotensis AnalyzedLanceolated Warbler Locustella lanceolata AnalyzedJapanese Bush Warbler Cettia diphone AnalyzedSiberian Rubythroat Luscinia calliope AnalyzedBull-headed Shrike Lanius bucephalus AnalyzedGray’s Grasshopper Warbler Locustella fasciolata RecordedLatham’s Snipe Gallinago hardwickii AnalyzedLong-tailed Rosefinch Uragus sibiricus AnalyzedGrey-capped Greenfinch Chloris sinica AnalyzedBrown-cheeked Rail Rallus aquaticus RecordedBrown Shrike Lanius cristatus Recorded

For first arrival date, we only analyzed the species for which we confirmed breeding behavior in more than one plot for a given habitat type. Therefore, we did not analyze Gray’s Grasshopper Warbler, Brown-cheeked Rail, or Brown Shrike (indicated in ‘Recorded’).

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Appendix 3. Abundance of each species.Black circles indicate model-predicted values of the number of territories; open circles indicate measured values; bars indicate 95% CIs. W: wetlands; A: abandoned farmland; P: pasture; C: cropland; S: solar power plants. We could not show the model-predicted values and 95% CIs of some or all habitat types in (d)-(q). This is because the models including habitat types where no individuals occurred (e.g., wetlands in (f)) did not converge, hence we excluded the data of these habitat types from the analyses. However, the model for the abundance of Japanese Bush Warbler (i.e., (i)) did not converge. We could not obtain 95% CIs for the abundance of Brown-cheeked Rail or Brown Shrike since they only occurred in single plots (i.e., (p), (q)).

original article an evaluation of ˜ve agricultural habitat

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