Shifts in bird ranges and conservation priorities in China under climate change

observation bias, reporting bias, and geographic bias due to lack of a standardized field proto- col [40], these useful large-scale and full-taxon data can be used with data cleaning and correc- tion [41]. In fact, for modeling range shifts under climate change scenarios, occurrence data from birdwatching is the only choice in China. In this paper, we collected 161,630 localities of 1,111 bird species in China from Bird Report as occurrence data and applied the dataset to MaxEnt [42] to predict distribution range maps of each species both at present and in 2070. We also mapped the conservation priorities of birds in China and the corresponding shifts in different climate scenarios using the Zonation planning model based on these maps and the percentage change of each species range. We aim to understand the pattern and direction of each species range shift, as well as variations in bird hotspots, to provide insights for future conservation priorities. 2. Material and methods 2.1 Data sources We collected occurrence (presence-only) data for birds from a citizen science project, Bird Report (http://www.birdreport.cn/). Bird Report is the largest nationwide project involving the submission of birdwatching records in China, including records of more than 1,390 species of birds (approximately 92% of bird species in China) since 1998 [36]. To ensure the accuracy of location and species identification information, each submitted record was checked by an experienced reviewer (only birdwatchers who have submitted more than 300 bird species and

100 birding reports in China are eligible to become reviewers). After collecting 4.7�104 birding reports (each report may contain dozens of records) from 1998 to 2017, we verified the accu- racy of coordinates from the place names of each bird record according to the Google Maps API. We used all occurrence data (including breeding records and migratory records) for a single species because different subpopulations of many species may have different reproduc- tive and migratory habits at such a large scale, making it difficult to clearly distinguish between breeding and nonbreeding occurrence data from solo birdwatching records. Because bird watching does not always meet the requirements of systematic sampling [43], we measured the uniformity of the dataset for all localities by using the Measuring Geographic Distributions toolset in ArcMap 10.2 (ESRI 2010, Redland, California). We found that 68% of the occurrence data are distributed in 44% of the country’s land area (by calculating the stan- dard distance concentrated circle), and the distance between the median center and the mean center of features was 226.2 kilometers. This result suggested that there is indeed a bias, which may be due to gaps in species richness, the population density, and the traffic status in different regions. To avoid overfitting and high -variability predictions, we used two criteria: 1) bird species with fewer than five independent localities were excluded [44]; 2) if localities are highly concentrated for a species (the distance between any two localities is less than one arc-minute),

the excess localities were randomly removed (presence thinning). This data cleaning process has been proven to effectively match the results of the MaxEnt model and improve model per- formance [36, 39, 45–47]. Finally, we used 161,004 independent localities to create modeled distribution range maps for 1,042 bird species (for details, see S1 Table). We used all the localities collected for each species to model the total distribution range of that species. We did not determine whether these localities were breeding or nonbreeding sites. Because eastern China is an important part of the East Asian—Australasian Flyway (EAAF), many species such as geese and shorebirds breed in northern China or Russia, migrate past eastern China [48], or winter in southern China [49]. If only breeding ranges are considered, the key resting and wintering habitats for these birds to survive may be omitted from the conservation plan, and these potentially missing habitats may face serious threats [39, PLOS ONE Bird range changes call for innovative conservation in China PLOS ONE | https://doi.org/10.1371/journal.pone.0240225 October 8, 2020 3 / 20