Data in Brief 35 (2021) 106825 Contents lists available at ScienceDirect Data in Brief journal homepage: www.elsevier.com/locate/dib Data Article Data on swan arrival, departure, and population size on the Asadokoro tidal flat, Aomori Prefecture, Japan, from 1956 to 2010 Masaki Ogata a,b,1, Takeshi Mitsuya b, Yoshiyuki Tanaka c,∗ a Hiranai Town Board of Education, Shimotsuki 12-1, Kominato, Hiranai, Aomori 039-3321, Japan Hiranai Society for Swan Protection, Shimotsuki 12-1, Kominato, Hiranai, Aomori 039-3321, Japan c Department of Life and Environmental Science, Hachinohe Institute of Technology, Ohbiraki 88-1 Myo, Hachinohe, Aomori 031-8501, Japan b a r t i c l e i n f o Article history: Received 12 November 2020 Revised 28 January 2021 Accepted 29 January 2021 Available online 2 February 2021 Keywords: Citizen Cygnus cygnus Migratory bird Population record Bird watching Elementary school student Long term ∗ 1 a b s t r a c t The arrival and departure dates and the daily maximum populations of migrating swans (Cygnus cygnus) on the Asadokoro tidal flat, Hiranai town, Aomori Prefecture, Japan, were recorded by elementary school students for more than 50 years between 1956 and 2010. The Asadokoro tidal flat, which lies along the coast of Mutsu Bay, has been designated a National Special Natural Monument, known as “The swans of Kominato and their migration grounds.” This long history of observation unfortunately came to an end with the closure of the elementary school in 2012. If analyzed together with data on environmental factors, such as temperature changes or the effects of avian influenza, this dataset could provide a potentially valuable source of information, and consequently, future secondary use of the data is anticipated. © 2021 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) Corresponding author. E-mail address: y-tanaka@hi-tech.ac.jp (Y. Tanaka). Present address: Hiranai Central Hospital, Sotonosawa 1-1, Kominato, Hiranai, Aomori 039-3321, Japan https://doi.org/10.1016/j.dib.2021.106825 2352-3409/© 2021 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) 2 M. Ogata, T. Mitsuya and Y. Tanaka / Data in Brief 35 (2021) 106825 Specifications Table Subject Specific subject area Type of data How data were acquired Data format Parameters for data collection Description of data collection Data source location Data accessibility Biological Sciences Ecology, Behavior Table Visual observations and counting Raw Long-term continuous observations were considered. Elementary school students conducted these observations systematically as an extracurricular activity over more than 50 years. Elementary school students undertook observations and recording to the best of their ability. Hiranai Town, Aomori Prefecture Japan WGS84, Latitude: 40.93894166, Longitude: 140.97181666 Mendeley data [9] Published: 28 Jan 2021|Version 1| https://doi.org/10.17632/g9tcw92bgy.1 Value of the Data • Data on fluctuations in migratory bird populations were collected over a period of over 50 years, based on observations performed by elementary school students. • The study site and swans are designated as special natural monuments of Japan [1]. It is argued that a reduction in the number of swans in Hiranai town may have led to a decline in the tourism value of the local area. The data obtained can be used to influence administrative decisions at national and regional levels. • The data are also of potential value for analyzing changes in the number of swans flying to this site in relation to environmental factors, such as temperature [2], avian influenza [3,4], and human activities [5,6]. They may also prove useful for estimating the impact of migratory birds on the surrounding environment, such as vegetation [7,8]. For example, the arrival of migratory birds at this site has a substantial effect on the distribution of seagrass [1]. Data Description The data presented herein relate to the size of the swan population on the Asadokoro tidal flat and the dates on which the swans arrived at and departed from the study site. Table 1 shows the dates from 1956 to 2009 on which the first swans arrived at the Asadokoro tidal flat in autumn, together with the number of individuals observed on each date, whereas Table 2 shows the dates from 1957 to 2010 (mainly in spring) when the last swans departed from the site, together with the number of individuals observed on each date. Table 3 presents the monthly maximum numbers of observed swans per day from 1960 to 2010, and Table 4 summarizes the timing of data acquisition. The raw data file was deposited in Mendeley data (http://dx.doi.org/ 10.17632/g9tcw92bgy.1) Experimental Design, Materials and Methods In each of the years from 1956 to 2010, observations and recording of swan populations were carried out almost daily at Asadokoro tidal flat (Fig. 1). Each year, students from the Asadokoro Elementary School, which was adjacent to the survey site, formed a team of dozens of individuals under the guidance of teachers, and conducted daily observations in rotation. Teachers gave the students clear instructions to count the number of swans visible from the designated observation location (Fig. 1) within the prescribed time (Table 4). If possible, they also tried to distinguish between adult and young birds. Adult birds are white, whereas young birds are gray, 3 M. Ogata, T. Mitsuya and Y. Tanaka / Data in Brief 35 (2021) 106825 Table 1 The date on which the first swans arrived at Asadokoro tidal flat and the number of individuals. The breakdown of adults and juveniles is also indicated. Year Month Day Number of individuals 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 20 0 0 2001 2002 2003 2004 2005 2006 2007 2008 2009 10 10 10 10 10 11 10 11 11 10 10 11 11 11 11 11 10 11 11 11 10 10 10 10 11 10 11 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 23 19 15 15 20 2 10 2 2 31 21 11 9 7 1 8 26 1 1 2 14 19 28 29 10 20 4 19 7 15 16 15 17 21 11 15 15 16 21 24 12 24 22 20 20 20 21 20 20 24 24 25 31 20 6 8 8 8 18 8 5 5 5 4 3 6 1 4 3 7 4 6 4 11 6 2 7 13 13 24 2 20 3 3 7 10 16 4 3 2 30 5 18 7 3 2 18 27 52 17 27 70 22 135 36 96 39 1 Remarks Adult 6 Adult 3, Young 1 Adult 3 Adult 2, Young 5 Adult 2, Young 4 Adult 2, Young 2 Adult Adult Adult Adult 2, Young 4 2 5, Young 2 4, Young 9 Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult Adult 20, Young 4 2 16, Young 4 3 3 5, Young 2 10 16 4 3 2 26, Young 4 4, Young 1 14, Young 4 7 3 2 14, Young 4 24, Young 3 38, Young 14 9, Young 8 24, Young 3 58, Young 12 22 103, Young 32 33, Young 3 88, Young 8 30, Young 9 1 4 M. Ogata, T. Mitsuya and Y. Tanaka / Data in Brief 35 (2021) 106825 Table 2 The date on which the last swans departed from Asadokoro tidal flat and the number of Individuals. The breakdown of adults and juveniles is also indicated. Year Month Day Number of individuals Remarks 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 20 0 0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 3 2 2 5 6 3 3 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 5 5 4 5 4 4 4 5 5 4 4 4 5 5 4 5 4 4 4 4 4 5 4 4 4 4 3 15 11 10 24 18 10 21 26 12 4 8 8 13 6 6 2 16 20 18 7 12 13 5 20 18 19 23 14 4 28 13 27 18 19 17 7 26 27 28 20 1 30 1 28 27 22 30 23 2 24 18 16 27 18 1 28 3 1 35 2 12 4 6 7 4 5 7 4 4 5 23 1 1 38 2 19 13 3 6 23 3 2 2 4 3 1 3 2 3 1 1 4 3 6 5 1 5 4 6 7 3 3 8 9 11 10 2 1 Record Record Record Record by by by by Mr. Mr. Mr. Mr. Wada Wada Wada Wada Adult 4 Adult 1, Young 3 Adult 2, Young 3 Adult 1 Adult 1 Young 2 Adult 6, Young 13 Adult 8, Young 5 Adult 1, Young 2 Adult 4, Young 2 Adult 23 Adult 3 Adult 1, Young 1 Adult 1, Young 1 Adult 4 Adult 1, Young 2 Young 1 Adult 3 Adult 2 Adult 1, Young 2 Young 1 Adult 1 Adult 2, Young 2 Adult 3 Adult 5, Young 1 Adult 2, Young 3 Adult 1 Adult 4, Young 1 Adult 4 Adult 6 Adult 6, Young 1 Adult 2, Young 1 Adult 3 Adult 8 Adult 7, Young 2 Adult 8, Young 3 Adult 4, Young 6 Adult 2 Adult 1 5 M. Ogata, T. Mitsuya and Y. Tanaka / Data in Brief 35 (2021) 106825 Table 3 Monthly maximum numbers of swan observed each day. The underlined numbers denote the highest population counts during each fiscal year, including the following April. Fiscal year Sep Oct Nov Dec Jan Feb Mar Apr 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 20 0 0 2001 2002 2003 2004 2005 2006 2007 2008 2009 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 39 0 8 0 0 4 3 0 0 0 0 0 34 0 0 0 6 24 11 23 3 157 0 71 126 125 80 33 55 101 58 148 30 156 66 10 115 40 49 45 76 68 297 347 48 135 39 96 39 2 120 60 70 58 68 94 24 61 27 29 76 66 256 261 489 174 151 251 150 250 325 195 327 182 223 206 182 233 195 180 392 273 204 158 167 158 202 240 240 166 165 279 145 154 203 128 117 201 46 13 180 172 160 170 174 166 206 77 64 352 401 482 446 597 333 433 514 501 364 466 644 426 351 447 354 503 612 470 815 447 542 511 372 403 422 361 394 418 376 402 320 270 325 219 277 411 219 170 138 113 200 420 300 260 243 703 623 450 613 1,123 630 545 508 514 526 372 666 553 677 625 644 754 742 745 722 751 806 626 950 745 950 688 567 878 583 649 670 659 591 476 462 317 432 350 315 339 324 344 243 154 210 304 265 606 616 1,058 447 789 636 834 460 411 438 472 551 434 614 698 532 638 634 679 690 744 758 720 795 738 705 684 788 733 527 827 704 654 704 690 625 517 411 390 406 408 302 365 249 317 203 190 120 18 50 105 203 91 225 379 282 326 316 259 207 343 269 360 345 485 444 470 509 623 618 585 688 682 503 714 435 486 507 657 485 484 472 440 557 540 592 465 360 334 380 303 310 291 199 256 186 5 0 0 0 4 4 7 24 8 24 18 34 5 7 54 32 38 21 81 75 131 113 94 153 292 149 105 188 117 104 57 83 283 75 132 104 154 114 48 118 110 141 65 99 78 63 31 20 35 0 0 May 11 2 10 10 6 21 5 5 8 making them easy to distinguish. In this paper, we present a summary of the observational data relating to the day when the first swans arrived (Table 1), the day on which the last swans departed from the tidal flat (Table 2), and the maximum number of swans observed per day in each month of the observational period (Table 3). Tables 1 to 3 show compilations of the raw data extracted by teachers and students. The timing of observations is given in Table 4. As some of the raw data are missing, it is not possible to provide the timing of observations prior to 6 M. Ogata, T. Mitsuya and Y. Tanaka / Data in Brief 35 (2021) 106825 Table 4 Timing of observations. ◦ = research was conducted. R = rest, no research. N.D. = no data (although the original data were lost, conditions appear to have been similar to those in the previous and subsequent years. Survey time zone Weekend Fiscal year AM PM AM PM New Year 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 20 0 0 2001 2002 2003 2004 2005 2006 2007 2008 2009 8:00 8:00 8:00 N. D. 8:00 8:00 N. D. 8:00 8:00 N. D. 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 8:00 10:00 10:00 10:00 10:00 10:00 10:00 10:00 10:00 3:00 3:00 3:00 N. D. 3:00 3:00 N. D. 3:00 3:00 N. D. 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 3:00 R R ◦ ◦ ◦ N. D. ◦ ◦ N. D. ◦ ◦ N. D. ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ R R R R R R R R R R R R R R R R R R R R ◦ ◦ ◦ N. D. ◦ ◦ N. D. ◦ ◦ N. D. R R ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ R R R R R R R R R R R R R R R R R R R R ◦ ◦ ◦ N. D. ◦ ◦ N. D. ◦ ◦ N. D. ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ R (29 R (29 R (28 R (29 R (29 R (28 R (28 R (29 R (29 R (29 R (28 R (29 R (28 R (29 R (29 R (29 R (29 R (29 R (27 R (18 Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec Dec -3 Jan) -3 Jan) -5 Jan) -3 Jan) -3 Jan) -7 Jan) -5 Jan) -4 Jan) -3 Jan) -3 Jan) -3 Jan) -3 Jan) -5 Jan) -4 Jan) -3 Jan) -3 Jan) -3 Jan) -3 Jan) -4 Jan) -18 Jan) 1965; however, it is assumed that data were acquired according to schedules similar to those used after 1966, as summarized in Tables 1 to 3. From 1966 to 1989, observations were carried out from the time of arrival of the first swans to their departure, including during the yearend and New Year holidays and weekends. However, after 1990, observations were suspended for approximately one week during the year-end and New Year holidays, and observations were not made on Saturdays or Sundays. In 2009, observations were conducted only on Tuesdays and Thursdays, as contact with wild birds at this time was discouraged owing to the death of swans from avian influenza in Aomori Prefecture in 2008 [3,4]. However, during arrival and departure periods, intensive observations were carried out regardless of the day of the week. M. Ogata, T. Mitsuya and Y. Tanaka / Data in Brief 35 (2021) 106825 7 Fig. 1. Study site. The figure was modified from a Google Earth Pro image. The red ellipse indicates the area around which the elementary school students walked to observe the swans. The blue ellipse indicates the approximate area in which the swans under observation were present. Observations were conducted twice daily, at approximately 8:00 am before the start of classes and at approximately 3:00 pm after classes had finished. From 2002 until the final year of observations in 2010, the timing of the morning survey was changed to approximately 10:00 am, coinciding with the morning break. Observations during each survey period were conducted for approximately 20 min. Of the two daily counts, the one yielding the largest number of individuals was taken as the population number for that particular day. Given that swans differ considerably from other migratory birds that fly to this area with respect to size and color, it is assumed that the elementary school students are unlikely to have confused the swans with other species. However, it is conceivable that they may not have been able to distinguish between the whooper swan Cygnus cygnus and the tundra swan C. columbianus. Nevertheless, the results of a recent survey conducted by the Hiranai Society for Swan Protection have indicated that most of the swans observed in this area are whooper swans (Mitsuya et al., unpublished data). Although the survey was conducted for the final time in the fiscal year 2010, the data for that year were excluded from the dataset presented herein, owing to the lack of certain population 8 M. Ogata, T. Mitsuya and Y. Tanaka / Data in Brief 35 (2021) 106825 data. In March 2012, Asadokoro Elementary School closed down, and the monitoring of swans that had continued for more than 50 years ended. To date, there has been no resumption of similar monitoring. Ethics Statement Not applicable. CRediT Author Statement Masaki Ogata: Resources, Writing - Original Draft; Takeshi Mitsuya: Resources, Data Curation; Yoshiyuki Tanaka: Data Curation, Funding acquisition, Writing - Review & Editing. Declaration of Competing Interest The authors declare that they have no competing financial interests or personal relationships that influenced or could be perceived to have influenced the work reported in this article. Acknowledgments This valuable data set could not have been produced without the continuous efforts of all the elementary school students and teachers who participated in the monitoring. Mrs. Keiko Mitsuya and Mr. Tadayoshi Shukunobe helped us input the raw data. Publication of the dataset was supported by Environmental Policy Division, Department of Environment and Public Affairs, Aomori Prefectural Government with the project, “Research and Development of Education Model for Environmental Studies by Universities”. References [1] F. Sato, S. Tanaka, S. Kirihara, Y. Tanaka, The influence of migratory birds on the distribution of the seagrass Zostera japonica, Bot. Mar 63 (2020), doi:10.1515/bot- 2020- 0045. [2] J. Månsson, L. Hämäläinen, Spring stopover patterns of migrating Whooper Swans (Cygnus cygnus): temperature as a predictor over a 10-year period, J. Ornithol. 153 (2) (2012) 477–483, doi:10.1007/s10336- 011- 0763- 5. [3] Y. Uchida, M. Mase, K. Yoneda, A. Kimura, T. Obara, S. 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