DOI: 10.5061/dryad.hhmgqnkp8
title: Selection of a diversionary field and other habitats by large grazing birds in a landscape managed for agriculture and wetland biodiversity

description: Several populations of cranes, geese, and swans are thriving and
 increasing in modern agricultural landscapes. Abundant populations are
 causing conservation conflicts, as they may affect agricultural production
 and biodiversity negatively.  Management strategies involving
 provisioning of attractive diversionary fields where birds are tolerated
 can be used to reduce negative impact to growing crops. To improve such
 strategies, knowledge of how the birds interact with the landscape and
 respond to current management interventions is key. We used GPS locations
 from tagged common cranes (Grus grus) and greylag geese (Anser anser) to
 assess how they use and select differentially managed habitats, such as
 diversionary fields to decrease impact on agriculture and wetlands
 protected for biodiversity conservation. Our findings show a high
 probability of presence of common cranes and greylag geese in the
 protected area and in the diversionary field, but also on arable fields,
 potentially causing negative impact on agricultural production and wetland
 biodiversity. We outline recommendations for how to improve the practice
 of diversionary fields and complementary management to reduce risk of
 negative impact of large grazing birds in landscapes tailored for both
 conservation and conventional agriculture.
description: <strong><em>Study area
 </em></strong> The study was conducted in
 the vicinity of lake Kvismaren (59°10′N,15°23′E), southeast of Örebro in
 south-central Sweden (Fig.1) from 2017 to 2022. The landscape is flat and
 dominated by highly productive arable land. The central parts of the study
 area consist of a mosaic of shallow, eutrophic lakes, reed beds and grazed
 wet meadows, designated as both a Natura 2000 (<em>i.e.,</em>
 SPA and SAC) and a Ramsar site (<em>Wetlands: a global disappearing
 act</em> 1970; EC 2016). Kvismaren is a national key area for
 protection of multi-functional wetland habitats and aimed for staging,
 breeding, and threatened bird species, <em>e.g.,</em> waders,
 waterfowl, gulls. It is also intended to serve as a refuge area for large
 grazing birds (common cranes and several goose species; EC 2009). The
 shallow lakes and wetlands provide good roost sites and the surrounding
 agricultural landscape favourable foraging opportunities. A diversionary
 field and various scaring practices are employed in the study area to
 reduce the risk of crop damage caused by large grazing birds. 
 <em><strong>Capturing and tagging
 birds</strong></em> This study was based on
 location data from 17 common cranes and 55 greylag geese equipped with GPS
 transmitters. We captured pre-fledgling common cranes after a short run
 from a car or a hide and equipped them with leg or harness mounted GPS
 transmitters (Ornitela) in July- early August in 2016-2020 within 70 km of
 Grimsö Wildlife Research Station, Lindesberg (59°43′N,15°28′E; for details
 about capture procedures, see Månsson, Nilsson, & Hake, 2013).
 Juvenile common cranes accompany their parents  to the wintering grounds,
 where parents and juveniles usually part in January (Alonso, Veiga,
 & Alonso, 1984). They most often visit the study area (Kvimaren
 the second time as yearlings but sometimes postpone the second visit until
 they are older. Tagged cranes often return for several seasons (for
 details see Table S2in Supplemental Information). Greylag geese were
 captured as adults and equipped with neckband GPS transmitters (OT-N35,
 OT-N44) in June in 2017-2019. Captures took place in Kvismaren in early
 mornings by herding moulting, flightless greylag geese by canoes and by
 foot into net corrals (for capture details see Månsson et al., 2022). The
 GPS-tagged greylag geese present in the study area were included in the
 study, often for several consecutive seasons.
 <strong><em>Data
 management</em></strong> To model relative
 presence of common cranes and greylag geese in differentially managed
 habitats during the season of the supplemental feeding in the diversionary
 field (May 1 to August 15 each year), we compared the GPS locations of the
 birds (hereafter<em> </em>referred to as <em>‘used’
 </em>locations<em>)</em> with randomly distributed
 locations (<em>‘available’</em>) (<em>i.e.,</em>
 Resource Selection Functions, RSF´s; Lele & Keim, 2006a).For the
 studyperiod, we assume that crops are growing and coincide with associated
 damage risk when the diversionary field was in operation. The analyses
 were conducted in two steps for both species by assessing; 1) probability
 of presence in different habitats (<em>e.g.,</em> arable land,
 protected area; model 1, and 2) probability of presence on different crop
 types in arable fields (<em>e.g.,</em> barley, ley,
 diversionary field; model 2). We defined an uptake area for the
 diversionary field (<em>i.e.,</em> assumed to be within reach
 for the birds during the daily foraging activities) by using distance from
 the previous night’s roost location, within our study area, to all daytime
 locations the following day. The 95% percentile of all these measured
 distances were then used to define a radius for the uptake area around the
 diversionary field (5.80 km for common cranes and 3.82 km for greylag
 geese). W e included the GPS locations and randomly distributed available
 locations (ratio 1:1) within the uptake area, mirroring the available area
 for the birds’ daily foraging bouts<em>.</em> The time until
 the common cranes and greylag geese started using the diversionary field
 was assessed as either: 1) the number of days until first use after the
 first supplemental feeding, or if the feeding had started prior to
 arrival, or 2) as the number of days after arriving to the uptake
 area. To ensure highly precise spatial data, we
 excluded locations with horizontal dilution of precision &gt;7 (D’eon
 & Delparte 2005) as well as locations fixed by less than three
 satellites (<em>i.e.,</em> 2D). As the study focuses on
 habitat and field selection on the ground and during daytime foraging
 activities (<em>i.e.,</em> damage risk), locations assumed to
 be when in flight with speed &gt;10km/h were excluded, as were night
 locations. Day and night locations were defined by the time of sunset and
 sunrise, <em>i.e</em>., all locations between sunset and
 sunrise were defined as night locations and subsequently excluded. The
 programming of GPS transmitters and the frequency of location fixes varied
 between 15 and 60 minutes. Thus, to standardize the positioning frequency
 and to meet the assumption of independence between consecutive individual
 locations to allow for potential individual movement to another habitat or
 field, the positioning frequency was standardized to one location/hr
 (Fieberg et al. 2010). Habitat types were derived from the national land
 cover data base (0.1 × 0.1 km; Naturvårdsverket, 2020) and the extent of
 the protected area (Ramsar site; Kvismaren) from the Swedish Environmental
 Protection Agency. To avoid over-fitting of models, habitats with similar
 environmental characteristics and management were combined into the
 following categories: arable land (<em>i.e.,</em>
 conventionally farmed fields with short rotation crops), diversionary
 field, non-protected wetland and water, other land
 (<em>e.g.,</em> forest, exploited land), pasture
 (<em>i.e., </em>permanent grassland for grazing), and
 protected area ((step 1; Table S1). For the locations on arable land (step
 2), crop types were derived from the SAM14 database (The Swedish Board of
 Agriculture), which provides spatially explicit information about
 cultivated crops at the field level. Crop types were lumped into nine
 categories based on similar characteristics or sporadic occurrences:
 barley, beans and peas, diversionary field, ley
 (<em>i.e.,</em> fertilized, productive grasslands for silage
 production), oat, potatoes, rye and triticale, wheat, and other crop
 (<em>e.g.,</em> rape seed, vegetables; step 2). Data
 management was done in ArcGIS (version 10.7) and R (version
 4.2.1).
description: # This README\_Nilsson\_et\_al.txt file was generated on 2024-01-04 by
 Lovisa Nilsson GENERAL INFORMATION 1\. Title of Dataset: Data from:
 Selection of a diversionary field and other habitats by large grazing
 birds in a landscape managed for agriculture and wetland biodiversity 2\.
 Author Information ``` Corresponding author Name: Dr. Lovisa Nilsson
 Institution: Grimsö Research Station, Dept. of Ecology, Swedish University
 of Agriultural Sciences (SLU), SWE Email: lovisa.uk.nilsson@slu.se
 Co-authors Name: Ass. Prof. Johan Månsson Institution: Grimsö Research
 Station, Dept. of Ecology, Swedish University of Agriultural Sciences
 (SLU), SWE Name: Prof. Johan Elmberg Institution: Department of
 Environmental Science and Bioscience, Kristianstad University, SWE Name:
 Dr. Niklas Liljebäck Institution: Grimsö Research Station, Dept. of
 Ecology, Swedish University of Agriultural Sciences (SLU), SWE Name: Dr.
 Ingunn Tombre Institution: Department of Arctic Ecology, Norwegian
 Institute for Nature Research (NINA), Tromsø, NOR ``` 3\. Date of data
 collection: 2017-2022 4\. Geographic location of data collection:
 Kvismaren, Sweden (59°10'N, 15°23'E) 5\. Funding sources that
 supported the study: FORMAS no.2018-00463, The Swedish Environmental
 Protection Agency no. 19/128, 19/129 6\. Recommended citation for this
 dataset: Nilsson et al. (2024), Data from: Selection of a diversionary
 field and other habitats by large grazing birds in a landscape managed for
 agriculture and wetland biodiversity. Dryad, Dataset DATA & FILE
 OVERVIEW 1\. Description of dataset The study is based on location data
 obtained 2017-2022 from 17 common cranes (Grus grus) and 55 greylag geese
 (Anser anser) with GPS-equipped neckbands/legbands, made by Ornitela. 2\.
 File List: ``` Name: Fieldselection_data_Nilsson_et_al.csv Description:
 Locations used for analyses of field selection Name:
 Habitatselection_data_Nilsson_et_al.csv Description: Locations used for
 analyses of habitat selection ``` METHODOLOGICAL INFORMATION The study is
 based on location data obtained 2017-2022 from 17 common cranes and 55
 greylag geese with GPS-equipped neckbands/legbands, made by Ornitela. All
 captures and tagging of birds adhered to ethical requirements for research
 on wild animals after approval from the Animal Ethics Committee of central
 Sweden (common cranes: C104/10, C53/13, greylag geese: 5.8.18–03584/2017).
 DATA-SPECIFIC INFORMATION FOR: Fieldselection_data_Nilsson_et_al.csv 1\.
 Number of variables: 15 2\. Number of cases/rows: 85678 3\. Variable List:
 ``` date: date UTC_time_day_location: UTC time for day location
 satcount_day_location: number of satelites used for deriving location
 hdop_day_location: precision of location speed_km_h: travel speed of
 individual id_factor: individual id UTC_time_night_location: time for
 night roost location (to define distance from day location to roost site)
 lat_night_location: latitude of night roost location (wgs84)
 lon_night_location: longitude of night roost location (wgs84) used: used
 (1) or available (0) location lon_day_location: longitude of day location
 (wgs84) lat_day_location: latitude of day location (wgs84) species:
 species (crane/greylag) crop_original_text: original crop (in Swedish)
 crop_category: collapsed crop category ``` 4\. Missing data codes: ```
 None ``` DATA-SPECIFIC INFORMATION FOR:
 Habitatselection_data_Nilsson_et_al.csv 1\. Number of variables: 14 2\.
 Number of cases/rows: 313410 3\. Variable List: ``` date: date
 UTC_time_day_location: UTC time for day location satcount_day_location:
 number of satelites used for deriving location hdop_day_location:
 precision of location speed_km_h: travel speed of individual id_factor:
 individual id UTC_time_night_location: time for night roost location (to
 define distance from day location to roost site) lat_night_location:
 latitude of night roost location (wgs84) lon_night_location: longitude of
 night roost location (wgs84) used: used (1) or available (0) location
 lon_day_location: longitude of day location (wgs84) lat_day_location:
 latitude of day location (wgs84) species: species (crane/greylag)
 habitat_category: habitat category ``` 4\. Missing data codes: ``` None
 ```