DOI: 10.5061/dryad.79cnp5ht8
title: Habitat selection of foraging male Great Snipes on floodplain meadows: importance of proximity to the lek, vegetation cover and bare ground

description: Drainage of wetlands and agricultural intensification has resulted in
 serious biodiversity loss in Europe, not least in grasslands.
 Consequently, many meadow birds have drastically declined, and the
 habitats they select for breeding currently rely on land management.
 However, the selection of habitats maintained by agriculture may
 contribute to reduced fitness and thus remain maladaptive for individuals,
 which makes conservation challenging. An understanding of the
 relationships between species’ habitat selection, food supply and land
 management in the context of species’ behaviour is therefore crucial for
 conservation. Lowland populations of Great Snipe Gallinago media are
 currently declining at a moderate rate, causing a conservation concern. We
 examined the daytime site selection (assumed as foraging sites) and food
 supply of radiotracked Great Snipe males breeding on a floodplain in NE
 Poland. Foraging sites were classified at micro- and macro-scale levels
 using the logistic regression in a use–availability design. On the
 microscale level, males selected moderate sward height and density, and a
 large amount of bare ground patches, and the importance of these increased
 as the breeding season progressed. On the macro-scale level, these
 conditions were associated with (1) meadows mown twice per season and
 grazed thereafter (associated with the most abundant food resources –
 earthworms) and (2) extensively managed pastures, suggesting the
 importance of grazing. Abandoned or late-mown meadows under
 agri-environmental schemes (AES) were avoided by foraging males. However,
 parcels with delayed mowing offer safe breeding sites for females nesting
 close to leks, unlike land-use types preferred by foraging males, which
 may act as an ecological trap. Effective conservation of Great Snipes on
 floodplain meadows requires precisely targeted AES schemes that will
 provide a mosaic of intensive and extensive land-use patches in the
 vicinity of identified leks.
description: <b>General study
 design</b> To examine habitat selection of
 the Great Snipe, we applied a use–availability design in two spatial
 scales (a micro-scale model and macro-scale model), where environmental
 characteristics at the male Great Snipe daytime presence sites (‘used’)
 were contrasted with characteristics at random sites (‘available’) within
 the study area. The study area was located in NE Poland in the upper Narew
 river valley. To localize foraging locations, Great Snipe males were
 trapped in May 2013 and 2014 on two leks (lek1 and lek2) and equipped with
 VHF transmitters. When an individual was approached, we locate the precise
 feeding site from where it was flushed and then sampled the attributes of
 the habitat. Some non-tagged birds were flushed by coincidence during
 fieldwork, and when their exact foraging site was detected we applied the
 same sampling protocol and included the data in our analyses (n = 41). To
 determine available resources within the study area in 2013 and 2014, we
 generated 200 and 250 random locations, respectively. Random sites in
 dense bushes and forest were omitted as non-potential foraging sites. In
 total, 383 random sites were sampled. <strong>Invertebrates
 data</strong> To assess subsurface
 invertebrates (different taxa, see README file) we collected soil samples
 (15x15x10 cm depth, cut with a steel frame) from the center of the plot.
 All potential prey (&gt; 0.5 mm) were searched within those samples in
 the lab, when washed through a 1 mm mesh. Invertebrate abundance (total
 wet biomass of identified class, order or family weight, ±0,001 g) was
 then analyzed in the lab. <b>Statistical
 analyses</b> We coded sites where we found
 birds as 1 (“used”) and randomly selected sites from within our study
 domain as 0 (“available”), and used this as a binary response to model
 Great Snipe habitat selection as a function of candidate predictors
 measured at two spatial scales (see Micro-scale variables in Table 1, see
 Usage Notes). We used generalized linear models (GLMs) with a binomial
 error structure and logit link function to model the relationship between
 the presence/absence of birds and candidate predictors at the micro (GLM1)
 and the macro scale (GLM2). For more details go to published
 article. <b>Micro-scale
 model</b> For the micro-scale models, we
 considered nine candidate predictors (three of them in the squared form)
 as main terms and included also interactions between those variables and
 the date. For more details go to published article. <b>Macro-scale
 model</b> At the landscape scale, we
 considered seven candidate predictors (four of them in the squared form,
 see Macro-scale variables in Table 1 and Table 2, see Usage Notes) as main
 terms to build a global model. We used R environment (R Core Team 2019) to
 fit GLMs (for more details go to published article). Biomass of food
 resources was not included in model selection because these variables were
 not assessed on all sampling sites (for more details go to published
 article).
description: Variable codes in Table 1
 and Table 2 refers to headings columns of uploaded file:
 Korniluk_et_al_2000_Great_Snipe_habitat_selection_data. Additional column headers are
 described in uploaded README file. Table 1. Variables at two levels
 – micro- and macro-scale. <b>Scale</b> <b>Variable code*</b> <b>Variable name and unit </b> <b>Description</b>         Micro-scale variables Date Date of sampling [days] Relative date within the breeding season, 1= 01 May VegHeight Vegetation height [cm] Mean in a 50x50cm plot, measured with a ruler VegCovV Vertical vegetation cover [%] Vegetation coverage of 10x10 cm paper blank placed in the center of the plot VegCovH Horizontal vegetation cover [m] Mean of four perpendicular direction maximum distance from where we could not see a Great Snipe decoy BareGr Bare ground [%] % of bare ground within the plot Penetr Soil penetrability [cm] A mean of measured in the center of the plot by dropping 3 times a pointed iron pin (8 mm diameter and 180 g) from 1.5 m height Tussok Tussock height [cm] Mean for all tussocks in the 50x50 cm plot, measured with a ruler Moist Moisture [1-6] On a scale from 1 (dry) to 6 (flooded) DistLek Mean distance to leks [m] Mean distance to the two leks (lek1 and lek 2)                 Macro- scale variables Elev Elevation [m] A mean in 3 m radius based on Digital Terrain Model (Project ISOK of Head Office of Geodesy and Cartography GUGIK – Poland, 1 m resolution). DistLek Mean distance to leks [m] Mean distance to the two permanent leks DistTree Distance to nearest single tree [m] Distance between foraging and random sites to nearest landscape elements DistShrub Distance to nearest shrubs [m] DistForest Distance to nearest forest [m] DistWater Distance to nearest water surface [m]   LandUse Land use type Land use regime and type affects sward structure (Land use types listed in Table 2.)         <br> Table 2. Land use types used in the macro-scale model. <b>Variable code</b> <b>Variable name</b> <b>Variable class and code</b>   LandUse Land use type Meadows mowed twice and extensively grazed (2xMOW+COW)       Meadows mowed twice a year (2xMOW)       Meadows mowed once a year (1xMOW)       Abandoned meadows (ABAND)       Extensive pastures (COW)