DOI: 10.5061/dryad.kh189328n
title: Feeding sites characteristics of the Northern shoveler Spatula clypeata in prenuptial stopover

description: Dabbling ducks choose a multitude of habitats throughout their life cycle.
 This choice depends on the abundance, diversity, and accessibility of food
 resources. Wetlands such as the Marais breton and Marais poitevin
 (Atlantic coast, France) are common habitats for several Anatidae,
 especially during their prenuptial migration. However, studies on the food
 ecology of Anatidae at stopover sites are limited. Therefore, this study
 focused on the Northern shoveler Spatula clypeata, a species that
 regularly inhabits the two marshes during the breeding and migration
 periods and is highly dependent on freshwater invertebrates as the food
 resource because of its bill morphology. Fifteen Northern shoveler were
 equipped with a GPS/GSM tag and monitored during their prenuptial
 migration. The study objectives were to understand the strategies used by
 the Northern shoveler to select the foraging sites and describe the
 characteristics of these sites (such as freshwater invertebrates’
 abundance and diversity and the habitat type). In addition, home range
 (HR), space use, and habitat selection were studied.
description: <strong>Northern
 shoveler capture and tagging</strong>
 This study was conducted on
 two large wetlands on the French Atlantic coast in Vendée: the MB (N2000
 FR5212009 and Ramsar 2283) and the MP (N2000
 FR5200659). During the prenuptial migration period, shovelers were
 captured using cage traps and live male or female shovelers as decoys. A
 camera (NATURACAM – STDX2) was positioned near each trap to monitor the
 presence of birds in the traps, which were kept every day from March 01 to
 March 17, 2020, and from March 01 to April 10, 2021. Overall, 15 shovelers
 were caught and equipped with a GPS-GSM tag (Ornitela, OrniTrack-E10,
 solar-powered GPS-GSM); these included 4 females (F) and 11 males (M) and
 8 juveniles (less than two years old) and 7 adults (more than two years
 old). Eight individuals were caught in the MB and 7 in the MP. The
 equipment (GPS-GSM tag, harness, and metal tag) weighed less than 3% of
 the body mass. The shovelers were ethically captured and handled
 (Authorization from Ministry of Ecological Transition by Research Center
 on the Biology of Bird Populations PP: 1821).The movements of the
 individuals were monitored during the prenuptial period (from March 01,
 2020, to April 30, 2020, and from March 01, 2021, to April 30, 2021) with
 a recording frequency of once every 5 minutes. Thus, the data analysed
 were obtained from the 15 birds that used either the MB or MP over a
 period of at least 15 days after being tagged (Table 1). This period
 corresponds to the minimum amount of time a majority of the individuals
 spend at the stopover site before leaving for the breeding
 site.  
 <strong>Trophic
 Resources and Environmental Parameter Measurement at the Feeding
 Sites</strong> To describe the abundance and energy value of
 the freshwater invertebrates at the shovelers’ main feeding sites,
 invertebrates more than 200µm in size were sampled from March 1 to April
 30, 2021, in some sites exploited by the tagged individuals. The sites, 31
 in total, were selected for sampling only if the tagged birds exploited
 their freshwater sites for a minimum of 72 consecutive hours. The sites
 were classified into three categories according to the habitat type: wet
 meadow, pond, and channel (Fig. 2). In each site, freshwater invertebrates
 were sampled thrice using a plankton net (mesh of 200 µm, frame size of
 35.5 x 15.0 cm) on a transect of 2 m at 35 cm of the water column, which
 corresponded to the shovelers’ feeding depth. The contents obtained using
 the net were preserved in 70° ethanol (Balcombe et al. 2005) and quickly
 analysed. The individuals from each sample were counted and identified
 using a binocular magnifier (Euromex, Series Z, 7-45 x). The
 invertebrates’ family was identified (except copepods, subclass;
 Cladocera, superorder; Hydrachnidia, suborder; and Ostracods,
 class) (Moisan 2010, Thorp and Rogers 2011).
 The feeding sites were
 characterized by the environmental variables. The sediment height, water
 level, salinity (using a multiparameter probe VWR MU 6100 H Multimeter),
 and percentage cover of riparian helophytes and of emerged and submerged
 aquatic vegetation were noted in each site. Other factors were coded into
 three classes: sediment type (class 1: loamy sediment; 2: loamy / muddy;
 3: muddy), slope (class 1: &lt; 5% soft slope; 2: 5%–10% moderate
 slope; 3: &gt; 10% steep slope), and habitat (class 1: meadows; 2:
 ponds; 3: channels). The surface of the sites was measured using the
 geographic information system QGIS (QGIS Development Team 2009). The site
 boundary corresponded to the hydraulic entity of the
 birds.
description: This two dataset describes the 15 Northern shoveler captured in
 stopover during the prenuptial migration
 (File :"data_shovelers.txt") and their feeding sites
 characteristics (File :"data_sites.txt") .