Data from: Factors influencing nest site selection in a rapidly declining shorebird, the Eurasian curlew
Abstract
In this period of rapid human-induced environmental change, it is vital that influences of habitat on the distribution and productivity of threatened species are understood. Ground-nesting birds are declining more rapidly across Europe than any other group, with large-bodied birds at the greatest risk of extinction. Productivity and adult survival cannot both be maximised concurrently, and individuals will make decisions during the nest-placement phase which will favour one outcome or the other, however under conditions of accelerating change, these decision processes may become decoupled from positive fitness outcomes. The Eurasian curlew (Numenius arquata) is Europe’s largest wader and is showing steep declines in breeding productivity. Curlews are known to use a diverse range of habitats for nesting, where anthropogenic or natural features may influence distribution. There is an urgent need to understand the spatial scales of these impacts, and whether habitat characteristics have a positive or negative impact on nest survival. In our study site in Southern England, curlew showed a marked preference for nesting in wetter habitats, primarily mire, and a weaker selection of dry heathland. Nest survival improved in wetter habitats, and the area of mire round a nest site was positively associated with increased levels of nesting success, whilst area of scrub had a negative association. These both point to likely modulation of predator behaviour. Woodland significantly excluded curlew from potentially suitable breeding habitat, with an impact observed up to 2km from the nest site, but nest survival did not improve with distance from woodland. Curlews strongly avoided nesting near a major road passing through the study site, despite seemingly suitable habitat nearby. Understanding landscape effects will assist in planning future habitat management for curlew, impacts of forestry and avoidance of additional pressures on a species of high conservation concern.
[Access this dataset on Dryad]DOI:10.5061/dryad.1zcrjdg24
Contained here is the raw data we used in our analysis.
(allyearsdata.csv), all nest location data gathered over 3 yr period and used to compare against randomly generated locations, (allyearsdataRMark), the raw datafile of nest locations, found date, visits and fate set up as per RMark protocol, (2022_detection_history) containing data for analysis of the detectability of curlews on each survey visit, and folder (home ranges) containing csv’s exported from Movebank of location data taken from the GPS-tagged adult curlews included in the study.
Descriptions
allyearsdata.csv
- year : the year the data was collected
- Lat & Long : latitude and longitude coordinates of nest site, reduced in accuracy to 0.1 decimal place to preserve safety of a declining species.
allyearsdataRMark
- Year : the year the data was collected.
- Lat & Long : latitude and longitude coordinates of nest site, reduced in accuracy to 0.1 decimal place as above.
- nocc : ‘number of capture occasions’, in this case the number of times the nest was visited during the recorded incubation period.
- FirstFound : days are numbered from 1-54, 1 being the first day of the season when a nest was found, and 54 being the last day of the season when a bird in the study population was actively incubating. FirstFound is the number of day within this range when that particular nest was discovered.
- LastPresent : the number of the day when the nest was last visited and the bird was still incubating.
- LastChecked : the number of the day when the nest was last checked for signs of activity or a continuing nesting attempt.
- Fate : whether the nesting attempt failed or hatched successfully. 0 = hatched, 1 = failed.
- Freq : denotes whether the day numbers associated with that nesting attempt are unique, or whether they appear in a separate attempt. Therefore 1 = unique dates, 2 = 2nd attempt with the same dates.
2022_detection_history
- first column (blank) : unique identifiers for each site included in the analysis.
- detection : whether a curlew was detected during the visit.
- survey number : which visit number it was.
- effort level : due to having the involvement of a number of different agencies and volunteers, the surveys were conducted by various different individuals who did not have equal experience or time capacity as each other. Their individual search intensity was ranked numerically in ‘effort level’ to capture this and control as much as possible for the inter-individual differences.
[variables which were tested for effect on curlew detectability below] - habitat : which habitat was the nest located in, of the four utilized by curlew in the New Forest.
- nest : distance in metres to the next nearest curlew nest.
- carpark : distance in metres to the nearest car park, and so on for the remaining variables listed in the columns. a31 and a35 are the names of the trunk roads crossing the National Park. settlement was any town, village or hamlet.
home ranges
The column names in the csvs included here were generated by the Movebank system when they were exported, and they vary slightly depending on the age of the GPS tag or the manufacturer. Each csv represents a unique bird. In the case of some older models of GPS tag not so many fields of information are available as with the newer tags, so there are blank areas under some of the headers - these have been infilled with N/A for clarity that it was expected for that information to be missing.
The column headers in each file are as follows:
- timestamp - The date and time corresponding to a sensor measurement or an estimate derived from sensor measurements. Containing the full date (day, month, year) and time (hours, minutes, seconds)
- location-long - The geographic longitude of the location as estimated by the sensor. Positive values are east of the Greenwich Meridian, negative values are west of it. In decimal degrees using the WGS84 reference system.
- location-lat - The geographic latitude of the location as estimated by the sensor. In decimal degrees using the WGS84 reference system.
- acceleration-raw-x - Raw acceleration values provided by the tag for the X axis. Range and units may vary by provider, tag, and orientation of the sensor on the animal.
- acceleration-raw-y - Raw acceleration values provided by the tag for the Y axis. Range and units may vary by provider, tag, and orientation of the sensor on the animal.
- acceleration-raw-z - Raw acceleration values provided by the tag for the Z axis. Range and units may vary by provider, tag, and orientation of the sensor on the animal.
- gps:hdop - horizontal dilution of precision, a measure of accuracy of location data
- gps:satellite-count - The number of GPS satellites used to estimate the location.
- ground-speed - The estimated ground speed provided by the sensor or calculated between consecutive locations, in metres/second
- heading - The direction in which the tag is moving, in decimal degrees clockwise from north, as provided by the sensor or calculated between consecutive locations. Values range from 0-360: 0 = north, 90 = east, 180 = south, 270 = west.
- sensor-type - the type of sensor which was used to collect the positions
- individual-local-identifier - An individual identifier for the animal, provided by the data owner. Values are unique within the study.
- study-name - The unique name of the overall study
- utm-easting - The easting of the location as estimated by the sensor, in metres using the WGS84 reference system
- utm-northing - The northing of the location as estimated by the sensor, in metres using the WGS84 reference system
- utm-zone - The UTM zone used to convert locations from decimal degrees to UTM. Selected based on the location of each event
- study-timezone - The time zone at the study reference location, determined using the IANA Time Zone Database and a shapefile of these zones provided by efele.net
- study-local-timestamp - The date and time a sensor measurement was taken, converted from the values in ‘timestamp’ to the time zone of the study reference location. The time zone for the study reference location is determined using the IANA Time Zone Database and a shapefile of these zones provided by efele.net
The files contained within the home ranges folder are as follows:
- 887.csv, 892.csv, 1103.csv, 15573.csv, 220568.csv, 220916.csv, DHS22.csv, DHS23.csv, HN23.csv, HS23.csv