Published December 30, 2021 | Version v1
Dataset Open

Earthworm abundance and availability does not influence the reproductive decisions of black-tailed godwits in an agricultural grassland

  • 1. University of Groningen & RSPB*
  • 2. University of Groningen
  • 3. University of Groningen & NIOZ*
  • 4. University of Groningen & University of South Carolina*

Description

  1. Maintaining the biodiversity of agricultural ecosystems has become a global imperative. Across Europe, species that occupy agricultural grasslands, such as Black-tailed Godwits (Limosa limosa limosa), have undergone steep population declines. In this context, there is a significant need to both determine the root causes of these declines and identify actions that will promote biodiversity while supporting the livelihoods of farmers.
  2. Food availability, and specifically earthworm abundance (Lumbricidae), during the pre-breeding period has often been suggested as a potential driver of godwit population declines. Previous studies have recommended increasing the application of nitrogen to agricultural grasslands to enhance earthworm populations and aid agricultural production. Here we test whether food availability during the pre-breeding period affects when and where godwits breed.
  3. Using large-scale surveys of food availability, a long-term mark-recapture study, focal observations of foraging female godwits, and tracking devices that monitored godwit movements, we found little evidence of a relationship between earthworm abundance and the timing of godwit reproductive efforts or the density of breeding godwits. Furthermore, we found that the soils of intensively managed agricultural grasslands may frequently be too dry for godwits to forage for those earthworms that are present.
  4. The increased application of nitrogen to agricultural grasslands will therefore likely have no positive effects on godwit populations. Instead, management efforts should focus on increasing the botanical diversity of agricultural grasslands, facilitating conditions that prevent hardening soils, and reducing the populations of generalist predators.

Notes

All files are numbered, a new number for each analysis/topic. Related files are given the same number but a different letter, i.e. files 3a, 3b, 3c, 3d are related to each other. 

1a.March2013_soil invertebrate sampling data
This file contains the results from our invertebrate sampling in March 2013. It has a tab containing all the worms and a tab containing all the non-worms. The section refers to the depth of the sample; 1=0-5cm, 2=5-10cm, 3=10-15cm, and 4=14-20cm.

1b.May2013_soil invertebrate sampling data
This file contains the results from our invertebrate sampling in May 2013. It has a tab containing all the worms and a tab containing all the non-worms. The section refers to the depth of the sample; 1=0-5cm, 2=5-10cm, 3=10-15cm, and 4=14-20cm.

1c.March2014_soil invertebrate sampling data
This file contains the results from our invertebrate sampling in March 2014. It has a tab containing all the worms and a tab containing all the non-worms. The section refers to the depth of the sample; 1=0-5cm, 2=5-10cm, 3=10-15cm, and 4=14-20cm.

1d.May2014_soil invertebrate sampling data
This file contains the results from our invertebrate sampling in May 2014. It has a tab containing all the worms and a tab containing all the non-worms. The sections refer to the depth of the sample; 1=0-5cm, 2=5-10cm, 3=10-15cm, and 4=14-20cm.

2.Bill length of Female godwits caught in Haanmeer
This file contains the measured bill lengths of females in the Haanmeer

3a.2013+2014_Worms_top 10cm_with management intensity
This file contains the average worm biomass of worms in the top 10cm in March and May and has a column that identifies the management intensity.

3b2013+2014_.Worms_top 10cm_with soil type
This file contains the average worm biomass of worms in the top 10cm in March and May and has a column that identifies the soil type.

4a.2013 soil penetration data
This file contains the soil penetration resistance data collected in 2013.

4b.2014 soil penetration data
This file contains the soil penetration resistance data collected in 2014.

5.2013+2014_foraging observation data
This file contains the foraging observations made in 2013 and 2014 and the average number of worms in the field of foraging in order to fit intake rates.

6.2013+2014_sightings in field and worm biomass
This file contains the number of sightings in a field in 2013 and 2014, the size of the field and the field's worm biomass in order to look for a relationship.

7.2013+2014_nesting density and worm biomass
This file contains the number of nests in a field in 2013 and 2014, the size of the field and the field's worm biomass in order to look for a relationship.

8.2013+2014_Arrival-Laying Date of marked females and worm biomass
This file contains the arrival date, laying date and the arrival-laying interval of females as well as the worm biomass within 200 and 300 meters of the nest.

9a.2013+2014_all laydates and worm biomass within 200m
This file contains all of the known lay dates of godwits in 2013 and 2014 and the worm biomass within 200 meters of those nests in order to look for a relationship.

9b.2013+2014_all laydates and worm biomass within 300m
This file contains all of the known lay dates of godwits in 2013 and 2014 and the worm biomass within 300 meters of those nests in order to look for a relationship

10a.2013+2014_all egg volumes and worm biomass within 200m
This file contains all the average egg volumes of nests from 2013 and 2014 in which all 4 eggs were measured and includes the worm biomass within 200 meters of those nests in order to look for a relationship.

10b.2013+2014_all egg volumes and worm biomass within 300m
This file contains all the average egg volumes of nests from 2013 and 2014 in which all 4 eggs were measured and includes the worm biomass within 300 meters of those nests in order to look for a relationship.

11a.2013+2014+2015_Distance of tracking location from nesting location for FigS1
This file contains the distance from the nest of three females that were tracked via GPS-transmitters in 2014 and 2015.

11b.2013+2014_Locations of observation and field centers for FigS1
This file contains the distance from the nest to the center of the field of observation of 42 individually-marked females that were resighted during the 2014 pre-breeding period.

12a.2013_March_sampling location and worm biomass
This file contains the worm biomass in the top 10cm in March 2013 for each sampling point and the location (latitude + longitude) of that sampling location, used to look for the presence of spatial autocorrelation of worm biomass.

12b.2014_March_sampling location and worm biomass
This file contains the worm biomass in the top 10cm in March for each sampling point and the location (latitude + longitude) of that sampling location, used to look for the presence of spatial autocorrelation of worm biomass.

Funding provided by: Nederlandse Organisatie voor Wetenschappelijk Onderzoek
Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100003246
Award Number: Shorebirds in Space (854.11.004)

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10a.2013_2014_all_egg_volumes_and_worm_biomass_within_200m.csv

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