Data from: Winter game crop plots for gamebirds retain hedgerow breeding songbirds in an improved grassland landscape
Data files
Jan 08, 2024 version files 127.50 KB
Abstract
The cause of recent population declines in some farmland / hedgerow breeding bird species in the UK is related to a lack of cover and food resources in winter. In improved grassland areas some of those declines have been particularly acute and some have been shown to be related to the availability of grass and weed seed in winter. The provision of seed-bearing crops as part of AES options has been shown to benefit some of these birds. Game crop plots sown on shooting estates for holding and driving gamebirds in autumn and winter have been shown to hold relatively high densities of farmland and wood-edge birds during the winter.
We studied breeding songbirds in hedges in a primarily improved grassland area in the SW of England where there are some large shooting estates that sow relatively large game crop plots (1 - 5 ha) in the landscape. In this study we found that otherwise similar hedges in terms of size and density near to those winter game crop plots, had between 1.5 and 2 times as many breeding resident songbirds per unit length the following spring compared to hedges further away from game crop plots. This was despite game management in these plots being wound down during February and in many cases, the crops themselves being removed by mid-March. Hedges within approximately 350m from game crop plots had more breeding birds. We discuss possible mechanisms and suggest that some passerines preferentially establish breeding territories in hedges near to game crops in late winter. We suggest how to distribute game crop plots to maximise any benefit in an improved grassland landscape.
README: Winter game crop plots for gamebirds retain hedgerow breeding songbirds in an improved grassland landscape
Authors:
Rufus Sage (lead author), Maureen Woodburn, Sam McCready, Jenny Coomes (processed the data and did the analysis).
Sage, Rufus; Woodburn, Maureen; McCready, Sam; Coomes, Jenny (2023), Winter game crop plots for gamebirds retain hedgerow breeding songbirds in an improved grassland landscape, Dryad, Dataset, https://doi.org/10.5061/dryad.7wm37pvzs
Files uploaded:
- R code for analysis: Exmoor data - for upload.R
- CSV of data: exmoordatafull.csv
The dataset contains information about the hedges and game cover, as well as the number of birds seen per survey.
Column headings in dataset:
ID: unique to all rows
site: 1, 2 or 3
site.new: categorical version of site (a, b or c)
transect.orig: the original transect number
transect.code: unique transect number for each different cover plot, with five hedges within it.
distance: five bands: 1 to 5. (changed to categorical in the code). 0-50m, 75-150m, 200-350m, 500-800, 1.1km+
visit: early spring or late spring, 1 or 2.
date: numbers. Starting 1st April.
covertype1: main plant species in the cover plot
covertype2: secondary plant species in the cover plot
coverarea.map: measured area of the cover plot from a map. Metres squared.
coverarea.keeper: the area that the gamekeeper gave for the cover plot
cover.manage: how the cover plot was managed
weather
time
length: length of the hedge in metres
num.hedge.types: number of distinct hedge types in the hedge line.
status: category of how 'good' the hedge seems to be for birds (only recorded on second visit).
hedge.den: hedge density: category of 1 (least dense), 2 or 3 (most dense).
cut: If recently cut in the preceding winter, put a 1. If not, put a zero.
bank.height: height of bank that the hedge is on.
width: hedge width - bottom part of tall hedges
hedge.height: height of hedge (without the bank)
standards: presence/absence of standard (tall) trees in the hedge. 0 = no standards to 2 = lots of standards.
gaps: 0 (no gaps), 1 or 2 (many gaps).
crop1: In adjacent field. Improved permanent grass (0), unimproved permanent grass, grazed areas and moorland (1), leys (2), game cover (3), arable (4), track or road (5), scrub (6)
crop2: In adjacent field. Improved permanent grass (0), unimproved permanent grass, grazed areas and moorland (1), leys (2), game cover (3), arable (4), track or road (5), scrub (6)
double.hedge: 1 if both sides were included in survey. 0 if not.
road: 1 = road, 0 = grassy track
plant.spp: Dominant plant species in the hedge. Hz – hazel, Ok- oak, Wil – willow, Bt – blackthorn, Be – beech, Hw – hawthorn, Eld – elder, Bir – birch, Syc – sycamore, Gor - gorse
The following are all the bird species recorded: Robin, Wren, Chaffinch, Blue Tit, Blackbird, Great tit, Goldfinch, Dunnock, Linnet, Yellowhammer, Chiffchaff, Willow warbler, Blackcap, Wood Pigeon, Magpie, Spotted Flycatcher, Stonechat, Carrion Crow, Bullfinch, Goldcrest, Buzzard, Meadow Pipit, Osprey, Wheatear, Green Finch, Siskin, Redstart, Pied Wagtail, Long Tailed Tit, Coal Tit, Whitethroat, Sparrowhawk, House Sparrow, Garden Warbler, Jackdaw, Stock Dove, Swallow, GS Woodpecker, Raven, Lesser Redpol, Jay, Grasshopper Warbler, Skylark, Nuthatch, Song Thrush, and Mistle Thrush.
Some of these species were not used in analysis - see main text.
The birds that were used in analysis were split into resident and migrant - see R code for these calculations.
Cells containing NA are missing data either because the survey was not undertaken or because the data was not known.
Methods
This dataset was collected on Exmoor by two researchers. They undertook bird surveys along hedges at differing distances from wild bird cover plots. The data is the number of birds recorded on each survey and measurements of the hedges such as height, density and width etc.
The data is a csv file and analysis has been performed in R.