Above nestbox scale |
Above nestbox scale |
Tree canopy closure
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Total percentage of tree canopy and understorey vegetation cover above
the focal nestbox estimated as the average cover from two measurements
in May and July (to account for seasonal variability in leaf growth).
Cover was defined as the percentage of black pixels in processed photos
taken with an Apple iPhone 11 levelled-flat on a tripod set at 1 metre
from the ground and as close to the nestbox as possible without
including the box in the photo. Original photos were desaturated to
grayscale with the colour curve adjusted to make all pixels either black
or white using GIMP 2.10.24.
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5m radius |
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Tree canopy cover
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Percentage of the tree canopy (in 10% increments) occupied by trees of
the same species taller than 4 m within a 5m radius circular area around
the focal nestbox.
10 separate variables for each identified species: Ash
Fraxinus excelsior, Beech Fagus sylvatica, Field Elm
Ulmus minor, Field Maple Acer campestre, Holly Ilex
aquifolium, Lime Tilia x europaea, Oak Quercus spp.,
Sweet Chestnut Castanea sativa, Sycamore Acer
pseudoplatanus, Yew Taxus baccata.
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Understorey cover
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Percentage of the canopy (in 10% increments) occupied by trees of the
same species smaller than 4 m within a 5m radius circular area around
the focal nestbox.
19 separate variables for each identified species: Alder
buckthorn Frangula alnus, Ash Fraxinus excelsior, Beech
Fagus sylvatica, Blackthorn Prunus spinosa, Cherry Plum
Prunus cerasifera, Elder Sambucus nigra, Field Elm
Ulmus minor, Field Maple Acer campestre, Hawthorn
Crataegus monogyna, Holly Ilex aquifolium, Lime
Tilia x europaea, Oak Quercus spp., Rowan Sorbus
aucuparia, Spindle Euonymus europaeus, Sycamore Acer
pseudoplatanus, Wayfaring Tree Viburnum lantana, Whitebeam
Sorbus aria, Wild Cherry Prunus avium, Hazel Corylus
avellana.
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Field layer cover
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Percentage of the field layer (in 10% increments) occupied by plants of
the same species within a 5m radius circular area around the focal
nestbox. Climbing species cover was estimated up to a height of 10 m.
16 separate variables for each identified species or group:
Bluebells Hyacinthoides non-scripta, Bramble Rubus
fruticosus agg., Cleavers Galium aparine, Cow Parsley
Anthriscus sylvestris, Dogs Mercury Mercurialis perennis,
Ground Ivy Glechoma hederaceae, Hedge Woundwort Stachys
sylvatica¸ Speedwell Veronica spp., Herb Robert Geranium
robertianum, Honeysuckle Lonicera pericylmenum, Lords and Ladies
Arum maculatum, Meadow Buttercup Ranunculus acris, Nettles
Urtica dioica, Yellow Archangel Lamiastrum galeobdolon,
Fern (group, not identified to species)”, Grass (graminoid group, not
identified to species).
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Ground cover
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Percentage of the ground (in 10% increments) occupied by bryophytes
within a 5m radius circular area around the focal nestbox.
[Data were also collected for cover of fungi, leaf litter and bare
ground too but due to low variability among sites were not considered in
the analyses].
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Quadrat |
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Quadrat cover
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Mean percentage cover of individual species over four 2m x 5m quadrats
starting 5 m from the focal nestbox and running North, South, East and
West.
2 separate variables for each key species identified: Bramble
Rubus fruticosus agg. and Honeysuckle Lolium
periclymenum.
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5 m + quadrat |
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Tree abundance
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Relative abundance of individual tree species within a 10m radius from
the focal nestbox. Obtained by adding the total number of individual
trees with a trunk circumference >40cm within a 5m radius
circular area and in four 2m x 5m quadrats starting 5 m from the focal
nestbox and running North, South, East and West. Abundance within the 5m
radius area included every individual tree, whilst the four quadrats
provided relative abundance within the area 5m-10m from the nestbox
based on quadrat totals.
20 separate variables for each identified species: Ash
Fraxinus excelsior, Beech Fagus sylvatica, Blackthorn
Prunus spinosa., Cherry Plum Prunus cerasifera, Elder
Sambucus nigra, Field Elm Ulmus minor, Field Maple
Acer campestre, Guelder Rose Viburnum opulus, Hawthorn
Crataegus monogyna, Hazel Corylus avellana, Holly
Ilex aquifolium, Lime Tilia x europaea, Oak Quercus
spp., Plum Prunus domestica, Spindle Euonymus europaeus,
Sweet Chestnut Castanea sativa, Sycamore Acer
pseudoplatanus, Wayfaring Tree Viburnum lantana, Wild Cherry
Prunus avium, Yew Taxus baccata.
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Total trees
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Combined relative tree abundance. Sum of “Tree abundance” for all 20
recorded species at each nestbox.
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Tree richness
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Observed tree species richness calculated adding all species with “Tree
abundance”>0 for each nestbox.
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Local (GIS) |
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Distance to nearest footpath
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Distance in metres from focal nestbox to the nearest footpath. Collected
via GPS with minimum 3m accuracy and mapped using ARCGIS
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Distance to nearest nestbox
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Distance in metres from focal nestbox to the nearest nestbox. Collected
via GPS with minimum 3m accuracy and mapped using ARCGIS
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Distance to nearest woodland margin
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Distance in metres from focal nestbox to the nearest woodland margin.
Collected via GPS with minimum 3m accuracy and mapped using ARCGIS
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