Birds and green lanes_ Breeding season bird abundance,

Biological Conservation 126 (2005) 540–547 www.elsevier.com/locate/biocon

Birds and green lanes: Breeding season bird abundance, territories and species richness M.P. Walker a

a,¤

, J.W. Dover a, S.A. Hinsley b, T.H. Sparks

b

Institute for Environment and Sustainability Research, Applied Sciences, Faculty of Health and Science, StaVordshire University, Mellor Building, College Road, Stoke-On-Trent ST4 2DE, UK b CEH Monks Wood, Abbots Ripton, Huntingdon, Cambridgeshire PE28 2LS, UK Received 3 November 2004 Available online 2 September 2005

Abstract This study examines bird occurrence on 20 green lanes (farmland tracks with un-sealed surfaces, bordered on each side by hedgerows) and on 20 paired single hedgerows during the 2002 breeding season in Cheshire, UK. Measures of bird abundance, territories and species richness were all found to be signiWcantly greater on green lanes than on single hedgerows. SigniWcantly more birds were also found to occur on the inside rather than on the outside of green lanes in terms of abundance and species richness. All measures of bird occurrence on green lanes were inXuenced by hedge width and surrounding land use. Bird abundance on single hedgerows was inXuenced by the number of trees and amount of hawthorn in the hedge. Seventeen of the 18 most abundant bird species recorded in this study were found to occur in greater numbers on green lanes rather than in single hedgerows; for half of these species the diVerence was signiWcant. The importance of green lanes for birds, and other wildlife is discussed, as well as their possible future within the UK landscape.  2005 Elsevier Ltd. All rights reserved.

Keywords: Bird abundance; Green lanes; Farmland birds; Field boundaries; Hedges; Species richness

1. Introduction Field boundaries, in particular hedgerows, are now widely regarded as valuable habitat for birds in an otherwise largely hostile agricultural environment (Lack, 1992; Parish et al., 1994).

Hedgerows are used by birds for foraging and nesting, and as physical shelter, roost sites and song posts (Osborne, 1984; Green et al., 1994; Sparks et al., 1996; Hinsley and Bellamy, 2000), as well as providing movement and dispersal corridors (Demers et al., 1995). As farmland landscape features, hedgerows have been

*

Corresponding author. Tel.: +44 01244 279 823.

E-mail addresses: m.p.walker@staVs.ac.uk, hotmail.com (M.P. Walker).

mikewalked@

0006-3207/$ - see front matter  2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocon.2005.07.005

found to be second only to woodland in the abundance of birds that they can support (Lack, 1992).

Many studies have been carried out to determine what features of a hedgerow inXuence its usage by birds (e.g., Arnold, 1983; Parish et al., 1994, 1995; Sparks et al., 1996). It is generally agreed that for most woodland passerines, a tall, wide hedgerow with trees is favourable, possibly due to the relatively greater provision of resources and shelter, and protection from predators. It is also the type of hedgerow that most closely resembles woodland edge habitat. Other factors thought to increase the value of hedges, particularly for granivorous birds, but also for some insectivorous/omnivorous species, include the presence of a wide, species rich verge/ bank and a ditch (Parish et al., 1995). These features can increase the eVective area of breeding and foraging habitat of a hedge.

M.P. Walker et al. / Biological Conservation 126 (2005) 540–547

Green lanes are not uniform in composition (Dover et al., 2000) but here we use the deWnition of an unmetalled track bordered by two hedgerows (Croxton et al., 2002, 2005); green lanes have only recently been identiWed as distinct boundary features with clear potential as biodiversity reservoirs (Dover and Sparks, 2001). A few studies investigating their structure and botanical composition have revealed that bees, butterXies and wild Xowers occur in greater numbers, and with greater species richness, than in other common Weld boundary types such as single hedgerows and grassy banks (Dover et al., 1997, 2000; Dover and Sparks, 2001; Croxton et al., 2002, 2005; Walker et al., in press). Features of green lanes probably contributing to their greater biodiversity include substantially larger uncropped verges than grass banks or hedgerows (Dover et al., 2000), enhanced shelter, modiWed microclimate, lower agricultural inputs and management regime impacts, and higher structural diversity (Dover and Sparks, 2001).

The precise number of green lanes throughout England is not yet known, but at last estimate there were thought to be about 8500 km (from 1976; report in Belsey, 1998), thus making them relatively rare in comparison with the 449,000 km of hedgerow in England and Wales as revealed by the Countryside Survey 2000 (Haines-Young et al., 2000).

Dover and Sparks (2001) suggested that the features making green lanes valuable for the taxa so far studied would also make them beneWcial to birds by providing a greater abundance of refuge and foraging habitat than oVered by other Weld boundary types in agricultural landscapes. If true, then the argument would be strengthened to provide more protection for green lanes, which at present are not recognised by the Countryside Survey 2000 (Haines-Young et al., 2000) as speciWc landscape elements (Dover et al., 2000) and only have loose protection under current hedgerow regulations (Sparks et al., 1999). Active management of existing green lanes and the creation of new ones could provide another tool to help combat the current declines in farmland, and other, birds (Gregory et al., 2002).

This study seeks to investigate the value of green lanes for farmland birds by comparing species richness and abundance of birds in green lanes compared to that in single hedgerows of similar structure.

Precise deWnitions of green lanes vary, but for this research a green lane was deWned as a track bordered on each side by a hedgerow running through farmland and used by farm vehicles, livestock or horses. The width of a green lane between its hedges may range from under 2 m up to about 40 m (Belsey, 1998), however, in this study only lanes between 2 and 15 m wide were used. All but one of the tracks were unmetalled, the one exception being made where a previously metalled track had been almost entirely overgrown by grass or moss.

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2. Materials and methods 2.1. Selection of sites Twenty sections of green lanes between 100 and 500 m in length were selected from farmland within a 10 km radius of the city of Chester in the UK (Walker et al., in press). Sections were deemed suitable if the section contained no more than 5% gaps in either hedgerow, and the lane remained of similar orientation throughout its length. Due to low availability of suitable green lanes throughout the local region, the lanes could not be chosen using more speciWc criteria. Within the lanes, however, sections were chosen to diVer as much as possible in physical characteristics such as width, orientation, vegetation and track type to represent a range of lane types. In the case of three green lanes, more than one section was chosen to be surveyed per green lane.

Seven sections were chosen in this way, with each ‘samelane’ section separated by an average of 250 m. Sections were only chosen if they diVered in a number of the physical characteristics described above.

Single hedgerows, paired with each of the chosen lanes, were selected on the basis of their similar orientation and surrounding land use to their paired lane.

Each lane and hedgerow was marked out using bamboo canes positioned at 30 m intervals along the inside and outside of the lane and both sides of each hedgerow.

Wool markers were tied to the hedge at the same points as backup.

2.2. Bird surveys Between April and July 2002 and from dawn to 11.30 am, seven bird surveys were carried out on each of the green lanes and paired hedgerows by the same person (MPW). Each site was walked and all birds seen or heard, and their observed behaviour, were recorded on a map of the site. The surveyor stopped at regular intervals to listen for bird calls, and used the bamboo markers as guides to correctly locate bird records. Special care was taken not to record the same bird twice on one survey. All lanes were walked down the inside as well as along both outer sides of the hedgerows whilst recording bird observations. If a bird of the same species was observed or heard at a similar place on both sides of a hedge it was noted, but not recorded as a diVerent bird on the same survey. The order in which the insides and outsides of the lanes were walked was varied between visits. The times at which each site was walked was also varied, although the hedge was always walked within a similar time to its paired lane and usually on the same day. Any management activities carried out by landowners on or around the sites throughout the survey period were also noted.

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M.P. Walker et al. / Biological Conservation 126 (2005) 540–547

3. Analysis 3.1. Bird occurrence For all sites, bird records were combined to identify territories following the methodology of Bibby et al. (1992).

The relative occurrence of birds on green lanes and hedgerows was explored using three measures: (i) the mean number of birds (abundance) per 50 m of lane/100 m hedge; (ii) the number of territories recorded per 50 m of lane/100 m hedge; (iii) the mean number of bird species recorded per surveyed length of lane and hedgerow (species richness).

The diVerent lengths of lane and hedgerow allow a comparison of the same total length of hedgerow, i.e., 100 m.

Two-way analysis of variance (factors: pair and lane/ hedge) was performed on all three bird measures to test for signiWcant diVerences between lanes and hedgerows. To explore the possibility of non-independence (spatial correlation) between sites, similarities (measured by correlation) between sites in bird abundance and species richness were compared with the physical distances between sites.

The occurrence of birds in green lanes was also examined in more detail in relation to whether the birds were sighted inside the hedgerows of the lane or outside of them.

“Inside” birds were counted as those observed between the two hedgerows of the lane or on the inner half of the hedgerows. “Outside” birds were counted as any bird seen on the outer half of either hedgerow (Weld-side) of the lane or observed on land within 2 m of the outer edge. These data were then used to calculate the mean bird abundance per 50 m of lane and mean species richness of birds in these two categories. DiVerences were tested using two-way analysis of variance (factors: lane and inside/outside).

3.2. Regression analysis Data describing vegetation structure and plant species composition (Table 1) were used as independent variables in linear stepwise regression using the Minitab 13 statistical package, to explore the inXuence of habitat characteristics on the three measures of bird occurrence described above. Analyses were performed separately for

Table 1 Predictor variables used in stepwise regression analysis and their mean values for both green lanes and single hedgerows sampled Lanes Tree number Vegetation width

Vegetation height

Hedge volume Hedge density Woody area Orientation Hawthorn Blackthorn Hazel Bramble Elder Dog rose Hedge species Grassland Number of ditches Ditch width

Number of trees present per 100 m of green lane or single hedgerow Total width of ground vegetation recorded on each lane and hedgerow (cm). The central tracks of lanes are not included in this measurement Mean height of vegetation growing in verges of green lanes and hedgerows (cm) For single hedgerows this is the mean of two verges (each side of the hedgerow), for lanes it is the mean of four verges (each side of the two verges). Central track vegetation is not included.

Mean hedgerow volume (width £ height) for lanes and hedgerows (m2) Mean hedgerow density for lanes and hedgerows (1–5).

Density obtained by counting the proportion of gaps in each hedgerow Mean area of woody stands other than hedgerows on green lanes (m2) Orientation of lanes and hedgerows either North–South (1), or East–West (0) Mean hawthorn (Crataegus monogyna) % composition of hedgerows of green lanes and single hedgerows Mean blackthorn (Prunus spinosa) % composition of hedgerows of green lanes and single hedgerows Mean hazel (Corylus avellana) % composition of hedgerows of green lanes and single hedgerows Mean bramble (Rubus fruticosus agg) % composition of hedgerows of green lanes and single hedgerows Mean elder (Sambucus nigra) % composition of hedgerows of green lanes and single hedgerows Mean dog rose (Rosa canina agg) % composition of hedgerows of green lanes and single hedgerows Mean number of woody plant species growing in hedgerows of green lanes and single hedgerows Whether green lanes and single hedgerows are bordered by grassland on neither side, one side, or both sides Number of ditches recorded on each green lane/single hedgerow Total combined ditch width for single hedgerow and green lanes (cm)

Hedges

P

6.6 § 0.8

1.6 § 0.3

<0.001

570.7 § 43.4

236.4 § 19.2

<0.001

57.8 § 3.7

43.9 § 3.8

0.18

5.5 § 0.5 3.6 § 0.1

4.5 § 0.5 3.7 § 0.2

0.07 N/A

19.9 § 6.6 0.3 § 0.1 46.4 § 4.3

N/A 0.3 § 0.1 69.4 § 4.6

N/A N/A 0.03

18.1 § 3.3

13.2 § 3.4

0.82

4.9 § 1.5

3.2 § 1.2

0.07

5.2 § 1.8

1.3 § 0.8

0.02

6.0 § 1.8

6.2 § 2.1

1.00

3.1 § 1.1

1.7 § 0.8

0.41

4.9 § 0.3

3.3 § 0.3

<0.01

1.0 § 0.1

0.7 § 0.1

N/A

0.7 § 0.1 76.3 § 18.3

0.6 § 0.1 50.5 § 15.7

N/A 0.18

SigniWcance values obtained where applicable from Friedman’s ANOVA performed between boundary types. N/A, not applicable for signiWcance testing; ns, P > 0.05; *P < 0.05; **P < 0.01; ***P < 0.001.

M.P. Walker et al. / Biological Conservation 126 (2005) 540–547

green lanes and single hedgerows. The length of each lane and hedgerow was logarithmically transformed and entered as a covariate into the regression analysis of bird species richness to remove diVerences in the data caused by the diVering lengths of each lane and hedgerow surveyed. Vegetation structure and plant species composition data were statistically compared between lanes and single hedgerows using the non-parametric Friedman two-way analysis of variance (Table 1).

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8 7 6 5 4 3 2

3.3. Bird species

1

The abundance of individual species of birds was examined on both green lanes and hedgerows. For the 18 most abundant species, diVerences in abundance between the two boundary types were tested using Friedman two-way analysis of variance.

3.4. Bird groups Bird species recorded more than Wve times during the sampling period and which could be easily categorised by the following criteria were placed into the following groups: (i) taxonomic group; (ii) preferred diet; (iii) whether resident or migratory. A summary of groups used and the bird species they contain is given in Table 2.

For each group type, the mean abundance of birds recorded per 50 m of green lane and 100 m of hedgerow was calculated. For each group, diVerences in mean abundances between green lanes and hedgerows were tested using Friedman two-way analysis of variance.

4. Results During the sampling period, 39 species of bird were recorded on green lanes and 27 species were recorded on single hedgerows. Green lanes had signiWcantly greater numbers of all measures of bird occurrence than did single hedgerows (all P < 0.001) (Fig. 1).

Table 2 Categorisations of bird species into groups Insectivores

Granivores

Tits

Summer migrants

Blackbird Song Thrush Mistle Thrush Blue tit Great tit Long-tailed tit Dunnock Treecreeper Wren Whitethroat ChiVchaV Robin

BullWnch ChaYnch GoldWnch GreenWnch Linnet Yellowhammer

Blue tit Great tit Long-tailed tit Coal tit

Whitethroat ChiVchaV

0 Abundance

Territories

Species Richness

Fig. 1. Mean bird abundance and number of bird territories found to occur per 50 m of green lanes (black Wll) and 100 m hedgerows (white Wll) sampled. Mean bird species richness per entire lane and hedgerow is also shown. SigniWcance obtained from two-way analysis of variance. For each measure of bird occurrence; P < 0.001 between inside and outside of bordering hedgerows.

Measures of both abundance and numbers of territories show over three times as many birds recorded on green lanes as on single hedgerows; when expressed as data per 50 m green lane and 100 m hedgerow the diVerence is still substantial with lanes holding almost 2 £ bird abundance and 1.7 £ number of territories.

When the eVects of distance between sites on similarities of bird abundance and bird species richness were assessed, only a modest pattern was found (abundance: r D ¡0.116, species richness: r D ¡0.187) which we considered would not adversely aVect results from the robust statistical techniques used.

When the positions of birds sighted on green lanes was examined, more than double the number of birds occurred “inside” the hedgerows than “outside” of them, both in terms of abundance and species richness (Fig. 2).

Using stepwise regression analysis, two variables (how many sides of the lane were bordered by grassland, and to a lesser extent the mean volume of the two hedges) explained 67% of the variation of bird abundance in green lanes (Table 3). Hedge volume was the only variable in the model for the number of territories in green lanes, describing 46% of the variation. Once lane length was accounted for, bird species richness was best explained by two variables (how many sides were bordered by grassland, and mean hedge volume). In all models for green lanes, the eVects of the signiWcant variables were positive. The regression model for bird abundance in single hedgerows contained two variables (the number of trees in the hedge and the percentage composition of Hawthorn) accounting for 41% of the variance (Table 3). Both variables had positive eVects on bird abundance. None of the variables used were found to have a signiWcant inXuence on bird species richness or the number of territories in single hedges. Five of the

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7

5. Discussion

6

This study shows that during the breeding season, bird abundance and bird species richness are both greater in green lanes than in single hedgerows, results consistent with the patterns for bees, butterXies and wild Xowers recorded in other studies (Dover et al., 1997, 2000; Dover and Sparks, 2001; Croxton et al., 2002; Walker et al., in press). The extent of the diVerence in bird populations in green lanes compared to single hedgerows appears similar to that of butterXies recorded

by Dover et al. (2000), where close to double the abundance and species richness was recorded in green lanes.

However, the diVerence in bird abundance is actually greater, as Dover et al. (2000) compared butterXy abundance using same lengths of lanes and hedgerows, whereas in this paper, bird abundance was compared using 50 m green lane compared with 100 m hedge.

Perhaps the most fundamental diVerence between green lanes and single hedgerows responsible for their diVering usage by birds is structure. A green lane is essentially two hedges, so more birds would be expected to occur on the lane simply from a doubling of the habitat area. However, the methods of analysing bird abundance and territories in this study accounted for this and yet the diVerence remained highly signiWcant. This suggests that there are aspects of green lanes other than the absolute amount of hedge that increases their value for birds.

Green lanes are more structurally diverse than single hedgerows, containing a central track as well as the hedgerows and verges. The central track not only provides a greater habitat area, but also a habitat type not usually found on single hedgerows. Many studies have concluded that an increase in habitat diversity increases bird abundance and species richness (e.g., Rands, 1986, 1987; Stoate et al., 1998). Previous work on the lanes and hedgerows used in this study found the central track vegetation community to be diVerent from that of the verges of green lanes and single hedge-

5 4 3 2 1 0 Abundance/100m

Species Richness

Fig. 2. Mean bird abundance per 100 m and species richness of green lane observed within the bordering hedgerows (black Wll) and observed outside the bordering hedgerows (white Wll). SigniWcance values obtained from two-way analysis of variance. For both measures of bird occurrence; P < 0.001 between lanes and hedgerows.

variables used in the regression analysis were found to be signiWcantly greater in green lanes than in single hedgerows. These were; the number of trees, the mean vegetation width, both hawthorn and bramble percentage composition of the hedge, and the woody plant species richness of the hedge (Table 1).

4.1. Individual species Seventeen of the 18 most abundant bird species were found in greater numbers on green lanes than in single hedgerows (Table 4). These diVerences were signiWcant for nine species (Table 4).

4.2. Bird groups Three of the four groups were found to contain signiWcantly (P < 0.05) greater numbers of birds in green lanes than in single hedgerows (Table 5), and for insectivorous birds this diVerence was highly signiWcant (P < 0.001).

Table 3 Stepwise regression analysis of bird abundance, species richness and the number of territories for green lanes and single hedgerows, using the variables listed in Table 1 Bird abundance green lanes

Number of territories green lanes

Variable

CoeYcient

t

Grassland Hedge volume Total r2

1.79 0.5 67.4

4.15 4.08

Bird species richness green lanes Log lane length 7.9 Grassland 1.43 Hedge volume 0.4 Total r2

83.1

P

Variable 0.001 0.001

Hedge volume Total r2

CoeYcient 0.9

t

P

3.93

0.001

2.86 2.22

0.011 0.040

46.2

Bird abundance single hedgerows 6.96 3.78 3.72

<0.001 0.002 0.002

Tree number Hawthorn Total r2

0.276 0.0156 40.5

For single hedgerows, no variables entered the models for the number of territories and bird species richness.

M.P. Walker et al. / Biological Conservation 126 (2005) 540–547 Table 4 Mean occurrence § SE of the 18 most abundant bird species per 50 m of green lanes and 100 m of single hedgerows Species

Lanes

Hedges

P

Blackbird Song Thrush Robin Great tit Blue tit Long-tailed tit Linnet ChaYnch GreenWnch GoldWnch Yellowhammer Wren Dunnock ChiVchaV Whitethroat Blackcap Magpie Wood pigeon

Means § SE 0.84 § 0.11 0.08 § 0.04 0.65 § 0.11 0.52 § 0.07 0.69 § 0.12 0.15 § 0.01 0.06 § 0.04 0.66 § 0.10 0.12 § 0.04 0.03 § 0.02 0.07 § 0.05 0.76 § 0.11 0.10 § 0.03 0.41 § 0.12 0.10 § 0.03 0.10 § 0.03 0.09 § 0.02 0.50 § 0.13

Means § SE 0.56 § 0.10 0.01 § 0.01 0.36 § 0.07 0.29 § 0.06 0.28 § 0.09 0.04 § 0.02 0.05 § 0.02 0.50 § 0.10 0.05 § 0.03 0.01 § 0.01 0.06 § 0.04 0.33 § 0.07 0.16 § 0.05 0.02 § 0.02 0.04 § 0.04 0.01 § 0.01 0.04 § 0.02 0.21 § 0.06

0.018 0.004 0.074 0.108 0.018 0.132 0.705 0.074 0.002 1.000 0.257 0.000 0.796 0.001 0.008 0.007 0.033 0.157

DiVerences between lanes and hedgerows tested using Friedman’s ANOVA.

Table 5 Mean occurrence § SE of the four groups of bird species (as described in Table 2) per 50 m of green lanes and 100 m of single hedgerows Green lane Insectivorous Granivorous Tits Summer migrants

4.33 § 0.55 0.96 § 0.17 1.37 § 0.19 0.52 § 0.13

Hedge 2.09 § 0.24 0.68 § 0.01 0.61 § 0.10 0.06 § 0.04

SigniWcance <0.001 0.074 0.002 0.001

DiVerences between lanes and hedgerows tested using Friedman’s ANOVA.

rows (Walker et al., in press). The inside verges of green lanes have also been found to contain diVerent vegetation communities to single hedgerow verges, as well as signiWcantly greater vegetation species richness (Croxton et al., 2002, 2005; Walker et al., in press). Green lane verges were found in this study to be signiWcantly wider than single hedgerow verges, providing a greater area of more species-rich habitat. Wider verges at the base of hedges are thought to reduce the incidence of bird predation (Chamberlain et al., 1995). All of these features of green lanes are likely to provide birds with a larger area of habitat for nesting, sheltering and roosting, for example, with an increased amount of resources at their disposal for activities such as feeding and nest building.

It appears that the main beneWt of a green lane to birds lies within the parallel hedgerows, although only a small proportion of birds were recorded on the central track (<5%). A recent study has shown the outside verges to be more akin to those of single hedgerows than

545

to the inside verges in several respects including plant species, community type and environmental conditions (Walker et al., in press). Thus the greater species richness of birds in green lanes over single hedgerows in this study is likely to be a direct result of the greater structural diversity found in green lanes.

5.1. Individual habitat factors In this study, the mean volume of the hedges was found to inXuence bird abundance, number of bird territories, and bird species richness in green lanes. Hedge size has been found in many other studies to inXuence bird abundance on single hedgerows (Arnold, 1983; Lack, 1992; Green et al., 1994; Hinsley and Bellamy, 2000). Again this can be explained by a simple increase in habitat volume, although wider hedgerows may also have a lower incidence of nest predation than their thinner counterparts (Arnold, 1983; Chamberlain et al., 1995), and be attractive to a wider range of bird species.

The presence of pasture adjacent to the lane had a positive eVect on bird abundance. This has also been recorded in other studies (Arnold, 1983; Parish et al., 1994; Peach et al., 2004) and stresses that in terms of their value to birds, which tend to be more mobile than many other groups of animals, green lanes, as well as all other Weld boundaries, form part of the surrounding landscape and are not isolated entities.

For the single hedgerows surveyed, bird abundance was inXuenced by the number of trees in the hedge, as in other studies (e.g., Parish et al., 1994, 1995). This is probably an eVect of increased nesting sites for hole nesting birds such as tits, as well as increased food, shelter, roost sites and song posts for territory establishment/advertisement for many farmland bird species. An increase in the numbers of trees in a hedge has been found to positively inXuence many bird species characteristic of woodland or woodland edge (Osborne, 1984; Green et al., 1994; Parish et al., 1995).

A possible reason for the numbers of trees not positively inXuencing either bird abundance or species richness on green lanes was the presence of trees on all lanes surveyed.

The results of this study were also suggestive of a positive relationship between the amount of hawthorn in a single hedgerow and the number of bird species present.

It is important to note, however, that this does not show that a decrease in hedge woody species richness is beneWcial to birds. The evidence from the great majority of studies published so far strongly suggest the opposite, and although these beneWcial hedgerows may contain more hawthorn, they may also contain many other hedge forming species. In this study, the great majority of hedgerows were either dominated by hawthorn, blackthorn or privet. Thus, the implication of this result

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M.P. Walker et al. / Biological Conservation 126 (2005) 540â&#x20AC;&#x201C;547

is that hawthorn-based single hedgerows were more beneWcial for bird species richness than hedgerows dominated by either blackthorn or privet.

mental and Sustainability Research (IESR) during this doctoral research.

5.2. Bird species and groups

Appendix A

In this study, almost all bird species occurred in greater abundance on green lanes. The species that beneWted most were those more characteristic of woodland/woodland edge habitat, again suggesting that green lanes resemble woodland edge more closely than do single hedgerows. These birds are likely to beneWt from the dense shrubby areas and woody stands of blackthorn, hawthorn and elder found on lanes, but not on single hedgerows. Lanes also tend to hold a greater number of trees along their length than single hedgerows, a variable commonly found to increase the abundance of many woodland/woodland edge bird species in hedgerows (e.g., Arnold, 1983; Green et al., 1994; Sparks et al., 1996).

Bird species recorded in green lanes (L), single hedgerows (H), or both (L/H) within the surveying period

5.3. Management of green lanes Concerns have been aired in a number of other papers on green lanes (e.g., Dover et al., 2000; Walker et al., in press) that without suitable management the wildlife value of green may be lost. The unsealed nature of lane central tracks needs preserving by prevention of inappropriate resurfacing, e.g., with tarmac or concrete, and also by maintaining usage to prevent scrubbing up and the eventual formation of linear woodland. Such woodland, although beneWting some species, would be detrimental to others that favour the resources provided within the parallel hedges of green lanes, and would probably result in an overall loss of bird species. For those lanes used too infrequently to maintain a central track, carefully timed mowing may beneWt bird species richness by suppressing scrub growth and maintaining a diverse vegetation community/sward height. This study shows that the principal beneWt of a green lane to birds lies within its two hedgerows. To maintain the value of a green lane to birds, both hedgerows must therefore be preserved.

Guidelines designed to protect the countryside, such as those of the Hedgerow Regulations (Anon., 1997), need to recognise green lanes as speciWc landscape elements worthy of protection.

Acknowledgements The authors thank all the Cheshire farmers and landowners of hedgerows and green lanes used in this study for granting permission to access their land, and for answering questions on management regimes.

M. Walker gratefully acknowledges the Wnancial support of StaVordshire Universityâ&#x20AC;&#x2122;s Institute for Environ-

Common name

Latin name

Blackbird Song Thrush Mistle Thrush Robin Dunnock Blue tit Great tit Coal tit Long-tailed tit ChaYnch GreenWnch GoldWnch BullWnch Yellowhammer Linnet Redpoll Wren Treecreeper Blackcap Whitethroat ChiVchaV Starling Swallow House Martin House Sparrow Great Spotted Woodpecker Cuckoo Wood Pigeon Collared Dove Pheasent Grey Partridge Magpie Rook Carrion Crow Jackdaw Jay Buzzard Kestrel Sparrowhawk Tawny Owl Little Owl Mallard Moorhen

Turdus merula Turdus philomelos Turdus viscivorus Erithacus rubecula Prunella modularis Parus cauruleus Parus major Parus ater Aegithalos caudatus Fringilla coelebs Carduelis chloris Carduelis carduelis Pyrrhula pyrrhula Emberiza citrinella Acanthis cannabina Acanthis Xammea Troglodytes troglodytes Certhia familiaris Sylvia atricapilla Sylvia communis Phyllascopus collybita Sturnus vulgaris Hirundo rustica Delichon urbica Passer domesticus Dendrocopos major

Where recorded L/H L/H L L/H L/H L/H L/H L L/H L/H L/H L/H L L/H L/H L L/H L L L/H L/H L/H H L L L

Cuculus canorus Columba palumbus Streptopelia decaocto Phasianus colchicus Perdix perdix Pica pica Corvus frugilegus Corvus corone Corvus monedula Garrulas glandarius Buteo buteo Falco tinnunculus Accipiter nisus Strix aluco Athene noctua Anas platyrhynchos Gallinula chloropus

L L/H L L H L/H L/H L/H L/H L L/H L L L L H H

M.P. Walker et al. / Biological Conservation 126 (2005) 540–547

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