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

a 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 2004Available 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 hedge-rows) and on 20 paired single hedgerows during the 2002 breeding season in Cheshire, UK. Measures of bird abundance, territoriesand species richness were all found to be signiWcantly greater on green lanes than on single hedgerows. SigniWcantly more birds werealso found to occur on the inside rather than on the outside of green lanes in terms of abundance and species richness. All measuresof bird occurrence on green lanes were inXuenced by hedge width and surrounding land use. Bird abundance on single hedgerowswas inXuenced by the number of trees and amount of hawthorn in the hedge. Seventeen of the 18 most abundant bird speciesrecorded in this study were found to occur in greater numbers on green lanes rather than in single hedgerows; for half of these speciesthe diVerence was signiWcant. The importance of green lanes for birds, and other wildlife is discussed, as well as their possible futurewithin 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 nowwidely regarded as valuable habitat for birds in an other-wise largely hostile agricultural environment (Lack,1992; Parish et al., 1994).

Hedgerows are used by birds for foraging and nest-ing, 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 move-ment and dispersal corridors (Demers et al., 1995). Asfarmland landscape features, hedgerows have been

* Corresponding author. Tel.: +44 01244 279 823.E-mail addresses: [email protected], mikewalked@

hotmail.com (M.P. Walker).

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 abundanceof birds that they can support (Lack, 1992).

Many studies have been carried out to determinewhat 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 woodlandpasserines, a tall, wide hedgerow with trees is favourable,possibly due to the relatively greater provision ofresources and shelter, and protection from predators. Itis also the type of hedgerow that most closely resembleswoodland edge habitat. Other factors thought toincrease the value of hedges, particularly for granivorousbirds, but also for some insectivorous/omnivorous spe-cies, include the presence of a wide, species rich verge/bank and a ditch (Parish et al., 1995). These features canincrease the eVective area of breeding and foraging habi-tat of a hedge.

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M.P. Walker et al. / Biological Conservation 126 (2005) 540–547 541

Green lanes are not uniform in composition (Doveret al., 2000) but here we use the deWnition of an unme-talled track bordered by two hedgerows (Croxton et al.,2002, 2005); green lanes have only recently been identi-Wed as distinct boundary features with clear potential asbiodiversity reservoirs (Dover and Sparks, 2001). A fewstudies investigating their structure and botanical com-position have revealed that bees, butterXies and wildXowers occur in greater numbers, and with greater spe-cies richness, than in other common Weld boundary typessuch 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 greenlanes probably contributing to their greater biodiversityinclude substantially larger uncropped verges than grassbanks or hedgerows (Dover et al., 2000), enhanced shel-ter, modiWed microclimate, lower agricultural inputs andmanagement regime impacts, and higher structuraldiversity (Dover and Sparks, 2001).

The precise number of green lanes throughoutEngland is not yet known, but at last estimate there werethought to be about 8500 km (from 1976; report in Bel-sey, 1998), thus making them relatively rare in compari-son with the 449,000 km of hedgerow in England andWales as revealed by the Countryside Survey 2000(Haines-Young et al., 2000).

Dover and Sparks (2001) suggested that the featuresmaking green lanes valuable for the taxa so far studiedwould also make them beneWcial to birds by providing agreater abundance of refuge and foraging habitat thanoVered by other Weld boundary types in agriculturallandscapes. If true, then the argument would be strength-ened to provide more protection for green lanes, whichat present are not recognised by the Countryside Survey2000 (Haines-Young et al., 2000) as speciWc landscapeelements (Dover et al., 2000) and only have loose protec-tion under current hedgerow regulations (Sparks et al.,1999). Active management of existing green lanes andthe creation of new ones could provide another tool tohelp combat the current declines in farmland, and other,birds (Gregory et al., 2002).

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

Precise deWnitions of green lanes vary, but for thisresearch a green lane was deWned as a track borderedon each side by a hedgerow running through farmlandand used by farm vehicles, livestock or horses. Thewidth of a green lane between its hedges may rangefrom under 2 m up to about 40 m (Belsey, 1998), how-ever, in this study only lanes between 2 and 15 m widewere used. All but one of the tracks were unmetalled,the one exception being made where a previouslymetalled track had been almost entirely overgrown bygrass or moss.

2. Materials and methods

2.1. Selection of sites

Twenty sections of green lanes between 100 and500 m in length were selected from farmland within a10 km radius of the city of Chester in the UK (Walkeret al., in press). Sections were deemed suitable if the sec-tion contained no more than 5% gaps in either hedge-row, and the lane remained of similar orientationthroughout its length. Due to low availability of suitablegreen lanes throughout the local region, the lanes couldnot be chosen using more speciWc criteria. Within thelanes, however, sections were chosen to diVer as much aspossible in physical characteristics such as width, orien-tation, vegetation and track type to represent a range oflane types. In the case of three green lanes, more thanone section was chosen to be surveyed per green lane.Seven sections were chosen in this way, with each ‘same-lane’ section separated by an average of 250 m. Sectionswere only chosen if they diVered in a number of thephysical characteristics described above.

Single hedgerows, paired with each of the chosenlanes, were selected on the basis of their similar orienta-tion and surrounding land use to their paired lane.

Each lane and hedgerow was marked out using bam-boo canes positioned at 30 m intervals along the insideand outside of the lane and both sides of each hedgerow.Wool markers were tied to the hedge at the same pointsas backup.

2.2. Bird surveys

Between April and July 2002 and from dawn to11.30 am, seven bird surveys were carried out on eachof the green lanes and paired hedgerows by the sameperson (MPW). Each site was walked and all birdsseen or heard, and their observed behaviour, wererecorded on a map of the site. The surveyor stopped atregular intervals to listen for bird calls, and used thebamboo markers as guides to correctly locate birdrecords. Special care was taken not to record the samebird twice on one survey. All lanes were walked downthe inside as well as along both outer sides of thehedgerows whilst recording bird observations. If a birdof the same species was observed or heard at a similarplace on both sides of a hedge it was noted, but notrecorded as a diVerent bird on the same survey. Theorder in which the insides and outsides of the laneswere walked was varied between visits. The times atwhich each site was walked was also varied, althoughthe hedge was always walked within a similar time toits paired lane and usually on the same day. Any man-agement activities carried out by landowners on oraround the sites throughout the survey period werealso noted.

542 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 ter-ritories following the methodology of Bibby et al. (1992).The relative occurrence of birds on green lanes and hedge-rows was explored using three measures: (i) the mean num-ber of birds (abundance) per 50m of lane/100m hedge; (ii)the number of territories recorded per 50m of lane/100mhedge; (iii) the mean number of bird species recorded persurveyed length of lane and hedgerow (species richness).The diVerent lengths of lane and hedgerow allow a com-parison of the same total length of hedgerow, i.e., 100m.Two-way analysis of variance (factors: pair and lane/hedge) was performed on all three bird measures to test forsigniWcant diVerences between lanes and hedgerows. Toexplore the possibility of non-independence (spatial corre-lation) between sites, similarities (measured by correlation)between sites in bird abundance and species richness werecompared with the physical distances between sites.

The occurrence of birds in green lanes was also exam-ined in more detail in relation to whether the birds weresighted inside the hedgerows of the lane or outside of them.“Inside” birds were counted as those observed between thetwo hedgerows of the lane or on the inner half of thehedgerows. “Outside” birds were counted as any bird seenon the outer half of either hedgerow (Weld-side) of the laneor observed on land within 2m of the outer edge. Thesedata were then used to calculate the mean bird abundanceper 50m of lane and mean species richness of birds in thesetwo categories. DiVerences were tested using two-wayanalysis of variance (factors: lane and inside/outside).

3.2. Regression analysis

Data describing vegetation structure and plant spe-cies composition (Table 1) were used as independentvariables in linear stepwise regression using the Minitab13 statistical package, to explore the inXuence of habitatcharacteristics on the three measures of bird occurrencedescribed above. Analyses were performed separately for

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

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

Lanes Hedges P

Tree number Number of trees present per 100 m of greenlane or single hedgerow

6.6 § 0.8 1.6 § 0.3 <0.001

Vegetation width Total width of ground vegetation recorded on eachlane and hedgerow (cm). The central tracks oflanes are not included in this measurement

570.7 § 43.4 236.4 § 19.2 <0.001

Vegetation height Mean height of vegetation growing in verges ofgreen lanes and hedgerows (cm) For single hedgerowsthis is the mean of two verges (each side of the hedgerow),for lanes it is the mean of four verges (each side of thetwo verges). Central track vegetation is not included.

57.8 § 3.7 43.9 § 3.8 0.18

Hedge volume Mean hedgerow volume (width £ height) for lanes and hedgerows (m2) 5.5 § 0.5 4.5 § 0.5 0.07Hedge density Mean hedgerow density for lanes and hedgerows (1–5).

Density obtained by counting the proportion of gaps in each hedgerow3.6 § 0.1 3.7 § 0.2 N/A

Woody area Mean area of woody stands other than hedgerows on green lanes (m2) 19.9 § 6.6 N/A N/AOrientation Orientation of lanes and hedgerows either North–South (1), or East–West (0) 0.3 § 0.1 0.3 § 0.1 N/AHawthorn Mean hawthorn (Crataegus monogyna) % composition

of hedgerows of green lanes and single hedgerows46.4 § 4.3 69.4 § 4.6 0.03

Blackthorn Mean blackthorn (Prunus spinosa) % composition ofhedgerows of green lanes and single hedgerows

18.1 § 3.3 13.2 § 3.4 0.82

Hazel Mean hazel (Corylus avellana) % composition ofhedgerows of green lanes and single hedgerows

4.9 § 1.5 3.2 § 1.2 0.07

Bramble Mean bramble (Rubus fruticosus agg) % compositionof hedgerows of green lanes and single hedgerows

5.2 § 1.8 1.3 § 0.8 0.02

Elder Mean elder (Sambucus nigra) % composition ofhedgerows of green lanes and single hedgerows

6.0 § 1.8 6.2 § 2.1 1.00

Dog rose Mean dog rose (Rosa canina agg) % compositionof hedgerows of green lanes and single hedgerows

3.1 § 1.1 1.7 § 0.8 0.41

Hedge species Mean number of woody plant species growing inhedgerows of green lanes and single hedgerows

4.9 § 0.3 3.3 § 0.3 <0.01

Grassland Whether green lanes and single hedgerows arebordered by grassland on neither side, one side, or both sides

1.0 § 0.1 0.7 § 0.1 N/A

Number of ditches Number of ditches recorded on each green lane/single hedgerow 0.7 § 0.1 0.6 § 0.1 N/ADitch width Total combined ditch width for single hedgerow and green lanes (cm) 76.3 § 18.3 50.5 § 15.7 0.18


green lanes and single hedgerows. The length of eachlane and hedgerow was logarithmically transformed andentered as a covariate into the regression analysis of birdspecies richness to remove diVerences in the data causedby the diVering lengths of each lane and hedgerow sur-veyed. Vegetation structure and plant species composi-tion data were statistically compared between lanes andsingle hedgerows using the non-parametric Friedmantwo-way analysis of variance (Table 1).

3.3. Bird species

The abundance of individual species of birds wasexamined on both green lanes and hedgerows. For the 18most abundant species, diVerences in abundancebetween the two boundary types were tested using Fried-man two-way analysis of variance.

3.4. Bird groups

Bird species recorded more than Wve times during thesampling period and which could be easily categorisedby the following criteria were placed into the followinggroups: (i) taxonomic group; (ii) preferred diet; (iii)whether resident or migratory. A summary of groupsused and the bird species they contain is given in Table 2.For each group type, the mean abundance of birdsrecorded per 50 m of green lane and 100 m of hedgerowwas calculated. For each group, diVerences in meanabundances between green lanes and hedgerows weretested using Friedman two-way analysis of variance.

4. Results

During the sampling period, 39 species of bird wererecorded on green lanes and 27 species were recorded onsingle hedgerows. Green lanes had signiWcantly greaternumbers of all measures of bird occurrence than did sin-gle hedgerows (all P < 0.001) (Fig. 1).

Table 2Categorisations of bird species into groups

Insectivores Granivores Tits Summer migrants

Blackbird BullWnch Blue tit WhitethroatSong Thrush ChaYnch Great tit ChiVchaV

Mistle Thrush GoldWnch Long-tailed titBlue tit GreenWnch Coal titGreat tit LinnetLong-tailed tit YellowhammerDunnockTreecreeperWrenWhitethroatChiVchaV

Robin

Measures of both abundance and numbers of territo-ries show over three times as many birds recorded ongreen lanes as on single hedgerows; when expressed asdata per 50 m green lane and 100 m hedgerow the diVer-ence is still substantial with lanes holding almost2 £ bird abundance and 1.7 £ number of territories.

When the eVects of distance between sites on similari-ties of bird abundance and bird species richness wereassessed, only a modest pattern was found (abundance:r D ¡0.116, species richness: r D ¡0.187) which we con-sidered would not adversely aVect results from therobust statistical techniques used.

When the positions of birds sighted on green laneswas examined, more than double the number of birdsoccurred “inside” the hedgerows than “outside” of them,both in terms of abundance and species richness (Fig. 2).Using stepwise regression analysis, two variables (howmany sides of the lane were bordered by grassland, andto a lesser extent the mean volume of the two hedges)explained 67% of the variation of bird abundance ingreen lanes (Table 3). Hedge volume was the only vari-able in the model for the number of territories in greenlanes, describing 46% of the variation. Once lane lengthwas accounted for, bird species richness was bestexplained by two variables (how many sides were bor-dered by grassland, and mean hedge volume). In allmodels for green lanes, the eVects of the signiWcant vari-ables were positive. The regression model for bird abun-dance in single hedgerows contained two variables (thenumber of trees in the hedge and the percentage compo-sition of Hawthorn) accounting for 41% of the variance(Table 3). Both variables had positive eVects on birdabundance. None of the variables used were found tohave a signiWcant inXuence on bird species richness orthe number of territories in single hedges. Five of the

Fig. 1. Mean bird abundance and number of bird territories found tooccur per 50 m of green lanes (black Wll) and 100 m hedgerows (whiteWll) sampled. Mean bird species richness per entire lane and hedgerowis also shown. SigniWcance obtained from two-way analysis of vari-ance. For each measure of bird occurrence; P < 0.001 between insideand outside of bordering hedgerows.

0

1

2

3

4

5

6

7

8

Abundance Territories Species Richness


variables used in the regression analysis were found to besigniWcantly greater in green lanes than in single hedge-rows. These were; the number of trees, the mean vegeta-tion width, both hawthorn and bramble percentagecomposition of the hedge, and the woody plant speciesrichness of the hedge (Table 1).

4.1. Individual species

Seventeen of the 18 most abundant bird species werefound in greater numbers on green lanes than in singlehedgerows (Table 4). These diVerences were signiWcantfor nine species (Table 4).

4.2. Bird groups

Three of the four groups were found to contain signiW-

cantly (P < 0.05) greater numbers of birds in green lanesthan in single hedgerows (Table 5), and for insectivorousbirds this diVerence was highly signiWcant (P< 0.001).

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

0

1

2

3

4

5

6

7

Abundance/100m Species Richness

5. Discussion

This study shows that during the breeding season,bird abundance and bird species richness are bothgreater in green lanes than in single hedgerows, resultsconsistent with the patterns for bees, butterXies and wildXowers 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 inbird populations in green lanes compared to singlehedgerows appears similar to that of butterXies recordedby Dover et al. (2000), where close to double the abun-dance and species richness was recorded in green lanes.However, the diVerence in bird abundance is actuallygreater, as Dover et al. (2000) compared butterXy abun-dance using same lengths of lanes and hedgerows,whereas in this paper, bird abundance was comparedusing 50 m green lane compared with 100 m hedge.

Perhaps the most fundamental diVerence betweengreen lanes and single hedgerows responsible for theirdiVering usage by birds is structure. A green lane isessentially two hedges, so more birds would be expectedto occur on the lane simply from a doubling of the habi-tat area. However, the methods of analysing bird abun-dance and territories in this study accounted for this andyet the diVerence remained highly signiWcant. This sug-gests that there are aspects of green lanes other than theabsolute amount of hedge that increases their value forbirds.

Green lanes are more structurally diverse than sin-gle hedgerows, containing a central track as well as thehedgerows and verges. The central track not only pro-vides a greater habitat area, but also a habitat type notusually found on single hedgerows. Many studies haveconcluded that an increase in habitat diversityincreases bird abundance and species richness (e.g.,Rands, 1986, 1987; Stoate et al., 1998). Previous workon the lanes and hedgerows used in this study foundthe central track vegetation community to be diVerentfrom that of the verges of green lanes and single hedge-

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

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

Bird abundance green lanes Number of territories green lanes

Variable CoeYcient t P Variable CoeYcient t P

Grassland 1.79 4.15 0.001 Hedge volume 0.9 3.93 0.001Hedge volume 0.5 4.08 0.001Total r2 67.4 Total r2 46.2

Bird species richness green lanes Bird abundance single hedgerows

Log lane length 7.9 6.96 <0.001 Tree number 0.276 2.86 0.011Grassland 1.43 3.78 0.002 Hawthorn 0.0156 2.22 0.040Hedge volume 0.4 3.72 0.002

Total r2 83.1 Total r2 40.5


rows (Walker et al., in press). The inside verges of greenlanes have also been found to contain diVerent vegeta-tion communities to single hedgerow verges, as well assigniWcantly greater vegetation species richness (Crox-ton et al., 2002, 2005; Walker et al., in press). Greenlane verges were found in this study to be signiWcantlywider than single hedgerow verges, providing a greaterarea of more species-rich habitat. Wider verges at thebase of hedges are thought to reduce the incidence ofbird predation (Chamberlain et al., 1995). All of thesefeatures of green lanes are likely to provide birds with alarger area of habitat for nesting, sheltering and roost-ing, for example, with an increased amount ofresources at their disposal for activities such as feedingand nest building.

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

Table 4Mean occurrence § SE of the 18 most abundant bird species per 50 mof green lanes and 100 m of single hedgerows

DiVerences between lanes and hedgerows tested using Friedman’sANOVA.

Species Lanes Hedges P

Means § SE Means § SE

Blackbird 0.84 § 0.11 0.56 § 0.10 0.018Song Thrush 0.08 § 0.04 0.01 § 0.01 0.004Robin 0.65 § 0.11 0.36 § 0.07 0.074Great tit 0.52 § 0.07 0.29 § 0.06 0.108Blue tit 0.69 § 0.12 0.28 § 0.09 0.018Long-tailed tit 0.15 § 0.01 0.04 § 0.02 0.132Linnet 0.06 § 0.04 0.05 § 0.02 0.705ChaYnch 0.66 § 0.10 0.50 § 0.10 0.074GreenWnch 0.12 § 0.04 0.05 § 0.03 0.002GoldWnch 0.03 § 0.02 0.01 § 0.01 1.000Yellowhammer 0.07 § 0.05 0.06 § 0.04 0.257Wren 0.76 § 0.11 0.33 § 0.07 0.000Dunnock 0.10 § 0.03 0.16 § 0.05 0.796ChiVchaV 0.41 § 0.12 0.02 § 0.02 0.001Whitethroat 0.10 § 0.03 0.04 § 0.04 0.008Blackcap 0.10 § 0.03 0.01 § 0.01 0.007Magpie 0.09 § 0.02 0.04 § 0.02 0.033Wood pigeon 0.50 § 0.13 0.21 § 0.06 0.157

Table 5Mean occurrence § SE of the four groups of bird species (as describedin Table 2) per 50 m of green lanes and 100 m of single hedgerows

DiVerences between lanes and hedgerows tested using Friedman’sANOVA.

Green lane Hedge SigniWcance

Insectivorous 4.33 § 0.55 2.09 § 0.24 <0.001Granivorous 0.96 § 0.17 0.68 § 0.01 0.074Tits 1.37 § 0.19 0.61 § 0.10 0.002Summer migrants 0.52 § 0.13 0.06 § 0.04 0.001

to the inside verges in several respects including plantspecies, community type and environmental conditions(Walker et al., in press). Thus the greater species richnessof birds in green lanes over single hedgerows in thisstudy is likely to be a direct result of the greater struc-tural diversity found in green lanes.

5.1. Individual habitat factors

In this study, the mean volume of the hedges wasfound to inXuence bird abundance, number of bird ter-ritories, and bird species richness in green lanes. Hedgesize has been found in many other studies to inXuencebird abundance on single hedgerows (Arnold, 1983;Lack, 1992; Green et al., 1994; Hinsley and Bellamy,2000). Again this can be explained by a simple increasein habitat volume, although wider hedgerows may alsohave a lower incidence of nest predation than theirthinner counterparts (Arnold, 1983; Chamberlainet al., 1995), and be attractive to a wider range of birdspecies.

The presence of pasture adjacent to the lane had apositive eVect on bird abundance. This has also beenrecorded in other studies (Arnold, 1983; Parish et al.,1994; Peach et al., 2004) and stresses that in terms oftheir value to birds, which tend to be more mobile thanmany other groups of animals, green lanes, as well as allother Weld boundaries, form part of the surroundinglandscape and are not isolated entities.

For the single hedgerows surveyed, bird abundancewas inXuenced by the number of trees in the hedge, asin other studies (e.g., Parish et al., 1994, 1995). This isprobably an eVect of increased nesting sites for holenesting birds such as tits, as well as increased food,shelter, roost sites and song posts for territory estab-lishment/advertisement for many farmland birdspecies. An increase in the numbers of trees in a hedgehas been found to positively inXuence many bird spe-cies 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 posi-tively inXuencing either bird abundance or species rich-ness on green lanes was the presence of trees on alllanes surveyed.

The results of this study were also suggestive of a pos-itive relationship between the amount of hawthorn in asingle hedgerow and the number of bird species present.It is important to note, however, that this does not showthat a decrease in hedge woody species richness is beneW-

cial to birds. The evidence from the great majority ofstudies published so far strongly suggest the opposite,and although these beneWcial hedgerows may containmore hawthorn, they may also contain many otherhedge forming species. In this study, the great majorityof hedgerows were either dominated by hawthorn,blackthorn or privet. Thus, the implication of this result


is that hawthorn-based single hedgerows were morebeneWcial for bird species richness than hedgerows dom-inated by either blackthorn or privet.

5.2. Bird species and groups

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

5.3. Management of green lanes

Concerns have been aired in a number of other paperson green lanes (e.g., Dover et al., 2000; Walker et al., inpress) that without suitable management the wildlifevalue of green may be lost. The unsealed nature of lanecentral tracks needs preserving by prevention of inap-propriate resurfacing, e.g., with tarmac or concrete, andalso by maintaining usage to prevent scrubbing up andthe eventual formation of linear woodland. Such wood-land, although beneWting some species, would be detri-mental to others that favour the resources providedwithin the parallel hedges of green lanes, and wouldprobably result in an overall loss of bird species. Forthose lanes used too infrequently to maintain a centraltrack, carefully timed mowing may beneWt bird speciesrichness by suppressing scrub growth and maintaining adiverse vegetation community/sward height. This studyshows that the principal beneWt of a green lane to birdslies within its two hedgerows. To maintain the value of agreen lane to birds, both hedgerows must therefore bepreserved.

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

Acknowledgements

The authors thank all the Cheshire farmers and land-owners of hedgerows and green lanes used in this studyfor granting permission to access their land, and foranswering questions on management regimes.

M. Walker gratefully acknowledges the Wnancial sup-port of StaVordshire University’s Institute for Environ-

mental and Sustainability Research (IESR) during thisdoctoral research.

Appendix A

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

Common name Latin name Whererecorded

Blackbird Turdus merula L/HSong Thrush Turdus philomelos L/HMistle Thrush Turdus viscivorus LRobin Erithacus rubecula L/HDunnock Prunella modularis L/HBlue tit Parus cauruleus L/HGreat tit Parus major L/HCoal tit Parus ater LLong-tailed tit Aegithalos caudatus L/HChaYnch Fringilla coelebs L/HGreenWnch Carduelis chloris L/HGoldWnch Carduelis carduelis L/HBullWnch Pyrrhula pyrrhula LYellowhammer Emberiza citrinella L/HLinnet Acanthis cannabina L/HRedpoll Acanthis Xammea LWren Troglodytes troglodytes L/HTreecreeper Certhia familiaris LBlackcap Sylvia atricapilla LWhitethroat Sylvia communis L/HChiVchaV Phyllascopus collybita L/HStarling Sturnus vulgaris L/HSwallow Hirundo rustica HHouse Martin Delichon urbica LHouse Sparrow Passer domesticus LGreat Spotted

WoodpeckerDendrocopos major L

Cuckoo Cuculus canorus LWood Pigeon Columba palumbus L/HCollared Dove Streptopelia decaocto LPheasent Phasianus colchicus LGrey Partridge Perdix perdix HMagpie Pica pica L/HRook Corvus frugilegus L/HCarrion Crow Corvus corone L/HJackdaw Corvus monedula L/HJay Garrulas glandarius LBuzzard Buteo buteo L/HKestrel Falco tinnunculus LSparrowhawk Accipiter nisus LTawny Owl Strix aluco LLittle Owl Athene noctua LMallard Anas platyrhynchos HMoorhen Gallinula chloropus H


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