Microhabitat Selection by Three Common Bird Species of Montane Farmlands in Northern Greece

RESEARCH

Microhabitat Selection by Three Common Bird Speciesof Montane Farmlands in Northern Greece

Rigas Tsiakiris Æ Kalliopi Stara Æ John Pantis ÆStefanos Sgardelis

Received: 21 January 2009 / Accepted: 24 July 2009 / Published online: 25 August 2009

� Springer Science+Business Media, LLC 2009

Abstract Common farmland birds are declining

throughout Europe; however, marginal farmlands that

escaped intensification or land abandonment remain a

haven for farmland species in some Mediterranean moun-

tains. The purpose of this study is to identify the most

important anthropogenic microhabitat characteristics for

Red-Backed Shrike (Lanius collurio), Corn Bunting (Mil-

iaria calandra) and Common Whitethroat (Sylvia com-

munis) in three such areas within the newly established

Northern Pindos National Park. We compare land use

structural and physiognomic characteristics of the habitat

within 133 plots containing birds paired with randomly

selected ‘‘non-bird’’ plots. Using logistic regression and

classification-tree models we identify the specific habitat

requirements for each of the three birds. The three species

show a preference for agricultural mosaics dominated by

rangelands with scattered shrub or short trees mixed with

arable land. Areas with dikes and dirt roads are preferred

by all three species, while the presence of fences and

periodically burned bushes and hedges are of particular

importance for Red-Backed Shrike. Across the gradient of

vegetation density and height, M. calandra is mostly found

in grasslands with few dwarf shrubs and short trees, S.

communis in places with more dense and tall vegetation of

shrub, trees and hedges, and L. collurio, being a typical

bird of ecotones, occurs in both habitats and in interme-

diate situations. In all cases those requirements are

associated with habitat features maintained either directly

or indirectly by the traditional agricultural activities in the

area and particularly by the long established extensive

controlled grazing that prevent shrub expansion.

Keywords Red-Backed Shrike � Corn Bunting �Common Whitethroat � Land abandonment �Selective burning � Cultural landscapes

Introduction

The widespread and continuing decline of populations of

many common farmland birds over large areas of Europe

(BirdLife International 2004) is an alarming and complex

continental-scale issue, which is a consequence of either

land use intensification (Donald and others 2006) or land

abandonment (Tucker and Evans 1997; Wretenberg and

others 2006). The various effects of land use intensification

on bird species have been widely studied especially in

Northern European countries, where there is extensive

extant data on bird population trends (Siriwardena and

others 1998; Kujawa 2002; Herzon and others 2008). In

contrast, the effect of land abandonment on farmland birds

is still controversial, depending on biogeographical zone,

species origin and vegetation successional stage (Blondel

and Farre 1988; Suarez-Seoane and others 2002; Sirami

and others 2008). Marginal agricultural areas within the

Mediterranean mountains are known to hold one of the

richest flora and fauna in the world and are characterized as

global biodiversity ‘‘hotspots’’ (Myers and others 2000).

However, such landscapes have experienced widespread

land abandonment for various socioeconomic reasons and

there is little knowledge of specific management practices

that could help maintain the populations of common

R. Tsiakiris (&) � J. Pantis � S. Sgardelis

Department of Ecology, School of Biology, Aristotle University

of Thessaloniki, P.C. 54124, Thessaloniki 45500, Greece

e-mail: [email protected]

K. Stara

Hellenic Ornithological Society, Vasileos Irakleiou 24, P.C.

10681, Athens, Greece

123

Environmental Management (2009) 44:874–887

DOI 10.1007/s00267-009-9359-8

farmland bird species (Preiss and others 1997; Laiolo and

others 2004; Scozzafava and De Sanctis 2006).

Several studies have shown that habitat structure in both

vertical and horizontal dimensions and successional status

of the vegetation strongly affect bird community compo-

sition, especially in mixed grassland and shrubland eco-

systems (Willson 1974; Rotenberry and Wiens 1980;

Prodon and Lebreton 1981; Blondel and Farre 1988). Thus,

it is of special importance to understand how past and

modern agricultural activities shape habitats used by

farmland birds. We use the example of Pindos Mountain

range, because approximately 90% of all European bird

species associated with traditional orchards, agriculture

areas, open shrubland and alpine and sub alpine grasslands

(Tucker and Evans 1997) have been recorded within the

newly established Northern Pindos National Park.

The aim of this study is to reveal which microhabitat

characteristics are selected or avoided by declining com-

mon farmland birds in montane Mediterranean landscapes

where traditional agricultural practices are partly pre-

served, side by side with land abandonment and intensifi-

cation. Studies on micro-scale habitat assessment in such

fragmented landscapes as well as available ornithological

data are limited and this study could help reconcile small-

scale agricultural production and nature conservation

within Mediterranean montane environments.

Study Area

Description of the Study Area

The study area is located in northwest Greece close to the

border with Albania (between 39540–39490 latitude and

20400–20440 longitude) and comprises three characteristic

mountain plains (plateaus) totalling approximately 950

hectares formed of karst depressions and having bands of

thin-bedded flysch on their southern margin. With an

average altitude of 850–950 m above sea level, the area

belongs to the humid Mediterranean bioclimatic zone with

cold winter and a dry summer lasting 2–3 months; the

mean annual precipitation is about 1000 mm (Hanlidou

and Kokkini 1997).

Although classed as Mediterranean mixed deciduous-

evergreen woodland of the Ostryo-Carpinion sub-forest

zone most of the area is now covered by dense sclero-

phyllous shrub of prickly oak (Quercus coccifera) and

young mixed broadleaved oak forest resulting from recent

cessation of goat grazing. However, within the plateaus and

in the most accessible fallow/pasture land, a savannah-like

landscape has developed with a mosaic of xeric pseud-

osteppe dry grasslands (as defined by Suarez and others

1997) mixed with parkland type pastoral woodland

characterized by scattered groups or individual trees,

mainly oaks. This is the area where flocks of sheep, goats

and cows are still extensively and seasonally grazed by

3000 animals. Parts of the plateaus, where soil is deep and

productive, are cultivated for cereals in rotation with clover

or lucerne. These arable fields are usually small and

interspersed with natural grasslands that are used as hay

meadows. There is no large-scale irrigation but some very

small vegetable gardens are watered from wells. Use of

agro-chemicals is very limited. Part of the area is naturally

seasonally flooded and is covered by a diversity of wet

grasslands, rivulets, ponds and ditches.

At the edge of each plateau there is a small village

(Fig. 1). The population of these villages declined sharply

after WWII leading to the abandonment of marginal agri-

cultural fields that were transformed to pasturelands or hay

meadows. In the 1970s the land was redistributed and some

of the wet grasslands were drained. Consequently, at the

present time productive agriculture and land abandonment

coexist within the same area (Zomeni and others 2008),

while traditional agriculture is partly maintained in a rel-

atively small part of the plateaus and supports small-scale

extensive livestock rearing of sheep, goats and cows. Parts

of the three plateaus are included in the newly established

Northern Pindos National Park, which has incorporated the

older Vikos—Aoos National Park.

Methods

Bird Data Collection

Bird surveys were conducted during the breeding season

(from 10/5/2003 to 13/7/2003) when birds are easily

detectable due to territorial display and nesting activities.

We used a high resolution ortho-rectified map of the study

area (scale 1:5000) provided by the Ministry of Food and

Agriculture, Department of Topography (based on a

Quickbird satellite image acquired on the 5/8/2000). We

superimposed a one kilometre grid over the study area and

selected 22 sub-units to completely enclose the study pla-

teaus (Fig. 1). On each sampling occasion we visited one

randomly selected sub-unit from those not yet visited. We

walked slowly across two south-north transects defined on

each sub-unit to detect birds. Transects were approximately

500 m apart to ensure that the same individuals were not

counted twice (Bibby and others 1992; Gibbons and others

1996), while ensuring even coverage of the sub-unit. Bird

survey was conducted during 18 days, visiting 1 or 2 sub-

units per day, depending on the roughness of the topogra-

phy. Species were identified by sight and sound, from 6:00

to 13:00 and from 17:30 to 20:30 each day. Only locations

of displaying males were recorded at the beginning of the

Environmental Management (2009) 44:874–887 875

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breeding season; after nest construction females were also

recorded along with family groups in the first 5 post

fledging days. Windy and rainy days were excluded.

Selection of ‘‘Bird’’ and ‘‘Random’’ Sampling Plots

When a bird was found, its location was registered using a

global positioning system (GPS). Taking the bird location

as a centre, a fixed 25 m radius (0.19 ha) circular sample

plot was defined on the ground using a tape-measure. This

is a standard size for small scale species-habitat compari-

sons and facilitates the measurement of precise habitat

variables in close proximity to the bird (Bibby and Robins

1985). In addition, for each such ‘‘bird’’ plot, a nearby

similarly sized ‘‘non-bird’’ plot was randomly selected

(Bibby and others 1992). The centres of these random plots

were defined using two series of random numbers: the first

giving a distance between 25 to 150 m from the periphery

of the ‘‘bird’’ plot and the second the bearing to the centre

of the random plot (from 1 to 360).

Habitat Variables Within ‘‘Bird’’ and ‘‘Random’’

Sampling Plots

A combination of habitat variables was either estimated or

measured inside all ‘‘bird’’ and ‘‘random’’ sample plots.

Neither general habitat categories nor broad vegetation

coverage could adequately represent the diversity and

juxtaposition of several different situations found within

plots in this savanna type ecosystem. We therefore defined

and measured several additional variables to capture the

fine-scale habitat heterogeneity and physiognomy that we

wished to evaluate. Contemporaneous measurements were

done at three discrete levels (Table 1):

1. Broad habitat features:

(a) Habitat types were defined as homogeneous

patches based on vegetation physiognomy with

the percentage horizontal coverage of each patch

estimated to the nearest 5%. The 5% precision

was found to be consistent with pilot measure-

ments made on the high-resolution ortho-rectified

map in several training plots. The percent cov-

erage of the plot of each habitat type was taken as

the projected vertical area of the canopy, so that

the sum over all habitat types to be 100%.

(b) Current land use was similarly estimated using

the variables defined in Table 1.

2. Presence–absence of the three most prominent specific

microhabitat characteristics as defined in Table 1.

3. Vegetation structure, such as horizontal percentage

coverage of trees, shrub (woody vegetation below 4 m

height), grass, soil and rocks was also estimated on 5%

interval scale, while vertical vegetation structure (trees

and scrubs) was measured with a marked walking stick

into 0.5 m height classes. Maximum height of grass

and rocks, was measured using the same method, but

into 5 cm height classes marked with tape on the base

of the stick. Average woody vegetation height was

measured as the mean height from a small selection of

trees and scrubs that were assumed to be representative

of the plot, while average grass height as the mean of

20 measurements of sward height of the dominant

grassland types within the plot.

Species Selection and Data Analysis

The data set consisted of plot-based habitat descriptions for

67 plots for Lanius collurio, 32 plots for Miliaria calandra,

34 plots for Sylvia communis and 68 plots for less common

farmland passerine species of the area (Lesser Grey Shrike

Lanius minor, Woodchat Shrike L. senator, Common

Linnet Carduelis cannabina, Wood Lark Lullula arborea,

Fig. 1 The three plateaus of the study area, the location of the three

villages and the 22 1 km2 sub-units. An example of the predefined

line transects is shown in sub-units 18 and 21

876 Environmental Management (2009) 44:874–887

123

Stonechat Saxicola torquata, Sombre Tit Parus lugubris

and Cirl Bunting Emberiza cirlus). Moreover, House

Sparrow (Passer domesticus) was present but was excluded

from the study due to its colonial behaviour. Only the first

three species that were recorded in more than 30 places

were included in further statistical analysis.

Table 1 Definitions of habitat variables

1. Broad habitat features Variables: coverage (%)

1(a). Habitat types

Pastureland Dense shrubland & young forest ([80% shrub/woody coverage)

Shrub-wood pasture (40–80% shrub/woody coverage)

Open shrub/wood pasture (20–40% shrub/woody coverage)

Grassland with scattered shrubs / trees (\20% shrub/woody coverage)

Grassland with non woody vegetation

Wet grassland

Arable land or meadows Cereals (wheat, barley, rye)

Vegetable gardens

Cultivated hay meadows (with sown clover or lucerne)

Natural hay meadows (with indigenous vegetation)

Set-aside or fallow land

Uncut field margins

Isolated hedges

Groups of hedges (similar to shrubland or forests patches)

Agricultural infrastructure Ditches

Paved roads

Dirt roads

Other structures (fences, barns, folds, farmhouses etc.)

1(b). Current land use

Pastureland Grazed

Not grazed

Abandoned (for more than 2 years obvious by vegetation succession)

Arable land or meadows Mowed / cropped

Not mowed / uncropped

Set aside / fallow land

Abandoned

Agricultural infrastructure

2. Specific microhabitat characteristics

Category Presence/absence of

Dense vegetation Impenetrable scrub, young forest stands and groups of trees

Diverse meadows All types of natural and semi-natural grasslands, set-aside, fallows, weedy margins,

not cropped parts or recently abandoned arable land

Wet grassland Seasonally flooded areas, as well as ponds, rivulets, ditches etc.

Single shrubs/trees Isolated woody vegetation (shrubs or dwarf trees) within grassland or arable land

Dead/burned shrub/tree Any kind of shrub/woody vegetation that has been recently burned or modified (cut, pruned etc.)

Group of hedges Isolated groups or lines of shrub or trees frequently managed (pruned, grazed, cut etc)

Abandoned hedges Not managed hedges higher than 4 m resembling linear forest patches

Fence presence Field margins with fences of any kind (with wood or iron posts, with barbed or modern type wires etc)

Road presence Paved or dirt roads within farmland

Poles presence Transmission poles and lines (regular perching sites of raptors or corvids)

Buildings All kinds of farmland buildings (barns, stables, hutch, shed, etc.)

Pastureland types are based on Papanastasis and Noitsakis (1992), Gibson (2009)


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In total 201 random plots were recorded. However,

when the bird species plots and random plots were overlaid

it was found that many of the random plots intersected

‘‘bird’’ plots recorded on a different occasion. Furthermore

the size of the home range of the target species was found

to be greater than the 25 m ‘‘bird’’ plot, so random plots

needed to be 70 m from the centre of a ‘‘bird’’ plot to be

truly representative of habitats not selected as breeding

territory by the birds. Bird and ‘‘non-bird’’ plots for each

species were then defined using the rules shown in Fig. 2.

Application of these rules resulted to 91 ‘‘non-bird’’ plots

for Lanius collurio, 119 for Miliaria calandra and 135 for

Sylvia communis (Table 2). Thereafter we tested for dif-

ferences in specific habitat features between the ‘‘bird’’

plots and ‘‘non-bird’’ plots using the Mann-Whitney U test.

Logistic regression with stepwise variable selection and

classification tree models were used to predict the presence

of the target birds from the specific microhabitat variables

and fine-grained vegetation structure. Both methodologies

are suitable for species-microhabitat analysis; however,

they are conceptually different regarding both the model

building strategy and the final model structure. With

logistic regression we actually fit a continuous function to

the data, while the classification tree method (Breiman and

others 1984) splits the data domain into a number of sub-

sets and continues sub-division until pre-defined stopping

rules are reached. The splitting is done on critical thresh-

olds in a set of predictor variables selected so that the two

sub-sets produced in each step are as ‘‘homogeneous’’ as

possible. The final model is a dichotomous tree like

structure (a cascading series of ‘‘if–then–else’’ rules) with

nodes (ifs) expressed as Boolean operators based on the

critical value of a predictor. Evaluating the expression to

true (then) or false (else) we move towards the left or right

branch of the tree, where there is either another node or a

terminal leaf containing the final prediction. This makes

the whole model transparent and easy to follow. Among

other advantages of this methodology is the ability to

handle correlation between predictor variables and the

ability to separate noisy data (outliers) into isolated bran-

ches early in the splitting process (Dalaka and others 2000).

The structure of tree-based models complements the

development of hierarchical models that are noted as being

the most appropriate when coarse-scale variables deter-

mines an envelope of possible responses, while more local

factors are responsible for fine tuning (Kallimanis and

others 2007), as might be the case of nest site selection by

some migratory birds. However, special attention should be

given to generalization errors associated with this kind of

modeling approach. Attempts to increase the prediction

accuracy can produce a model with as many terminal

leaves as cases used to build the model and the resulting

model then simply reproduces its knowledge database (it is

‘‘parroting’’). We wanted to build a general model able to

predict correctly the state of ‘‘yet unseen data’’. One way of

testing the extrapolative power of a model is to use a sub-

set of data points to build the model (training set) and a

different set for testing its predictions (test set). This is a

good strategy if the dataset is large but even with small

datasets, as in our case; there are still various ways to cope

with generalization errors. Cross-validation and tree prun-

ing can both be adopted for this purpose. The model tree

can be pruned either during the model building (pre-

pruning) or after the model is built (post-pruning). We used

pre-pruning by imposing a stopping rule if there were 4 or

fewer cases at a node.

For the analysis of presence-absence data, both logistic

regression and classification trees could end up with an

unacceptable result when absences outnumber presences,

as in our case, predicting absence for all cases. To avoid

this problem we used all ‘‘bird’’ plots of the given species

and an equal number of randomly selected ‘‘non-bird’’

plots for model building. As the models may be influenced

by the membership of the ‘‘non-bird’’ set of plots, we

performed a sensitivity analysis by building 50 logistic

regression and 50 classification tree models for each spe-

cies, each with a different set of ‘‘non-bird’’ plots. This

allows evaluating the robustness of the prediction and more

specifically to evaluate the contribution of each predictor

Fig. 2 An example of the location and the selection of ‘‘bird’’ and

‘‘random’’ plots based on breeding buffer zone exclusion: in this case

‘‘non-bird’’ plots for Lanius collurio are R2 and R3, while ‘‘non-bird’’

plots for Miliaria calandra are R1, R2 and R3


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by looking how often it is included in any out of the 50

models. For the logistic regression models we also esti-

mated the ranges of fitted coefficients. The criteria for

selecting the final model among the 50 fitted were: low

classification errors, better prediction of presences, small

number of predictors used or small tree size in the case of

classification trees and inclusion of predictors used with

high frequency in the formulation of the 50 models. That

set of criteria was needed because it could happen that the

classification error of some substantially different models

could be very similar. We used SPSS—Statistical Package

for the Social Sciences (2007) Version 15.0 for Windows

statistical package for the Mann-Whitney U test and

logistic regression and WEKA – Waikato Environment for

Knowledge Analysis (Witten and Eibe 2005) to develop

the classification trees (with 10 fold cross validation and

pre-pruning).

Results

Broad Habitat Features

Most ‘‘bird’’ plots were located within agricultural mosaics

dominated mainly by several types of natural grassland

used as pastureland. In 49 out of 133 ‘‘bird’’ plots of the

three commonest species the entire plot was pure pasture-

land. In contrast, there were no plots wholly covered by

arable land. Grasslands with scattered trees or shrubs, as

well as dirt roads, were the most common feature of ‘‘bird’’

Table 2 Mann–Whitney U test for the comparison of habitat variables associated with the three studied common farmland bird species

Habitat variables Lanius collurio Miliaria calandra Sylvia communis

Mean values Mann–

Whitney

U test

Mean values Mann–

Whitney

U test

Mean values Mann–

Whitney

U test

Bird

plots

n = 67

Non-bird

plots

n = 91

Uvalues

Pvalues

Bird

plots

n = 32

Non-bird

plots

n = 119

Uvalues

Pvalues

Bird

plots

P = 34

Non-bird

plots

P = 135

Uvalues

Pvalues

Percentage cover of habitat types

Grassland with

scattered

shrubs / trees

30.67 17.81 2423.5 \0.01 35.94 15.34 1491.0 \0.05 32.65 14.62 1849.0 \0.05

Dirt roads 3.96 1.18 2438.0 \0.01 4.53 1.18 1540.0 \0.01 3.68 1.33 1991.0 \0.05

Ditches 5.60 0.90 2455.5 \0.01 5.31 0.90 1341.0 \0.01 3.38 1.63 2157.5 n.s

Meadows with

isolated hedges

24.48 12.08 2450.0 \0.01 8.13 12.08 1719.0 n.s 20.00 9.32 1927.5 \0.05

Natural hay meadows 3.28 33.09 2064.0 \0.01 19.69 35.34 1713.0 n.s 1.18 37.01 1370.5 \0.01

Cultivated hay

meadows

14.25 7.36 2385.5 \0.01 7.81 8.48 1733.5 n.s 6.32 11.97 2241.5 n.s

Set-aside or fallow land 1.87 1.40 2833.5 n.s 4.38 1.40 1691.0 \0.05 0.88 3.26 2225.0 n.s

Shrub-wood pasture 1.42 2.70 3001.5 n.s 0.00 2.70 1856.0 n.s 10.29 1.59 2058.0 \0.05

Meadows with groups

of hedges

2.31 2.02 2937.5 n.s 5.31 2.02 1832.5 n.s 10.59 0.72 2056.0 \0.01

Paved roads 0.45 0.45 3037.0 n.s 0.63 0.45 1877.5 n.s 2.65 0.68 2078.0 \0.05

Percentage cover of current land use

Agricultural

infrastructure

2.24 0.79 2656.0 \0.01 3.13 0.79 1654.5 \0.01 4.41 0.53 1872.5 \0.01

Not mown arable land 14.93 5.34 2278.0 \0.01 7.19 6.46 1839.5 n.s 11.03 12.12 2107.0 n.s

Abandoned pastureland 2.39 12.98 2631.0 \0.01 1.88 14.10 1704.0 n.s 1.76 8.98 2280.0 n.s

Mown meadows 16.27 7.30 2465.0 \0.01 5.78 10.67 1662.5 n.s 3.53 13.22 1996.5 n.s

Not mown meadows 15.00 10.00 2756.0 n.s 27.81 10.00 1398.5 \0.01 5.29 11.48 2212.0 n.s

Abandoned meadows 0.00 0.00 3048.5 n.s 0.00 0.00 1904.0 n.s 1.47 0.00 2227.5 \0.05

Grazed pastureland 29.33 46.24 2601.0 n.s 31.56 40.62 1780.5 n.s 60.15 37.01 1716.0 \0.05

n.s. non significant


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plots regardless of species, while this habitat type was less

frequent in the ‘‘non-bird’’ plots (Table 2, U test P \ 0.05).

Lanius collurio and M. calandra showed an additional

similarity, as their plots both contained more frequently

ditches than ‘‘non-bird’’ plots (P \ 0.01). Moreover Lanius

collurio and S. communis plots included significantly more

meadows with isolated hedges and less natural hay mead-

ows than ‘‘non-bird’’ plots (P \ 0.05).

Each species showed some specific habitat type prefer-

ences: L. collurio was found in plots having more fre-

quently cultivated hay meadows (P \ 0.01), M. calandra

in set-aside areas or fallow land, while S. communis terri-

tories included more scrub-wood pastures, as well as

meadows with groups of hedges and paved roads

(P \ 0.05).

Considering land uses, all species preferred plots with

agricultural infrastructure, which were mainly fences and

dirt roads in between agricultural fields. On the other hand,

each species showed some different land use preferences:

L. collurio plots included not mown arable land, were not

located in abandoned pasturelands and had significantly

more frequently mown meadows (P \ 0.01). In contrast,

M. calandra was located in plots including significantly

greater proportion of not mown meadows (P \ 0.01),

while S. communis plots were located more frequently in

abandoned meadows and grazed pastureland (P \ 0.05).

Logistic Regression of Microhabitat Characteristics and

Vegetation Structure

The presence of dead or burnt shrub/trees was the most

frequent specific microhabitat characteristic included in

logistic regression models for L. collurio presence

(Table 3, 49 out of 50 models). The presence of all kinds of

fences, as well as the maximum sward height, appeared

very frequently not only in L. collurio, but also in M.

calandra logistic regression models. In addition, for L.

collurio models, the present of roads, the average shrub

height and the presence of single shrubs/trees were sig-

nificant and positive contributions to the predictions, while

the presence of bare soil was negative. On the other hand,

for S. communis, maximum shrub height (39 out of 50

models), tree coverage and groups of hedges were found to

be important. Lastly, maximum tree height had a statisti-

cally significant negative contribution to predictions of the

presence of both S. communis and M. calandra, while wet

grassland only appeared in M. calandra logistic regression

models.

Classification Trees

The best (in terms of classification errors and tree size)

classification tree models by species are given in Fig. 3a–c

along with the corresponding classification matrices. For L.

collurio, presence is predicted in plots where the grassland

coverage is less than 92.5% and either there are fences and

average grass height is less than 0.60 m or (in the lack of

fences) maximum shrub height is more than 1.65 m. In the

later case the species is present if there are roads in the plot,

or (in the absence of roads) grassland coverage is between

62.5% and 92.5% and burned scrubs or trees are present,

while tree coverage is less than 17.5% (Fig. 3a).

M. calandra is predicted to be present in specific

grassland types. Thus the birds thrive in productive natural

grasslands such as wet grasslands or other tall grassland

(height more than 1.45 m) if tall trees are absent. More-

over, the bird is predicted to be absence when grass cover

is less than approximately 50% of the plot or in short

grassland with maximum grass height less than 0.65 m.

However, when grass dominated the plot (grass cover

higher than 87.5%) the bird was also predicted to be absent

(Fig. 3b).

Lastly, the absence of S. communis, is predicted by sort

scrubs (average height less than 1.90 m) and sort grass

(average grass height less than 0.55 m). In contrast the bird

presence is associated with tall scrubs or trees (Fig. 3c).

Discussion

Broad Habitat Features

Relic pre-industrial agricultural landscapes characterized

by diverse habitat types and land uses dominate several

mountain plateaus in Greece that escaped recent land

reforms (Grove and Rackham 2001) and still hold signifi-

cant bird populations that are declining in other parts of

Europe. Such cultural landscapes where pastures (set-aside

or recently abandoned agricultural land) are located within

arable dominated land are of special importance for many

farmland birds (Soderstrom and Part 2000; Robinson and

others 2001). Small scale habitat heterogeneity and land

use diversity increase patchiness and bird species diversity,

providing opportunities for efficient exploration of seasonal

resources, provide shelter, low predation risk and increased

prey detectability (Butler and Gillings 2004; Whittingham

and Evans 2004).

Indeed, in our study area, the majority of ‘‘bird’’ plots

include some type of pastureland, indicating that these

three species are associated with open diverse natural or

semi-natural grasslands maintained by grazing. This is not

surprising, as the original habitat of most farmland birds in

Europe is open grassland initially maintained by large wild

herbivores and extinct megaherbivores (Pykala 2000).

Traditional agriculture mimicked these landscapes and

provided a viable habitat for these birds. Nowadays, this


123

type of habitat will only remain ‘‘open’’ and favorable to

farmland birds if extensive mixed flock grazing continues

to suspend shrub and tree invasion (Aich and Waterhouse

1999; Moskat and Fuisz 2002; Laiolo and others 2004).

However, this is not the whole story. In other areas of

Europe L. collurio and S. communis are associated with

arable land (Brickle and others 2000; Vanhinsbergh and

Evans 2002), but although arable land is abundant in the

plateaus it was not apparently favoured by the birds. Also

M. calandra, which prefers cereal fields to fallows in other

areas (Delgado and Moreira 2000) was not found to be

associated with arable land. We found that our birds rather

preferred some special microhabitat features within arable

land, such as dirt roads with roadside verges, fences,

scattered shrubs, trees, hedges and uncut weedy vegetation

stripes. This is not surprising as these features all support

high invertebrate densities and increase bird feeding

opportunities (Lefranc 1997). Only L. collurio uses culti-

vated hay meadows (with clover or lucernes) before

mowing, because of the temporal food availability there,

but only if hunting perches are available (Titeux and others

2007).

On the contrary loss of rural character and urbanization

seems to be detrimental, as none of the studied birds has

been found breeding in the smallest Aspraggeloi plateau,

where several new buildings serve the recent influx of

Table 3 Structural variables and specific microhabitat characteristics of the best logistic regression model for each common farmland bird

species. In addition we present minimum and maximum values as well as frequency of each variable appearing in the 50 regression models

Predictor Coefficients (b), standard errors (SE), Wald statistic and significance

(P) of the predictors of the best logistic regression model

Range of coefficient values as estimated from the

50 models fitted and frequency

b SE Wald P Minimum Maximum N

Lanius collurio

Dead-burned shrub/tree 1.80 0.53 11.44 0.001 1.38 3.28 49

Fence presence 2.78 0.76 13.29 0.000 1.48 4.31 49

Road presence 3.38 1.31 6.65 0.010 2.08 21.82 45

Average shrub height 1.04 0.29 12.52 0.000 0.57 1.36 37

Maximum grass height 2.59 0.89 8.43 0.004 1.30 3.44 29

Soil coverage (%) -0.08 0.03 5.38 0.020 -0.10 -0.06 17

Single shrubs/trees 1.46 0.52 7.83 0.005 0.92 1.68 15

Average grass height -4.8 2.05 5.61 0.018 -5.24 0.67 8

Constant -4.37 1.09 15.97 0.000 -6.29 -2.23

Miliaria calandra

Fence presence 2.76 1.13 5.91 0.015 1.51 21.67 28

Maximum grass height 2.26 0.98 5.28 0.022 1.82 3.46 20

Maximum tree height -0.31 0.14 5.00 0.025 -6.19 -0.24 19

Wet grassland presence 1.80 0.95 3.60 0.058 1.7 22.03 15

Constant -2.43 1.07 5.11 0.024 -8.79 0.46

Sylvia communis

Maximum shrub height 1.83 0.72 6.33 0.012 0.63 1.83 39

Average grass height 12.01 4.86 6.10 0.014 4.27 12.01 19

Tree coverage (%) 1.10 0.43 6.33 0.012 0.04 1.10 13

Group of hedges 3.49 1.41 6.11 0.013 1.34 3.49 8

Maximum tree height -2.08 0.90 5.31 0.021 -2.08 -0.48 2

Constant -9.85 3.45 8.13 0.004 -9.85 6.39

Prediction statistics for the best fit models

Best model % Correct Model summaries

-2 log likelihood Cox and Snell R2 Nagelkerke R2

Lanius collurio 78.4 108.76 0.43 0.58

Miliaria calandra 81.3 56.96 0.39 0.52

Sylvia communis 88.2 32.29 0.59 0.79


123

tourists. Similarly, in other areas of Europe M. calandra

(Scozzafava and De Sanctis 2006) and L. collurio (Titeux

and others 2007) strongly select open landscapes and seem

to avoid buildings. Urbanization is a serious threat for

many agricultural birds in Europe (Tucker and Evans

1997). Nevertheless L. collurio at least can co-habit with

man and it has been observed breeding within the vegetable

gardens of some very old villages surrounded by dense

shrublands or forest, in the vicinity of the study area.

Species Specific Microhabitat Requirements

Logistic regression and classification tree models showed

the importance of fine-grained heterogeneity, as expressed

by grassland type and grass height for the presence of the

three species in the area, which accords with findings for

several other farmland birds (Moreira 1999; McCracken

and Tallowin 2004; Atkinson and others 2005; Wilson and

others 2005). M. calandra is often found in the periphery of

seasonal wet grasslands (mostly dried out during summer),

while it appears that M. calandra and L. collurio are able to

make use also of dikes and ditches occurring in the field

boundaries (see also Mason and MacDonald 2000a; Herzon

and O’Hara 2007) as they provide moist areas with fleshy

vegetation, high insect density and consequently are used

by birds for feeding (Brickle and others 2000). Being a

ground nesting species M. calandra avoids extended areas

of mowed meadows, but prefers grassland with patches of

tall grass, such as set aside and fallows, that provide food,

shelter and breeding sites (Stoate and others 2000; Meyer

and others 2007). On the contrary L. collurio occurs fre-

quently in mown meadows and areas with short average

grass height, where prey accessibility is high, given the sit-

and-wait strategy of the species. This is probably the reason

for the special association of L. collurio with grazing

(Moskat and Fuisz 2002; Vanhinsbergh and Evans 2002;

Fig. 3 a Classification Tree Model for the prediction of Laniuscollurio occurrence and the corresponding classification matrix

(p = presence, a = absence). b Classification Tree Model for

Miliaria calandra (p = presence, a = absence). c Classification Tree

Model for Sylvia communis (p = presence, a = absence)


123

Laiolo and others 2004; Golawski and Meissner 2008).

However, the later species occurs also in hay meadows,

recently abandoned pastureland and not mowed arable

land, indicating probably that the heterogeneous mosaic of

grass heights, sward structure and the mixture of land uses

are the key habitat features for the species; the same

probably applies for M. calandra (Holzkamper and others

2006; Titeux and others 2007; Fox and Heldbjerg 2008).

Fine-grained heterogeneity is maintained within rangelands

with ‘‘light’’ extensive herding coupled with small arable

fields giving a rotation of sowing, grazing and alteration of

set-asides, fallows, semi-natural grasslands and meadows.

We have also found that natural grasslands with scat-

tered single shrubs and small trees, resembling open

savanna-like landscapes, are indispensable for all species

but especially so for M. calandra and L. collurio (Part and

Soderstrom 1999; Verhulst and others 2004; Muller and

others 2005; Meyer and others 2007). Both species have

been observed frequently to claim the top of the same

single shrub, while L. collurio often places its nest within

shrubs. Most isolated shrubs are dense pigmy pyramid

shape thorny bushes that will retain this shape only if goat

grazing continues. On the other hand shrubs will be unfa-

vorable for L. collurio if overgrazing depresses them to less

than 1.65 m or if they grow high because grazing has been

suspended.

Shrub average height is also important for S. communis,

(Fig. 3c). Several studies suggest that S. communis is a

hedge specialist (Fuller and others 2001; Elle 2003),

especially when hedges are low and sparse (Green and

others 1994), but as hedges are cultural elements of

farmland landscapes, they can be seen only as an expedient

or surrogate habitat in the absence of some similar feature

of the primeval landscape. Our study reveals that S. com-

munis occurs in both shrub-wood pastures (with scattered

shrubs and trees) and meadows with groups of hedges

(Table 2) similar to the Sudan savanna, where its western

population overwinters (Stoate and others 2001b). Grassy

field margins are also found to be favorable for S. com-

munis (Mason and MacDonald 2000b; Stoate and Szczur

2001) (Table 3; Fig. 3c), which probably explains why it

occurs in abandoned meadows and similar habitats else-

where (Berg and Part 1994). Most interestingly, around

2 m is apparently the optimum hedge height (Stoate and

others 2001b), but what controls the height if not humans

by pollarding trees and shrub at the optimum human hand

working height? The importance of human practices in

summer and wintering areas of S. communis has already

been pointed out; complete abandonment or over use of

shrub and trees are both detrimental (Stoate and others

2001a; b). However, we found the species to be present

also in tall hedges and our classification tree predicts its

presence in tall woody vegetation. Nevertheless, all three

species seem to avoid areas where abandoned hedges

resemble forest strips as they do in other parts of Europe

(Fuller and others 2001), probably because such places are

used by avian predators and several forest species (Stoate

and others 2000; Roos and Part 2004).

Direct Anthropogenic Effects on Habitat

All types of fences, mainly handmade short wooden posts

with barbed wire are strongly selected by M. calandra and

L. collurio for the same reason as single shrubs and trees

(Vanhinsbergh and Evans 2002). However, although

reported elsewhere, L. collurio was never observed

impaling food on barbed wire perhaps because there is no

need for food storage during the hot and dry summers of

the area (Lefranc and Worfolk 1997). Dead or burned

woody vegetation (shrub and trees) was found to be

favored by L. collurio and this can probably again be

linked with its primeval habitat, which is supposed to be

natural complex ecotones within forests created by natural

fires, natural disasters (storms, insect outbreaks etc) and

grazing of wild herbivores (Lefranc and Worfolk 1997).

Summarizing the above, we found a clear difference

between the three species habitat preferences, from an

ecotone forming a ‘‘sequence’’ from open grasslands with

very few dwarf shrubs and short trees favored by M. cal-

andra, to the mixed farmland with more dense and tall

vegetation of shrub, trees and hedges favored by S. com-

munis. Being a typical bird of such ecotones L. collurio

occurs in both habitats and intermediate situations. All

analyzed microhabitat features are shaped directly or

indirectly by human activities but special emphasis has to

be given on the positive impact of long established agri-

cultural uses particularly extensive controlled mixed flock

grazing.

Conclusion and Management Implications

The study of specific physiognomic and structural habitat

characteristics contemporarily with microhabitat features

selected by farmland birds within small ‘‘bird’’ plots seems

to be a precise and accurate methodology that reveals

specific habitat requirements, if adequate analysis is done

in a hierarchical scale, from the coarse filter of land use and

habitat coverage types to fine-grained structural charac-

teristics revealed by regression tree models (Kallimanis

and others 2007, Schlossberg and King 2009). We also

found that the elaborate selection of ‘‘non-bird’’ plots, not

only overcomes the frequent problem of pseudo-absence

and spatial autocorrelation, but also the limitation on data

available; a commonplace in similar studies in such highly

fragmented landscapes.


123

The knowledge of micro-scale habitat selection is

urgently needed for the implementation, evaluation and

assessment of locally adapted nature conservation mea-

sures, especially for species such as the three studied,

which are still locally very common, but not well studied in

Greece (Catsadorakis 1997, Kazantzidis 2007), are very

widespread in Europe and have been proposed as good

monitoring indicators on a wide variety of farmland eco-

systems (Siriwardena and others 1998; Baldi and others

2005; Gregory and others 2005; Vorısek and others 2007;

Kati and Sekercioglu 2006). Good knowledge of the impact

of agricultural activities to biodiversity in Mediterranean

anthropogenic ecosystems is important also from the eco-

nomical point of view, to reconcile and promote sustain-

able agriculture production and nature conservation

(Bignal 1998; Mitchley and others 2006; Henle and others

2008). Unfortunately traditional agricultural activities,

such as these that we found to be preferable to common

farmland birds, are already unattractive and young people

flee the mountains due to a lack of socio-economic

opportunities (Boyazoglu 2002; Bernues and others 2005;

de Rancourt and others 2006; Scozzafava and De Sanctis

2006; Soliva and others 2008). Consequently, there is an

urgent need to understand deeply the underling forces and

the functions of long established ancient Mediterranean

landscapes before they are extinguished due to land aban-

donment or extirpated by more profitable land uses, such as

urbanization, recreation or tourist development.

Agro-silvo-pastural cultural landscapes in Mediterra-

nean mountains have been shaped by moderate disturbance

regimes with small scale prescribed fires and mixed flock

grazing, which in conjunction with the ancient rotation of

cereal cropping and fallows date back at least to the time of

Homer (Blondel and Aronson 1999). Nevertheless in

present day Greece burning in particular is prohibited as in

some other European countries (Moreira and others 2001;

Herrando and others 2003; Pons and others 2003). This

prohibition results from concerns with recent and past

overgrazing in islands (Giourga and others 1998) and also

forest fire risk that has monopolized the views of policy

makers and bureaucrats (Grove and Rackham 2001; Tza-

nopoulos and others 2007).

However, grazing used as a tool for nature conservation

is an emerging multidisciplinary topic and more research is

needed to investigate its historical co-evolutionary rela-

tionship with mountain biodiversity (Bignal and McCrac-

ken 1996). Our study focuses directly on how grazing and

traditional active management shape landscape and

microhabitat features and favor common farmland birds.

Therefore, experimental research is needed to investigate

the stocking density, season and mix of grazing animals to

preserve specific habitat features.

In the above context we could propose the experimental

use of small scale prescribed fire and mixed flock grazing,

as a delicate management tool to control natural expansion

of woody species or slowing down the natural vegetation

succession. These practices seem as an important future

research topic (Laiolo and others 2004) either in Mediter-

ranean (Lasseur 2005) or in the wintering areas of those

bird species in Africa and ideally in both, also within the

context of the recently described ‘‘pyric herbivory’’ spatial

and temporal perspective (Fuhlendorf and others 2009).

Such habitat restoration (Papanastasis 2004; Sirami and

others 2008) should focus on montane protected areas

where grazing and the use of fire is often stereotypically

prohibited, as in the case of the core area of Vikos-Aoos

National Park, resulting in a more vulnerable and suscep-

tible vegetation to wild destructive fires (Petrakis and

others 2005), that threat ancient Mediterranean cultural

landscapes.

Acknowledgments This research has been funded by the European

Union, the Hellenic State-Ministry of Development, General Secre-

tariat of Research and Technology and private sources through the 3rd

Community Support Program ‘‘PENED’’ (Action 8.3 Operational

Program ‘‘Competitiveness’’). We would like also to thank the Hel-

lenic Ministry of Environment and Public Works and the Munici-

pality of Central Zagori for partly funding the field work in the frame

of the Sustainable Development Project 2003 (ETERPS funds). We

would like to thank Professors Vassilis Goutner and Vassilios Pa-

panastasis for inspiring the ornithological research, as well as the

members of the Hellenic Ornithological Society Antonia Galanaki,

Theodoros Kominos and Lavrentis Sidiropoulos for their contribution

in the literature review. Lastly, we want to thank Alkis Betsis for help

with the maps and Dr. Jenny Wong, who revised the English for her

constructive comments and suggestions.

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Microhabitat Selection by Three Common Bird Species of Montane Farmlands in Northern Greece

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