Diversity, ecological structure, and conservation of the landbird community of Dadia reserve, Greece

Abstract

Birds are integral to many environmental monitoring schemes. However, there has been little research on the ecological basis of utilizing bird species as indicators of their respective communities and habitats. We used point counts to survey 72 landbird species, 16 of conservation concern, in the Dadia Nature Reserve, Greece, in order to understand the ecology of bird diversity patterns, analyse community composition, identify species characteristic of major vegetation types, and improve long-term management and monitoring protocols. We sampled 36 sites representing 21 vegetation types. Highly heterogeneous sites were the most species rich and rural mosaics (small fields and pastures of low intensity land use, separated by thick hedgerows and tree lines) were twice as rich as intensified crop monocultures. Using multivariate analysis, we found that vegetation cover and height affected the composition of the avifauna. Twenty-one predefined vegetation categories clustered into eight distinct bird habitat types: field crops, rural mosaics, mosaic sites, poplar trees, broadleaved woods, pinewoods, shrubs, and heaths. Ten bird species were highly characteristic of the main bird habitat types in the study area. Our results emphasize the importance of conserving rural mosaics, hedgerows, and openings within forests for landbird conservation in the Mediterranean countryside. We also provide evidence in support of maintaining horizontal heterogeneity at a local scale. Finally, we suggest that monitoring populations of certain indicator bird species can be a cost-effective and efficient way to monitor the state and habitat quality of the entire landbird community, thereby integrating the knowledge of community structure into conservation decision-making.

Full text

DOI: 10.1111/j.1366-9516.2006.00288.x © 2006 The Authors
620
Journal compilation © 2006 Blackwell Publishing Ltd www.blackwellpublishing.com/ddi
Diversity and Distributions, (Diversity Distrib.)
(2006)
12
, 620–629
BIODIVERSITY
RESEARCH
ABSTRACT
Birds are integral to many environmental monitoring schemes. However, there has
been little research on the ecological basis of utilizing bird species as indicators of
their respective communities and habitats. We used point counts to survey 72
landbird species, 16 of conservation concern, in the Dadia Nature Reserve, Greece,
in order to understand the ecology of bird diversity patterns, analyse community
composition, identify species characteristic of major vegetation types, and improve
long-term management and monitoring protocols. We sampled 36 sites representing
21 vegetation types. Highly heterogeneous sites were the most species rich and rural
mosaics (small fields and pastures of low intensity land use, separated by thick
hedgerows and tree lines) were twice as rich as intensified crop monocultures. Using
multivariate analysis, we found that vegetation cover and height affected the
composition of the avifauna. Twenty-one predefined vegetation categories clustered
into eight distinct bird habitat types: field crops, rural mosaics, mosaic sites, poplar
trees, broadleaved woods, pinewoods, shrubs, and heaths. Ten bird species were
highly characteristic of the main bird habitat types in the study area. Our results
emphasize the importance of conserving rural mosaics, hedgerows, and openings
within forests for landbird conservation in the Mediterranean countryside. We also
provide evidence in support of maintaining horizontal heterogeneity at a local scale.
Finally, we suggest that monitoring populations of certain indicator bird species can
be a cost-effective and efficient way to monitor the state and habitat quality of the
entire landbird community, thereby integrating the knowledge of community
structure into conservation decision-making.
Keywords
Agricultural policy, biodiversity monitoring, habitat heterogeneity, indicator
species, landscape ecology, protected area management
INTRODUCTION
Since the conservation status, distributions, and population
trends of European birds are particularly well-known (Heath
et al
., 2000; BirdLife International, 2004), birds are widely used
in European conservation planning (Council of Europe, 1979)
and population trends of farmland bird species are one of the
15 ‘Quality of Life’ indicators used by the UK government
(BirdLife International, 2004; Gregory
et al
., 2004). Given the
significance of birds for conservation planning and environmental
assessments, there is a need for a better ecological understanding
of the role of bird diversity patterns and avian community structure
in conservation decision-making.
Small landbirds in particular have often been proposed as
potential indicators for the presence of other unrelated taxa
(Prendergast
et al
., 1993; Lombard, 1995; Howard
et al
., 1998;
Kati
et al
., 2004a) or as environmental change indicators to be
integrated into broader monitoring schemes (Gregory
et al
.,
2004). They are also frequently included in evaluation studies for
overall biodiversity conservation (Dobson
et al
., 1997; Lawton
et al
., 1998; Vessby
et al
., 2002; Kati
et al
., 2004b).
This study took place in the Dadia forest reserve (Greece),
which was designed particularly for the protection of Eurasian
black vultures (
Aegypius monachus
), a globally endangered
species that is officially ‘vulnerable’ in Europe (Poirazidis
et al
.,
2004)
.
The reserve has high conservation value for the birds of
prey, as 36 of the 38 European species of raptors have been
observed there. A special management plan (Adamakopoulos
et al
., 1995) and a pilot monitoring project (Poirazidis
et al
.,
2002) are currently in practice in the Dadia reserve, targeting the
biodiversity conservation of the reserve and particularly focused
on raptor species of conservation concern. Our study explores
1
Department of Environmental and Natural
Resources Management, University of Ioannina,
Seferi 2, 30100 Agrinio, Greece and
2
Center for
Conservation Biology, Department of Biological
Sciences, Stanford University, Stanford, CA
94305-5020, USA
*Correspondence: Vassiliki I. Kati, Department of
Environmental and Natural Resources
Management, University of Ioannina, Seferi 2,
30100 Agrinio, Greece. E-mail: vkati@cc.uoi.gr
Blackwell Publishing, Ltd.
Diversity, ecological structure, and
conservation of the landbird community
of Dadia reserve, Greece
Vassiliki I. Kati
1
* and Cagan H. Sekercioglu
2

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the ornithological value of the reserve for the landbird community,
highlighting an easy-to-survey component of local biological
diversity as an important parameter to be taken into consideration
in reserve management. We define landbirds as the species
belonging to the orders Passeriformes, Piciformes, Coracii-
formes, and Columbiformes.
The aims of this study were: (1) to assess the importance of
different habitats for landbird diversity, (2) to analyse the
ecological structure of this community, (3) to identify indicator
species, defined as typical species for the main habitat types, and
(4) to integrate these findings into the conservation management
and long-term monitoring protocols of the reserve.
METHODS
Study area
The study area is situated in north-eastern Greece (40
°
59
′−
41
°
15
′
N, 26
°
00
′−
26
°
19
′
E). It covers 430 km
2
, almost all of which
belongs to the Dadia Nature Reserve. It is a hilly area with
elevation ranging from 10 to 650 m. The climate is submediter-
ranean. Temperature ranges from
−
19
°
to 40
°
C and the mean
annual rainfall varies between 556 mm and 916 mm (Adamako-
poulos
et al
., 1995). Forests are dominated by Aegean pine (
Pinus
brutia
) and black pine (
Pinus nigra
), oaks or a mixture cover 75%
of the reserve, followed by agricultural land (16%), shrubs and
mosaics (5%), and open areas consisting of grasslands and
heaths (4%). The reserve was declared in 1980 and consists of
two strictly protected zones (72.9 km
2
), which, in combination,
have 85% cover of pinewoods and mixed pine–oak woods and
are of great importance as nesting sites for Eurasian black
vultures (Poirazidis
et al
., 2004). The buffer zone of the reserve
(351.7 km
2
) has 72% forest cover and has more open or semi-open
areas. A detailed map of the vegetation types in the study area is
presented in Kati
et al
. (2004c).
Sampling
We distinguished 21 vegetation types in the study area, using the
Corine typology database (Devillers & Devillers-Terschuren,
1996) as a reference system (19 Corine habitat types present in
the study area). In two cases (Corine codes 41.733 and 4285A) we
further distinguished two vegetation subcategories, on the basis
of vegetation physiognomy (bushy undergrowth or not). One
site or usually two sites (indicated with ‘a’ or ‘b’ next to the site
code) were randomly selected to represent each one of the 21
vegetation types of the study area. We sampled 36 sites with 310
point counts (Blondel
et al
., 1970; Bibby
et al
., 1992). In a point
count, the territorial-breeding song of a male represents a future
breeding pair and is therefore counted as two individuals (Bibby
et al
., 1992). Every call different from the male breeding song is
counted as one individual. We recorded all bird species seen or
heard within a circle of 100-m radius. Each count lasted for
10 min and took place between 30 min before sunrise and 4 h
after sunrise. In order to sample both sedentary and late migrant
species, we conducted two sets of 155 point counts between 15
April to 15 May and 15 May to 15 June, 1999. Because of the
differences in area extent sampled, we could not have the same
sampling effort at all sites and adjusted the sampling effort based
on the site’s area. We sampled 25 sites of 20 ha with five point
counts, and 11 smaller sites with two to four point counts
(Table 2). Sampling stations were at least 200 m away from each
other and 100 m away from the site edge.
Each point count was located at the centre of a quadrat of
50
×
50 m, within which we estimated the overall vegetation
cover of trees and bushes (> 0.5 m), in order to describe the
general vegetation physiognomy of the site sampled (Table 1).
The vegetation cover is defined as the total vertical projection of
the crown area of trees and bushes, using the Braun–Blanquet
scale for cover estimation: 1 = 1–5%, 2 = 6–25%, 3 = 26–50%,
4 = 51–75%, and 5 = 76–100%. Based on Kent & Coker (1994),
we characterized the four main vegetation layers as follows:
(1) trees > 7 m, (2) low trees (4–7 m), (3) high bushes (2–4 m),
and (4) bushes (0.5–2 m). We defined the dominant vegetation
layers as the ones contributing more than 25% to the overall
vegetation cover (Table 1).
Data analysis
The species diversity of sites was estimated in terms of species
richness (
S
), weighted species richness (
WS
), and Shannon–
Weiner index (
H
) (Magurran, 2004)
.
Weighted species richness is
the species richness of the site, with each species having a different
weight based on its conservation status (SPEC category)
(BirdLife International, 2004). We gave a standard weight (
w
= 1)
to the species of SPEC 4 category, which are concentrated in
Europe and have either a favourable conservation status or are
not covered by any SPEC category. We gave double weight
(
w
= 2) to the species of SPEC 3 category, which are not concen-
trated in Europe but have an unfavourable conservation status.
Finally we gave quadruple weight (
w
= 4) to the species of SPEC
2 category, which are concentrated in Europe and have an un-
favourable conservation status and to the species of Annex I of
the European Directive 79/409 EU, which includes all bird
species subject to special conservation measures in Europe. We
calculated
H
of each site using as relative abundance of bird
species the maximum abundance of the two values recorded in
the two sampling seasons.
Using the

3 software package (Legendre & Vaudor, 1991), we
analysed the bird community composition by creating a similarity
matrix of the samples on the basis of relative abundance data
(Steinhaus coefficient of similarity — S17). A distance matrix
was produced from the similarity matrix, and it was used as an
input into the spatial visualization in the Euclidian space, using
Principal Coordinate Analysis with corrected eigenvalues (DistPCoA),
a method that resolves the problem of ‘non-Euclideanarity’
(Legendre & Anderson, 1998). We used the samples’ coordinates
of DistPCoA as an input into the k-means partitioning
procedure, using the
 
procedure (SAS, 1985). We applied
the above procedure for k algorithm computation, k being the
final number of clusters produced. Computation was repeated
1000 times, randomly reallocating samples as initial seeds at each

V. I. Kati and C. H. Sekercioglu
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run. From the n dimensions of samples’ coordinates we used the
first ordination axes capturing a standard percentage of 85% of
data variance, avoiding thus the noise of the last axes. The final
output was the non-hierarchical up-to-down robust dendro-
gram with k clusters, including only samples with a level of
persistence > 75%. These k clusters are also shown as 80%
confidence ellipses in the ordination of point counts (SAS, 1985).
Finally, we used the indicator value procedure (Dufrêne &
Legendre, 1997) in order to find out the typical species that
characterize each of the clusters. The indicator value of each species
Table 1 Ve getation types in the study area based on the Corine typology system (Devillers & Devillers-Terschuren, 1996) and descriptions of
the sites sampled
Corine vegetation type Vegetation type description Site code
Site area
(ha)
Dominant
vegetation
layer
Vege tation
cover
estimation
Shrubs (S) 32.313 High dense maquis (Arbutus sp.) S1a 20 3 5
without undergrowth S1b 20 3 5
32.161 Deciduous oak mattoral (Quercus S2 20 3 3–4
pubescens) with Phillyrea latifolia
undergrowth
32.21A4 × 34.53 Bushes (Phillyrea latifolia) with grassy S3 10 3 2
undergrowth
Heaths (H) 32.32 Low (< 0.5) ericaceous maquis (Erica Ha 10 3 1
arborea) with sparse oak trees Hb 10 3 1
Grasslands (G) 37.4 (× 41.8221) Humid grasslands with sporadic G1a 10 1,3 2
broadleaved trees and Juniperus bushes G1b 5 3 2
34.53 Xeric grasslands with sporadic low G2a 5 2 1
pine trees G2b 10 2 1
34.2 Serpentine grasslands with sporadic G3 5 3 2
pines
Mosaics (M) 32.71 × 38.1 Mosaic of pseudomaquis × pastures M1a 20 1,3,4 1–3
Sporadic mature oak and fruit trees M1b 20 1,3,4 2–3
with bush undergrowth
32.71 × Mosaic of pseudomaquis × pastures M2 10 1,3 2–3
38.1 37.1 × × humid grassland × willow shrubs
44.12 × 41.733 × oakwoods
Forests (F) 41.1B × 41.19311 Mediterraneo–Moesian beech forests F1a 20 1 5
F1b 20 1 5
41.76 Oakwoods (Quercus frainetto/cerris)F2a 20 1 5
F2b 20 1 5
41.733 Oakwoods (Quercus pubescens)F3a 20 2 4
F3b 20 2 4
Oakwoods (Quercus pubescens)F4a 20 2,4 3
with bush undergrowth F4b 20 2,4 3
43.7 Mixed pine–oak woods F5a 20 1 5
F5b 20 1 5
42.661(C) Pinewoods (Pinus nigra)F6514
42.85 A Pinewoods (Pinus brutia)F72015
Pinewoods (Pinus brutia)F8a 10 1,4 4
with bush undergrowth F8b 5 1,4 4
44.514 Riparian vegetation — tree line along F9a 20 1 5
streams of Alnus glutinosa F9b 20 1 5
44.615 Riparian vegetation — tree line F10a 20 1 5
along streams of Populus sp. F10b 20 1 5
Agricultural 84.4 Rural mosaics. Small agricultural plots A1a 20 3 2
land (A) separated by hedges and tree lines A1b 20 3 2
82.11 Field crops. Agricultural land without A2a 20 4 0–1
bush cover A2b 20 4 0–1
Total 19 21 36 575
Dominant vegetation layer: 1, trees > 7 m; 2, low trees (4–7 m); 3, high bush (2– 4); 4, bush: (0.5–2 m).
Vegetation cover estimation of trees and bushes: 1 = (1–5)%, 2 = (6–25)%, 3 = (26–50)%, 4 = (51–75)%, 5 = (76–100)%.

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for a given cluster is calculated as: IndVal = A
×
B
×
100, where
A =
mean number of the individuals across the sites of the cluster
,
which is the sum of mean number of the individuals in all
clusters, and B =
number of sites in the cluster where the species is
present
, which is the total number of sites in that cluster.
IndVal is a percentage that ranges between 0 and 100 and takes
its maximum value when the species is present only in one clus-
ter and in all sites of this cluster. All calculations were carried out
using

software (Dufrêne, 1999). A species is considered
to be a ‘symmetrical indicator’ (IndVal > 50%) for one cluster
when it is present in > 70% of the sites of the cluster and when
> 70% of its individuals occur in the cluster. A random realloca-
tion procedure (1000 iterations) of sites among site groups was
used to test the significance level of IndVal (alpha = 0.05). In
order to represent all the bird species in the study area, we drew a
complementary network of sites starting with the most important
site in terms of conservation and, using a stepwise procedure,
added the sites that contributed new species to the network,
giving priority to species with high conservation value (criteria
WS
and then
S
).
RESULTS
During our point count sampling, we counted 9305 individuals
of 72 bird species (Appendix I), distributed among the orders of
Passeriformes (61), Piciformes (6), Coraciiformes (3), and
Table 2 Bird diversity and sampling effort at each site. Sites are ranked by descending species richness (S), then by descending weighted species
richness (WS)
Site S WS H′Mean S Mean WS
No. point
counts
M1a Mosaic 37 59 3.26 22.00 35.60 5
A1b Rural mosaic 35 65 3.17 17.80 35.40 5
A1a Rural mosaic 35 60 3.11 17.60 29.80 5
M2 Mosaic 34 53 2.96 15.80 22.40 5
M1b Mosaic 32 48 2.99 15.80 21.00 5
F9a Alder vegetation 29 36 2.94 15.40 19.40 5
F4b Oakwood with bush undergrowth 28 52 2.89 14.40 24.40 5
S2 Oak mattoral 28 42 2.96 16.40 23.80 5
F10b Poplar vegetation 28 41 2.85 11.40 14.00 5
G1a Humid grassland 27 49 2.94 15.25 26.75 4
F4a Oakwood with bush undergrowth 26 43 2.81 14.60 24.80 5
F1a Beech wood 25 37 2.79 13.40 17.80 5
F2b Oakwood 24 40 2.75 11.60 19.00 5
F5b Mixed pine–oakwood 24 39 2.83 15.60 21.60 5
S1b High maquis 24 38 2.67 13.20 22.00 5
S1a High maquis 24 35 2.74 13.60 20.20 5
S3 Phillyrea bushes 23 36 2.91 17.00 24.00 3
F10a Poplar vegetation 23 36 2.87 11.80 15.40 5
F2a Oakwood 22 38 2.69 11.20 16.60 5
Ha Heath 22 37 2.70 12.67 23.67 3
G3 Serpentine grassland 22 32 2.78 16.50 25.00 2
G2b Xeric grassland 22 30 2.83 16.00 19.50 2
F1b Beech wood 22 29 2.67 12.00 13.40 5
G2a Xeric grassland 21 40 2.65 16.00 22.00 2
F8a Pinewood with bush undergrowth 21 31 2.65 9.75 15.25 4
F9b Alder vegetation 21 28 2.75 11.00 13.40 5
F5a Mixed pine–oakwood 20 27 2.67 12.80 16.40 5
A2b Field crops 19 48 2.29 8.00 21.40 5
F3b Oakwood 19 35 2.31 8.80 15.40 5
F7 Pinewood 19 29 2.30 9.00 10.60 5
Hb Heath 18 36 2.38 10.33 24.67 3
F3a Oakwood 17 34 2.29 8.20 15.80 5
F6 Black pinewood 16 22 2.22 10.50 13.50 2
A2a Field crops 15 35 2.05 8.20 19.40 5
F8b Pinewood with bush undergrowth 15 14 2.48 12.50 12.00 2
G1b Humid grassland 13 22 2.38 9.33 15.33 3
S, species richness; WS, weighted species richness; H′, Shannon diversity index; Mean S, mean species richness of point counts; Mean WS, mean
weighted species richness of point counts.

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Columbiformes (2 species). Sixteen species were of special
conservation concern since they belonged to SPEC 2 category or
to the Annex I of the Bird Directive 79/409 EU. Thirteen more
species belonged to SPEC 3 category.
Diversity
The most important sites for bird conservation were highly
heterogeneous sites, combining grassy openings, hedges, and
wood plots, such as rural mosaic (A1) and mosaic sites (M1,
M2), because they hosted the greatest number of species (
S
) and
the greatest number of species of concern (
WS
) (Table 2). These
mosaic character sites are proven also to be the most diverse,
based on the Shannon’s diversity index as a ranking criterion
(M1a, A1b, A1a, M1b, M2).
To better compare the site species richness regardless of the
variations in site area and the sampling effort, we also used the
mean species richness of point counts as the main ranking
criterion. Mosaic (M1a) and rural mosaics (A1a, A1b) again
emerged as the three most important sites, followed by smaller
sites such as grasslands with
Phillyrea
bushes (S3), serpentine
grasslands (G3), or xeric grasslands (G2). These sites are
openings within the expanded pine forest zone (Table 2). Oak
matorral with shrubs (S2) also ranked as one of the most species-
rich sites. Pinewoods hosted few species, including only two
breeding species of conservation concern (
Streptopelia turtur
,
Picus viridis
), which also bred in the broadleaved woods of the
study area.
Ecological structure
Considering all the 155 point counts together, the ordination
procedure (DistPCoA) clustered the 10 point counts in field
crops (A2), positioning them on the right part of the horizontal
axis that explained 23% of the variation. Therefore, agricultural
land with almost no tree or bush cover is clearly distinguished
from the remaining sites. We then excluded these point counts
and re-analysed our data set, in order to discern the environmental
gradients within the remaining 145 point counts. Shaded sites
with high vegetation cover were positioned on the left of the
horizontal axis which explained 19% of the variation, semi-open
sites in the centre, and open sites on the right. On the other hand,
the vertical axis that explained 16% of the variation separated
sites with tall trees from those with shrubs (Fig. 1). Hence, two
major environmental gradients affect bird distribution in the
study area: vegetation cover and vegetation height.
The first cluster set apart in the clustering procedure encom-
passed all point counts conducted in the field crops (A2). We
recorded three bird species exclusively in the field crops:
Melano-
corypha calandra
,
Calandrella brachydactyla, and Anthus campestris
(IndVal = 20%, 20% and 10%, respectively).
Figure 2 shows the main habitat types defined by their bird
communities and the typical species for each cluster, using the
145 point counts analysed with the k-means and IndVal proce-
dures. Some bird species are generalists and they are common
throughout the study area, having no indicator value for a precise
vegetation type (i.e.
Fringilla coelebs
,
Turdus merula
,
Luscinia
megarynchos
,
Erithacus rubecula, Garrulus glandarius
,
Oriolus
oriolus
,
Parus major
,
Carduelis chloris
,
S. turtur
, and
Upupa epops
).
Combining the results from ordination and clustering procedures
(Figs 1 & 2), seven different bird habitat types can be distin-
guished: heaths, shrubs and low trees, pinewoods, broadleaved
woods, mosaic sites and forest openings, rural mosaics, and poplar
vegetation.
Lullula arborea
characterizes heaths, while
Certhia
brachydactyla
is a typical species of the broadleaved woods.
Emberiza cirlus
characterizes the mosaic sites and the grassy
openings inside forest areas. Five species are typical of agricultural
fields separated by hedges and trees:
Emberiza melanocephala
,
Galerida cristata
,
Hippolais pallida, Milaria calandra, and Sylvia
communis. Emberiza hortulana characterizes areas with low trees,
shrubs, and heaths, while Parus caeruleus characterizes forest
habitats. No characteristic species exist for shrubs and low trees,
pinewoods, and poplar habitats.
Species representation
All bird species found in the study area can be represented in a
network of 10 sites. This network includes one site from each
bird habitat type (Fig. 2), with the exception of rural mosaics
that contribute two sites in the network. The network sites are
Figure 1 Ordination of 145 point counts
using Principal Coordinate Analysis
(DistPCoA) in two axes explaining 19% and
16% of the data set variability. Different shape
spots refer to the point counts of the different
clusters, which are shown as 80% confidence
ellipses.

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prioritized as follows, with complementary weighted species
richness of each site and complementary species richness
(number of new species contributed to the network) given in
parentheses: rural mosaic A1b (65, 35), mixed pine–oak wood
F5b (21, 9), field crops A2b (17, 6), poplar tree line F10a (11, 8),
xeric grassland G1b (5, 4), heath Ha (5, 4), high maquis S1a (4,
1), rural mosaic A1a (3, 2), beech wood F1a or F1b (2, 2), and
mosaic M1b (2, 2).
DISCUSSION
Ecological structure
Vegetation cover and height determine the composition of the
avifauna in our study area, which is in agreement with other
studies in the Mediterranean region (Blondel et al., 1970; Prodon
& Lebreton, 1981; Catsadorakis, 1997). The height gradient
mainly corresponds to vegetation successional stage and the veg-
etation cover to disturbance intensity, caused either by humans
(agriculture, logging, livestock grazing) or by natural processes
(fire, native herbivore grazing).
Birds discriminate landscape features at a coarse scale, perceiving
the 21 vegetation types of the study area as eight distinct bird
habitat types: field crops, rural mosaics, semi-open mosaics and
grasslands, poplar vegetation, broadleaved woods, pinewoods,
shrubs, and heaths. The habitat typology as revealed by the landbird
community does not necessarily correspond to the predefined
vegetation classifications (Fig. 2), thus emphasizing the importance
of planning habitat conservation from the perspective of the
taxon of interest. Each of these bird habitat types is also represented
in the complementary network constructed to include all bird
species, with rural mosaics being represented twice. Kati et al.
(2004b) also found that for various taxonomic groups, including
landbirds, any number of sites selected at random with the
Figure 2 Habitat types as defined by birds
and the indicator values of bird species (in
parentheses) for the hierarchy produced by k-
means clustering procedure. Species names in
bold are symmetrical indicators with IndVal
> 50% and underlined species names have
their maximum IndVal in that habitat.
Vege tation codes are from Table 1. Vegetation
types that belong to more than one cluster are
given in parentheses.

V. I. Kati and C. H. Sekercioglu
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626 Diversity and Distributions, 12, 620–629, Journal compilation © 2006 Blackwell Publishing Ltd
condition that each site belonged to a different cluster, conserves
more species than an equal number of sites selected at random
from different vegetation types defined after Corine typology.
Hence, bird typology provides us with a guideline for specific
habitats to be maintained for avifauna conservation.
Even though some of the species recorded are generalists, there
are 10 specialist species that are highly characteristic and strongly
dependent on the habitat types they are found in, as they are
found in almost all sites of that habitat type and rarely in others.
Monitoring the populations of such ‘indicator’ bird species may
be a cost-effective and efficient way to monitor the overall landbird
community and their habitats.
Conservation of landbird diversity
The rural mosaics were the most diverse and important sites for
conserving the breeding bird fauna in our study area. Cultivated
areas are generally known to play a fundamental role in main-
taining breeding bird diversity in the Mediterranean region (e.g.
Farina, 1997; Suarez-Seoane et al., 2002). Not only human-
dominated habitats can support a substantial proportion of
native bird diversity (Hughes et al., 2002; Sodhi et al., 2005) but
these birds in return also provide key ecosystem services such as
seed dispersal and pest control (Sekercioglu et al., 2004). However,
agricultural intensification has led to a dramatic decline in
farmland bird diversity in many European countries (Pain &
Pienkowski, 1997; Chamberlain et al., 2000; Donald et al., 2001),
although not all of them (Fox, 2004). In Greece, the policy
followed by the Ministry of Agriculture during the last 50 years
aimed at the unification of small agricultural proprieties into
expanded agricultural land in order to permit the use of large
machinery and the intensification of crop production. Small
properties were exchanged through a procedure of land reallotment,
simultaneously removing ‘living fences’ and tree and bush
vegetation that comprised the natural borders of former small-scale
properties. Our results show that rural mosaics, defined as small
fields and pastures separated by natural vegetation of thick
hedgerows and tree lines were twice as rich in bird species
number than intensified crop monocultures. Removing hedges
and lines of trees, even exotic conifer species (Pithon et al., 2005),
can have negative effects on farmland birds. Our study provides
additional evidence supporting the European common agricul-
tural policy (CAP) towards the maintenance of the rural mosaic
landscape as a habitat of great importance for farmland breeding
birds in the Mediterranean region.
We found that semi-open mosaic sites and forest openings are
also among the most species-rich sites in our study area and host
species of conservation concern. Mosaics are heterogeneous sites
combining patches of woodland, shrubs, and pastures in a small
area, whereas openings in forest enhance landscape heterogeneity.
Spatial heterogeneity is often the main factor that increases avian
species diversity within habitat and landscape scales (Roth, 1976;
Huston, 1994; Bohning-Gaese, 1997; Farina, 1997; Sekercioglu, 2002).
Forest openings are also important habitats for other taxonomic
groups in the study area, such as insects (Grill & Cleary, 2003;
Kati et al., 2004c) and several raptor species that use them for
hunting (Adamakopoulos et al., 1995; Poirazidis et al., 2004).
The forested zone includes fewer landbird species, but large areas
of core habitat may be important to maintain viable populations
of certain specialized forest-dwelling species. There is a need for
research in the Mediterranean region to determine the threshold
size of forest openings that will not harm forest-dependent bird
species and hinder forest regeneration (Sekercioglu, 2002).
We found that all bird species sampled in the year 1999 can be
represented in a complementary network of 10 sites. Reserve
designers usually target to maximize protected biodiversity while
minimizing reserve size (Cabeza & Moilanen, 2001). One of the
best practices to do so is to pick up complementary areas with the
maximum combined species richness (Pressey et al., 1993;
Margules & Pressey, 2000), rather than species-rich areas, or
areas representative of the vegetation types that are found at local
(e.g. Kati et al., 2004b) or regional scales (e.g. Lombard, 1995;
Howard et al., 1998). In the current study, our network of 10
selected sites is not intended as a proposal for a new subnetwork
within the existing protected area of the Dadia Nature Reserve.
These 10 sites by themselves are unlikely to maintain viable
populations of the bird species of the reserve as units isolated
from their landscape context. This network, however, highlights
habitats that are important for local bird conservation. The
network also confirms the importance of monitoring and
conserving different bird habitat types represented in the clustering
procedure, given that at least one site from the different clusters
is represented in the network.
Interestingly, most species-rich habitats are located in the
buffer zone, which is less forested, than in the strictly protected
zone, which is covered mostly by pinewoods (85% cover). The
high value of the buffer zone has also been shown for other
biological groups studied in the reserve (e.g. Grill & Cleary, 2003;
Kati et al., 2004c). The main conservation value of pinewoods is
for the maintenance of the Eurasian black vulture population
(Poirazidis et al., 2004) as well as for some forest-dwelling raptor
species, rather than for the landbird community. It is encouraging
that the management plan of the reserve (Adamakopoulos et al.,
1995), which targets mainly the conservation of its birds of prey,
is also compatible with the conservation of the landbird community
in general. The management plan proposes to conserve rural
mosaics with hedges and woodland patches and to maintain
forest openings in the core area through livestock grazing, wood-
cutting, and the reintroduction of natural herbivore populations.
Hence, there is no conservation conflict in the reserve as far as
management practices are concerned.
Conservation proposals
The current study implies the importance of horizontal hetero-
geneity for bird conservation at the local and landscape scales, as
shown by the high species richness of mosaic character sites and
of openings in the forested zone, respectively. We also provide
evidence against land reallotment and agricultural intensification
and emphasize the importance, for breeding birds, of conserving
rural mosaics in the Mediterranean landscape. Our findings also
indicate that the knowledge of bird community structure should

Conservation biogeography of a Greek bird community
© 2006 The Authors
Diversity and Distributions, 12, 620–629, Journal compilation © 2006 Blackwell Publishing Ltd 627
be integrated into conservation decision-making focused on
landbird communities.
An ecological analysis of bird community structure resulted in
the identification of eight distinct bird habitat types and 10 indicator
bird species that are highly dependent on the habitat types they
breed in. We propose the landbird community to be integrated as
a monitoring parameter in the ongoing pilot monitoring project
of the reserve and we provide a list of indicator bird species to
monitor. Monitoring these indicator species is an efficient method
to monitor the ecological state of the landbird community in the
reserve and it gives a more direct insight into bird habitat quality,
than surveying all vegetation types defined after standard habitat
typologies such as Corine. Finally, reserve authorities should be
aware of the importance of the buffer zone for local landbird
diversity and consider the high conservation value of rural mosaics,
mosaic character sites, and forest openings, especially when
putting the reserve management plan into practice. Our conclusions
have broader implications, both for the conservation of landscape
heterogeneity in the European countryside and for the use of
birds as indicator species worldwide.
ACKNOWLEDGEMENTS
V. Kati expresses her thankfulness to Bodossakis Foundation and
to the A. Onassis Foundation for supporting this research in the
context of a PhD scholarship on biodiversity issues. C. Sekercioglu’s
research is funded by the Christensen, Koret, Moore Family and
Winslow foundations, and National Geographic and Wildlife
Conservation societies. We are grateful to G. Daily, P. Ehrlich,
and K. Al-Khafaji for their helpful comments that greatly
improved this manuscript.
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Conservation biogeography of a Greek bird community
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Diversity and Distributions, 12, 620–629, Journal compilation © 2006 Blackwell Publishing Ltd 629
Appendix I Inventory of bird species sampled and weighted index (w) according to their conservation status (SPEC category 2004)
Species SPEC w Species SPEC w Species SPEC w
Columbiformes Tro g lodytes troglodytes 1Parus lugubris 41
Streptopelia decaocto 1Erithacus rubecula 41Parus caeruleus 41
Streptopelia turtur 32Luscinia megarhynchos 41Parus major 1
Coraciiformes Phoenicurus phoenicurus 24Sitta europaea 1
Alcedo atthis 3* 4 Saxicola rubetra 41Certhia familiaris 1
Merops apiaster 32Saxicola torquata 1Certhia brachydactyla 41
Upupa epops epops 32Oenathe oenathe 32Remiz pendulinus 1
Piciformes Turdus merula 41Oriolus oriolus 1
Picus viridis 24Tu rdus philomelos 41Lanius collurio 3* 4
Dryocopus martius 1Turd us viscivorus 41Lanius senator 24
Dendrocopos major 1Cettia cetti 1Garrulus glandarius 1
Dendrocopos syriacus 4* 4 Hippolais olivetorum 4* 4 Pica pica pica 1
Dendrocopos medius 4* 4 Sylvia cantillans 41Corvus corone 1
Dendrocopos minor 1Sylvia melanocephala 41Corvus corax 1
Passeriformes 1 Sylvia hortensis 32Sturnus vulgaris vulgaris 1
Melanocorypha calandra 3* 4 Sylvia curruca 1Passer domesticus 32
Calandrella brachydactyla 3* 4 Sylvia communis 41Fringilla coelebs coelebs 41
Galerida cristata 32Sylvia atricapilla 41Serinus serinus 41
Lullula arborea 24Phylloscopus bonelli 24Carduelis chloris 41
Alauda arvensis 32Phylloscopus collybita 1Carduelis carduelis 1
Riparia riparia 32Regulus ignicapillus 41Coccothraustes coccothraustes 1
Hirundo rustica 32Hippolais olivetorum 4* 4 Emberiza cirlus 41
Delichon urbica 32Muscicapa striata 32Emberiza hortulana 2* 4
Anthus campestris 3* 4 Aegithalos caudatus 1Emberiza melanocephala 24
Motacilla cinerea 1Parus palustris 1Milaria calandra 24
Motacilla alba 1
*species in Annex I of 79/409EU. SPEC2: \concentrated in Europe and with unfavourable conservation status. SPEC3: not concentrated in Europe but
with unfavourable conservation status. SPEC4: concentrated in Europe and with favourable conservation status.