factors responsible for the presence and distribution of

Ardeola 54(2), 2007, 205-215
FACTORS RESPONSIBLE FOR THE PRESENCE
AND DISTRIBUTION OF BLACK-BELLIED SANDGROUSE
PTEROCLES ORIENTALIS IN THE NATURE PARK
“VALE DO GUADIANA”
Ana Cristina CARDOSO* 1, Ana Sofia POEIRAS** and Carlos CARRAPATO***
SUMMARY.—Factors responsible for the presence and distribution of black bellied sandgrouse Pterocles orientalis in the Natura Park “Vale do Guadiana”.
Aims: Identify factors that are responsible for the presence and distribution of black-bellied sandgrouse
in the nature park of ‘Vale do Guadiana’ so that management actions can be undertaken.
Localization: Southern Portugal.
Methods: Kruskal-Wallis non-parametric tests and Bailey’s tests was used to analyse the preferences
among biotopes, while logistic regression analysis was utilized to obtain an explanation model for species
distributions during breeding and non-breeding seasons. Variables considered in the analysis included
presence or absence of cattle; ground vegetation coverage, height and vertical density; tree density; bush
coverage; slope exposition; stone coverage and number of stones; wind direction; habitat; soil capacity;
distance to roads, drinking places and villages; and altitude.
Results: The results of biotope selection indicated that sandgrouses preferred fields of leguminous
plants during both breeding and non-breeding periods and tillage during the breeding period. Montado
and fallows older than two years were avoided during the non-breeding season. Cereal fields were used
according to their availability. Besides not significantly, fallows were highly used.
For the explanation model, six variables that explain the species distribution during the breeding season were selected: cattle presence, stony ground and distance to secondary roads had a positive effect,
while vegetation cover, stone cover and distance to the drinking places had a negative effect. During the
non-breeding period, the model was not adjusted to validation sample.
Conclusions: It was found that the most important biotopes are leguminous cultivations and fallows
with extensive pastures. Grazing can have either a positive or a negative effect on these fields, depending
on cattle density. Besides the number of small dams, drinking places are still a limiting factor for this
species. Dispersion of settlements and roads is also negative to sandgrouse distribution. Finally conservation implications, namely management actions such as an enlargement of leguminous fields, cattle grazing control and modifications of Territory Management Plans, are discussed.
Key words: habitat selection; logistic regression; management actions; Pterocles orientalis; seasonal
variation.
RESUMEN.—Factores responsables de la presencia y distribución de la ganga ortega Pterocles orientalis en el Parque Natural “Vale do Guadiana”.
* Parque Natural do Vale do Guadiana, Apartado 45, 7750-352 Mértola, Portugal.
** Bairro do Bacelo, Rua dos Altos, nº 6, 7000-693 Évora, Portugal.
*** Parque Natural do Vale do Guadiana, Apartado 45, 7750-352 Mértola, Portugal.
1
Corresponding author: [email protected]
206
CARDOSO, A. C., POEIRAS, A. S. and CARRAPATO, C.
Objetivos: Identificar los factores que son los responsables de la presencia y distribución de la ganga
ortega Pterocles orientalis en el Parque Natural “Vale do Guadiana” para que las acciones de manejo y
conservación puedan ser adoptadas.
Localización: Sur de Portugal.
Métodos: Pruebas no paramétricas de Kruskal-Wallis y de Bailey se utilizaron para analizar las preferencias entre biotopos, mientras que regresiones logísticas lo fueron para obtener modelos que explicaran
la distribución de la especie durante el periodo reproductor y durante el resto del año. Las variables que se
incluyeron en los análisis fueron: presencia de ganado vacuno, cobertura vegetal, altura y densidad vertical, densidad del arbolado, cobertura arbustiva, pendiente, cobertura de rocas y su número, dirección del
viento, hábitat, capacidad del suelo, distancias a carreteras, bebederos y pueblos, y la altitud.
Resultados: Se muestra que las gangas ortega seleccionan campos de leguminosas durante todo el año
y campos labrados durante el periodo reproductor. Montado y barbechos de más de dos años son evitados durante el periodo no reproductor, mientras que los campos con cereales eran utilizados de acuerdo
a su disponibilidad. A pesar de ser un resultado no significativo, los barbechos eran altamente utilizados.
En el modelo explicativo fueron seis las variables que explicaban la distribución de la especie durante
el periodo reproductor: presencia de ganado vacuno, presencia de rocas, y la distancia a carreteras secundarias tenían un efecto positivo, mientras que la cobertura vegetal, la cobertura de rocas y la distancia a
bebederos tenían un efecto negativo. Durante el periodo no reproductor, el modelo final no fue adecuado.
Conclusiones: El trabajo muestra que el biotopo más importante para esta especie y en el área de estudio fueron los campos de leguminosas y los barbechos con extensos pastos. La presencia de ganado puede ser tanto positiva o negativa, dependiendo de la densidad de cabezas vacunas. A pesar del bajo número de zonas con agua, los bebederos son un factor limitante para esta especie. La fragmentación del hábitat
y las carreteras actúan de forma negativa. Finalmente, se discute las implicaciones en la conservación de
la especie que tendrían el aumento de los campos de leguminosas, el control del tamaño del ganado vacuno y las modificaciones en los planes de manejo del territorio.
Palabras clave: selección de hábitat; regresión logística; acciones de manejo, Pterocles orientalis;
variación estacional.
INTRODUCTION
Steppe-land birds are one of the most endangered groups of species in the world, especially in developed countries (Bota et al., 2005).
The black-bellied sandgrouse Pterocles orientalis is a steppe-land species whose distribution in Europe is limited mainly to Turkey
and the Iberian Peninsula (Cramp and Simmons, 1983; Tucker and Heath, 1994; De
Juana, 1999).
Major changes in EU Common Agriculture
Policy have occurred in the last few decades,
causing significant alterations in agricultural
and grassland habitats (Tucker and Evans,
1997; Donald et al., 2001). The black-bellied
sandgrouse European population has suffered
a clear decline in the last thirty years mainly
Ardeola 54(2), 2007, 205-215
due to changes in agricultural practices and
the loss of habitat (Tucker and Heath, 1994).
There are no more than 300 individuals in Portugal - a reason why the bird has an unfavourable status ‘Endangered’ in Portugal
(Almeida et al., 2005). The European population is classified as ‘Vulnerable’, and it is listed as SPEC 3 – a species whose global populations are not concentrated in Europe, but
which has an unfavourable status in Europe
(Tucker and Heath, 1994).
In Portugal, the main threat to steppe-land
birds is the abandonment of traditional farming and replacement by intensive agriculture
or forestation (Moreira et al., 2004; Silva et al.,
2004; Pinto et al., 2005). In southern Portugal since the launch of wheat campaign, agriculture has been supported by European Union
BLACK-BELLIED SANDGROUSE IN THE NATURE PARK “VALE DO GUADIANA”
subsidies. Actually, abandonment of land due
to the soil depletion and forestation, which is
also funded by the European Union, can be
negative to steppe-land birds.
The objective of this study was to collect
information on the ecology of the black-bellied sandgrouse that could be used to support
management measures in a nature park. In
particular, there was a focus on evaluating
habitat use and understanding the role of habitat characteristics in determining the sandgrouse distribution in the nature park of ‘Vale
do Guadiana’.
MATERIAL AND METHODS
Study area
The study took place in an area of 24000 ha
in the nature park of ‘Vale do Guadiana’ (total area: 70000 ha; 37º42’ N 07º39’ W). The
park is also a Special Protection Area under
Birds Directive CE/79/409. The region is under Mediterranean influence, with hot summers and cold and rainy winters. Average annual rainfall is 455 mm. The area is crossed by
the Guadiana River and includes hills and
plains, cultivated areas, fallows and cereal
fields, scrubland and open woodland. Cereal
cultivation follows traditionally a cycle of 3 9 years: wheat (1st year), oats or barley (2nd
year) and fallow (3rd to 9th years). Older fallows are occupied by shrubs, mostly cistus,
Cistus ladanifer.
Data collection
The population of black-bellied sandgrouse
living in the nature park has been previously
estimated at ca. 80 individuals (Cardoso and
Carrapato, 2002). Because of the species’ secretive habits, small population size and mostly open landscape, it was decided to survey all
the open areas to identify presence points of
207
the species. Fieldwork was carried out between
April 2002 and March 2003.
During the non-breeding period (October May), the study area was intensively surveyed
for two days once a month. The whole study area
was visited by car and by foot. Each flock or isolated bird detected at the ground was defined as
a presence point. Drinking places and flying
birds were not considered in the analysis.
During the breeding period (June - September), observation of black-bellied sandgrouse
was difficult because the birds stayed in couples, choosing and occupying breeding places.
With the purpose of finding breeding and feeding areas, observation points were selected near
drinking places, where departure and arrival
directions of the birds could be recorded and
their point of origin and destination estimated.
Later, these areas were explored more intensively by foot. During this season, field work
lasted for four consecutive mornings each
month due to hot temperatures.
The main biotopes were mapped at different periods: spring - summer and autumn - winter (Table 1). Absence points were marked on
the corners of a 1 x 1 Km UTM system map.
These were later visited in the field and took the
same variables rather than the presence points.
The same number of observations for presences
and absences were used: 50 for the breeding period and 45 for the non-breeding-period.
Nineteen variables were included in the initial logistic regression model (Table 2). Biotope
composition was determined using a 1 000-m
buffer and Table 1 shows the classification.
Coordinates of measuring points were taken
with an error rate of 3-12 meters using a GPS. A
50 cm x 50 cm square area was used to measure vegetation and stone coverage and number.
Vegetation vertical density was measured by using a vegetation profile board (a 100 cm x 32 cm
plate, with black and white stripes of 12.5-cm
width; adapted from Hays et al., 1981). These
variables were measured in 5 replicates: one in
the centre and 4 located 10 meters away from the
centre in different directions. Inclination was
Ardeola 54(2), 2007, 205-215
208
CARDOSO, A. C., POEIRAS, A. S. and CARRAPATO, C.
TABLE 1
Main types of biotopes in the study area.
[Principales biotopos en el área de estudio.]
Biotope
Code
Description
Tillage
Leguminous cultivations
TILL
LEGU
Cereal fields
Brushwood
CERE
BRUS
Montados
MON
Fallows
FALL
Old-fallows
FALO
Naked soil, mostly without vegetation
Cultivation of: chickpea, yellow-lupin, common vetch,
hairy vetch and subterranean clover.
Fields of wheat, oats or barley
Bushy ground occupied by: cistus Cistus ladanifer,
sargasso Cistus monspeliensis, rock-rose Cistus crispus,
Cistus salvifolius, french lavander Lavandula stoechas or
dwarf furze Genista triacanthos.
Very open woodland of holm-oak Quercus rotundifolia,
also used as pasture or for cereal cultivation
Cereal fallows with one or two years, with herbaceous
coverage and some stony areas; usually used as pastures
Cereal fallows with more than two years, usually colonized
by some bushes
measured as described in Hays et al. (1981). Soil
capacity was classified from 1 (good quality) to
6 (poor quality) according to soil capability maps
for agricultural use. Distances were calculated
with the help of aerial photographs and Spatial
Analyst of ArcView 3.1.
Statistical analysis
Habitat selection was analysed by comparing the use of each biotope with its availability in the study area. Biotope use was defined
as the percentage of presences in each biotope.
Biotope availability was defined as the percentage occupied by each type of habitat in the
study area.
Whether sandgrouse were using habitats according to their availability was tested with
Kruskal-Wallis non-parametric test (Zar, 1996).
Positive and negative selections were analysed
with Ivlev’s Electivity Index (Jacobs, 1974)
and their significance was tested using Bailey’s
tests (Cherry, 1996).
Ardeola 54(2), 2007, 205-215
A univariate analysis was performed for each
of the nineteen variables, by measuring their
association with the response variable, according to the results of Wald and G (maximum
likelihood ratio) tests (Hosmer and Lemeshow,
1989). In multivariate analysis, variables were
ranked according to the results of the statistical tests used previously. Then a forward stepwise elimination process was applied, in which
all variables with a P > 0.05 in the Wald test
and those where the odds ratio estimation (95
% confidence) included value 1 were removed
from the model (Hosmer and Lemeshow, 1989).
To assess the fit of the model, we used the Pearson chi-square and classification table (Hosmer and Lemeshow, 1989).
RESULTS
Habitat selection: biotope types
Habitat use of sandgrouse differed significantly from random (χ2 = 9.49; P < 0.001).
BLACK-BELLIED SANDGROUSE IN THE NATURE PARK “VALE DO GUADIANA”
209
TABLE 2
Variables that entered in the initial logistic regression model to analysing the presence/absence of blackbellied sandgrouse.
[Variables que se utilizaron en la regresión logística para analizar la presencia/ausencia de gangas ortega.]
Variable
Code
Description of the variable
Units
Wind direction
Cattle
Vegetation height
Vegetation coverage
Vertical density
Tree density
Coverage of shrubs
Inclination
Slope exposure
Stone coverage
Number of stones
Distance to the villages
WIND
CATT
VEGH
VEGC
VEGP
TREN
SHRC
INCL
SLEX
STOC
STON
DVIL
Wind direction at the time of observation
Cattle presence or absence
Vegetation height
Vegetation coverage
Vegetation cover at different heights
Number of trees within a 50 m radius
Proportion of shrubs within a 50 meters radius
Ground inclination
Exposure to the sun
Proportion of ground covered with stones
Number of stones
Distance to the nearest village (settlement with
more than 100 inhabitants)
Distance to the nearest rural agglomerates
(settlement with less than 100 inhabitants)
Distance to the nearest monte - small group of
rural houses that belongs to the same family;
typical structure of Alentejo
Distance to the nearest drinking place
Distance to the nearest main road – national roads
Distance to the nearest secondary road, asphalted
(municipal roads) or not asphalted
Soil capacity to agriculture and forest
1–4
0/1
M
m2
%
Distance to rural agglomerates DRAG
Distance to montes
DMON
Distance to drinking places
Distance to main roads
Distance to secondary roads
DRNK
ROAM
ROAS
Soil Capacity
SOIL
During the breeding period, sandgrouse preferred leguminous cultivations and tillage
(Table 3). Crops and fallow were apparently
used according to their availability. Fallow was
the most used biotope, and it was also the most
easily available (Fig. 1).
Old fallows were used only during the breeding period (Table 3 and Fig. 1). The observations at this habitat type were made at artificial feeding places developed by hunters to
attract partridges and pigeons during this period. Usually these spots have an area of 20 x
50 sq. m. The land is ploughed and a large
amount of seeds (mainly wheat, oats and bar-
0-1
0-45º
1-4
m2
m
m
m
m
m
m
1-6
ley) is spread. A nest of black-bellied sandgrouse was found close to one of these spots.
During non-breeding period, only leguminous cultivated areas were chosen (Table 3).
Habitat selection: habitat variables
Table 4 shows the results of the univariate
analysis, for the variables with P-value less
than 0.05 in the Wald test.
All the variables with significant P-values
in the univariate analysis were included in the
initial logistic regression model. While assessArdeola 54(2), 2007, 205-215
210
CARDOSO, A. C., POEIRAS, A. S. and CARRAPATO, C.
TABLE 3
Habitat selection analysis using Ivlev and Bailey tests. Ns: non significant result; (+) positive selection;
(-) negative selection (CERE: cereal fields; LEGU: leguminous cultivation; TILL: tillage; MONT: montado; FALL: fallow; FALO: old-fallow).
[Analysis de selección de hábitat usando las pruebas de Bailey e Ivlev. Ns: resultado no significativo; (+)
selección positiva; (-) selección negativa.]
Breeding period
Non-breeding period
Biotope
Ivlev
Bailey
Selection
Ivlev
Bailey
Selection
CERE
LEGU
TILL
MONT
FALL
FALO
0.219
0.872
0.652
-1
0.045
- 0.237
[0.041; 0.297]
[0.051; 0.319]
[0.027; 0.252]
[- ; 0.086]
[0.234; 0.586]
[0.062; 0.340]
ns
+
+
ns
ns
- 0.027
0.922
0.544
-1
0.358
-1
[0.018; 0.273]
[0.105; 0.452]
[5x10-5-; 0.181]
[- ; 0.104]
[0.37; 0.761]
[- ; 0.104]
ns
+
ns
ns
-
FIG. 1.—Availability versus use of different biotopes by sandgrouses (CERE – cereal fields; LEGU- leguminous cultivation; TILL - tillage; MON - montados ; FALL- fallow ; FALO - old fallows).
[Disponibilidad frente a uso de diferentes biotopos por la ganga ortega en Portugal.]
ing the linearity of the variables, the square root
transformation of variable STOC was included in the model (Table 5).
The final model is adjusted effectively to
the data and to the validation sample during
the breeding period (Table 6). During the nonbreeding period, the model is adjusted to the
data but not to validation sample. In fact, this
season is longer than the other one and land
use suffers a lot of transformation. The heteroArdeola 54(2), 2007, 205-215
geneity of this period can explain the inadaptability of the model.
DISCUSSION
Habitat selection: biotope types
At the nature park though the leguminous
cultivations are rare, they are of major impor-
211
BLACK-BELLIED SANDGROUSE IN THE NATURE PARK “VALE DO GUADIANA”
TABLE 4
Variables with significant differences (P < 0.05) in the univariate analysis (VEGC – vegetation cover;
STON - number of stones; DRNK - distance to drinking places; ROAS - distance to secondary roads;
DRAG -distance to rural agglomerates; SLEX - slope exposure; LEGU - leguminous cultivation; CATT
- cattle; VEGH - vegetation heigh; BRUS - brushwood; TREN - tree density; FALL - fallow; STOC - stone
cover; TILL - tillage; DVIL - distance to the villages; INCL - inclination; SHRC - coverage of shrubs;
SOIL - soil capacity).
[Variables con diferencias significativas (P < 0.05) en los análisis univariantes (véase texto).]
Breeding period
Non-breeding period
Variables
P
G-test
Relationship
with the response
variable
P
G-test
Relationship
with the response
variable
VEGC
STON
DRNK
sqrtROAS
logDRAG
SLEX
LEGU
CATT
VEGH
BRUS
TREN
FALL
STOC
TILL
logDVIL
INCL
SHRC
SOIL
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
0.004
0.003
0.010
0.013
0.014
0.016
0.030
0.031
50.24
27.50
18.97
18.62
15.48
13.18
8.64
6.63
6.11
5.99
5.80
4.71
4.66
+
+
+
+
+
+
+
-
< 0.001
0.001
< 0.001
0.038
0.009
24.50
11.78
32.50
4.29
6.79
+
+
+
< 0.001
13.00
+
0.076
0.002
0.003
3.15
9.88
8.84
-
0.001
0.001
0.016
0.024
0.030
0.029
11.99
10.11
5.76
5.07
4.70
4.78
+
+
+
-
tance to sandgrouse in both periods. In Spain,
besides Extremadura, black-bellied sandgrouse
does not use or select leguminous fields (Suárez
et al., 1999a). From a reading of works of different authors (Martínez, 1994; Barros et
al.,1996; Suárez et al., 1999a; Moreira et al.,
2004; Silva et al., 2004), it is understood that
leguminous fields are not quite equal and in
the majority of the cases the authors do not classify them; they can be either alfalfa or broccoli
fields, which can be used by little bustard Tetrax
tetrax, but not by sandgrouses.
Moreover, stomach contents of the sandgrouse show that leguminous plants were very
important (Suárez et al. 1999b). This preference is probably explained by their high nutritive value and digestibility (Jarrigue, 1981;
Abreu et al., 2000).
The use of tillage during breeding season
may be related with reproduction, because this
type of ground coverage can provide better
camouflage for adults and chicks (Barros et
al., 1996). In fact, some nests were found in
this biotope (pers. obs.).
Ardeola 54(2), 2007, 205-215
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CARDOSO, A. C., POEIRAS, A. S. and CARRAPATO, C.
TABLE 5
Coefficients and P-value of different variables in the logistic regression model for habitat selection of
black-bellied sandgrouse in the breeding and non-breeding periods.
[Coeficientes y valores de probabilidad para las diferentes variables introducidas en la regresión logística para caracterizar la selección de hábitat de la ganga ortega en el periodo reproductor o no.]
Breeding period
Variable
Constant
CATT
VEGC
Sqrt STOC
STON
ROAS
DRNK
TREN
STOC
G-test
Non-breeding period
Coefficient
P
2.076
4.801
-0.083
-0.712
1,293
0.004
-0.002
0.254
0.015
0.014
0.053
2.351
0.058
0.070
75.617
Coefficient
P
-0.204
0.009
-0.003
-0.340
-0.244
67.949
0.013
0.055
0.024
TABLE 6
Classification rates of correct presences (CP), correct absences (CA) and overall correct classification
((CP+CA)/CT), considering a cut-off point of 0.5.
[Tasas de clasificación como presencia correcta (CP), ausencia correcta (CA) y clasificación correcta
general ((CP+CA)/CT), considerando un punto de corte de 0,5.]
Breeding period
Classification rates
CP
CA
CT
χ2
Pearson
Model sample Validation sample
0.97
0.91
0.94
21.69
(d = 63)
0.93
1
0.96
6.63
(d = 23)
Crops were used in two different periods: after sowing during non-breeding season and stubble during breeding season. During both periods, birds can easily find seeds to feed on
(Barros et al., 1996). This is very important to
the diet of these birds as Suárez et al. (1999b)
have reported. We also observed them eating
Ardeola 54(2), 2007, 205-215
Non-breeding period
Model sample Validation sample
0.94
0.94
0.94
20.95
(d = 58)
0.69
0.88
0.78
39.94
(d = 22)
soft leaves from sprouts at newly sown fields.
The annual agriculture cycle dynamic is important to these birds once they can find easily seeds
during late autumn and summer when availability of seeds from natural vegetation is low.
Fallow land was also frequently used (Fig.
1). This can be explained by the presence of
BLACK-BELLIED SANDGROUSE IN THE NATURE PARK “VALE DO GUADIANA”
grazed low vegetation that promotes an efficient vigil (Barros et al., 1996) and easier
progress in the field. Fallow presents the highest floristic diversity (unpub. data), and so more
opportunities to feed on different kind of seeds.
Otherwise, there is a predominance of pioneer
species producing abundant seeds (Fenner,
1985). This is especially relevant in cultivated areas that are characterized by their structural simplicity and by the poverty of natural
vegetation due to agriculture (Martínez, 1994).
Montado was never used by sandgrouse.
In fact, wooded or forested habitats have reduced use or are of no use to sandgrouse (Barros et al., 1996; Suárez et al., 1999a) - a fact
that could be related to lack of visibility. Ferns
and Hinsley (1995) verified that the amount of
ground not visible to drinking sandgrouse surrounding each water hole was the most important factor influencing the birds’ choice. The
trees in the montados may have a similar effect
by hiding potential predators.
Habitat selection: habitat variables
Vegetation coverage seems to be a very important component in the habitat selection by
black-bellied sandgrouse, mainly during the
breeding season, due to its influence on one of
the basic requirements of this species - visibility (Ferns and Hinsley, 1995). On the other
hand, cattle presence is an important factor as
it influences vegetation coverage. Nevertheless, overgrazing can be unfavourable to this
species as happens in Extremadura, Spain
(Suárez et al., 1999c).
According to the logistic regression model
applied, sandgrouse prefer areas with reduced
stone coverage but it is positively related with
stone number. It is believed that such an amount
of stones is related to the soil capacity. In the
majority of the study area, the layer of fertile
soil is very thin and stony. This type of agricultural soil needs long fallows, and this is the
biotope that sandgrouse mostly used. On the
213
other hand, stony ground can provide good camouflage for adults and chicks.
The model has only chosen one of the disturbance factors. During the breeding season,
sandgrouse avoided secondary roads. This negative relation was also reported by Rocha (pers.
obs.) between great bustards Otis tarda and
both secondary and main roads. Silva et al.
(2004) found that the little bustard avoids the
proximity of roads and inhabited houses. Univariate analyses also indicated that sandgrouse
avoided the vicinity of villages, rural agglomerates and montes in different seasons
(Table 4).
Besides the number of small dams (majority less than 4000 m2) used by cattle in study
area, the model revealed drinking place distribution as a limiting factor. In fact, this species
needs to drink regularly. Parental expenditure
is greatest during breeding period. The role
of males as water carriers increased their energy expenditure and decreased their time available for foraging (Hinsley and Ferns, 1994).
Distances between feeding areas, brood and
drinking places and flight time are determinant
to the energy budget (Hinsley and Ferns, 1994);
hence, a good net of water holes is a determinant for the presence of species. The most
important drinking places in the present study
area were a dam (2000 m2) in the middle of the
study area in a pine forestation of c. 6/7 years
growth, and a part of the Chança dam (a Spanish dam of more than 9 Km2) near one reproduction area (Cardoso and Carrapato, 2002).
Conservation and management implications
In conclusion, agricultural environment seems
to provide suitable biotopes for sandgrouse as
was reported by other authors (Barros et al.,
1996; Suárez et al., 1999a). It has been shown
that the most important biotopes are leguminous
cultivations and fallows with extensive pastures.
It is suggested that the nature park should promote agricultural mosaic and especially increase
Ardeola 54(2), 2007, 205-215
214
CARDOSO, A. C., POEIRAS, A. S. and CARRAPATO, C.
the relative proportion of these two biotopes.
Nowadays, agriculture subsidies for forestation
and wheat cultivation are higher than those for
leguminous or for extensive pastures (fallow).
The nature park must develop appropriate mechanisms to reverse these facts.
Extensive pasture has an important role in
controlling vegetation and giving economic advantage to fallows. In a certain way, it can delay
agriculture intensification or abandonment if
sheep market value does not fall. Even sheep
production, for example, for making cheese,
could be of negative conservation interest in the
short term. Increase of production will be followed by the implementation of irrigated cultures, such as sorghum, and it will be of negative value to sandgrouse and other steppe-land
birds. Cattle density is the determinant factor in
achieving proper habitat availability for sandgrouse. This can be attained by implementing a
Good Practice Agriculture Code adaptable to
the soil poverty of this region.
Finally, Territory Management Plans must
take into account the results of disturbance factors. It is the opinion of the authors that the existence of large concentrated settlements is more
favourable to sandgrouse than several dispersed
small agglomerations of houses. This fact will
also contribute to reducing the need for roads.
ACKNOWLEDGEMENTS.—We thank Prof. Teresa
Batista and Doctor José Carlos Brito for their valuable help in GIS and statistics analysis, respectively. We also thank Célia Medeiros and Teresa Silva
for help in collecting field data. This study was supported logistically and co-funded by Instituto da
Conservação da Natureza and FAUNATRANS - INTERREG project.
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[Recibido: 20-12-06]
[Aceptado: 28-09-07]
Ana Cristina Cardoso is a biologist, pos/graduated on Management and Environmental Politics
who have been working on Nature Park, studying
the ecology of black-bellied sandgrouse populations, also coordinate the national census of
black-bellied sandgrouse and pin-tailed sandgrouse,
is also co-author of Portuguese steppe-land birds
Action Plan. At present is doing her master thesis
on incentive measures for conservation of steppeland species. Ana Sofia Poeiras is licensed on
Environment Sciences, and did this work to obtain
the degree of licentiate. Actually, is working with
GIS at several institutions. Carlos Carrapato is a
nature vigilant and photographer, helping several
biologists in the field work, mainly with steppe-land
species. Developed and tried several methods to
capture sandgrouses, and spending a lot of time
studying their behaviour at drinking places.
Ardeola 54(2), 2007, 205-215