Factors Responsible for the Presence and Distribution of Black-Bellied Sandgrouse Pterocles Orientalis in the Nature Park “Vale Do Guadiana”

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 Ptero- cles 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 prefe- rencias 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 evita- dos 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 secun- darias 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 pue- de ser tanto positiva o negativa, dependiendo de la densidad de cabezas vacunas. A pesar del bajo núme- ro 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 due to changes in agricultural practices and the loss of habitat (Tucker and Heath, 1994). Steppe-land birds are one of the most en- There are no more than 300 individuals in Por- dangered groups of species in the world, espe- tugal - a reason why the bird has an un- cially in developed countries (Bota et al., 2005). favourable status ‘Endangered’ in Portugal The black-bellied sandgrouse Pterocles orien- (Almeida et al., 2005). The European popula- talis is a steppe-land species whose distribution is classified as ‘Vulnerable’, and it is list- tion in Europe is limited mainly to Turkey ed as SPEC 3 – a species whose global popu- and the Iberian Peninsula (Cramp and Sim- lations are not concentrated in Europe, but mons, 1983; Tucker and Heath, 1994; De which has an unfavourable status in Europe Juana, 1999). (Tucker and Heath, 1994). Major changes in EU Common Agriculture In Portugal, the main threat to steppe-land Policy have occurred in the last few decades, birds is the abandonment of traditional farm- causing significant alterations in agricultural ing and replacement by intensive agriculture and grassland habitats (Tucker and Evans, or forestation (Moreira et al., 2004; Silva et al., 1997; Donald et al., 2001). The black-bellied 2004; Pinto et al., 2005). In southern Portu- sandgrouse European population has suffered gal since the launch of wheat campaign, agri- a clear decline in the last thirty years mainly culture has been supported by European Union

Ardeola 54(2), 2007, 205-215 BLACK-BELLIED SANDGROUSE IN THE NATURE PARK “VALE DO GUADIANA” 207 subsidies. Actually, abandonment of land due the species. Fieldwork was carried out between to the soil depletion and forestation, which is April 2002 and March 2003. also funded by the European Union, can be During the non-breeding period (October - negative to steppe-land birds. May), the study area was intensively surveyed The objective of this study was to collect for two days once a month. The whole study area information on the ecology of the black-bel- was visited by car and by foot. Each flock or iso- lied sandgrouse that could be used to support lated bird detected at the ground was defined as management measures in a nature park. In a presence point. Drinking places and flying particular, there was a focus on evaluating birds were not considered in the analysis. habitat use and understanding the role of habi- During the breeding period (June - Septem- tat characteristics in determining the sand- ber), observation of black-bellied sandgrouse grouse distribution in the nature park of ‘Vale was difficult because the birds stayed in cou- do Guadiana’. ples, choosing and occupying breeding places. With the purpose of finding breeding and feeding areas, observation points were selected near MATERIAL AND METHODS drinking places, where departure and arrival directions of the birds could be recorded and Study area their point of origin and destination estimated. Later, these areas were explored more inten- The study took place in an area of 24000 ha sively by foot. During this season, field work in the nature park of ‘Vale do Guadiana’(to- lasted for four consecutive mornings each tal area: 70000 ha; 37º42’ N 07º39’ W). The month due to hot temperatures. park is also a Special Protection Area under The main biotopes were mapped at differ- Birds Directive CE/79/409. The region is un- ent periods: spring - summer and autumn - win- der Mediterranean influence, with hot sum- ter (Table 1). Absence points were marked on mers and cold and rainy winters. Average an- the corners of a 1 x 1 Km UTM system map. nual rainfall is 455 mm. The area is crossed by These were later visited in the field and took the the Guadiana River and includes hills and same variables rather than the presence points. plains, cultivated areas, fallows and cereal The same number of observations for presences fields, scrubland and open woodland. Cereal and absences were used: 50 for the breeding pe- cultivation follows traditionally a cycle of 3 - riod and 45 for the non-breeding-period. 9 years: wheat (1st year), oats or barley (2nd Nineteen variables were included in the ini- year) and fallow (3rd to 9th years). Older fal- tial logistic regression model (Table 2). Biotope lows are occupied by shrubs, mostly cistus, composition was determined using a 1 000-m Cistus ladanifer. 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 Data collection 50 cm x 50 cm square area was used to meas- ure vegetation and stone coverage and number. The population of black-bellied sandgrouse Vegetation vertical density was measured by us- living in the nature park has been previously ing a vegetation profile board (a 100 cm x 32 cm estimated at ca. 80 individuals (Cardoso and plate, with black and white stripes of 12.5-cm Carrapato, 2002). Because of the species’ se- width; adapted from Hays et al., 1981). These cretive habits, small population size and most- variables were measured in 5 replicates: one in ly open landscape, it was decided to survey all the centre and 4 located 10 meters away from the the open areas to identify presence points of 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 TILL Naked soil, mostly without vegetation Leguminous cultivations LEGU Cultivation of: chickpea, yellow-lupin, common vetch, hairy vetch and subterranean clover. Cereal fields CERE Fields of wheat, oats or barley Brushwood BRUS 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. Montados MON Very open woodland of holm-oak Quercus rotundifolia, also used as pasture or for cereal cultivation Fallows FALL Cereal fallows with one or two years, with herbaceous coverage and some stony areas; usually used as pastures Old-fallows FALO Cereal fallows with more than two years, usually colonized by some bushes measured as described in Hays et al. (1981). Soil A univariate analysis was performed for each capacity was classified from 1 (good quality) to of the nineteen variables, by measuring their 6 (poor quality) according to soil capability maps association with the response variable, accord- for agricultural use. Distances were calculated ing to the results of Wald and G (maximum with the help of aerial photographs and Spatial likelihood ratio) tests (Hosmer and Lemeshow, Analyst of ArcView 3.1. 1989). In multivariate analysis, variables were ranked according to the results of the statistical tests used previously. Then a forward step- Statistical analysis wise elimination process was applied, in which all variables with a P > 0.05 in the Wald test Habitat selection was analysed by compar- and those where the odds ratio estimation (95 ing the use of each biotope with its availabili- % confidence) included value 1 were removed ty in the study area. Biotope use was defined from the model (Hosmer and Lemeshow, 1989). as the percentage of presences in each biotope. To assess the fit of the model, we used the Pear- Biotope availability was defined as the per- son chi-square and classification table (Hos- centage occupied by each type of habitat in the mer and Lemeshow, 1989). study area. Whether sandgrouse were using habitats according to their availability was tested with RESULTS Kruskal-Wallis non-parametric test (Zar, 1996). Positive and negative selections were analysed Habitat selection: biotope types with Ivlev’s Electivity Index (Jacobs, 1974) and their significance was tested using Bailey’s Habitat use of sandgrouse differed signifi- 2 tests (Cherry, 1996). cantly from random (χ = 9.49; P < 0.001).

Ardeola 54(2), 2007, 205-215 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 black- bellied 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 WIND Wind direction at the time of observation 1 – 4 Cattle CATT Cattle presence or absence 0/1 Vegetation height VEGH Vegetation height M Vegetation coverage VEGC Vegetation coverage m2 Vertical density VEGP Vegetation cover at different heights % Tree density TREN Number of trees within a 50 m radius Coverage of shrubs SHRC Proportion of shrubs within a 50 meters radius 0-1 Inclination INCL Ground inclination 0-45º Slope exposure SLEX Exposure to the sun 1-4 Stone coverage STOC Proportion of ground covered with stones m2 Number of stones STON Number of stones Distance to the villages DVIL Distance to the nearest village (settlement with m more than 100 inhabitants) Distance to rural agglomerates DRAG Distance to the nearest rural agglomerates m (settlement with less than 100 inhabitants) Distance to montes DMON Distance to the nearest monte - small group of m rural houses that belongs to the same family; typical structure of Alentejo Distance to drinking places DRNK Distance to the nearest drinking place m Distance to main roads ROAM Distance to the nearest main road – national roads m Distance to secondary roads ROAS Distance to the nearest secondary road, asphalted m (municipal roads) or not asphalted Soil Capacity SOIL Soil capacity to agriculture and forest 1-6

During the breeding period, sandgrouse pre- ley) is spread. A nest of black-bellied sand- ferred leguminous cultivations and tillage grouse was found close to one of these spots. (Table 3). Crops and fallow were apparently During non-breeding period, only legumi- used according to their availability. Fallow was nous cultivated areas were chosen (Table 3). the most used biotope, and it was also the most easily available (Fig. 1). Old fallows were used only during the breed- Habitat selection: habitat variables ing period (Table 3 and Fig. 1). The observations at this habitat type were made at artifi- Table 4 shows the results of the univariate cial feeding places developed by hunters to analysis, for the variables with P-value less attract partridges and pigeons during this pe- than 0.05 in the Wald test. riod. Usually these spots have an area of 20 x All the variables with significant P-values 50 sq. m. The land is ploughed and a large in the univariate analysis were included in the amount of seeds (mainly wheat, oats and bar- initial logistic regression model. While assess-

Ardeola 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 0.219 [0.041; 0.297] ns - 0.027 [0.018; 0.273] ns LEGU 0.872 [0.051; 0.319] + 0.922 [0.105; 0.452] + TILL 0.652 [0.027; 0.252] + 0.544 [5x10-5-; 0.181] ns MONT - 1 [- ; 0.086] - - 1 [- ; 0.104] - FALL 0.045 [0.234; 0.586] ns 0.358 [0.37; 0.761] ns FALO - 0.237 [0.062; 0.340] ns - 1 [- ; 0.104] -

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 geneity of this period can explain the in- transformation of variable STOC was includ- adaptability of the model. ed in the model (Table 5). The final model is adjusted effectively to the data and to the validation sample during DISCUSSION the breeding period (Table 6). During the non- breeding period, the model is adjusted to the Habitat selection: biotope types data but not to validation sample. In fact, this season is longer than the other one and land At the nature park though the leguminous use suffers a lot of transformation. The hetero- cultivations are rare, they are of major impor-

Ardeola 54(2), 2007, 205-215 BLACK-BELLIED SANDGROUSE IN THE NATURE PARK “VALE DO GUADIANA” 211

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 P G-test Relationship with the response with the response variable variable VEGC < 0.001 50.24 - < 0.001 24.50 - STON < 0.001 27.50 + 0.001 11.78 + DRNK < 0.001 18.97 - < 0.001 32.50 - sqrtROAS < 0.001 18.62 + 0.038 4.29 + logDRAG < 0.001 15.48 + 0.009 6.79 + SLEX 0.004 13.18 + LEGU 0.003 8.64 + < 0.001 13.00 + CATT 0.010 6.63 + VEGH 0.013 6.11 - 0.076 3.15 - BRUS 0.014 5.99 - 0.002 9.88 - TREN 0.016 5.80 - 0.003 8.84 - FALL 0.030 4.71 + STOC 0.031 4.66 - 0.001 11.99 - TILL 0.001 10.11 + logDVIL 0.016 5.76 + INCL 0.024 5.07 + SHRC 0.030 4.70 - SOIL 0.029 4.78 - tance to sandgrouse in both periods. In Spain, Moreover, stomach contents of the sand- besides Extremadura, black-bellied sandgrouse grouse show that leguminous plants were very does not use or select leguminous fields (Suárez important (Suárez et al. 1999b). This prefer- et al., 1999a). From a reading of works of dif- ence is probably explained by their high nutri- ferent authors (Martínez, 1994; Barros et tive value and digestibility (Jarrigue, 1981; al.,1996; Suárez et al., 1999a; Moreira et al., Abreu et al., 2000). 2004; Silva et al., 2004), it is understood that The use of tillage during breeding season leguminous fields are not quite equal and in may be related with reproduction, because this the majority of the cases the authors do not clas- type of ground coverage can provide better sify them; they can be either alfalfa or broccoli camouflage for adults and chicks (Barros et fields, which can be used by little bustard Tetrax al., 1996). In fact, some nests were found in tetrax, but not by sandgrouses. this biotope (pers. obs.).

Ardeola 54(2), 2007, 205-215 212 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 logís- tica para caracterizar la selección de hábitat de la ganga ortega en el periodo reproductor o no.]

Breeding period Non-breeding period Variable Coefficient P Coefficient P Constant 2.076 0.254 CATT 4.801 0.015 VEGC -0.083 0.014 -0.204 0.009 Sqrt STOC -0.712 0.053 STON 1,293 2.351 ROAS 0.004 0.058 DRNK -0.002 0.070 -0.003 0.013 TREN -0.340 0.055 STOC -0.244 0.024 G-test 75.617 67.949

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 Non-breeding period Classification rates Model sample Validation sample Model sample Validation sample CP 0.97 0.93 0.94 0.69 CA 0.91 1 0.94 0.88 CT 0.94 0.96 0.94 0.78 2 χ 21.69 6.63 20.95 39.94 Pearson (d = 63) (d = 23) (d = 58) (d = 22)

Crops were used in two different periods: af- soft leaves from sprouts at newly sown fields. ter sowing during non-breeding season and stub- The annual agriculture cycle dynamic is impor- ble during breeding season. During both peri- tant to these birds once they can find easily seeds ods, birds can easily find seeds to feed on during late autumn and summer when availabil- (Barros et al., 1996). This is very important to ity of seeds from natural vegetation is low. the diet of these birds as Suárez et al. (1999b) Fallow land was also frequently used (Fig. have reported. We also observed them eating 1). This can be explained by the presence of

Ardeola 54(2), 2007, 205-215 BLACK-BELLIED SANDGROUSE IN THE NATURE PARK “VALE DO GUADIANA” 213 grazed low vegetation that promotes an effi- other hand, stony ground can provide good cam- cient vigil (Barros et al., 1996) and easier ouflage for adults and chicks. progress in the field. Fallow presents the high- The model has only chosen one of the dis- est floristic diversity (unpub. data), and so more turbance factors. During the breeding season, opportunities to feed on different kind of seeds. sandgrouse avoided secondary roads. This neg- Otherwise, there is a predominance of pioneer ative relation was also reported by Rocha (pers. species producing abundant seeds (Fenner, obs.) between great bustards Otis tarda and 1985). This is especially relevant in cultivat- both secondary and main roads. Silva et al. ed areas that are characterized by their struc- (2004) found that the little bustard avoids the tural simplicity and by the poverty of natural proximity of roads and inhabited houses. Uni- vegetation due to agriculture (Martínez, 1994). variate analyses also indicated that sandgrouse Montado was never used by sandgrouse. avoided the vicinity of villages, rural ag- In fact, wooded or forested habitats have re- glomerates and montes in different seasons duced use or are of no use to sandgrouse (Bar- (Table 4). ros et al., 1996; Suárez et al., 1999a) - a fact Besides the number of small dams (major- that could be related to lack of visibility. Ferns ity less than 4000 m2) used by cattle in study and Hinsley (1995) verified that the amount of area, the model revealed drinking place distri- ground not visible to drinking sandgrouse sur- bution as a limiting factor. In fact, this species rounding each water hole was the most impor- needs to drink regularly. Parental expenditure tant factor influencing the birds’ choice. The is greatest during breeding period. The role trees in the montados may have a similar effect of males as water carriers increased their en- by hiding potential predators. ergy expenditure and decreased their time available for foraging (Hinsley and Ferns, 1994). Distances between feeding areas, brood and Habitat selection: habitat variables drinking places and flight time are determinant to the energy budget (Hinsley and Ferns, 1994); Vegetation coverage seems to be a very im- hence, a good net of water holes is a determi- portant component in the habitat selection by nant for the presence of species. The most black-bellied sandgrouse, mainly during the important drinking places in the present study breeding season, due to its influence on one of area were a dam (2000 m2) in the middle of the the basic requirements of this species - visibil- study area in a pine forestation of c. 6/7 years ity (Ferns and Hinsley, 1995). On the other growth, and a part of the Chança dam (a Span- hand, cattle presence is an important factor as ish dam of more than 9 Km2) near one repro- it influences vegetation coverage. Neverthe- duction area (Cardoso and Carrapato, 2002). less, overgrazing can be unfavourable to this species as happens in Extremadura, Spain (Suárez et al., 1999c). Conservation and management implications According to the logistic regression model applied, sandgrouse prefer areas with reduced In conclusion, agricultural environment seems stone coverage but it is positively related with to provide suitable biotopes for sandgrouse as stone number. It is believed that such an amount was reported by other authors (Barros et al., of stones is related to the soil capacity. In the 1996; Suárez et al., 1999a). It has been shown majority of the study area, the layer of fertile that the most important biotopes are leguminous soil is very thin and stony. This type of agri- cultivations and fallows with extensive pastures. cultural soil needs long fallows, and this is the It is suggested that the nature park should pro- biotope that sandgrouse mostly used. On the mote 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. mental data. Instituto Superior de Agronomia, Nowadays, agriculture subsidies for forestation Universidade Técnica de Lisboa. Laboratório and wheat cultivation are higher than those for Químico Agrícola Rebelo da Silva. Lisboa. leguminous or for extensive pastures (fallow). ALMEIDA, J., (coord), CATRY, P., ENCARNAÇÃO, V. , The nature park must develop appropriate mech- FRANCO C., GRANADEIRO J. P.; LOPES R., MOREIRA anisms to reverse these facts. F., OLIVEIRA P., ONOFRE N., PACHECO C., PINTO M., PITTA GROZ M. J., RAMOS J. and SILVA L. 2005. Extensive pasture has an important role in Pterocles orientalis Cortiçol-de-barriga-preta. controlling vegetation and giving economic ad- In: M. J. Cabral, J. Almeida, P. R. Almeida, T. vantage to fallows. In a certain way, it can delay Dellinger, N. Ferrand de Almeida, M. E. Oliveira, agriculture intensification or abandonment if J. M. Palmeirim, A. I. Queiroz, L. Rogado and S. sheep market value does not fall. Even sheep Reis (Eds.): Livro Vermelho dos Vertebrados de production, for example, for making cheese, Portugal, pp. 321 - 322. Instituto da Conservação could be of negative conservation interest in the da Natureza. Lisboa. short term. Increase of production will be fol- BARROS, C., BORBÓN, M. N. and DE JUANA, E., 1996. lowed by the implementation of irrigated cul- Selección de Hábitat del Alcaraván (Burhinus oe- tures, such as sorghum, and it will be of nega- dicnemus), la Ganga (Pterocles alchata) y la Or- tive value to sandgrouse and other steppe-land tega (Pterocles orientalis) en pastizales y culti- birds. Cattle density is the determinant factor in vos de La Serena (Badajoz, España). In: J. achieving proper habitat availability for sand- Fernández Gutiérrez and J. Sanz-Zuasti (Eds.): grouse. This can be attained by implementing a Conservación de las Aves Estepárias y su Hábi- Good Practice Agriculture Code adaptable to tat, pp. 221 - 228. Junta de Castilla y León, Va- the soil poverty of this region. lladolid. BOTA, J., MORALES, M. B., MAÑOSA, S. and Finally, Territory Management Plans must CAMPRODON, J., 2005. Ecology and Conservation take into account the results of disturbance fac- of Steppe-land birds. Lynx Ediciones and Centre tors. It is the opinion of the authors that the ex- Tecnològic Florestal de Catalunya, Barcelona. istence of large concentrated settlements is more CARDOSO, A. C. and CARRAPATO C., 2002. Breves favourable to sandgrouse than several dispersed Notas sobre o Cortiçol-de-barriga-preta Ptero- small agglomerations of houses. This fact will cles orientalis no Parque Natural do Vale do Gua- also contribute to reducing the need for roads. diana. Airo, 2: 113-116. CHERRY, S., 1996. A comparison of confidence in- terval methods for habitat use-availability stud- ACKNOWLEDGEMENTS.—We thank Prof. Teresa ies. Journal of Wildlife Management, 60: 653- Batista and Doctor José Carlos Brito for their valu- 658. able help in GIS and statistics analysis, respective- DONALD, P. F., GREEN, R. E. and HEATH, M. F., 2001. ly. We also thank Célia Medeiros and Teresa Silva Agricultural intensification and the collapse of for help in collecting field data. This study was sup- Europe’s farmland bird populations. Proceedings ported logistically and co-funded by Instituto da of the Royal Society London, B 268: 25-29. Conservação da Natureza and FAUNATRANS - IN- FENNER, M., 1995. Seed ecology. Chapman and Hall. TERREG project. London. FERNS, P. N. and HINSLEY, S. A., 1995. Importance of topography in the selection of drinking sites BIBLIOGRAPHY by sandgrouse. Functional Ecology, 9: 371- 375. ABREU, J. M., BRUNO-SOARES, A. M. and CALOURO, HAY S, R. L., SUMMERS, C. and SEITZ, W. 1981. Es- F., 2000. Intake and nutritive value of medi- timating wildlife habitat variables. U.S.D.I. terranean forages and diets, 20 years of experi- Fish and Wildlife Service. FWOS/OBS-81/47.

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HINSLEY, S. A. and FERNS, P. N., 1994. Time and en- pp. 215-229. Ministerio de Medio Ambiente, Or- ergy budgets of breeding males and females in ganismo Autónomo Parques Nacionales. sandgrouse Pterocles species. Ibis, 136: 261-270. SUÁREZ, F., OÑATE, J. J. and HERRANZ, J. 1999c. Es- HOSMER, D. W. and LEMESHOW, S., 1989. Applied tado y problemática de conservación de las gan- Logistic Regression. John Wiley and Sons, New gas ibérica y ortega en España. En: J. Herranz and York. F. Suárez: La Ganga Ibérica (Pterocles alchata) JACOBS, J., 1974. Quantitative Measurement of Food y la Ganga Ortega (Pterocles orientalis) en Es- Selection - A Modification of the Forage Ratio paña, pp. 273-302. Ministerio de Medio Ambien- and Ivlev’s Electivity Index. Oecologia, 96: 413- te, Organismo Autónomo Parques Nacionales. 417. TUCKER, G. M. and EVANS, M. I. 1997. Habitats for JARRIGUE, R., 1981. Alimentación de los ruminates. birds in Europe: a Conservation Strategy for Institut National de la Recherche Agronomique, the Wider Environment. BirdLife Conservation Mundi-Prensa, Madrid. Series No.6, Cambridge, UK, BirdLife Interna- MARTÍNEZ, C., 1994. Habitat selection by the little tional. bustard Tetrax tetrax in cultivated areas of cen- TUCKER, G. M. and HEATH, M. F., (Eds), 1994. Birds tral Spain. Biological Conservation, 67: 125-128. in Europe: Their Conservation Status. BirdLife MOREIRA F., MORGADO, R. and ARTHUR, S., 2004. Conservation Series No. 3. Cambridge, UK: Great bustard Otis tarda habitat selection in re- BirdLife International. lation to agricultural use in southern Portugal. ZAR, J. H. 1984. Biostatical Analysis. Prentice-Hall. Wildlife Biology, 10: 4. New Jersey. PINTO, M., ROCHA, P. and MOREIRA, F., 2005. Long- term trends in great bustard (Otis tarda) [Recibido: 20-12-06] populations in Portugal suggest concentration in [Aceptado: 28-09-07] single high quality area. Biological Conservation, 124: 415-423. SILVA, J. P., PINTO, M. and PALMEIRIM, J. M., 2004. Ana Cristina Cardoso is a biologist, pos/gra- Managing landscapes for the little bustard Tetrax duated on Management and Environmental Politics tetrax: lessons from the study of winter habitat who have been working on Nature Park, studying selection. Biological Conservation, 117: 521-528. the ecology of black-bellied sandgrouse popula- SUÁREZ, F., HERRANZ, J., MARTÍNEZ, C., MANRIQUE, tions, also coordinate the national census of J., ASTRAIN, C., ETXEBERRIA, A., CURCO, A., ES- black-bellied sandgrouse and pin-tailed sandgrouse, TRADA, J. and YANES, M. 1999a. Utilización y seis also co-author of Portuguese steppe-land birds lección de hábitat de las gangas ibérica y ortega Action Plan. At present is doing her master thesis en la península ibérica. In: J. Herranz, and F. Suá- on incentive measures for conservation of steppe- rez: La Ganga Ibérica (Pterocles alchata) y la land species. Ana Sofia Poeiras is licensed on Ganga Ortega (Pterocles orientalis) en España, Environment Sciences, and did this work to obtain pp. 127-156. Ministerio de Medio Ambiente, Or- the degree of licentiate. Actually, is working with ganismo Autónomo Parques Nacionales. GIS at several institutions. Carlos Carrapato is a SUÁREZ, F., HERVÁS, I., LEVASSOR, C. and CASADO, nature vigilant and photographer, helping several M. A. 1999b. La alimentación de la ganga ibéri- biologists in the field work, mainly with steppe-land ca y la ganga ortega. En: J. Herranz and F. Suá- species. Developed and tried several methods to rez: La Ganga Ibérica (Pterocles alchata) y la capture sandgrouses, and spending a lot of time Ganga Ortega (Pterocles orientalis) en España, studying their behaviour at drinking places.

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