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THE DRAMATIC DECLINE OF THE LITTLE TETRAX TETRAX IN ()

PREOCUPANTE DISMINUCIÓN DEL SISÓN COMÚN TETRAX TETRAX EN EXTREMADURA (ESPAÑA)

Eduardo DE JUANA*

The little bustard Tetrax tetrax, one of the found a range of 41,482 – 86,195 males in two European breeding of the breeding season (García de la Morena et (Otididae), is regarded as ‘near-threatened’on al., 2006). These were chiefly confined to a global scale (BirdLife International, 2000) just two autonomous communities: Castilla- and ‘SPEC 1’ and ‘vulnerable’ in a European La Mancha (46 % of the breeding popula- context (BirdLife International, 2004). Al- tion) and Extremadura (21 %). A comparison though its geographical spread is still very ex- of these totals with previous estimates (100,000 tensive – ranging from Portugal to north-east – 200,000 breeding males by de Juana and China – since the 19th century it has suffered Martínez, 1996; 50,000 – 100,000 breeding population declines which have led to its ex- males by García de la Morena et al., 2004) sug- tinction in many countries, such that it is gests a major decline, although admittedly those now relatively numerous only in Iberia, south- estimates were based on relatively limited in- ern Russia and Kazakhstan (Snow and Per- formation (Morales et al., 2006a y b). On a re- rins, 1998; de Juana and Martínez, 2001). The gional scale, the review by García de la Iberian population may comprise 50 – 70 % Morena et al. (2004) drew attention to the ex- of its global numbers (Collar, 1996) and is thus istence of drastic declines in all regions for of prime importance for the conservation of which quantitative data existed. The com- this species. plete absence of information from Castilla-La Nevertheless, current demographic trends Mancha is also noted and the data from Ex- in Spain and Portugal appear to be negative and tremadura came from only one area, the the core of the population is now concentrat- Cáceres plains (Llanos de Cáceres), where there ed in only a few regions. The numbers in Por- had been a 60 % decline between 1985/86 and tugal have been assessed at 10,000 – 20,000 1994/95; López Ávila and Hidalgo de Trucios, (BirdLife International, 2004) but pre- 1998). Given our awareness of the relative im- liminary results of a recent census in the Alen- portance of the Extremaduran population, on tejo, which may hold 90 % of the Portuguese both iberian and global scales, it is worth pre- population, suggest that it may exceed senting here the results of a series of breeding 20,000 individuals (Silva et al., 2006). season censuses which have been carried out The first national census of this species in since 1993 and which point to a marked gen- Spain, carried out by SEO/BirdLife in 2005, eral decline in numbers.

* Departamento de Zoología y Antropología Física, Facultad de Biología. Universidad Complutense de Madrid, C/. José Antonio Novais, 2, E-28040 Madrid (Spain). [email protected] ARDEOLA 56(1) 2aver2 16/6/09 10:48 Página 120

120 DE JUANA, E.

sexes were noted. This allowed us to estimate an abundance index, defined as the individu- als detected on average per point count. Cen- suses took place in spring, between late April and mid-May, and were confined to the first three hours after dawn and the final two hours before sunset. The morning or evening timing of counts was the same for each site in all years. Each survey route comprised about 20 listening stations (minimum 16, maximum 27) and these too were used annually with minor variations occasioned by road works or similar unavoidable circumstances. In gener- FIG. 1.—Yearly changes in the abundance index (numbers of little bustards censused per point count) al, tracks and local roads with little traffic were for the whole of the study area, with means of the used. We looked for among-years differences six census localities and 95 % confidence intervals. in the abundance index by using ANOVA Bars denote mean ± confidence interval. test. Statistical analyses were performed with [Cambios interanuales en el índice de abundan- the Statistica 6 (StatSoft) programme. cia (individuos por estación de escucha) para el Considering the whole study period and the conjunto del área de estudio, con las medias de whole region, we found significant differences las seis localidades de censo y los intervalos de con- among years in the abundance index for the lit- fianza del 95 %.] tle bustard, this variable decreasing along the study period (figure 1). Changes in abundance index per locality are shown in figure 2. Ap- The census sites, six in all, are situated in pendix 1 details census results by years and lo- agricultural areas dedicated to cereal crops or calities. extensive ranching. They fall within areas clas- A comparison of the totals of individuals sified as important for steppe species, both on censused in 1993 and in 2008 (excluding an international scale (Heath and Evans, 2000) Llanos de Cáceres, which was not censused in and nationally (Traba et al., 2007). They also 1993) shows a decline of 65 %. Nevertheless, hold the highest densities of little bustards in 1993 was an abnormally dry year, when little Extremadura (Corbacho et al., 2005; García bustard densities were probably lower than usu- de la Morena et al., 2006). Three are in Cáceres al (de Juana and García, 2005). If, therefore, province: Brozas, Llanos de Cáceres and Tru- only data from years of normal or high rainfall jillo, and the other three in province: are considered, the 2008 numbers represent , and 24.9 % of those in 1998, equivalent to a decline (for more information of 75.1 %. If only very dry years are compared, see de Juana and García, 2005). Censuses took these being 1993, 1999 and 2005 (de Juana and place during ten seasons: 1993, 1998 – 2000 García, 2005), the 2005 count is 32 % of the (three seasons) and 2003 – 2008 (six seasons). 1993 count. One site (Llanos de Cáceres) was not censused Declines from 1998 to 2008 by locality in the first year. The census technique employed ranged from 50 % in Cabeza del Buey to 100 listening for three minutes at a series of sta- % in Brozas, the remainder all exceeding 70 tions spaced at approximately 1km intervals %. In some localities, notably in Cabeza del along fixed routes. At each station the num- Buey, there was substantial variation between bers of little bustards seen or heard and their years, (figure 2).

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DECLINE OF THE LITTLE BUSTARD 121

The results point to a 75 % decline of little bustards in Extremadura in just 11 years (1998 – 2008), affecting all the study sites. Declines of this magnitude correspond to those of an ‘endangered’ species according to IUCN cri- teria (showing a decline of ≥ 50 % in ten years or three generations; IUCN, 2001). In to assess trends in particular lo- calities, it seems important to take into account the possibility of substantial variation between years. In our study (figure 2) this was especial- ly evident in Cabeza del Buey, where abun- dance indices were usually high or very high FIG. 2.—Annual changes in the abundance index- in comparison to the other sites, but where there es (average numbers of individuals per point count) was a complete or almost complete absence of for each of the six census sites (in the legend, little bustards during some very dry springs (as “Cáceres” stands for Llanos de Cáceres, “Valencia” in 1993 and 2005). We have suggested in a pre- for Valencia de las Torres, “Granja” for Granja de vious paper (de Juana and García, 2005) that Torrehermosa and “Cabeza” for Cabeza del Buey). this may be related to changes in habitat struc- [Cambios interanuales en los índices de abundan- ture, since Cabeza del Buey, in the district of cia (individuos por estación de escucha) para cada una de las áreas estudiadas (en la leyenda “Cáce- La Serena, is a grassland area with high res” equivale a Llanos de Cáceres,“Valencia” a Va- sheep densities, where the resulting overgraz- lencia de las Torres, “Granja” a Granja de Torre- ing could mean that little bustards may not find hermosa y “Cabeza” a Cabeza del Buey.] suitable places to hide their nests during very dry springs. In contrast, Trujillo shows the high- est relative abundances in those same very dry years, which suggests that regional scale move- bón, in García de la Morena et al., 2004), al- ments in search of more favourable habitat con- though without supporting quantitative data. ditions occur when necessary. Among the six However, in this latter area (which includes our study sites, Trujillo has the highest and Cabeza Cabeza del Buey site) a density of at least 24 del Buey the lowest average rainfall levels: for males/km2 was noted in 1987 (Aguilar et al., example, in the very dry year of 1993, from 1987), but only 4.6 males/km2 in 1993 (at January to April, 170.7 mm of rain were record- ; de Juana and Martínez, 1996), while ed at Trujillo and just 75.2 mm at Cabeza del at Sierra de Fuentes (close to our Llanos de Buey, (data from the Instituto Nacional de Me- Cáceres site), 3.8 males/km2 were censused in teorología, Madrid). 1988 but only 2.4 males/km2 in 1994 (Hellmich Data obtained by López Ávila and Hidal- and Núñez Arjona, 1996). go de Trucios (1998) indicate an earlier and During the 2005 national census (García de very considerable decline in the Llanos de la Morena et al., 2006) the mean densities Cáceres, where breeding season density fell for localities in Extremadura were 1.7 from 6.0 individuals/km2 in 1985/86 to 2.4 in- males/km2 in Badajoz province and 1.4 dividuals/km2 in 1994/95. males/km2 in Cáceres province, with site max- Declines of the little bustard in Extremadu- ima of 11 males/km2 in the former (in Llere- ra have been reported also for the Vegas Altas na district) and 6 males/km2 in the latter (in del Guadiana (Pérez Chiscano, 1975) and the Trujillo district). In view of these population pastures of La Serena (C. Barros and N. de Bor- densities, the counts from La Serena by Aguilar

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et al. (1987) may seem inordinately high, but ulation during the last decade has been even it is worth noting that relatively proximate ar- greater than the 30 % suggested by García de eas of Portugal, quite similar to La Serena in la Morena et al. (2006). A decline also seems terrain and land-use, have yielded similar or apparent in Portugal, at least in the Alto Alen- even higher densities of little bustards: in the tejo, a region where recently densities of only Alto Alentejo, Ferguson-Lees (1967) found 13 0.7 males/km2 have been found in Cabrela and – 16 males/km2 and Schulz (1985) reported 0.79 males/km2 in Campo Maior (Faria and 13.8 males/km2, whereas at Castro Verde, Mor- Rabaça, 2004). eira and Leitão (1996) give mean densities It is not the purpose of this paper to dis- of 26 males/km2 in cereal fallows with up to cuss the causes of the declines of the little 47 males/km2 in old fallows. bustard, but a brief reference seems advis- The Spanish Red Data book (García de la able. Generally speaking, agricultural inten- Morena et al., 2004) reveals a strong decline sification is presently regarded as the main in other regions, up to 40 % in six years in threat to the conservation of the species, as Cataluña (from 1994 to 2001) and about 27 % it affects both habitat extent and habitat qual- in four years in Navarra (from 1997 to ity through processes like the reduction of 2001). The Red Data book was unable to pro- fallows and field margins, the expansion of vide comparable information for the Meseta irrigation and arboreal crops (such as olive Sur (Castilla-La Mancha and Madrid), and almond plantations), the decrease of which is precisely the region with the highest arthropod availability due to insecticide use, populations and highest provincial densities the loss of ground cover to overgrazing, etc. of little bustards (Martínez, 2005; García de (see for example Wolff et al., 2001 and 2002; la Morena et al., 2006). Nevertheless, Morales Martínez and Tapia, 2002; Inchausti and Bre- et al. (2008) show a big decline between 2000 tagnolle, 2005; Morales et al., 2005; García and 2007 in the main area for the species in et al., 2007; Traba et al., 2008). However, the Madrid, while for Castilla-La Mancha the pre- huge extent of the decline here reported for liminary results from the common birds mon- Extremadura seems disproportionate to the itoring programme of SEO/BirdLife (SACRE) magnitude of recent habitat changes in the also suggest an important decline (Escandell region, and to the population trends exhibit- and Palomino, 2007). ed by other species sharing the steppe- Taking Spain as a whole, the national cen- like habitat (pers. obs.) and certainly much sus results point to a decline of at least 30 % in more research is needed in order to fully ten years (García de la Morena et al., 2006), in understand and eventually halt the decline of line with the rates of annual change detected the little bustard. by the SACRE programme (2.8 % between Given the importance of the Iberian popu- 1998 and 2005; Escandell and Palomino, 2007) lations to the global conservation of the species, but rather less than seen here in the results from particularly since it has declined very greatly Extremadura. Not only is this region no excep- in France (Morales et al., 2005; Jolivet et al., tion to the general negative trend of little bus- 2007) and has become extremely rare or ab- tards in Spain but it is also experiencing large- sent in countries such as Ukraine and Algeria scale population losses, comparable to those where it was formerly very common or abun- in peripheral regions of the species’range, such dant (Schulz, 1985; Collar, 1996), it is advis- as Cataluña or Navarra. Taking into account able that an urgent and substantial increase in the decline which also appears to be occurring current conservation efforts in Spain should be in Castilla-La Mancha and Madrid, it is high- implemented (de Juana and Martínez, 2001; ly probable that the decline in the Spanish pop- García de la Morena et al., 2006).

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DECLINE OF THE LITTLE BUSTARD 123

RESUMEN.—Este trabajo documenta los by the Spanish Ministry of Science and Technolo- cambios detectados en las poblaciones re- gy (Project REN2000-0765/GLO). productoras de sisón común en la región de Extremadura (suroeste de España) desde el año 1993. Se basa en censos llevados a cabo BIBLIOGRAPHY en un conjunto de seis localidades de impor- AGUILAR, A., DE JUANA, E. and TELLERÍA, J. L. 1987. tancia para la especie, repartidas entre las pro- Importancia ornitológica de los pastizales de La vincias de Cáceres (Brozas, Llanos de Cáce- Serena (Badajoz). Poster in the IX Jornadas Or- res y Trujillo) y Badajoz (Cabeza del Buey, nitológicas Españolas. Sociedad Española de Or- Granja de Torrehermosa y Cabeza de las To- nitología. Madrid. rres) y en diez años diferentes (1993, 1998- BIRDLIFE INTERNATIONAL. 2000. Threatened birds 2000 y 2003-2008); los censos se efectuaron of the world. BirdLife International and Lynx Edi- por medio de estaciones de escucha distri- cions. Cambridge and Barcelona. buidas de forma regular a lo largo de reco- BIRDLIFE INTERNATIONAL. 2004. Birds in Europe II. rridos fijos y siempre entre finales de abril y BirdLife International. Cambridge. mediados de mayo. Los resultados muestran COLLAR, N. J. 1996. Little Bustard Tetrax tetrax. In, amplias variaciones para las distintas locali- J. del Hoyo, A. Elliott, and J. Sargatal (Eds.): Hand- dades de unos años a otros, que en parte se book of the Birds of the World, Vol. 3. Hoatzin to pueden explicar por la irregular distribución Auks, p. 273. Lynx Edicions. Barcelona. espacio-temporal de las lluvias y que, inevita- CORBACHO, C., COSTILLO, E. and ACEDO, F. 2005. Abundancia de Sisón (Tetrax tetrax) en zonas blemente, dificultan las comparaciones inter- esteparias de Extremadura. In, J. M. Caballero anuales en el conjunto regional. No obstante, (Ed.): Conservación de la Naturaleza en Extre- si sólo se utilizan los datos correspondientes madura. Comunicaciones en Jornadas y Congre- a años con precipitaciones normales o eleva- sos 2002-2004, pp. 405-411. Consejería de das, se evidencia una caída en las cifras de Agricultura y Medio Ambiente, Junta de Extre- aves censadas del 75 % entre 1998 y 2008. Este madura. Mérida. descenso poblacional tan brusco, ocurrido en DE JUANA, E. and GARCÍA, Á. M. 2005. Fluctua- poco más de una década, justificaría según los ciones relacionadas con la precipitación en la criterios de la UICN la catalogación del sisón riqueza y abundancia de aves de medios estepa- común como especie “en peligro” en Extrema- rios mediterráneos. Ardeola, 52: 53-66. dura. Dada la importancia de las poblaciones DE JUANA, E. and MARTÍNEZ, C. 1996. Distribu- españolas en el conjunto mundial (pues se tion and conservation status of the Little Bustard estima que pueden suponer alrededor del 60 Tetrax tetrax in the Iberian Peninsula. Ardeola, % del total) y la importancia a su vez de Ex- 43: 157-167. tremadura en el conjunto de España (los re- DE JUANA, E. and MARTÍNEZ, C. 2001. European Union Species Action Plan for the Little Bustard sultados del censo nacional llevado a cabo por (Tetrax tetrax). BirdLife International–European SEO/BirdLife en 2005 sitúan en ella el 21 % Commission.Brussels. de los efectivos reproductores totales), se hace http://ec.europa.eu/environment/nature/conserva- evidente la necesidad de incrementar sustan- tion/wildbirds/action_plans/docs/tetrax_tetrax.pdf cialmente y con urgencia los actuales esfuer- ESCANDELL, V. andPALOMINO, D. 2007. Programa zos de conservación de la especie. SACRE, Seguimiento de Aves Comunes Repro- ductoras en España. In, V. Escandell (Ed.): Pro- ACKNOWLEDGEMENTS.—T. Santos helped in gramas de seguimiento de SEO/BirdLife en 2005, different ways, E. F. J. Garcia revised the English, pp. 4-9. SEO/BirdLife. Madrid. and F. de Lope and an anonymous referee suggest- FARIA, N. and RABAÇA, J. E. 2004. Breeding habi- ed improvements. Fieldwork was partly financed tat modelling of the Little Bustard Tetrax tetrax

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in the site of community importance of Cabrela, protegidos en Extremadura, pp. 115-121. Junta Portugal. Ardeola, 51: 331-343. de Extremadura. Mérida. FERGUSON-LEES, I. J. 1967. Studies of less famil- MARTÍNEZ, C. 2005. Distribución, abundancia, re- iar birds. 142. Little Bustard. British Birds, 60: querimientos de hábitat y conservación de aves 80-84. esteparias de interés especial en Castilla-La GARCÍA, J., SUÁREZ-SEOANE, S., MIGUÉLEZ, D., OS- Mancha. Museo Nacional de Ciencias Naturales, BORNE, P. E. andZUMALACÁRREGUI, C. 2007. Spa- Consejo Superior de Investigaciones Científi- tial analysis of habitat quality in a fragmented po- cas. Madrid. pulation of little bustard (Tetrax tetrax): MARTÍNEZ, C. and TAPIA, G. C. 2002. Density of the implications for conservation. Biological Con- Little Bustard Tetrax tetrax in relation to agricul- servation, 137: 45-56. tural intensification in Central Spain. Ardeola, GARCÍA DE LA MORENA, E. L., DE JUANA, E., MAR- 49: 301-304. TÍNEZ, C., MORALES, M. B. and SUÁREZ, F. 2004. MORALES, M. B., BRETAGNOLLE, V. andARROYO, Sisón Común, Tetrax tetrax. In, A. Madroño, C. B. 2005. Viability of the endangered little bus- González and J. C. Atienza (Eds.): Libro Rojo de tard population of western France. Biodiversity las Aves de España, pp. 202-207. Dirección Ge- and Conservation, 14: 3135-3150. neral de Conservación de la Naturaleza – Socie- MORALES, M. B., GARCÍA, J. T. and ARROYO, B. 2005. dad Española de Ornitología. Madrid. Can landscape composition changes predict spa- GARCÍA DE LA MORENA, E. L., BOTA, G., PONJOAN, tial and annual variation of little bustard male A. and MORALES, M. B. 2006. El sisón común en abundance? Conservation, 8: 167-174. España. I Censo Nacional (2005). SEO/BirdLife. MORALES, M. B., GARCÍA DE LA MORENA, E. L., DEL- Madrid. GADO, M. P. andTRABA, J. 2006a. Tendencia re- HEATH, M. F. and EVANS, M. I. 2000. Important Bird ciente y viabilidad futura de las poblaciones de si- Areas in Europe: Priority sites for conserva- són común (Tetrax tetrax) en la Comunidad de tion. 2: Southern Europe. BirdLife International. Madrid. In, J. de la Puente, J. Pérez-Tris, M. Juan Cambridge. and A. Bermejo (Eds.): Anuario Ornitológico de HELLMICH, J. and NÚÑEZ ARJONA, J. C. 1996. Nota Madrid 2006, pp. 40-55. SEO-Monticola. Madrid. sobre densidades de población del Sisón (Tetrax MORALES, M. B., GARCÍA, E., SUÁREZ, F. and DE tetrax) en Cáceres, Extremadura. In, J. Fernán- JUANA, E. 2006b. Population trends, seasonal dez Gutiérrez and J. Sanz-Zuasti (Eds.): Conser- movements and conservation problems of the Lit- vacion de las aves esteparias y su hábitat, pp. tle Bustard Tetrax tetrax in Spain: a synthesis of 303-305. Junta de Castilla y León. Valladolid. recent results. In, D. Leitão, C. Jolivet, M. Ro- INCHAUSTI, P. andBRETAGNOLLE, V. 2005. Predict- dríguez and J. P. Tavares (Eds.): Bustard conser- ing short-term extinction risk for the declining vation in Europe in the last 15 years: current Little Bustard (Tetrax tetrax) in intensive agri- trends, best practice and future priorities, pp. 51- cultural habitats. Biological Conservation, 122: 54. RSPB. Sandy, 375-384. MOREIRA, F. and LEITÃO, D. 1996. A preliminary IUCN. 2001. IUCN Red List Categories and Crite- study of the breeding bird community of fa- ria: Version 3.1. IUCN Species Survival Com- llows of cereal steppes in southern Portugal. Bird mission. IUCN, Gland, Switzerland and Cam- Conservation International, 6: 255-259. bridge, UK.. PÉREZ CHISCANO, J. L. 1975. Avifauna de los cul- JOLIVET, CH., BRETAGNOLLE, V., BIZET, D. and WOLFF, tivos de regadío del Guadiana (Badajoz). Arde- A. 2007. Statut de l’Outarde canepetière Tetrax ola, 21: 753-794. tetrax en France en 2004 et mesures de conser- SCHULZ, H. 1985. A review of the world status of vation. Ornithos, 14: 80-94. the Little Bustard. Bustard Studies, 2: 131-151. LÓPEZ ÁVILA, P. and HIDALGO DE TRUCIOS, S. 1998. SILVA, J. P., LEITÃO, D., SANTOS, E., MOREIRA, F., Revisión del status del sisón: evolución en PREGO, I., PINTO, M., LECOQ, M., CATRY, T. and Extremadura. In, Junta de Extremadura (Ed.): PEDROSO, R. 2006. In, D. Leitão, C. Jolivet, M. Conservación de la naturaleza y los espacios Rodríguez and J. P. Tavares (Eds.): Bustard con-

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servation in Europe in the last 15 years: current (Tetrax tetrax) males in Central Spain: the role of trends, best practice and future priorities, pp. 55- arthropod availability. Ecol. Res., 23: 615-622. 59. RSPB. Sandy. WOLFF, A., PAUL, J. P., T., MARTIN, J. L. and BRETAG- SNOW, D. W. and PERRINS, C. M. (Eds.). 1998. The NOLE, V.2001. The benefits of extensive agri- Birds of the Western Palearctic, concise edition. culture to birds: the case of the little bustard. Jour- Oxford University Press. Oxford & New York. nal of Applied Ecology, 38: 963-975. TRABA, J., GARCÍA DE LA MORENA, E., MORALES, WOLFF, A., DIEULEVEUT, T., MARTIN, J. L. and M. B. and SUÁREZ, F.2007. Determining high va- BRETAGNOLE, V.2002. Landscape context and lit- lue areas for steppe birds in Spain: hot spots, com- tle bustard abundance in a fragmented steppe: im- plementarity and the efficiency of protected are- plications for reserve manegement in mosaic land- as. Biodiversity and Conservation, 16: 3255-3275. scapes. Biological Conservation, 107: 211-220. TRABA, J., MORALES, M. B., GARCÍA DE LA MORE- NA, E. L., DELGADO, M. P. andKRI TIN, A. 2008. [Recibido: 10-07-2008] Š Selection of breeding territory by little bustard [Aceptado: 15-05-2009]

APPENDIX 1

Numbers of little bustards detected in each year and locality (Cáceres was not visited in 1993). [Individuos de sisón común detectados en cada año y localidad de censo (no se visitó la localidad de Cáceres en 1993).]

Brozas Cáceres Trujillo Cabeza Granja de Valencia de Total del Buey Torrehermosa las Torres 1993 8 - 50 3 37 16 114 1998 4 56 23 36 50 28 197 1999 3 25 18 14 28 4 92 2000 4 37 15 28 36 27 147 2003 5 25 13 20 23 20 106 2004 1 15 4 19 25 973 2005 2 12 18 0 15 2 49 2006 0 20 15 18 10 6 69 2007 0 21 9 8 24 8 70 2008 0 9 6 18 8 8 49

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