Suchergebnisse

The Gran Canaria Blue Chaffinch Fringilla polatzeki is a threatened, endemic, forest‐dwelling bird species of the Canary Islands, whose core population at the end of the 20th century was restricted to the pine forests of Inagua Nature Reserve (38 km2). A translocation programme released birds from a breeding centre into the nearby (<3 km) pine forests of La Cumbre in the years following 2010. From 2015 to 2019 the La Cumbre population was reinforced by translocation of wild juveniles from the source population of Inagua. We estimate the population size, the spatial variation of abundance, and recent temporal changes in density of the species in Inagua and La Cumbre by means of line transects, distance sampling, and habitat suitability modelling using random forests. The average density of the Blue Chaffinch in Inagua Nature Reserve was 10.2 birds/km2 in spring 2019, with a population estimated at 362 birds (95% CI: 257–489). The most important variables affecting the distribution of the Blue Chaffinch in Inagua were the amount of precipitation during the summer (July September), the solar radiation in June, and the northern position in the reserve, highlighting the importance of abiotic factors related to thermal and hydric stress during the breeding season. The density was considerably lower in the translocated population inhabiting 21 km2 of pine forests in La Cumbre (3.3 birds/km2), with an estimate of 68 Blue Chaffinches (35–141) breeding freely in the wild. The translocation programme successfully contributed to the establishment of a second viable nucleus, accounting for 16% of the total population within a time span of 10 years. This result reinforces the role of translocations in preventing extinctions of endangered species with very low population sizes restricted to only one isolated area. ; This study was supported by several conservation programmes funded by the Gobierno de Canarias (1991–2004), Cabildo de Gran Canaria (2005–2015), and the European Union (2015-2019: LIFE14 NAT/ES/000077). ; Peer reviewed

[ES] Striking resilience of an island–endemic bird to a severe perturbation: the case of the Gran Canaria blue chaffinch. Evidence regarding population trends of endangered species in special protection areas and their recovery ability from catastrophic disturbances is scarce. We assessed the population trend of the Gran Canaria blue chaffinch (Fringilla polatzeki), a habitat specialist endemic to the pine forest of Inagua in the Canary Islands, following a devastating wildfire in July 2007. Using a standardized census program that accounts for detectability, we have monitored the population trend of the species since Inagua was declared a Strict Nature Reserve in 1994. The breeding population density of the blue chaffinch remained stable in Inagua from the beginning of the monitoring program in 1994 until the year before the wildfire. However, in spring 2008, the population density decreased by half with respect to density in the preceding years. Since 2008, the population has gradually increased, reaching its highest recorded density in 2016 (15.8 birds/km).This represents an average annual increase of 23.7%, indicating impressive resilience to catastrophic events. The creation of Inagua as a strict nature reserve did not therefore increase the global population or protect the blue chaffinch against a demographic crisis but probably prevented a deepening of the demographic crisis or further declines. Except for the two years immediately after the severe wildfire of 2007, the population density of the blue chaffinch in Inagua has remained relatively stable at around 9–16 birds/km, the lowest recorded abundance for a small woodland passerine in the Western Palearctic. ; [ES] Son pocos los datos disponibles sobre la tendencia demográfica de las especies en peligro de extinción en zonas de protección especial y su capacidad de recuperarse de perturbaciones catastróficas. Se estudia la tendencia demográfica del pinzón azul de Gran Canaria (Fringilla polatzeki), un especialista de hábitat endémico de las Islas Canarias, restringido al pinar de Inagua, que sufrió un devastador incendio forestal en julio de 2007. Mediante un programa de censo estandarizado que tiene en cuenta la variación en la capacidad de detección, se ha hecho un seguimiento de la tendencia demográfica de la especie desde la declaración de Inagua como reserva natural integral en 1994. La densidad reproductiva del pinzón azul se mantuvo estable en Inagua desde el inicio del programa de seguimiento en 1994 hasta un año antes del incendio. No obstante, en la primavera de 2008, la densidad de la población se redujo a la mitad en comparación con los años anteriores. A partir de 2008, la población del pinzón azul ha venido aumentando gradualmente hasta alcanzar la densidad más alta jamás registrada en 2016 (15,8 aves/km2), lo que equivale a un incremento anual medio del 23,7% y pone de manifiesto la resistencia impresionante de estas poblaciones ante catástrofes. Por lo tanto, la creación de la reserva integral de Inagua no promovió el aumento de población ni protegió al pinzón azul frente a una grave crisis demográfica, sino que probablemente evitó que la disminución de la población fuera más profunda o que se produjeran otras reducciones. Aparte de los dos años inmediatamente posteriores al incendio forestal de 2007, la densidad de población del pinzón azul en Inagua se mantuvo relativamente estable alrededor de 9–16 aves/km2, la menor abundancia jamás registrada para un paseriforme forestal de tamaño pequeño en todo el paleártico occidental. ; The study was supported by the Conservation Program for the blue chaffinch implemented by the Gobierno de Canarias (1991–2004), Cabildo de Gran Canaria (2005–2015), and was partially funded by the European Union (1995–1996: LIFE94 NAT/E/ 001159; 1999–2002: LIFE98 NAT/E/005354; 2016: LIFE14 NAT/ES/000077) and a research contract between MNCN/CSIC and GESPLAN, S. A. U. (2008). JS currently works within the Madrid's Government research group network REMEDINAL3–CM (S–2013/MAE–2719). ; Peer Reviewed

Afforestation programs such as the one promoted by the EU Common Agricultural Policy have spread tree plantations on former cropland. These afforestations attract generalist forest and ubiquitous species but may cause severe damage to open habitat species, especially birds of high conservation value. We investigated the effects of young (<20 yr) tree plantations dominated by pine P. halepensis on bird communities inhabiting the adjacent open farmland habitat in central Spain. We hypothesize that pine plantations located at shorter distances from open fields and with larger surface would affect species richness and conservation value of bird communities. Regression models controlling for the influence of land use types around plantations revealed positive effects of higher distance to pine plantation edge on community species richness in winter, and negative effects on an index of conservation concern (SPEC) during the breeding season. However, plantation area did not have any effect on species richness or community conservation value. Our results indicate that the effects of pine afforestation on bird communities inhabiting Mediterranean cropland are diluted by heterogeneous agricultural landscapes. ; The following grant information was disclosed by the authors: Spanish Ministry of Science and Education: CGL2010-18312, CGL2014-53308-P. Government of Madrid: S2009AMB-1783, REMEDINAL-2, S2013/MAE-2719, REMEDINAL-3. ; Peer reviewed

Afforestation programs such as the one promoted by the EU Common Agricultural Policy have spread tree plantations on former cropland. These afforestations attract generalist forest and ubiquitous species but may cause severe damage to open habitat species, especially birds of high conservation value. We investigated the effects of young (<20 yr) tree plantations dominated by pine P. halepensis on bird communities inhabiting the adjacent open farmland habitat in central Spain. We hypothesize that pine plantations located at shorter distances from open fields and with larger surface would affect species richness and conservation value of bird communities. Regression models controlling for the influence of land use types around plantations revealed positive effects of higher distance to pine plantation edge on community species richness in winter, and negative effects on an index of conservation concern (SPEC) during the breeding season. However, plantation area did not have any effect on species richness or community conservation value. Our results indicate that the effects of pine afforestation on bird communities inhabiting Mediterranean cropland are diluted by heterogeneous agricultural landscapes. ; Ministerio de Ciencia y Educación ; Comunidad de Madrid ; Fundación Internacional para la Restauración de Ecosistemas

We investigated the effects of local habitat structure and surrounding landscape characteristics (proportion of land use types and connectedness) on species density and composition of bird communities inhabiting the interior of young tree plantations on former cropland in central Spain, which were motivated by the Common Agrarian Policy. Variation of species density (number of species/0.78 ha) among tree plantations showed different environmental associations across seasons: local habitat was more important than landscape characteristics during winter, whereas they were similarly important during spring. Species density increased with the development of the tree layer in winter and with the presence of urban areas around tree plantations and cover of the herbaceous layer within them in the breeding season. We identified 15 species that exhibit high relative abundance in woodland habitats within the Mesomediterranean region of Central Spain that were absent in both seasons in the studied tree plantations, which were an attractive habitat for urban exploiter species but an unfavorable habitat for the regional forest species pool except for forest generalist species. Composition of bird assemblages was more related to local habitat structure than to landscape characteristics around tree plantations and was rather similar in winter and spring seasons. The very different effects of local habitat and landscape characteristics on bird communities make difficult suggesting management practices with positive effects for all avifauna species during the entire year. We conclude that the small size and low maturity of the studied tree plantations do not contribute to enhancing the bird diversity value of current CAP aids to afforest former cropland with pines in the Mediterranean region. ; Ministerio de Ciencia y Educación ; Comunidad de Madrid

Afforestation programs such as the one promoted by the EU Common Agrarian Policy have contributed to spread tree plantations on former cropland. Nevertheless these afforestations may cause severe damage to open habitat species, especially birds of high conservation value. We investigated predation of artificial bird nests at young tree plantations and at the open farmland habitat adjacent to the tree plantations in central Spain. Predation rates were very high at both tree plantations (95.6%) and open farmland habitat (94.2%) after two and three week exposure. Plantation edge/area ratio and development of the tree canopy decreased predation rates and plantation area and magpie (Pica pica) abundance increased predation rates within tree plantations, which were also affected by land use types around plantations. The area of nearby tree plantations (positive effect), distance to the tree plantation edge (negative effect), and habitat type (mainly attributable to the location of nests in vineyards) explained predation rates at open farmland habitat. We conclude that predation rates on artificial nests were particularly high and rapid at or nearby large plantations, with high numbers of magpies and low tree development, and located in homogenous landscapes dominated by herbaceous crops and pastures with no remnants of semi-natural woody vegetation. Landscape planning should not favour tree plantations as the ones studied here in Mediterranean agricultural areas that are highly valuable for ground-nesting bird species. ; Ministerio de Ciencia y Educación ; Comunidad de Madrid