Nicolás Ron-Arroyo

En este estudio demostramos por primera vez que las predicciones sobre el futuro de la fauna vertebrada amenazada realizadas en los inicios de las políticas de conservación en España (años 70 del siglo XX) tuvieron una probabilidad baja de acierto (0.29 [0.15-0.45] IC 95 %), y por lo tanto peor de lo esperable por puro azar (0.5). Las predicciones fueron especialmente pobres en el caso de las aves y de los depredadores, en contraste con mamíferos y no depredadores. En concreto, las predicciones de futuros declives, identificadas por nosotros en una búsqueda de literatura faunística de los años 70, acertaron mucho menos (0.20 [0.07-0.38]) que las predicciones de recuperación (0.62 [0.25-0.91]). Discutimos estos resultados dentro del marco de la conservación de especies y de espacios, pero también de los cambios socioeconómicos experimentados por el país en los últimos 50 años, poniendo especial énfasis en las inesperadas consecuencias directas (disminución de la persecución directa) e indirectas (cambios en el uso del suelo) del éxodo rural. Si tenemos en cuenta sólo las predicciones de declive, sugerimos que el abandono del medio rural estuvo detrás del fallo de predicción en un 53.1 % de los casos, frente al 46.9 % atribuible a la conservación. Además, se repasaron los distintos catálogos nacionales de fauna amenazada desde el primer Listado promovido por Blas Aritio en 1973, concluyéndose que en general no han reflejado bien la mejora del estatus de las antiguas especies amenazadas.

Material Suplementario de Ecosistemas, 35(1), 3151 (https://doi.org/10.7818/ECOS.3151): Fuentes consultadas y Bibliografía relacionada con la conservación de la fauna vertebrada amenazada en España, publicada entre los años 1970 y 1979, identificando predicciones realizadas acerca de la situación esperada para las especies en el futuro.

The intense human persecution of wildlife in the past forced many animal populations to look for refuge in human‐inaccessible habitats. With the decline of direct persecution, and the changes in the attitude of modern urban societies towards wildlife during the last few decades, an ecological process of abandonment of refuge habitats has become pervasive, and many species make habitat choices deemed surprising presently, such as colonizing sites that are more accessible to humans. We tested this process in the yellow‐legged gull Larus michahellis by analysing long‐term time series (1976–2022) of breeding pairs in seven colonies in southern Europe. Overall, yellow‐legged gull numbers showed a strong pattern of decrease during the study period, due to the recent closure of open‐air garbage dumps. However, while the number of pairs in colonies located in human‐inaccessible sites (islets with cliffs) declined rapidly, new colonization together with a monotonic linear population growth was detected in human‐accessible sites, coinciding in time with the departure from refuges. Moreover, we found that the new small yellow‐legged gull colonies acted as cores for the formation of multispecies waterbird colonies likely by heterospecific attraction, that provides an added unexpected conservation value to yellow‐legged gulls traditionally considered a pest species.

This study targeted prey type and prey size selection by a small but expanding population of the Eurasian oystercatcher (Haematopus ostralegus) at the southernmost range of its European distribution (Galicia, NW Spain). We compared consumption and availability of prey items delivered to chicks. Consumption was studied through piles of discarded shells and availability was sampled in the foraging grounds located around nesting sites on three different islets. The only two prey types present in shell piles were mussels (Mytillus galloprovincialis) and limpets (Patella sp.). Our chi-square analyses did not detect any prey type selection by oystercatchers, but the use of the Savage index with Manly’s method identified negative selection of limpets at one of the study sites. As a rule, the birds consumed limpets and mussels in proportion to their availability in their foraging grounds. At one of the study sites periwinkles (Littorina sp.) were present but not consumed. Regarding prey size, oystercatchers selected (1) mussels that were either similar to or larger than those available, and (2) limpets that were larger than those available. However, at one site out of three, the oystercatchers positively selected limpets of smaller size than those available. Hence, our results showed some heterogeneity among sites regarding prey type selection, but quite a consistent pattern of selection of larger prey. We suggest that oystercatcher foraging ecology is not explained solely by considering the balance between energy uptake and costs, but importantly by introducing additional variables such as the risk of chick predation, and current nesting as refugees on islets with no access to mainland beaches and sand dunes for breeding, where both adult and chick diet could be substantially different.