Caution Is Needed When Using Niche Models to Infer Changes in Species Abundance: The Case of Two Sympatric Raptor Populations

Despite the mounting evidence supporting positive relationships between species abundance and habitat suitability, the capacity of ecological niche models (ENMs) to capture variations in population abundance remains largely unexplored. This study focuses on sympatric populations of hen harrier (Circus cyaneus) and Montagu’s harrier (Circus pygargus), surveyed in 1997 and 2017 in an upland moor area in northwestern Spain. The ENMs performed very well for both species (with area under the ROC curve and true skill statistic values of up to 0.9 and 0.75). The presence of both species was mainly correlated with heathlands, although the normalized difference water index derived from Landsat images was the most important for hen harrier, indicating a greater preference of this species for wet heaths and peat bogs. The findings showed that ENM-derived habitat suitability was significantly correlated with the species abundance, thus reinforcing the use of ENMs as a proxy for species abundance. However, the temporal variation in species abundance was not significantly explained by changes in habitat suitability predicted by the ENMs, indicating the need for caution when using these types of models to infer changes in population abundance.

Expert knowledge assessment of threats and conservation strategies for breeding Hen Harrier and Short-eared Owl across Europe

Summary Hen Harrier Circus cyaneus and Short-eared Owl Asio flammeus are open-country birds of prey with overlapping distributions. Although both species face similar conservation threats across their ranges, work to date has largely been undertaken at a national scale with few attempts to collate and assess factors relevant to their conservation at an international scale. Here we use an expert knowledge approach to evaluate the impact of conservation threats and the effectiveness of conservation strategies for each species across Europe. We report results of responses to a questionnaire from 23 Hen Harrier experts from nine countries and 12 Short-eared Owl experts from six countries. The majority of responses for both species reported declines in breeding numbers. The perceived impact of threats was broadly similar for both species: ecological factors (predation, extreme weather and prey availability), changes in land use (habitat loss and agricultural intensification) and indirect persecution (accidental nest destruction) were considered to be the greatest threats to breeding Hen Harrier and Short-eared Owl. Short-eared Owl experts also highlighted lack of knowledge and difficulties associated with monitoring as a major conservation challenge. Despite broad-scale similarities, geographical variation was also apparent in the perceived importance of conservation threats, with some threats (such as direct persecution, large-scale afforestation or habitat degradation) requiring country-specific actions. Implementation of different conservation strategies also varied between countries, with the designation of protected areas reported as the most widespread conservation strategy adopted, followed by species and habitat management. However, protected areas (including species-specific protected areas) were perceived to be less effective than active management of species and habitats. These findings highlight the overlap between the conservation requirements of these two species, and the need for collaborative international research and conservation approaches that prioritise pro-active conservation strategies subject to continued assessment and with specific conservation goals.

Bird Bone Remains from Two Medieval Settlements in Debrecen (Eastern Hungary)

This paper presents results on three medieval avian bone assemblages found at Debrecen-Monostor-erdő and Debrecen-Tócó-part, respectively. Domestic chicken yielded most of the bird remains to evidence the exploitation of adult birds for egg production and flock maintenance in particular. In addition, feather harvesting and fat production could have been the target of goose (and possibly duck) husbandry. Although the goose bone sizes resemble the greylag goose, the keeping of an unimproved form of domestic goose rather than the hunting of the wild ancestor is suggested by the structure of the assemblage and the presence of healed bones. Wild birds seem to have been rarely consumed by the settlers of the two villages, but the feathers or wings or carcasses of diurnal birds of prey and crows may have been used for special purposes. Either killed for their symbolic meaning or only persecuted for protecting the backyard animals, the red kite (Milvus milvus) and the hen harrier (Circus cyaneus) represent new species for the medieval avifauna of Hungary, similarly to the Northern shoveler (Anas clypeata) and the Northern lapwing (Vanellus vanellus) that could have been hunted in the marshy environment provided by the Tócó creek. Moreover, the use of trained saker falcon (Falco cherrug) for hawking cannot be excluded either. In addition to the exploitation of birds for the abovementioned goods and values, two needle cases made from goose bones evidence the utilization of their skeletal parts as raw material for producing artefacts as well.