Heterospecific social attraction in migrant birds: habitat niche overlap between two threatened shrikes

Context Effective biodiversity conservation requires information about a species’ ecology and its relationship with the geographical context. To achieve this efficiently, species distribution models can be developed, also taking into account species associations. Aims I aimed to illustrate the habitat requirements of two threatened passerines of semi-open landscapes, i.e. the lesser grey shrike, Lanius minor, and the woodchat shrike, Lanius senator, in southern Italy. Further, I assessed whether there is heterospecific social attraction between them, by assessing how their habitat niches overlap. Methods Data were collected by territory mapping during the 2009–13 breeding seasons. The habitat requirements of the species were investigated with the help of ecological niche factor analysis (ENFA). In addition, the areas of sympatry between the two species were defined by indicator kriging and the habitat niche overlap was analysed using the generalised linear model (GLM). Key results The results showed that these two species inhabit open areas, with scattered vegetation such as shrubs and trees, while avoiding intensively cultivated permanent crops, such as vineyards and olive groves. Moreover, a little difference was observed in the percentage cover of shrublands, which were higher in the woodchat shrike territories than in the lesser grey ones. The strong overlap in their habitat niches suggests heterospecific social attraction between them, especially because of the species rarity. Conclusions The lesser grey and the woodchat shrike were found to occur in very similar environments, by evidencing the overlap of their macrohabitat niches. This suggests the presence of heterospecific social attraction, corroborating the understudied hypothesis that this phenomenon is valid for migrant birds as well. The lesser grey shrike, in particular, may use occurrences of the woodchat shrike as a cue for assessing habitat quality and, thus, to establish its territory. Implications Considering the high habitat niche overlap, habitat changes occurring in the landscape might affect them equally. Furthermore, the use of heterospecific social information in habitat selection potentially has many important conservation implications. Indeed, by reproducing the appropriate information, birds could be attracted to specific sites known to be high-quality habitat.

Protected area networks are insufficient for the conservation of threatened farmland species: A case study on corncrake (Crex crex) and lesser grey shrike (Lanius minor) in Serbia

To conserve threatened farmland species requires an estimate of the representation of their habitats within protected areas, especially in countries with inadequate mechanisms for protecting and managing habitats outside of protected areas. We conducted a gap analysis to evaluate the conservation status of suitable habitats for two threatened farmland bird species - corncrake (Crex crex) and lesser grey shrike (Lanius minor) - within the networks of national protected areas (NPAs) and important bird areas (IBAs) in Serbia. We determined the distribution of suitable habitats using MaxEnt based on climate, topography and land-cover variables. We found that the proportion of suitable habitats within the NPAs is very low (12.31% and 2.04% for the corncrake and lesser grey shrike, respectively), although it is significantly higher for both species within IBAs (25.86% and 9.91%, respectively). Upland farmland habitats (preferred by corncrake) are better represented within both networks (especially IBAs) than lowland habitats (preferred by lesser grey shrike). Our spatially explicit distribution models identify suitable habitats within and beyond the NPAs and IBAs that require monitoring and appropriate conservation measures. The low representation of suitable habitats within these networks is an obstacle to the conservation of both species and other farmland birds in Serbia.