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This study evaluates the relative contributions of landscape features and biotic (conspecific and heterospecific) relationships to habitat selection of three sympatric passerine species, Skylark (Alauda arvensis), Corn Bunting (Emberiza calandra) and Calandra Lark (Melanocorypha calandra) during winter. Between December 2007 and January 2008, winter populations of the three species were censused in three Central Spanish locations by means of linear transects (n = 60). An explanatory model-averaging approach was used to determine the weight and effect of different landscape and biotic variables in each species’ habitat selection patterns using their respective abundance as the dependent variable. A deviance partitioning approach was used to determine the relative contributions of these two sets of predictors. Only the Calandra Lark showed a significant influence of landscape variables, preferring relatively simplified landscapes with a low density of field margins. The three species showed preferences for proximity of con- and heterospecifics. This can be explained in relation to their gregarious behaviour during this season, which results in the formation of big multispecific flocks that confer some individual advantages (such as a better feeding efficiency or anti-predator benefits). This is also supported by the results of the deviance partitioning analysis, which showed the much higher importance of biotic interaction factors in relation to the contribution of landscape (which is negligible) for Skylark and Corn Bunting. However, for Calandra Lark, although biotic interactions are also the most important factors, both landscape and the combined effect of landscape and biotic interactions are slightly larger. Finally, we also found an effect of flock size on habitat selection, so that, for bigger flocks, habitat and biotic interaction factors will have a weaker effect on abundance and selection patterns.

We analysed female body mass change, corrected by tarsus length (body condition) in tawny pipits Anthus campestris during the nesting period in a population subject to high nest predation rates (between 70 and 85%), which leads to the need for replacement clutches. Decrease in female body condition over the nesting stage (6.8 g, around 27% of the initial mass during the whole nesting process) was related to laying date, clutch size and nesting period (incubation and nestling phases). Data from recaptured females indicated a decrease during each of the three nesting phases considered (the last days of incubation and first and last days of the nestling phase), with body mass always being higher in the first of the two measurements taken in each of these phases. The observation of a continuous decrease in body condition during the last days of incubation and first and last days of the nestling phase does not support the programmed anorexia hypothesis, but adjusts well to predictions of the stress hypothesis. These results suggest that the costs accumulated during the entire nesting stage in ground passerines subjected to high nest predation rates are linked to a superimposed effect of the cost of replacement clutches.