Identifying mismatches between habitat selection and habitat quality in a ground-nesting farmland bird

Human-induced habitat changes often generate novel or radically altered habitat characteristics, which can impair the ability of organisms to differentiate between suitable and unsuitable sites. This phenomenon, often termed an ecological trap, has been identified as a potential driver of biodiversity loss worldwide. However, few unequivocal examples have been documented, even in agricultural environments where contemporary habitat changes have been rapid and significant. Several problems complicate the detection of ecological traps in the field, including difficulties in measuring key parameters such as relative habitat preference. Here, we assess habitat selection preferences and breeding success of the yellow wagtail Motacilla flava, a UK red-listed declining passerine, in arable farmland. We combine habitat-specific density indices with measures of home range exclusivity to make inferences on relative habitat preference that are robust to the confounding effect of competitive exclusion. Using multiple measures of breeding success, we identify maladaptive habitat selection patterns at the scale of both territory and nest site choice. Yellow wagtails showed a preference for establishing territories within field bean crops, but subsequently suffered high nest predation rates. Similarly, pairs showed a preference for nesting close to tramlines within cereal fields, but nests further from tramlines achieved higher success due to lower predation rates. We found no evidence of competitive exclusion among neighbouring pairs, suggesting that density-based indices provided an accurate reflection of relative habitat preferences. Our findings highlight the potential role of maladaptive habitat selection in suppressing breeding success among farmland species

Mid-season shifts in the habitat associations of Yellow Wagtails Motacilla flava breeding in arable farmland

Declines in habitat quality through the breeding season within a bird's home-range can limit overall productivity. In environments where multiple breeding opportunities arise during the course of a season, these effects can be buffered by a shift to different breeding sites or habitats. We studied the distribution and habitat associations of a crop-nesting farmland bird, the Yellow Wagtail Motacilla flava, across an arable-dominated farming region in eastern England using both field-scale territory mapping and large-scale transect surveys. Surveys were repeated at monthly intervals to measure changes in both distribution and habitat use during the course of the season. The distribution of breeding birds changed markedly at both regional and field-scales, coinciding with a shift in crop preference. Initially, most territorial birds were recorded in autumn-sown cereal fields, but this crop was subsequently abandoned in favour of potato crops, which were more patchily distributed. Other habitat features influencing Yellow Wagtail distribution included local crop diversity, hedgerow presence and soil type, with organic soils supporting higher abundance than alluvial clays or silts. The mid-season switch in habitat associations might allow individuals to maximize the number of breeding attempts made in a single year by using multiple habitats sequentially. The use of multiple habitats could influence population regulation by buffering the effects of local within-season declines in habitat suitability. Seasonal habitat switching may be more prevalent than is currently recognized in seasonal environments