The effect of supplementary winter seed food on breeding populations of farmland birds: evidence from two large‐scale experiments

Abstract

Summary1. Low winter food availability is probably critical in the declines of many farmland bird species in Europe, leading to the implementation of ameliorative agri-environment scheme options. To date, however, there has been no experimental test of the effectiveness of such options. 2. We report the results of two large-scale, 3-year, controlled experiments investigating the effects of supplementary winter seed provision on breeding farmland bird abundance. In each experiment, the use of winter feeding sites by birds was monitored and the availability of alternative, seed-rich habitat in the surrounding area was measured. The Winter Food for Birds (WFFB) project also included variable levels of food provision. Breeding bird abundance was then monitored in experimental and control areas. The Bird Aid project targeted yellowhammer Emberiza citrinella L., corn bunting Emberiza calandra L. and tree sparrow Passer montanus L., while WFFB considered 11 species that used supplementary winter food. 3. Comparisons of trends in breeding abundance between experimental and control areas revealed little evidence for positive effects of feeding, but there was great variation in the use of feeding sites by each species, and therefore in the seed quantity birds received. 4. Declines for yellowhammer, robin and dunnock were less steep where more food was provided in WFFB areas (a fourfold difference in seed provision across 1·5 times the land area). 5. Analysing trends with respect to weight-of-use of winter food revealed significant, positive relationships for yellowhammer (both projects) and up to five other species, depending on the control terms applied. Thus, positive effects of feeding on population change depend on the effective supply of seed to the species of interest. The hypothesis that winter food is currently limiting the populations concerned is also supported. 6. Synthesis and applications . Effective winter food provision to farmland bird populations has the potential to halt, and perhaps to reverse, declines in abundance. In practice, this means that agri-environment measures supplying significant quantities of winter food, such as stubbles preceded by low-input cereals, should succeed in changing population trends if they provide resources at the times of greatest need and if there is sufficient uptake.

Habitat characteristics and seed crops used by Blue ChaffinchesFringilla teydeain winter: implications for conservation management

“…Buckingham & Peach 2006, Siriwardena et al 2007. Recent experimental research has also shown that seed-eating birds alter their foraging behaviour in response to vegetation manipulation (Devereux et al 2006, Whittingham et al 2006a) and the perceived predation risk has been suggested as a key factor explaining why granivorous birds prefer areas with greater visibility for foraging and feeding on the ground.…”

Landscape‐scale responses of birds to agri‐environment management: a test of the English Environmental Stewardship scheme

“…However, while this may explain some of the inconsistent results within species or option categories, the number of significant effects and their consistency in direction indicate that the general patterns in the stubble and WBS results are likely to be robust. Previous research has concluded that a shortage of winter seed drove the population declines of most granivorous farmland birds and it probably also prevents recoveries (Gillings et al 2005;Siriwardena et al 2000Siriwardena et al , 2007. Davey et al (2010) found few clear population benefits of ES overwinter food options for granivorous species, but with multiple years per survey square, a longer survey period and more powerful analyses, we found significant positive associations between population growth rates and stubble management for threequarters of the granivorous species tested, for one or more of three spatial scales and landscape types.…”

Habitat type, food resources, noise and light pollution explain the species composition, abundance and stability of a winter bird assemblage in an urban environment

“…The consumption of anthropogenic food is particularly important in winter, when natural sources of food are unavailable, vegetation growth having ceased and there being no insects (Moorcroft et al 2002). One of the basic sources of food in urban areas are bird-feeders, where a large number of species wintering in a town or city find their food (Siriwardena et al 2007;Jokimäki and Kaisanlahti-Jokimäki 2012); a high density of birdfeeders increases the chances of a larger number of species in an assemblage (Tryjanowski et al 2015b). However, apart from the deliberate feeding of birds at bird-feeders, the food parameter that we analysed included other sources of nourishment, such as fruit on garden trees, food laid out for domestic and other animals associated with humans and rubbish bins, all of which can provide significant sources of food during the winter (Kwit et al 2004;Bellebaum 2005).…”