The relationship between yellowhammer breeding performance, arthropod abundance and insecticide applications on arable farmland

Abstract

Summary1. The UK population of yellowhammers has declined since the mid-1980s. Concurrent increases in the use of pesticides are believed to have reduced the availability of food resources for farmland birds, including yellowhammers. To mitigate the consequences of insecticide applications on yellowhammer productivity, the relationships between insecticide application, arthropod food abundance and breeding success require quantification. 2. We studied nesting yellowhammers on a lowland arable farm in North Yorkshire between 2001 and 2003, to examine the effects of food abundance on breeding success and the effects of insecticide on food abundance. Arthropod abundances around individual nests were sampled and the timing and location of insecticide applications were recorded. 3. Nestling condition and mass on day 6 after hatching were positively correlated with the abundance of arthropods important in the diet of nestling yellowhammers. Greater mean body mass and condition corresponded with a lower incidence of brood reduction. 4. The abundance of arthropods important in the diet of nestling yellowhammers increased between mid-May and the end of July. However, arthropod samples collected within 20 days of an insecticide application did not show this seasonal increase in abundance and were depressed at levels likely to affect yellowhammer breeding performance adversely. 5. Synthesis and applications . We have demonstrated how insecticide applications can depress yellowhammer breeding productivity. We provide the requisite data for a framework that enables predictions to be made about the probable population effects of particular pesticide products. If the risk of indirect effects can be predicted accurately then appropriate mitigation and compensation measures could be incorporated into pesticide regulatory procedures and/or agri-environment schemes.

Provisioning with cereal grain depresses the body condition of insectivorous YellowhammerEmberiza citrinellanestlings

“…The present data are the first results to demonstrate a link between provisioning with cereal grain and reduced Yellowhammer nestling body condition. Although cereal grain is plentiful and easily collected, the energy content of barley and wheat are both lower than that of invertebrates (Potts 1986, Hart et al 2006, as is the protein content of wheat (Potts 1986). The low protein content of grain is likely to be a limiting factor because nestlings require food that is rich in protein and specific amino acids, which may be lacking in plant food (Ricklefs 1983, Potts 1986.…”

“…Invertebrate availability can, however, be highly variable owing to factors such as habitat, season, weather and management practices (Bryant & Turner 1982, Hart et al 2006. In agricultural landscapes, for example, management intensification over recent decades has reduced the abundance and accessibility of invertebrate food, contributing to population declines in a range of bird species (Newton 2004).…”

“…which breed on farmland, and are of high conservation concern (Yellowhammers E. citrinella, Cirl Buntings E. cirlus, Reed Buntings E. schoeniclus, Corn Buntings E. calandra [Eaton et al 2009]), require protein-rich invertebrates for growth and development, the availability of which are a key determinant of fledging success (Morris et al 2005, Hart et al 2006. Parents of these species may supplement nestling diet with cereal grain from ripening crops (Evans et al 1997, Stoate et al 1998, Brickle & Harper 1999, Brickle & Peach 2004, despite grain having a lower protein and energy content than the equivalent weight of invertebrates (Potts 1986, Hart et al 2006. The effects of cereal grain on the body condition of nestlings of these species are unknown.…”

Effects of breeding habitat and field margins on the reproductive performance of Skylarks (Alauda arvensis) on intensive farmland

“…Yet, the relationship between food availability and nestling condition or survival is not consistently positive, perhaps because factors like accessibility, prey profitability and nutrient composition are not always accounted for. Although some studies found improved nestling weight and survival when food availability around the nest was higher, for example for Yellowhammer Emberiza citrinella (Hart et al 2006), Linnet Carduelis cannabina (Bradbury et al 2003) and Corn Bunting Miliaria calandra (Brickle et al 2000;Boatman et al 2004), other studies could not detect such correlations for Chaffinch Fringilla coelebs (Bradbury et al 2003), Yellowhammer (Bradbury et al 2003) and Yellow Wagtail Motacilla flava (Gilroy et al 2009). For Skylarks, there are indications that nestling condition is significantly affected by the abundance of chick food within 100 m of the nest (Boatman et al 2004).…”

Breeding Barn Swallows Hirundo rustica on organic and conventional arable farms in the Netherlands

“…A reduction in food availability during the breeding season can reduce the breeding success (e.g. Hart et al 2006). Secondly, especially in arable areas, farm specialisation may be a major cause of Barn Swallow population declines (Evans and Robinson 2004).…”