FARMING RESEARCH - YELLOWHAMMERS | Margins for yellowhammers
The decline in yellowhammers has been linked to the intensification of agricultural practices, but Niamh McHugh has been looking at habitats farmers can implement to reverse the decline
he decline in breeding yellowhammers (Emberiza citrinella) on our farmland since the 1970s has often been linked to the intensification of agricultural practices. The introduction of agri- environment schemes (AES) across Europe was intended to address many of the issues facing declining farmland bird species – not just the yellowhammer, but other passerines including tree sparrows and corn buntings. By incentivising farmers to increase the availability and improve the suitability of nesting and foraging habitats, these schemes should provide most resources needed by farmland birds. We wanted to study just how appealing the different habitats were to this particular species.
T
We assessed the territory selection of yellowhammers on 18 farms in southern England over a two-year period. During the study we observed that yellowhammers were more likely to locate territories in areas containing enhanced margins; ie. where arable field margin habitats were sown with wild flowers and/or agricultural legumes. Yellowhammer territories had, on average, 65% more of this ‘enhanced margin’ habitat present within 100 metres, than random points. Since yellowhammer chicks are dependent on insects for the first weeks of life, we investigated whether chick-food abundance might relate to this habitat preference. We found that enhanced margins contained on average 46% more invertebrate food items than cereal crops and 37% more than floral crops. Chick-food abundance was similar between grass and enhanced field margins, but yellowhammers did not show a preference for the former. An alternative explanation for this preference may be that the habitats sward structure increases prey accessibility and improves predator avoidance. Enhanced margins may provide further benefits to yellowhammers if they are able to provide chick-food invertebrates over longer periods of time than grass margins. This is likely, as these habitats are sown with a diverse mixture of plants which should extend plant flowering times through the birds’ breeding season.
46%
more invertebrate food items were
found in enhanced margins than cereal crops
It was also observed that yellowhammers chose territories containing early succession hedgerows, as these constitute the most suitable nesting sites, and a suitable songpost. Male yellowhammers often perch and sing from elevated songposts during the breeding season when attracting a mate.
Our results suggest that management strategies aiming to conserve breeding yellowhammers should focus on increasing the coverage of invertebrate-rich AES habitats such as wildflower margins and pollen and nectar plots, and ensure that they are located within typical foraging ranges of hedgerows, which have been cut before the breeding season, that include elevated songposts.
Niamh McHugh is a postdoctoral ecologist in the Farmland Ecol- ogy team and is inter- ested in how lowland agricultural habitats can be enhanced to benefi t farmland wildlife.
Yellowhammers were more likely to locate territories in areas where field margins were sown with wild flowers and/or agricultural legumes. © Laurie Campbell
www.gwct.org.uk/research
GAMEWISE • SUMMER 2017 | 35
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