Yellowhammer

The yellowhammer (Emberiza citrinella) is a chunky bunting of farmland and other open countryside across most of Europe and into western and central Asia. Adults are about 15.5–17 cm long and weigh around 26 g. Breeding males are unmistakable, with a bright yellow head and underparts, dark-streaked brown back and rich chestnut rump. Females and juveniles are more heavily streaked and much less yellow.

The male’s simple, far-carrying song is one of the characteristic sounds of European farmland and is often rendered in English as “a little bit of bread and no cheese”. Males typically sing from exposed hedges, bushes, wires or other elevated perches.

Yellowhammers favour open agricultural and semi-natural landscapes broken up by hedges, scrub, field margins, ditches and woodland edges. This mosaic is important because the birds usually feed in open ground but need dense low vegetation for nesting, shelter and song perches.

Studies on lowland farmland in England and Wales have shown that different parts of the landscape are valuable at different times of year. Hedgerows and field margins provide breeding cover, while stubbles, unsown patches and other seed-rich areas become especially important during winter. Intensification that removes this small-scale variety can therefore reduce both nesting opportunities and food.

Seeds and grain dominate the diet outside the breeding season, including cereal grain and seeds from weeds and other wild plants. Yellowhammers usually feed on the ground and often gather in winter flocks where food is concentrated.

During breeding, insects and other small invertebrates become much more important because the chicks require protein-rich food for rapid growth. Adults therefore need breeding territories that combine safe nesting cover with nearby places where invertebrates remain abundant and accessible.

The species is resident or only partly migratory across much of its range. Birds from colder northern and eastern populations are more likely to move south or west in autumn, while many birds in milder regions remain close to their breeding areas.

Winter movements are also strongly influenced by local food availability. Flocks may shift repeatedly among farms, field margins, feeding sites and other places where grain or weed seeds remain accessible.

Breeding begins in spring and may continue well into summer. Pairs are generally monogamous during the breeding season. The female builds a cup-shaped nest on or close to the ground, usually concealed in grass, a hedge base, scrub or other dense vegetation. A typical clutch contains 3–5 eggs.

The female incubates for about 12–14 days. The chicks are altricial, hatching poorly developed and dependent on their parents, and normally leave the nest after roughly two weeks. Both parents feed them, and invertebrate prey is especially important during this stage. Pairs can raise two, and occasionally three, broods in a season.

Yellowhammers are only occasional hosts of the common cuckoo (Cuculus canorus). An experiment in the Czech Republic found that they rejected conspicuously non-mimetic foreign eggs in 92% of trials, suggesting that strong egg discrimination may help explain why cuckoo parasitism is uncommon in the species.

Yellowhammers were introduced from Britain to New Zealand during the 19th century and are now common and widespread in open country across much of the country, including several offshore islands. The clearance of native forest and expansion of farmland created large areas of suitable habitat and helped the species spread.

Its ecological impact appears to be limited. Yellowhammers feed mainly on grass seeds, grain and small invertebrates in open, often heavily modified landscapes, and they do not appear to be important competitors with native New Zealand species. Their most noticeable impact has instead been economic: they were once considered serious agricultural pests because large flocks ate newly sown grass seed and grain, and they can still cause local losses where seed is freshly sown.

The yellowhammer is classified as least concern on the IUCN Red List. It remains widespread across Europe and western Asia, although the global population trend is decreasing.

Long-term declines have been particularly marked in intensively farmed parts of Europe. Studies in British farmland have linked these declines to changes that reduce winter seed supplies, nesting cover and invertebrate-rich feeding habitat, showing how a species can remain globally common while becoming much scarcer within large parts of its former farmland range.