What diet do adult Yellowhammers switch to for provisioning chicks?

Insects, spiders, and other soft-bodied invertebrates

The Yellowhammer exhibits a significant dietary shift corresponding to the demands of the breeding cycle. While the adults rely heavily on seeds, such as wheat, barley, and oats, during the late autumn, winter, and early spring to meet their own energy needs, this changes drastically when they raise young. During chick-rearing, the nutritional requirement shifts dramatically to high-protein sources necessary for rapid growth. Therefore, adult Yellowhammers provision their nestlings almost exclusively with insects, spiders, and other soft-bodied invertebrates. The availability of suitable insect biomass, often found in less intensely managed field margins or weedy corners, becomes the critical factor limiting reproductive success, even if adult seed supplies are plentiful.