Published in support of the UK Biodiversity Action Plan for black grouse

Ecology

Food

Adults
The diet of adult black grouse varies between seasons, so they need a range of food plants within their habitat. Vital plants include bilberry and heather, which are eaten throughout the year, the latter particularly important in winter. The wide range of foods taken by adults is detailed in the table below.

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Annual diet of black grouse

There are also some regional differences in food preference across the UK. This may be due to recent adaptation as the birds are forced to survive on what is locally available. The table below outlines some of the differences.

Northern England Habitat Food
Spring blanket bog and in-bye land cotton grass flower buds, clover, buttercups, sorrel, marsh marigold and other herbs
Summer rough grassland, wet flushes Juncus seeds, seeds and flowers from grasses and herbs (adults). Invertebrates, especially sawfly larvae (young)
Autumn/Winter heather moor, rough grassland, in-bye land Ling heather, berries from shrubs
Scotland Habitat Food
Spring pine/birch woodland and heather moorland birch, larch shoots, bilberry, cotton grass
Summer wet flushes and heather often in woodland birch, bilberry (adults), invertebrates (young)
Autumn/Winter heather and birch woodland bilberry, crowberry, berries from shrubs such as rowan and hawthorn, birch, heather
Wales Habitat Food
Spring conifer woodland, bogs, heather moor bilberry, conifer buds, heather and cotton grass shoots
Summer wet sedge or rush flushes, usually on open moor bilberry, heather shoots, sedge (adults), invertebrates (young)
Autumn/Winter Woodland and moorland winter berries from shrubs such as rowan and hawthorn, bilberry, heather

Regional differences in typical diet of black grouse in the UK

Chicks
Chicks are largely dependent on invertebrates during their first two to three weeks. Moth caterpillars and sawfly larvae are particularly important, often forming the bulk of the diet. The hatching date of eggs may be timed to coincide with their peak abundance. Chicks also eat grasshoppers, beetles, spiders, ants and flies. As with the adults, there are regional differences influenced by what is available. Certain plants host a particularly high abundance of these invertebrates, and broods are often found in wet or damp habitats with relatively tall ground vegetation, such as grasses, rushes or bog myrtle, which provides cover from predators and a rich source of invertebrates. Moorland or field vegetation with plenty of bilberry is also important brood rearing habitat as this can include a great abundance of the insects that black grouse chicks prefer.

As the chicks mature, vegetation becomes more important in their diet, and by the age of three weeks they start to eat mostly high-protein plant material on which they will feed for the rest of their lives.

Recent research by Ludwig et al 2006 has shown that chicks are suffering higher mortality because of climate change. Using long-term data from Finland, the study showed that black grouse have responded to earlier spring warming by advancing both their egg-laying and their hatching times. However, early summer (when the chicks hatch) had not advanced and the chicks faced colder post-hatching conditions, which the study showed is a critical factor in survival rates.

More on black grouse ecology...
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