Insect shortage leaves sparrows starving

Last modified: 20 November 2008

One of Britain's best-known birds may be declining because its chicks have too little to eat.

Too few insects in summer means young house sparrows in towns and cities are starving in their nests especially when parent birds are trying to raise important second and third broods.

Increased development, the popularity of ornamental plants like Leylandii, the removal of trees and the conversion of front gardens for parking may explain the loss of insects in urban areas, new research suggests.

The study, by scientists from the RSPB, De Montfort University and Natural England, is the first to investigate the 20-year decline of house sparrows in suburbia.

'Where there were few insects, young house sparrows were likely to die'

Lead author, the RSPB's Dr Will Peach, said: 'Each pair of house sparrows must rear at least five chicks every year to stop their numbers falling. But in our study, too many chicks were starving in their nests.

'Others were fledging but were too weak to live for much longer than that. If the birds nested in areas rich in insects, they did much better. Where there were few insects, young house sparrows were likely to die. Young house sparrows need insects rather than seeds, peanuts or bread to survive.'

House sparrows have declined in Britain by 68 per cent since 1977. Numbers started falling in towns and cities in the mid-1980s and the species has now vanished from central London.

House sparrows are also disappearing from Bristol, Edinburgh and Dublin, and Hamburg, Prague and Moscow but curiously, they are faring better in Paris and Berlin.

The new research, published this month in the journal Animal Conservation, studied house sparrows in Leicester and surrounding villages.

The birds declined by 28 per cent during the three-year study. Most chicks failing to survive died within four days of hatching.

'Mysterious and complex'

Co-author of the study, Dr Kate Vincent, then of De Montfort University in Leicester, said: 'This is one of the most mysterious and complex declines of a species in recent years. The study highlights that sparrow chicks are hatching but they aren't surviving.

'This is partly down to the loss of green spaces within British cities through development on green space, tree removal and the conversion of front gardens for parking. The loss of deciduous greenery within urban areas may have made life much more difficult for birds like house sparrows that need large numbers of insects to feed their young.'

Phil Grice, Senior Ornithologist at Natural England, said: 'This study highlights the importance of using native varieties of plants in our urban green spaces which, in turn, support large numbers of insects that are important in the diet of house sparrows and a range of other birds that we love to see in our gardens'.

Make Homes for Wildlife

The RSPB has launched a new scheme, Homes for Wildlife, to give free, tailored advice on wildlife-friendly gardening. Options include patches of wildflowers or long grass in summer, native shrubs and a small pond, all of which would harbour many insects.

Dr Peach said: 'Peanuts and seeds are great for birds for most of the year but sparrows need insects in summer, and lots of them, to feed their hungry young.

'Honeysuckle, wild roses, hawthorn or fruit trees are perfect for insects and therefore house sparrows. The trend towards paving of front gardens and laying decking in the back, and the popularity of ornamental plants from other parts of the world, has made many gardens no-go areas for once common British birds. Many of the things we can do to help just mean being lazy, doing nothing and allowing the garden to be a little bit scruffy.'

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