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The decline in British bird populations

Britain's farmland birds have suffered dramatic population declines in the last 20 years.

The skylark population has declined by 75% and the turtle dove by 85%, while the lapwing population has halved in only the last 10 years. The countryside is now very different from two or three decades ago.

These losses have been linked to a variety of causes. Farming has become more intensive and specialised, encouraged by government subsidies, new technologies and changes in consumer demand.

These changes in farming have led to an increased use of agrochemicals, the loss of hay and pasture fields, changes in crop sowing times, drainage and ploughing of grasslands, and the removal or neglect of hedgerows - all activities incompatible with a thriving wildlife population.

Curriculum Links

AEB Biology, Section 3.6 (human activity can impose far-reaching effects on the environment)

OCR Modular Biology, Central Concepts in Biology Module 4802, Section 3 (energy and ecosystems), Ecology and Conservation Module 4803, Section 5 (national conservation) 

NEAB Biology, Topic 2 (Continuity of Life)

Resources 

Student Sheet 1 (click here) , pens

Age range

16 - 18 

The activity

In this exercise, students analyse and interpret data produced by the British Trust for Ornithology/Joint Nature Conservancy Council (Common Bird Census of 1996) charting the percentage population declines for a wide range of British farmland birds. Students decide for themselves how certain agricultural practices may lead to declines in farmland bird populations. The significance of favourable habitats and intact food webs for the survival of birds is also touched upon. You may wish to set questions 1 and 2 (data analysis tasks) as independent class work, and answer questions 3 and 4 as a whole class exercise.

Extension activities 

As a follow-up, question 4 could be used as the title for an essay set as homework. The main points to be covered in the essay would have been covered in class.

Teachers' answers

1 Which bird species has suffered the greatest population decline, on farmland only? (1 mark) turtle dove, 85%

2 (i)If in 1972 the population size for turtle doves on farmland was 50,000, what would the population size be in 1996? (1 mark)7,500; (ii)If in 1972 the population size for dunnocks on farmland and woodland was 15,000, what would the population size be in 1996? (1 mark) 10,350

3 The skylark population decline on farmland (75%) is greater than that for all other habitats combined (60%). What does this tell us about the habitat preferred by skylarks, or the susceptibility of their population numbers to agricultural practices? (2 marks) The data indicate that skylark population declines have been most marked on farmland. If skylarks were predominantly birds which did not live on farmland, changes in farming methods would not affect them to such a great degree.

4 Briefly, how could the following agricultural practices lead to farmland bird population declines? (6 marks)
(iii) Removal of hedgerows/lack of hedgerow management - loss of habitat (nest sites, cover from predators, song posts, source of food eg berries, seeds, insects).
(iv) Use of insecticides - loss of invertebrate food source; indirectly toxic to birds.
(v) Use of herbicides - loss of plant food source, loss of invertebrate food source (invertebrates rely on the weeds for their survival; indirectly toxic to birds.