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Different foods for different bills

The differences in birds' bills, and how they use them to eat different foods, have played a very important part in understanding natural history.

In 1853, Darwin used the variations in the beaks of native finch species on the Galapagos islands as evidence for his theory of adaptation and natural selection. The study, now referred to as 'Darwin's Finches', showed that the differences in the finches' bills corresponded to differences in their preferred foods, lending support to Darwin's notions that all organisms are supremely adapted for the 'job' they do.

Curriculum Links

England and Wales - Life Processes and Living Things - (5) a (Single and Double). How the distribution and relative abundance of organisms in a habitat can be explained in terms of adaptation, competition and predation).
Northern Ireland (e) Variation in organisms has both a genetic and environmental basis.

Resources

Student Sheet 1 (click here), pens, pencils

Age range

14 - 16

The Activity

In this brief exercise, students consider the bills of six hedgerow and farmland bird species. From this, they decide what each species would eat. Students may use other clues, such as the birds' size, ability to fly, and leg length to help them make their decisions. They are then asked to make some generalisations about the food items for which different bills are adapted. The concept of a 'niche' is finally introduced. 

Extension Activities

As a homework activity, students could research Darwin and his theories of natural selection and adaptation, producing a short presentation or display of their findings. If undertaken by the whole class, a fairly comprehensive summary could be achieved. Alternatively, students could consider the 'niche concept' further by looking into other aspects of each birds' niche: nest site, foraging location (hedge bottom, grasses, top branches of hedge), time of feeding (all day, mornings, evenings). How are the birds adapted to use these aspects of their niche?

Teachers' Answers

Answers to Student Sheet 1

Small insects and their larvae, and a few spiders - Wren
Tree seeds, weeds and berries - Bullfinch
Flying insects such as craneflies, butterflies and wasps - Spotted flycatcher
Mainly seeds of grasses and weeds, but also snails and caterpillars - Partridge
Mainly rodents, and moles, but also small birds, beetles, moths, frogs, and sometimes bats and fish - Barn owl
Fruit stones and large seeds - Hawfinch

What type of food item do you think each 'beak type' is adapted for? Why?

Thin and delicate - catching and eating insects
Short, stout and stubby - cracking seeds and eating berries
Short and hooked - tearing flesh