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REPRODUCTION IN BIRDS

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Question 3

The linnet is a species of finch found in Europe. It builds its nest in small bushes. The table below shows the number of linnet nests with eggs found by scientists during one year.

 Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Number of nests found with eggs 0 0 0 2 41 54 31 5 0 0 0 0

 1. Make a histogram from these results. 2. The linnet usually lays 5 eggs in a clutch during the month of June but only 4 eggs in the month of August. How can you explain this difference? 3. Read the following information and answer the questions which follow it: "On average a hen linnet lays 4 eggs in a clutch, one egg per day. She will start to incubate the eggs once the last one has been laid. She does this so that all the embryos inside the four eggs develop at the same time and all the eggs will hatch at the same time. The eggs are incubated for 12 days. Once they hatch, the chicks stay in the nest for 12 days before they learn to fly. When the chicks have just left the nest they are still fed by their parents for another 21 days. As their feathers grow longer and their wings become stronger they will finally become fully independent of their parents." (a) How long does it take the parents to raise their offspring? (From the laying of the first egg to the point where the young become fully independent.) (b) The breeding season for linnets is from April to August. If a pair of linnets begin to breed at the beginning of April, how many sets of chicks (broods) could they rear by the end of August? 4. A linnet nestling will usually leave the nest 12 days after hatching. If the nest is disturbed, however, the chicks will leave the nest as early as 9 days old. If the chicks leave the nest earlier they will be smaller and weaker. Can you explain why it is necessary for scientists and photographers to have a special permit to study birds whilst they are nesting?

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