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Q40 - Route Choice and Season Explain Cuckoo Population Trends

Theoretical A Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Orientation & Navigation Ecology

The Island of Great Britain is a critical hub for migrating birds, from as far away as Canada and South Africa, due to its mild climate and well preserved habitats. Cuckoos (Cuculus canorus) are one migratory species which has seen its population decline in recent years. Therefore, many cuckoos had trackers attached to them, and were monitored over several years. Their Autumn migration routes are shown (1). A roughly equal number of birds took the Eastern and Western routes through Africa. Points at which tracked birds died are shown. The change in cuckoo populations in different regions of Great Britain, and the migration route which these populations take are shown (2).

Figure for Q40: Route Choice and Season Explain Cuckoo Population Trends

Using the information and data, determine which of the statements are true or which are false.

A. Conditions for birds migrating along the western route have changed in recent years.
B. Crossing the Sahara desert is the biggest challenge for migrating cuckoos.
C. Mortality rates during migration have an important impact on the population sizes of cuckoos in different parts of Britain.
D. These data would be consistent with Summer conditions within Britain, before migration begins, determining mortality rates during migration.
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Question reproduced from IBO 2017, Theoretical Exam A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Official answer key & worked solutions