The British cuckoo population has displayed a 71% decline within the
previous 25 years. This decline has been a mystery to many until
monitoring was recently taken place. Tracking devices were attached to
42 male cuckoo birds prior to their migration. This survey had
discovered that these birds have 2 migratory routes. One route goes from
Britain to the African continent via Spain and another where they
bypass Italy. Those who flew threw Italy ( a longer route) had a
significantly lower mortality rate upon their return to Britain/
Ireland. It was noted that the majority of deaths had occurred prior to
reaching the continent of Africa and so it is hypothesized the decline
is primarily yet another result of climate change.
Spain have suffered from severe droughts and fires meaning there will be
less water source. More time had been spent in breeding sites for those
bypassing Italy with it being expected to be because they're developing
a greater deal of pre migratory fattening. Due to this lack of
precipitation there is also a decrease in vegetation growth that makes
up most of the caterpillar/ moth's diet. This is significant as the
caterpillar and moths are the major food source for the cuckoo bird.
This lack of food source and water availability will then quite
obviously cause death especially during a harsh migratory route.
Spring migration is commonly associated with energy selected migration
and Spring migration is related to time selected migration. There are
currently issues on the timing of Spring migration due to the
incompatible breeding resources available where the hosts nests are
located where the cuckoo wishes to lay leading to an exploitative
interaction.
https://en.wikipedia.org/wiki/File:Cacomantis_flabelliformis.jpg
- Briggs, H., 2016. Cuckoo Decline Finally Mapped. [online] BBC News. Available at: <https://www.bbc.com/news/av/science-environment-36837641/cuckoo-decline-finally-mapped> [Accessed 11 July 2020].
- Hewson, C., Thorup, K., Pearce-Higgins, J. and Atkinson, P., 2016. Population decline is linked to migration route in the Common Cuckoo. Nature Communications, 7(1).
