Bird of Prey Migration may be Affected by Climate Change

Scientific paper by GONHS reveals changes in migration trends.

A paper entitled ‘Trends in abundance of migrating raptors at Gibraltar in spring' was recently published in a high-profile Dutch ornithological journal, Ardea. 

Authored by Drs. Keith Bensusan, Ernest Garcia and John Cortes of the GONHS (Gibraltar Ornithological & Natural History Society), the paper examines trends in numbers of a range of species recorded at Gibraltar from the early 1970s to the mid 2000s.  Species studied were the Honey-buzzard, Black Kite, Egyptian Vulture, Griffon Vulture, Montagu's Harrier, Marsh Harrier, Eurasian Sparrowhawk, Common Buzzard, Booted Eagle and Short-toed Eagle.  Of these, Black Kites, Eurasian Sparrowhawks and Booted Eagles were found to have increased on passage across the Strait, whereas Honey-buzzards and Common Buzzards have decreased.

All other species were found to have remained stable.  Eurasian Sparrowhawks suffered severely from the use of organochlorine pesticides from the 1950s to the 1970s and have shown a recovery in Europe since these pesticides were banned.  The trend detected at Gibraltar reflects this. 

The decline in Honey-buzzards could reflect slight declines in parts of the species' range.  However, other factors may be involved.  Larger numbers of Honey-buzzards have been recorded crossing at the Strait of Messina between the Italian mainland and Sicily, and it may be that Honey-buzzards are shifting their route to Europe from Africa.  The decline in Common Buzzards is most surprising as the species increased in many European countries during the late 20^th Century.  These results suggest that many Common Buzzards are no longer flying as far south for the winter, quite possibly as a result of climate change.