Greg H

Journal Exercise 2

Raymond Klaassen and Mikael Hake of Lund University performed a study of mortality in migrant birds.  It was published in the Journal of Animal Ecology in 2014 vol 83 pages 176-184 and titled “When and where does mortality occur in migratory birds? Direct evidence from long-term satellite tracking of raptors”.  Their study spanned over sixteen years of data collection.  To gather their data they affixed satellite transmitters; or banded 69 adult raptors, and found that mortality rate was six times greater during migration.  Most of these moralities were linked to particularly rigorous legs of their journey,  including the crossing of the Sahara desert in the Spring.   To determine the cause of the transmission loss several criteria were used, probable transmission failure, confirmed transmission failure, probable death, and confirmed death.  Using simple statistical analysis they calculated the survival rates by month as well as for breeding season, autumn migration, winter and spring migrations. The article does good work at showing its results in many different forms, including multiple types of charts and graphs, and even includes a map displaying the geographic distribution of the deaths.  While the study seems to point out an obvious conclusion of increased mortality during migration periods, it also sheds light on the  complexities of the death and migration of diurnal raptors. Their study found that the spring migration seemed to have a particularly strong effect on the annual survival rate of many of the diurnal raptors. This article was of particular interest to me because these researchers found a topic which many researchers simply glossed over, concluding that death was greatest during migration periods, but they delved into it and found interesting results.

http://0onlinelibrary.wiley.com.books.redlands.edu/doi/10.1111/1365-2656.12135/pdf