Has the number of birds wintering in the Maghreb decreased?. A test in the Gibraltar strait

Alejandro Onrubia -This paper explores the changes in the number of diurnal migratory birds crossing the Strait of Gibraltar between 1977 and 2008, to test whether the numbers of birds wintering in the Maghreb have decreased over the last 30 years. Results show that the most abundant species in 1977 were the most abundant ones in 2008. However, they also showed a decrease in the relative contribution of partial migrant species. A similar analysis of data from the Falsterbo Observatory (Sweden) did not reveal any decreasing contribution of partial migrants to the flux of migrant birds moving from northern Scandinavia.