Runge, C. A., J. E. M. Watson, S. H. M. Butchart, J. O. Hanson, H. P. Possingham, and R. A. Fuller. 2015 . Protected Areas and the Global Conservation of Migratory Birds. Science 350: 1255-1258.
Just 9% of 1451 migratory birds are adequately covered by protected areas across all stages of their annual cycle, in comparison with 45% of nonmigratory birds. Read the full paper published in Science.