1. Bird Migration Research Station Faculty of Biology University of Gdańsk Wita Stwosza 59 80‐308 Gdańsk Poland
2. Animal Demography Unit Department of Biological Sciences University of Cape Town Rondebosch 7701 South Africa
3. PO Box 1276 Middelburg, Mpumalanga 1050 South Africa
4. Department of Oral Pathology and Oral Biology School of Dentistry University of Pretoria PO Box 1266 Pretoria 0001 South Africa
5. Department of Statistical Sciences Centre for Statistics in Ecology, the Environment and Conservation University of Cape Town Rondebosch 7701 South Africa
6. PO Box 5067 Vanderbijlpark 1900 South Africa
7. 23 Roy Campbell St Vanderbijlpark 1911 South Africa
8. Students’ Ornithological Group Department of Vertebrate Zoology Institute of Biology University of Białystok Ciołkowskiego 1K 15‐245 Białystok Poland
9. A.P. Leventis Ornithological Research Institute University of Jos PO Box 13404, Laminga Jos East Plateau State 930106 Nigeria
10. Department of Inorganic Chemistry Faculty of Chemistry Dostoevsky Omsk State University Prospect Mira 55A 644077 Omsk Russia