Transfer of nitrogen by migratory birds in the African-Western Eurasian Flyways

• Published in: Animal migration 2020-10, Vol.7 (1), p.52-57
• Main Authors: Varriano, Sofia, Mallon, Julie M., Folta, Cody, Coulibaly, Hawa, Krajcir, Kevin J., McClung, Maureen R., Fagan, William F., Moran, Matthew D.
• Format: Article
• Language: English
• Subjects: African-Eurasian flyways; Bird migration; Bird mortality; Nitrogen cycle; Nonbreeding season
• ISSN: 2084-8838; 2084-8838
• DOI: 10.1515/ami-2020-0101

Migrating animals are known to play an important role in nutrient transfer over short distances; however, this phenomenon has not been well studied for long-distance migrants. In this preliminary study, we focused on nitrogen (N) transfer by 44 bird species that migrate from Eurasia to two regions in sub-Saharan Africa that fall into the lowest 10% quantile of global N-deposition (mean annual deposition ≤ 10.44 mg/m /year). We estimated the number of birds that die during the non-breeding season in these areas and then used N content and species-specific mass values to calculate annual N-deposition rates. For these two areas of low N-deposition, we found that bird mortality contributed 0.2 – 1.1% of total nitrogen deposition, which is a relatively small proportion. Therefore, we conclude that nitrogen transfer by long-distance bird migrants using the East Atlantic Flyway and the West Asian-East African Flyway currently has limited impact on the sub-Saharan nitrogen cycle. However, it is worth noting that this impact may have been more important in the past due to larger bird populations and lower background N-deposition (i.e., less anthropogenic impact).