Geographical distribution of Gadwall.    Breeding  Migration  Year-round  Nonbreeding
Gadwall (Mareca strepera), In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. retrieved from Neotropical Birds Online: https://neotropical.birds.cornell.edu/Species-Account/nb/species/gadwal
BirdLife International. 2016. Mareca strepera. The IUCN Red List of Threatened Species 2016: e.T22680149A86020572. https://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T22680149A86020572.en. Downloaded on 30 June 2018.
Cephas