The smallest dabbling duck in North America. This male is probably a late hatching individual still showing juvenile remnants across its upper sides. Most males are in full bright plumage by November. The North American race A. c. carolinensis is replaced in Eurasia by nominate A. c. crecca which lacks the white vertical stripe, but has instead a white horizontal scapular stripe. Eurasian subspecies is treated as a separate species "Eurasian Teal" by IOC, but not by Clements, H&M4 or HBW. Genetically, the two show highly divergent mtDNA haplotypes between U.S. and Russia. One shared haplotype suggests limited hybridization. Digiscoped with Panasonic DMC-LX5 | Nikon FieldScope III | 30XWA | hand-held (no adapter).
References:
Carboneras, C., Christie, D.A. & Kirwan, G.M. (2018). Common Teal (Anas crecca). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/52868 on 5 December 2018).
Christidis et al. 2018. The Howard and Moore Complete Checklist of the Birds of the World, version 4.1 (Downloadable checklist). Accessed from https://www.howardandmoore.org.
Clements, J. F., T. S. Schulenberg, M. J. Iliff, D. Roberson, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2018. The eBird/Clements checklist of birds of the world: v2018. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/
Gill, F & D Donsker (Eds). 2018. IOC World Bird List (v8.2). doi : 10.14344/IOC.ML.8.2. Available at http://www.worldbirdnames.org/
Johnson, K. (1995). Green-winged Teal (Anas crecca), version 2.0. In The Birds of North America (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.193