Sav raises some interesting issues.
Northern Shoveler is monotypic – there are no recognised sub-species/races.
It breeds across most of the Palearctic and Nearctic except the high arctic – mostly between 40-60 degrees N, and most winter between 20-40 degrees North.
It is a regular non-breeding season visitor to Hawaii. http://hbs.bishopmuseum.org/birds/rlp-m ... e/NSHO.pdf
However a review noted the need for research to increase ‘understanding of movements of individuals that overfly the Hawaiian Islands’. I have been unable to track down any banding recoveries of birds from the Pacific.
Non-breeding birds regularly occur as far south as the Caribbean and Central America.
There is one record from Peru (11 degrees South) https://boletinunop.weebly.com/uploads/ ... p_vol._7_n
and one record from Argentina at 48 degrees South: https://drive.google.com/file/d/0B2uWlR ... pVSzQ/view
[Lake Ellesmere is 43 degrees South]. It was considered possible that the latter bird might be an escape as there is a captive population in Chile, it was concluded that it was probably a wild individual.
If any hunter bags one in New Zealand it would be very good to get the specimen to a museum and to consider the possibility of looking at stable isotopes to try to determine its geographic origin.