Typical ducks have wide flat bills:
Mergansers have long, serrated bills.
We saw several dozen Common Mergansers today in the Humber River at Lambton Woods.
Saw this on Facebook and thought it might be of interest to folks in your classes!
Then the golden hour
Will tick its last
And the flame will go down in the flower.
A briefer length of moon
Will mark the sea-line and the yellow dune. – Arna Bontemps (1902–73)