Egyptian Geese

Here is the explanation for these unusual birds from Wikipedia: Egyptian goose.

The Egyptian goose (Alopochen aegyptiaca) is a member of the duck, goose, and swan family Anatidae. It is native to Africa south of the Sahara and the Nile Valley.
Egyptian geese were considered sacred by the Ancient Egyptians, and appeared in much of their artwork. Because of their popularity chiefly as an ornamental bird, escapees are common and feral populations have become established in Western Europe. The Egyptian goose has escaped or been deliberately released in to Florida, USA. However Egyptian geese are also now present in many parts of Central and Southeastern Texas with more than 100 sightings just in 1Q 2018 as reported in ebird.org database.

These particular Egyptian geese were spotted in a park in Amsterdam, the Netherlands.