Could the left-hand bird in the pic be an offspring of the right-hand bird ?
There are apparently several birds like this in the Greylag Goose group to which the wannabe-Taiga associates, which are often visible next to it on pictures. These birds look superficially like Greylags owing to their relatively large size, pale head and largely orange bill -- but are certainly not merely "variatie binnen Grauwe". They differ from standard Greylags in having a black (not pale) nail to the bill, yellow-orange (not pink) legs, more extensive black in the tail, a dark blackish-brown (not grey) rump, and darker wings (the grey parts in the upperwing are less contrastingly pale, the underwing looks dark).
Four such birds can be seen flying in the second pic at https://old.waarnemingen.be/waarneming/view/261058336; see also, e.g., the last pic at https://old.waarnemingen.be/waarneming/view/261078961.
(For more pictures, see https://old.waarnemingen.be/soort/photos/338?from=2022-12-15&to=2022-12-25.)