Leucistische meerkoet in een wijk in Kampen.
bij navraag bij Harvey van Diek is het waarschijnlijk progessive greying, het verliezen van pigment bij ouder worden. Harvey is mede auteur van het boek Zwarte merels Witte merels
Progressive greying
Arises after a bird reaches a certain age. It is
defined as the progressive loss of pigment cells
with age. From the onset of the condition, the
bird will gain an increasing number of white
feathers after every moult and in many birds the
entire plumage eventually becomes white. The
causes for progressive greying are still unknown
and it may or may not be heritable. Some forms
may be related solely to age while in others the
progressive loss of pigment cells may be due to
heritable disorders such as vitiligo – a pigment
disease – or related to habitat. Progressive
greying is the most common cause of white
feathers in birds.”
Uit Evolve issue 18 “Why aren’t all blackbirds black?” Hein van Grouw
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