WINDEN J VAN DER & DIRKSEN S (2005) The Red-crested Pochard Netta rufina in the Netherlands: introduced or native?. LIMOSA 78 (4): 139-144.

The Red-crested Pochard is one of very few bird species with an ambiguous status in The Netherlands: it was at the same time on the Dutch Red List (1986, 1994) of characteristic and threatened bird species, and listed in an overview of introduced species. The reasons for doubting its wild origin are statements in some publications about birds in captivity in the major breeding areas. This contradictory status is not only of biological interest but also of conservation concern. Legislation for some introduced species differs considerably from native species. For this reason the origin of the Dutch Red-crested Pochard population was investigated. Based on our research, the Redcrested Pochard should be considered a native bird species.
      Since the mid 19th century, Red-crested Pochards have been documented in The Netherlands, and numbers have increased from 1940 onwards, like in adjacent countries. In the period 1950-1970, post-breeding peak numbers of 1600 individuals were counted near Flevoland, which certainly originate from adjacent European populations. Also the breeding population is predominantly wild for the following reasons: (1) At its start the Dutch subpopulation originates from wild birds. For many years captive birds are known from its breeding area and this has mislead ornithologists. An interview with an old farmer/hunter in the area revealed that during the Second World War, eggs of wild Red-crested Pochards were taken from their nests and used to raise captive birds. Sometimes eggs of Mallard Anas platyrhynchos were placed in the Red-crested Pochard nests for unclear reasons. (2) Although not confirmed, occurrence of the species during the breeding season (March-July) since 1849 makes it likely it was even breeding before 1900. (3) Red-crested Pochards only colonise suitable areas meeting habitat criteria such as clear water with abundant stoneworts (Characeae). (4) The Dutch breeding population behaves like a wild population with separate breeding, moulting and wintering areas. In recent years, the population has increased in response to improving water quality and expanding stonewort vegetations.
      These findings give enough evidence to be sure of a wild origin of Red-crested Pochard in The Netherlands. With a native population present, the fact that some birds will have escaped from captivity in recent years cannot be an argument to give a species the status of an introduced bird. Red-crested Pochard Netta rufina

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