Skeletonderdelen van zeevogels (4): Schedels

A find in December 2010 of a Jersey banded Atlantic Great Cormorant Phalacrocorax carbo carbo near Dordrecht, the Netherlands triggered the interest in the occurrence of this subspecies in the Netherlands. The bird was preserved as a study skin and is kept in the Natural History Museum Rotterdam. Along the way, two previously unrecorded specimens were found in the museum collection. All three birds are described in detail in this article. To date, 38 records of Atlantic Great Cormorants concerning 42 individuals are accepted in 1800-2008 by the Dutch rarities Committee (after 2008 the subspecies is no longer considered). Until 2000 most records concern ring recoveries and museum specimens. From 2000 onwards, observations in the field become more frequent. Three records, two of which are being described here, are still under consideration. In contrast, the Continental Great Cormorant, which breeds in trees near fresh water lakes and rivers, is a common breeding bird in the Netherlands. In 2008 the first case of breeding Atlantic Great Cormorant in the Netherlands was recorded near Neeltje Jans (Zeeland). It involved one individual presumably paired with a continental bird. In 2009 the same colony contained at least two Atlantic pairs and a possible mixed pair, while a confirmed and a possible mixed pair where discovered in a tree based colony at Lauwersmeer (Friesland). No Atlantic birds where found breeding in the colony at Lauwersmeer the following years. The colony near Neeltje Jans contained five Atlantic pairs in 2010 and six in 2011. The possibility that Atlantic Great Cormorants have been overlooked due to little attention paid by observers and poor knowledge of distinction between both subspecies in the field, is discussed.