OTTENBURGHS J (2017) Observations on hybrid geese in The Netherlands from 2005 to 2016. LIMOSA 90 (4): 167-174.

Hybrids, crosses between different species, are common in birds. Especially the Anseriformes (ducks, geese and swans) display high levels of hybridization. Worldwide, between the 17 species of geese, no less than 74 hybrid combinations have been reported. In this study, I explored the incidence of hybrid geese in the Netherlands based on sighting data between 2005 and 2016 as documented on waarneming.nl (Tab. 1). During this period, there was a steady increase in the number of observations of hybrid geese, which can be attributed to the improved identification and documentation of these hybrids (Fig.1). After correcting for the seasonal occurrence of geese, the data were analysed statistically to gain more insight into the incidence and distribution of hybrid geese in the Netherlands. The most commonly observed hybrid was Barnacle Goose x Cackling/Canada Goose (Branta leucopsis x Branta hutchinsii/canadensis), which was present throughout the year and mainly breeds in the province of Noord-Holland (Fig. 2). Another common hybrid was Greylag Goose x Greater Canada Goose (Anser anser x B. canadensis). This cross was also seen throughout the year and mostly resides in the proximity of big cities (Fig. 3). Hybrids between wild goose species (e.g., Greater White-fronted Goose A. albifrons or Tundra Bean Goose A. serrirostris) were being reported more frequently in winter, when these species migrate to the Netherlands (Fig. 4). Hybrids between non-native species (e.g., Bar-headed Goose A. indicus or Emperor Goose A. canagicus), on the other hand, were observed every month with a peak at the end of the summer (Fig. 5). This overview provides an important starting point for further studies into the incidence and distribution of hybrid geese in the Netherlands.

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