(Very) scarce species and the more regular vagrants are much more interesting than mega rarities. Why? Because patterns become visible. On this page I analyse these patterns. When's best time to see one? Where are the hotspots? How did their numbers develop over time? An analyses of Dutch records probably reflect the patterns for much of NW Europe. 

Dutch Birds


lesser golden plovers in the Netherlands (2017) These two closely related species have been recorded year-round, but yet the timing of both species is different. While Pacific is less rare in Holland, the opposite is true for the UK (2017)

Iberian Chiffchaff in the Netherlands (2017) A typical spring vagrant, that often stays for weeks on end. But this pattern might change now birds are also identified on call instead of on song only. Analyses of all records between 1967 and 2017.

Hume's Warbler in the Netherlands (2017) The peak season is not necessarily the best time to twitch one! And what are the best places? An analyses of this increasing vagrant of all Dutch records till 2016. 

Greenish Warbler in the Netherlands (2017) This species has increased, though there are still meagre years. There are two seasons to find one. And there's even a breeding record! Analyses of all Dutch records till 2017.

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Dusky Warbler in the Netherlands (2021) An analyses of all Dutch records till early 2021, with a focus on the unprecedented autumn 2020 influx .

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Blyth's Reed Warbler: the 2020 influx (with Diederik Kok) (2020)

The unprecedented influx of Blyth's Reed Warblers in spring 2020 in the Netherlands and Europe analysed. 

Aquatic Warbler migration (with Albert de Jong and Erik van Winden) (2018, 2020) The past and present migration of Aquatic Warblers in the Netherlands: has the autumn migration shifted?