Albert Vliegenthart (The Netherlands, 1975) works at 'de Vlinderstichting' - the Dutch butterfly conservancy and is specialized in butterflies and dragonflies, next to being a keen birdwatcher. Albert has contributed to many books on butterflies, including 12 Crossbill Guides. Bouke ten Cate (The Netherlands, 1985) practically grew up in the field and is out and about whenever he can. Bouke is an all-round naturalist with special interest in birds, reptiles, amphibians and mammals, but he is above all a keen naturalist. Bouke is co-author of the Crossbill Guide to North-east Poland. This is his second guidebook. Dirk Hilbers (The Netherlands, 1976), biologist, is the founder of the Crossbill Guides Foundation and travels Europe to write Crossbill Guides about the continent's most beautiful natural areas. When not in the field, Dirk Hilbers works as a lecturer in the field of science communication and environmental ethics. Kees Woutersen (The Netherlands, 1956) lives in Huesca and works as a nature guide in Spain. He runs his own nature travel company (Aragon Natuurreizen) and is the author of several books on birds and natural history of the Pyrenees. Apart from the current guidebook, Kees is the co-author of 4 Crossbill Guides: The Spanish Pyrenees, Canary Islands 1 - Lanzarote and Fuerteventura, Canary Islands 2 - Tenerife and La Gomera and South Portugal (forthcoming).