Birds occur frequently and for a variety reasons in visual art, as symbols, decoration or objects of study. The symbolism of birds differs in different period and regions. For the Egyptians a bird symbolized the soul. Birds are often encountered in 17th-century Dutch genre scenes, in which they usually have a sexual connotation because the Dutch word ‘vogelen’ (birding) means to engage in sex. In medieval books of hours, birds had a purely ornamental function and were incorporated as faithfully as possible in the decorative borders. From the beginning of the 16th century birds became the subject of scientific study. Voyages of discovery fuelled interest in unknown, exotic species, which was reflected in the first illustrated encyclopedias.