Sentence:  Besides his life as a student, Han [Henri Jacob Victor Sody] continued to be interested in ornithology, particularly <WSD>oology</WSD>. Apparently, he was a diligent collector of birds' eggs, both in the vicinity of Wageningen, and on excursion for this purpose to other places (Breda, Texel, etc.), and compiled a catalogue of eggs collected by him in The Netherlands. 
Meaning of the word marked with <WSD> tags:  The hobby or practice of collecting birds' eggs, especially those of wild birds.