A Basel court found the 45-year-old man, whose name was not given, guilty of aggravated theft and property damage between 2005 and 2012, and handed him a three-year prison sentence, the ATS news agency reported.
The court, which began hearing the case on Tuesday, also sentenced an accomplice to a 15-month suspended prison term.
The man would gain access to ornithology collections at various museums in countries including Switzerland, Germany and Austria, claiming he was doing scientific research, according to ATS.
He would then pluck feathers off exotic and valuable birds, stealing what were described as "very rare and precious objects, of inestimable scientific value".
His victims included red kites and buzzards, a variety of eagle and the endangered Usambara eagle owl of Tanzania.
The man was charged with the theft of feathers from 127 different species over more than seven years.
According to state prosecutors, the stolen feathers were worth a combined 427,000 Swiss francs ($443,000, 390,000 euros), while the various museums suffered an estimated six million Swiss francs ($6 million, 5.4 million euros) in damages.
Ever since the man's collection of some 10,500 feathers was seized in 2012, he has been undergoing psychotherapy to try to understand what led him to commit the thefts, ATS said.