Complex sentence: Dyar was independently wealthy and for a major part of his 31 years at the USNM he worked without compensation; his independence also made it possible for him to travel and collect extensively within North America.
Split into simpler sentences: Dyar was independently wealthy and for a major part of his 31 years at the USNM he worked without compensation. This also made it possible for him to travel and collect extensively within North America.