Complex sentence: The common redpoll is smaller, browner and more streaked than Arctic; there are two distinct populations (one lighter, one darker) united in islandica ", the relationships of which are unresolved Seutin" et al.
Split into simpler sentences: The common redpoll is smaller, browner and more streaked than the Arctic redpoll. There are two distinct populations (one lighter, one darker) united in islandica ", the relationships of which are unresolved Seutin" et al.