this may have already been suggested, but just in case...
maybe some seasons on niche islands?
forest/meadow islands : maybe the four seasons? winter has maybe one snow or two, but not cold enough to hurt or freeze nichelings who prefer heat. maybe shortage of food. spring could have more rain and a surplus of food. summer could maybe be a drier, hotter season with food surplus, and fall could be a season with average food but also the common cold. maybe each season