The fairy-wrens (genus Malurus) are an iconic model system in evolutionary ecology and one of the best-studied bird genera. A large-scale collaboration has resulted in detailed long-term data on 10 species from >20 populations from a single genus. This is an ideal system to investigate inter- and intraspecific variation in ecology and behaviour, without the problems encountered by many other systems where associations might be confounded by phylogeny. Using the long-term data we have shown that the use of large-scale oceanic climate indices often results in strong overestimation of the amount of climate sensitivity and spurious patterns as a result of geographic gradients. Furthermore, we have completed the world’s first comprehensive intrageneric test of many of the key ecological hypotheses concerning why individuals, populations and closely related species vary in their degree of promiscuity and tested the longstanding idea that conspicuous plumage increases predation risk. Several new projects are currently underway.