A few months ago my wife rescued a bedraggled zebra finch from a shopping centre carpark, and we've been looking after him ever since. (They're not native birds - this was an escaped pet.)
Anyway, today my wife brought home a female finch, and within ten seconds of adding her to the cage the male was hauling grass stalks to the corner and building a nest. I mean, it happened literally that quickly. So fast, in fact, that he didn't actually stop to ask the new bird whether she was up for it.
Simon Haynes is the author of the Hal Spacejock and Hal Junior series (Amazon / Smashwords / other formats)