•We describe two strategies of opportunism: rich patch exploiter and obligate.•Obligate opportunists (OBO) breed in response to unpredictable and rare resource pulses.•Rich patch exploiters (RPE) are highly mobile and move between resource patches.•RPE are predicted to invest more heavily in survival (e.g. HPA sensitivity in crossbills).•OBO are predicted to maintain reproductive readiness (e.g. HPG activity in zebra finch).