Anti-predator Behaviour in the Bell MinerManorina melanophrys

SummaryData on anti-predator and anti-competitor behaviour in the Bell Miner Manorina melanophrys were collected opportunistically during two breeding seasons at Healesville, south-eastern Victoria, and show that: (a) nest predators were mobbed by more Bell Miners than were competitors; (b) in general, nest predators were mobbed by more birds within a dense than within a less dense colony; (c) this difference in the mobbing response between colonies does not appear to lead to an increase in reproductive success in dense colonies; (d) intruders were mobbed by more birds early than late in the season; and (e) potential nest predators were mobbed by slightly more Bell Miners than were competitors when an active nest was close by. Mobbing behaviour in the Bell Miner may decrease the risks to individuals engaged in anti-predator defence and helpers' involvement in mobbing may benefit breeders through the ‘dilution’ of those risks.