Parental interference in sibling aggression in birds: What should we look for?

In many avian species, older nestlings within a brood may decrease the fitn ess of younger siblings by aggression or competition. While such a situatio n suggests a potential parent-offpring conflict, it is often assumed that p arents condone sibling aggression because there are few reports of adult bi rds intervening in fights between their young. However, parent bald eagles (Haliaeetus leucocephalus) interfered in 9% of bouts of sibling aggression using a variety of tactics not previously reported for birds. A review of t he literature revealed additional behaviours that may be used to mitigate s ibling aggression. We propose that parents may use "general remedial" behav iours as a long-term strategy to ensure adequate resources to disadvantaged offspring, and "acute responses" involving physical contact, distraction, or deception, to halt particular aggressive acts.