Parent birds make a calculated risk when they alert their young to the presence of a predator, a new study by Dr Tonya Haff and Professor Rob Magrath has found.

Parent white-browed scrub wrens only give alarm calls when their young are being particularly noisy and are therefore at high risk from being overheard by a predator.

"Parents were sensitive to the trade-off between silencing young and alerting predators to the presence of nests," says Haff, who carried out the research for her PhD.

Scrub wren photo by Ben Pitcher

Related links

• Haff, TM & Magrath, RD, To call or not to call: parents assess the vulnerability of their young before warning them about predators. Biology Letters.
• Birds decide when to call and not to call, ABC Science online.