Ngaire Myers of Balclutha asks :-

I observed baby? wax-eyes fluttering and vibrating their wings a lot. What are they saying?

Laura Molles, a behavioural ecologist at Lincoln University, responded.

Baby birds in the nest gape their mouths, stretch their necks, and often wiggle and shake their wings and bodies while begging for food. These movements enhance their vocal signals and have evolved to maximise their food intake by attracting mom or dad’s attention.

All begging signals are essentially aimed at out-competing siblings in order to get the lion’s share of the resources, or at blackmailing parents (“feed me or I’ll keep keep squawking, and a predator might find me – and neither of us wants that!”). However, because all of that screeching and dancing takes energy, begging is largely honest – hungrier babies will make a bigger fuss. This pattern probably continues once babies have fledged and are approaching independence, but still pestering mom and dad for food.

Wing fluttering while begging is a common behaviour in the fledglings of many bird species. It may, to an extent, be a begging signal less conspicuous to predators than calling noisily, which makes it a safer option for the hungry fledglings. However, adult females of many species flutter their wings during “courtship feeding” (males often feed their mates, particularly early in the breeding season). Adult birds of both sexes may also flutter their wings in highly charged aggressive situations. In fact, in aggressive interactions wing fluttering often indicates imminent attack! So, the signal may mean, in essence, “feed me… or else!” A baby bird probably wouldn’t actually attack its parent, but it may feel so motivated to get that tasty morsel that its body language gives that impression.

If the fluttering you see is happening in late spring, this is probably what the baby was saying. If you see the same thing early in spring, it’s probably two adults: either a bonding pair, or territorial rivals – watch what happens afterwards to find out.