Environment – Lumbering humans attract fantails

Insects startle quite easily. It’s a reasonable thing to do really, because any large-scale movement within an insect’s field of view will often be associated with approaching danger. Fleeing under those circumstances is a pretty good defence strategy because it helps improve the insect’s chance of survival. But startling comes at a risk because the very act of fleeing can put you straight into the mouth of a predator.

We recently returned from a family holiday to Botswana and Zimbabwe. One thing I noticed on that lovely trip was all the different bird species that hang around the big African mammals. Cattle egrets follow elephants around catching any startled insects. Fork-tailed drongos are often seen perched near any herd of mammals, also taking advantage of any startled prey. Animals often form associations with other animals if there is a potential benefit. And the birds in Africa follow the big mammals around because their lumbering size provides a mechanism to catch food.

This form of association between insect eating predators and big animals has also evolved here in New Zealand. Many people have had the experience of a pīwakawaka (fantail) following them around on a hike or while they are doing something in their garden. I love it when this happens – they just seem so curious and friendly. They follow you around like these little bird buddies in a Disney movie.

Hate to break it to you – but the fantails are probably not looking for friendship when they come checking out what you are up to. Instead, the pīwakawaka are more attracted to your lumbering size, and are just hoping that you might be rustling up a few insects to catch! 

This is very likely not a new strategy for the fantails. When New Zealand was populated with huge flightless moa, pīwakawaka would have undoubtedly been drawn to them as they moved around the forest floor. Those fantails that had an instinct to follow the big birds around would get more food. Now that the moa are gone, the instinct in fantails to follow big creatures around is still there – and they have just shifted that behaviour over to humans.

Pīwakawaka have another trick that they use to exploit the startle response of insects. The next time you see a fantail foraging around in a tree or shrub, take a moment to watch how they use their tails. The tails are exceptionally large and marked with high contrast white feathers that they repeatedly open and close while they clamber around looking for food. The sudden bold white flashes from the markings on the tail startle potential prey, and the pīwakawaka then swoop in for the kill.