Forget the turkey, let’s talk goose
Cape Town scientist Tess Gridley is known for her studies of dolphin calls and dreamy whale song. But the incessant screeching and honking of Egyptian geese opposite her house prompted a more urgent study of her feathered neighbours — with surprising results.
With the help of her sound recorders and a steady stream of goose chatter, Gridley has lifted the veil on what the goose noise is all about. She and co-author Courtney Gardiner published their findings last week, in an online paper entitled “To honk or to hiss: uncovering call complexity in the Egyptian Goose Alopochen aegyptiaca.”
They found eight distinct goose noises, suggesting the birds have their own vocabulary made up of distinct noises for specific situations.
“It’s like there is this soap opera going on above your head on a daily basis and most people don’t really give it any thought whatsoever,” Gridley told the Sunday Times this week. “Studying what is underneath your nose is really kind of interesting.”
The findings were also largely thanks to Covid-19 lockdown. Gridley and her colleagues at Sea Search, which operates from Muizenberg, were unable to go to sea to record whales and dolphins during last year’s hard lockdown; instead they turned their attention to noises closer to home.
Recordings were made on the roof of a block of flats where the geese like to congregate, directly adjoining Gridley’s house, and at a nearby golf course.
“We definitely weren’t able to go out to sea, and so with lockdown it was really about keeping busy,” said Gridley, who had the added satisfaction of listening to geese while writing her paper at home — not something she can do with marine mammals. “To hear the animals you are working on as you are writing a paper about them is really, really cool,” she said.
A total of 16 acoustic recordings were made in May 2019 and 2020. Data analysis revealed a goose repertoire of eight distinct call types: loud, honk, short honk, hiss, soft, short soft, flight and noisy. Honking was typically longer than other call types, particularly around members of the opposite sex.
“Our results document hidden complexity in the acoustic signalling of Egyptian geese and highlight avenues for future investigation into the behaviour of this urban adapted species,” the authors say in the study, published in the Ostrich Journal of African Ornithology.
Goose “conflict resolution” usually involved “harsh, buzzy, relatively low-pitched sounds”, whereas distress calls were “usually harsh, far-reaching sounds”. Specific calls were linked to a range of other behaviour, from begging and flight to territorial display.
Results also suggest female geese are noisier than males, particularly when calling out to other geese. “If they overhear another animal honking then they call three times as much, but if they don’t hear anything they just stop,” said Gridley.
She prefers the much gentler twittering of starlings and doves in a large conifer tree shadowing her house.