21 May 2023

Why do seagulls eat from garbage bins? Interpreting bird behaviour with bird behaviouralist Dr Grainne Cleary

From Sunday Morning, 10:10 am on 21 May 2023
Red-billed gull (tarāpunga) in flight

Red-billed gull (tarāpunga) in flight Photo: Phil Smith

Why do male birds have such impressive plumage, do birds dream in songs, and why do seagulls eat from garbage bins?

RNZ Sunday Mornings spoke to Irish wildlife ecologist and bird behaviouralist Dr Grainne Cleary, author of Your Backyard Birds and host of ABC show, Good Things Come in Trees, about the commonality between human behaviour and birds.   

Clearly says birds are very much like humans.  

"The more I learn about birds, the more I think they are so much like us because they live in societies the way we do, and you've gotta act proper when you're in a society.

"If you're not, you get kicked out. And that's what happens, especially with ravens. If you've looked at ravens, if an individual cheats, the other ravens will actually stop interacting with it, will actually ignore it and cut it out because they don't like cheaters."

Clearly said much like humans, birds play to learn how to interact with other individuals and each other.  

"A lot of our birds have these long childhoods, which means they're not ready. They don't get into sexual maturity until they reach about seven, about six or seven.  

"So, they have this long childhood and it's during this time they learn much like us, how to interact with other individuals.  

"If you think about children, what do they learn? They learn how to become little adults. They learn, you know you don't punch someone, you don't pull someone's hair. Birds learn the same and they will play with each other to learn, how far can I push this before the other bird says no you've hurt me, and they'll stop playing.

"So, they'll have to learn all these, these tricks as they grow. Very much the way kids play Mommy and Daddy," she said.  

Why do male birds have such impressive plumage?   

Clearly said it's meant to show the female bird that it can be a good dad.  

She said the male bird often has bright colours because it shows that it has reached its maturity.  

"Some birds will get a more impressive plumage to show that they have reached sexual maturity and also that they're strong.  

"It's like diet. If our diet is really bad, it shows in our skin. It shows in our hair, it's the same for birds.  

"So, birds that are competing with other males, the female will choose the one that has that bright, beautiful plumage because it shows that that male will make a good dad. It shows that he's nice and strong."  

Do birds dream in song?  

Clearly said they do, as she talked about the topic of her next book.  

"Did you know that when birds sleep they rehearse music in their head? So that song sounds better the next day.  

"So, if a bird doesn't get a good night's sleep, especially a young songbird, it doesn't learn its song properly and it can't sing as well the next day. So, sleep is very important for birds to learn, just as it is for our children," she said.  

Why do seagulls eat from garbage bins?

She said seagulls were capable of eating anything, however eating in human areas was an adaptation, as a result of overfishing.  

"Seagulls have kind of left the sea because, part of it is because, we are overfishing and it's harder for them to find food. If they come inland and they can find food a lot easier, especially around tips and rubbish where they can forage and if they eat something bad for them, something that doesn't agree with them, they can regurgitate it back up, so they don't have to live with it, if they've eaten the plastic.

"So that's a cool adaptation to allow them to learn what they can eat and what they can't."

Cleary said seagulls learned from watching each other and humans, and were one of the smartest birds.

* Dr Grainne Cleary is in New Zealand to speak about her latest book, Why Birds Do That? at the Auckland Writers Festival.