Hi Everybody. Nick here. Kevin C. Burns, School of Biological Sciences, Victoria University did a wonderful blog on plants a while back for Halo. We loved it so much we asked him for another one please. Kevin said no worries and so this time he shares his knowledge on New Zealand Robins. Thanks KC.
Thanks Nick !
Family life in New Zealand robins – Sound familiar?
We all know our native birds are in trouble because they are oblivious to introduced predators like cats, stoats, rats and possums. However, there is an upside to this situation – New Zealand birds are also oblivious to birdwatchers. Because of their fearlessness, our native birds will virtually open their front door and let you into their living room. Back-stage passes to their family life makes Zealandia a paradise for scientists studying animal behaviour. Below is a brief account of the astounding things our recent experiments have taught us about New Zealand robins: their loyalty would put most human couples to shame, their mathematics skills might be enough to pass National Standards, like any couple they enjoy a good squabble, which the woman always wins in the end. Our family lives are more similar to our feathered friends than you may think.
Life in the slow lane
New Zealand robins are the homebodies of the bird world. They live in small territories with the same partner for their entire lives. They literally will never know what’s around the next tree in the forest. Females spend most of the year caring for their kids. Males maintain the families’ territory year-round and help gather food for the family during the breeding season. Divorced is frowned upon and infidelity is rare.
Although this might sound idyllic to some, we all know that family life is not always so harmonious. Winter is a very difficult time and it places a lot of strain on their quiet, happy home life.
As days shorten and temperatures drop, insects become harder and harder for robins to find. So parents force their kids to relocate and fend for themselves. The cooperation between the sexes that characterises the summer breeding season is abandoned and partners begin to think selfishly.
Males and females spend more and more time at separate ends of the family’s territory and they squabble for what little food they can find. After all, there’s no guarantee that their partner will survive the winter, so goodwill and cooperation fades. As times get difficult, it’s every bird for themselves.
Male robins are at an obvious advantage to females during winter because they are bigger, stronger and more aggressive. So when times get really tough, males begin to bully females. Food that females work hard to find is always at the mercy of marauding males, who frequently chase females away from their next meal. Fights over food can even be violent… feathers literally fly.
Although winter is definitely a difficult time, robins have a special trick up their sleeve that plays a vital role in their survival. They store food. Some of the largest invertebrates on the planet are on the robin’s menu. Although they eat small bugs when they can find them, weta, stick insects and giant earthworms are big ticket meals. While highly prized, these big meals come at a cost. They are simply too big to be eaten all at once. Instead of abandoning the left-overs, robins bring them up into the tree tops for later use. This way a single kill can be stretched further and might even be the difference between life and death during the next cold southerly.
The closest analogy to robin food hoarding may seem a little strange. But robins actually behave more like leopards on the plains of Africa than their feathered relatives in the northern hemisphere. European tits hoard thousands of seeds in autumn that are retrieved throughout the winter, quite different to robins. Leopards on the other hand attack and kill big prey, which they immediately drag up into trees where they are safe from marauding lions and hyenas. Prehistoric New Zealand was once filled with large, ground-dwelling birds like adze-bills, which may have been played a similar role to lions and hyenas.
Although both male and female robins store food, females aren’t big enough to defend their caches against males. So their food is never safe from bigger, brutish males. On the face of it, women in the world of robins seem to be faithful servants of unfortunate circumstance. However, nothing could be further from the truth…
Women are smarter
After pairing up with a male, younger female robins eventually learn that fighting with partner for food is futile. But what females give up in brawn in this battle of the sexes they make up with brains.
No male can sit and guard their selfish hoards all day. If they don’t defend their territory against the neighbours, like all bad neighbours they will try to move the property line to their advantage. Because of his superior size, this job falls to the man of the house, and females take full advantage of this division of labour.
Although females must surrender their food to males, they quietly retire into the distance for most of the winter and keep a watchful eye on their man. From a safe distance away, females attentively study where males make their caches, and the instant males turn their attention away from their ‘secret’ stashes, females tip the balance firmly in their favour.
Females are five times more likely to retrieve food cached by males than the other way around. So while the man of the house might get his hands on the bacon first, women are far more likely to eat it in the end. Girl power at its finest!
Are robins mathematicians?
So what does this all mean? Does the family life of robins have a lesson for the world of science? Or are they just a reminder that we aren’t so different from our feathered friends.
A few years ago, a particularly insightful student of mine named Simon Hunt came into my office and asked “Did you ever notice that when females go to raid caches made by males, they always go to the cache site with the most food in it?”
Come to think of it, Simon was right. They did tend to steal from the biggest hoard first. This would mean that they are not only capable of remembering where another animal put something, which on its own is scientifically special, but they also could remember what they put there. But we didn’t have any data to back all this up. In the world of science, it’s speculation until you run an experiment. So Simon went out to test how well robins could distinguish quantities, something scientists have been fascinated with for decades.
He did this by hiding different numbers of small worms in a stick that had two shallow holes drilled in it. He did this while wild robins looked on and then covered each of them at the same time with pieces of leather attached to a swivel. The birds were then allowed to choose between the two holes.
It turned out that robins always went to the hole that had more worms. They could even tell the difference between 4 and 6, which to date is best performance of any untrained animal other than us… surpassing even chimpanzees.
So our native birds not only have sophisticated family lives, they’re also the math geniuses of the animal world!
Simon then ran a different type of experiment, where he basically measured how badly birds freaked-out when they were tricked with numbers. It was basically the same as the first experiment, except that the stick had only a single hole in it and this hole had a trap door, which he could use to hide worms from robins. So birds watched a certain number of worms go in, say two, but when they went to retrieve them, they only found one, because the other one was hidden under the trap door.
Results from this experiment were spectacular. Robins basically spit the dummy when they don’t get what they thought was coming to them. Here’s a video that compares two of Simon’s trials: http://www.youtube.com/watch?v=KwWDt8OEYww
So watching the private lives of New Zealand robins has taught the world of science a thing or two – and it all hinges on the very behaviour that makes their future survival so precarious – their fearlessness. Too bad they can’t learn to fear cats, rats and stoats but still let birdwatchers into their private lives.