|
| |
To listen to soundfile: click on the headphones icon
To download soundfile: click on the mp3 file name
|
|
| |
Dr Culum Brown, from the Department of Biological Sciences at Macquarie University, looks into the advantages of lateralisation in some native parrots. |
| Among parrots, the large bodies species are strongly lateralised, either being left footed or right footed, thought to be a result of the coordination needed when using beak and foot to feed.
Some simple cognitive tasks were designed to effectively test that theory. In effect, the parrots were asked to select seeds mixed in with pebbles, testing their foraging efficiency.
|
|
|
| |
|
| A set number of seeds were arrayed onto a glued pebble background and offered to the birds for two minutes.
The number of pecks was recorded, as was the number of successful seed discrimination, giving a measure of foraging efficiency.
In this test, strongly lateralised birds performed significantly better but the results were by no means overwhelming.
|
|
|
|
|
| |
|
| Further tests used the basis of a string pull problem, where a piece of food is tied to a piece of string some 70cm long which, when attached to a perch, dangles downward.
The small bodied birds such as lorikeets could not solve this problem whereas the large bodied birds successfully used beak and foot to draw the string upward, thus accessing the food.
|
|
|
|
|
| |
|
| Indeed, the strongly lateralised birds solved this problem usually on the first go and within seconds.
The task clearly reflects foraging behaviours that the birds use in the wild, reminding us that the way in which creatures engage successfully with their environment is part of the evolutionary process of natural selection.
The phylogeny of birds bears this out.
|
|
|
|
|
| |
|
| When small bodied birds first emerged, it seems it was a point in time when their foraging behaviours had shifted and therefore they lost the lateralisation needed in previous for their previous foraging mode.
In Australia, this shift in body size is linked by a shift from rainforest to increased aridity, hence a change in landscape from trees to grasses which the small bodied birds could exploit.
|
|
|
|
|
| |
|
| Dr Brown posits that a look at parrots from South America and Asia might reflect a similar change in laterality and feeding habits. That is certainly food for thought.
Dr Culum Brown was interviewed by Ruby Vincent for A Question of Balance. Images by Paul McQueen. Summary text prepared by Victor Barry June 2011.
|
|
|
|
|
|
|
|
|
|
|
 For more information, please contact us |
)
