Two wild bird species enter select club of smart animals


The Barbados bullfinch and Carib grackle are no birdbrains – but the ability to pass a tricky test wasn't correlated with traits such as shyness or problem-solving. Amy Middleton reports.


The Carib grackle (pictured) and bullfinch, both found in Barbados, have been inducted into a select group of animals.
Andrew Yarnold / EyeEm / Getty Images

Two species have just been added to the revered list of birds with the smarts to pass a complex cognitive test.

A trio of biologists at McGill University in Canada put wild birds from Barbados through their paces and found two species – the bullfinch and grackle – passed the "string-pull test".

The work was published in the journal PLOS One.

One of science's stalwart cognition tests, the string-pull assessment measures an animal's ability to figure out that tugging a piece of string a number of times will lead to food. It's been used in cats, dogs and other animals, as well as multiple studies into bird species.

Once thought to demand a complex combination of motor-skills, prediction and creativity, the string-pull test is the subject of scientific debate around just how much it reveals about its animal participants.

That's why Jean-Nicolas Audet, Simon Ducatez and Louis Lefebvre wanted to find out whether string-pulling was relative to other cognitive tests; that is, whether animals that succeeded at this test exhibited other related traits.

"It is generally assumed that string-pulling is a complex form of problem-solving, suggesting that performance on string-pulling and other problem-solving tasks should be correlated," the researchers write.

To test this relationship, the research team used two wild bird species from Barbados, the bullfinch (Loxigilla barbadensis) and the Carib grackle (Quiscalus lugubris fortirostris). They were chosen for the highly innovative behaviours they show in their natural environment in Barbados.

Individuals from both these species passed the test, with 18 of the 42 bullfinches succeeding, adding two more bird species to an esteemed club of successful string-pullers.



Among the grackles, though, only two of the 31 birds were successful, which wasn't enough to form a sturdy correlation with other traits.

So the researchers focused on bullfinches – and interestingly found no correlation between succeeding at the complex test, and other traits such as shyness, fear of new things, problem-solving and discrimination.

These traits were assessed using other tests. Shyness, for instance, was measured by an individual's willingness to emerge from hiding after being disturbed, while discrimination called on birds to choose the correct colour for a food reward.

The researchers were keen to perform these tests on wild birds, rather than captive, which dominate the literature to date. The researchers argue that captive birds may exhibit skewed results, as interaction with humans could potentially have facilitated their problem-solving ability.

"The fact that we did not detect any correlations in our study is puzzling, despite the fact that previous work on Barbados bullfinches and Carib grackles has found coherent relationships between the measures we tested against string-pulling," the paper reads.

  1. http://dx.plos.org/10.1371/journal.pone.0156112
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