Post by Regan MacKinlay & Rachael Shaw
Can a songbird’s song act as a signal of their cognitive ability for listeners? Individual birds produce slight variations on their species’ specific song. The amount of unique song components produced during a song bout, known as a song repertoire, is commonly used to measure song complexity. Previous research has shown that song repertoires are learnt, and individual learning is influenced by differences in genetics and events during early development. Both genetics and early developmental differences have also been shown to influence other cognitive processes. Importantly there is substantial evidence that both complex bird song and greater cognitive ability are the subjects of sexual selection. Given these links, it has been hypothesised that song complexity may be used by listeners to gauge the general cognitive ability of singers.
Early research indicated the existence of associations between complex song (typically measured as repertoire size) and cognitive ability in song sparrows (Melospiza melodia). One study found a positive correlation with detour reaching performance (a measure of inhibitory control), and another found a negative correlation with performance on a spatial learning task (a measure of spatial memory). However, a recent attempt to replicate these two studies failed, and in fact found opposing patterns. Re-examining these relationships in a species with a differing ecology to the song sparrow, namely a caching species, may offer a different perspective on the relationship between song complexity and cognitive ability. In a special issue of Intelligence we report that, despite adopting similar testing methodology and sample sizes as previous studies, song repertoire size was not correlated with cognitive performance in spatial memory or inhibitory control tasks in toutouwai (Petroica longipes).
It remains possible that other song features (i.e. besides repertoire size) are in fact associated with cognitive ability but evaluating this will require further research into biologically relevant markers of birdsong complexity. For now it appears that song repertoire is unlikely to be used as an indicator of cognitive ability by song listeners, and we recommend that song repertoire should not be used as a proxy for cognitive ability in song birds.
Toutouwai can take down some of the world’s largest invertebrates, but if you’ve caught a 50 cm long earthworm, what do you do with it all? One answer is to shake it to pieces and hide it around your territory to snack on over the next day or so. This ‘caching’ strategy lets toutouwai make the most of temporarily abundant food by saving some for later.
Caching is widespread in the animal kingdom, yet there have been very few studies looking at how individuals develop caching behaviour. For her MSc thesis, Latu Clark investigated how juvenile toutouwai learn to make their caches. The results of her work have just been published in Behavioural Processes.
After young birds left the nest, Latu visited them a couple of times a week for up to 12 weeks. Each visit, she fed the birds several mealworms and documented their behaviour. If a bird cached, Latu monitored what happened to their cache (check out the image below of one of her juveniles inspecting the camera – if you look closely you might spot a cached mealworm in the log in the background). Her work demonstrated that it takes several weeks for juveniles to develop some aspects of adult-like caching behaviour, but that other components of caching appear spontaneously and do not change during development.
These results suggest that learning how to handle prey and hide it for later comes naturally to young toutouwai, but that they also require extensive experience to do it well. Interestingly, it also seems that toutouwai caching behaviour follows similar developmental trajectories to other, distantly related Northern hemisphere bird species.
A juvenile robins gets up close and personal with a camera. Photo courtesy of Latu Clark.
It’s been a while since the last update, but that’s not to say that we haven’t been hard at work! The robin/toutouwai breeding season is well underway and this year we’ve also begun to look beyond the sanctuary fence, to try and understand what might be limiting the toutouwai’s survival. Meanwhile, we’ve been developing a new research project with kākā (watch this space…).
However, this year I also took time to reflect and focus on writing a review together with Martin Schmelz. Our paper, ‘Cognitive test batteries in animal cognition research: evaluating the past, present and future of comparative psychometrics’, was recently published in Animal Cognition. In it, we examine the various pitfalls and possibilities that lie ahead for non-human cognitive test battery research. (As an added bonus, it also includes discussion of the relationship between reproductive success and cognitive test battery performance in wild male North Island robins)
There’s already some exciting things happening in this rapidly growing field, but there is still a lot of room for improving how we design, implement and analyse non-human test batteries. We hope that our review will be a useful resource for anyone who is undertaking non-human cognitive test battery research.
The updates have been a little slow while my students and I have been wrapping up the latest round of breeding season monitoring and crunching numbers…
However, I did manage to make time this week to chat about our research to Sciblogs and Radio New Zealand.
To read about why I think it is important to study bird brains, check out this interview with Sciblogs.
To listen to me discuss how to attract an enraged researcher in the forest, among other, more scientific things, have a listen listen to this interview with Radio New Zealand.
The robins had some pretty distinguished visitors today. Professor Nicky Clayton and Artist and Writer Clive Wilkins of Cambridge’s Psychology Department paid a visit to Zealandia and met a few of the locals. While they are in town Nicky and Clive are also presenting the ‘The Captured Thought‘, a collaboration that explores thought and experience.
Bruiser participated in my first North Island robin cognition study in 2014 and is no stranger to cognitive tests. In my latest research, carried out in 2015 and recently published in Behavioural Processes, Bruiser quickly mastered opening swivel lids to grab a snack. By contrast, those robins that had never been tested were slow to catch on.
If prior experience affects performance in a cognitive task, how can we fairly compare naïve and experienced birds? Designing tests that can give us unbiased, accurate measures of cognitive ability in the wild gets even more complicated when we start to consider other factors, such as hunger or boldness.
As it turns out, I also found that hungry robins performed worse than their well-fed counterparts in a test of inhibitory control. These birds were more likely to keep pecking at food through a transparent barrier, rather than reaching around the barrier to retrieve it.
Lid-opening and ‘detour-reaching’ tasks are commonly used cognitive tests for birds. However, the robins’ performance reveals some pitfalls in relying on these tasks to measure individual cognitive ability. It hardly seems fair to compare a spoilt little Bruiser with a hungry bird who has never been to robin school…
Over the past few weeks Latu has been hard at work documenting the caching behaviour of the youngest birds in our study population. Judging from the footage, it looks like her efforts to film cache sites haven’t gone unnoticed by all of the juveniles…