Lauren M. Guillette

Sometimes slower is better: slow-exploring birds are more sensitive to changes in a vocal discrimination task

Animal personality, defined as consistent individual differences across context and time, has attracted much recent research interest in the study of animal behaviour. More recently, this field has begun to examine how such variation arose and is maintained within populations. The habitat-dependent selection hypothesis, which posits that animals with differing personality types may fare better (i.e. have a fitness advantage) in different habitats, suggests one possible mechanism. In the current experiment, we tested whether slow- and fast-exploring black-capped chickadees (Poecile atricapillus), determined by performance in a novel environment exploration task, perform differentially when the demands of an acoustic operant discrimination (cognitive) task were altered following successful task acquisition. We found that slow-exploring birds learn to reverse previously learned natural category rules more quickly than faster exploring conspecifics. In accordance with the habitat-dependent selection hypothesis, and previous work with great tits (Parus major), a close relative of the black-capped chickadee, our results suggest that fast-exploring birds may perform better in stable, predictable environments where forming a routine is advantageous, while slow-exploring birds are favoured in unstable, unpredictable environments, where task demands often change. Our results also support a hypothesis derived from previous work with great tits; slow-exploring birds may be generally more flexible (i.e. able to modify their behaviour in accordance with changes in environmental stimuli) in some learning tasks.

Exploration of a novel space is associated with individual differences in learning speed in black-capped chickadees, Poecile atricapillus

Individual variation in exploratory behaviour has been demonstrated in a diverse array of animal species. Understanding the evolutionary antecedents and ecological consequences of this variation is an active research area within animal behaviour. Here we investigate whether different exploration styles exhibited by black-capped chickadees (Poecile atricapillus) in a novel environment are related to how quickly these birds learn an acoustic discrimination task. We found that birds that readily enter a novel environment learn an acoustic discrimination task faster than birds that do not readily enter a novel environment. This result contrasts with previous work suggesting no correlation between exploration style and learning a spatial or associative task in great tits (Parus major), a close relative of the black-capped chickadee.

Cognition and personality: an analysis of an emerging field

It is now well established that individuals can differ consistently in their average levels of behaviour across different contexts. There have recently been calls to apply the same adaptive framework to interindividual differences in cognition. These calls have culminated in the suggestion that variation in personality and cognition should correlate. We suggest that both these appealing notions are conceptually and logistically problematic. We identify the first crucial step for establishing any cognition-personality relationship. This is to determine the degree to which cognitive abilities yield consistent task performance. We then suggest how to establish whether such consistency exists. Finally, we discuss why formulating predictions about how cognition might be related to personality is much more difficult than is currently realised.

Individual differences in learning speed, performance accuracy and exploratory behaviour in black-capped chickadees

Cognitive processes are important to animals because they not only influence how animals acquire, store and recall information, but also may underpin behaviours such as deciding where to look for food, build a nest, or with whom to mate. Several recent studies have begun to examine the potential interaction between variation in cognition and variation in personality traits. One hypothesis proposed that there is a speed–accuracy trade-off in cognition ability that aligns with a fast–slow behaviour type. Here, we explicitly examined this hypothesis by testing wild-caught black-capped chickadees in a series of cognitive tasks that assessed both learning speed (the number of trials taken to learn) and accuracy (post-acquisition performance when tested with un-trained exemplars). Chickadees’ exploration scores were measured in a novel environment task. We found that slow-exploring chickadees demonstrated higher accuracy during the test phase, but did not learn the initial task in fewer trials compared to fast-exploring chickadees, providing partial support for the proposed link between cognition and personality. We report positive correlations in learning speed between different phases within cognitive tasks, but not between the three cognitive tasks suggesting independence in underlying cognitive processing. We discuss different rule-based strategies that may contribute to differential performance accuracy in cognitive tasks and provide suggestions for future experimentation to examine mechanisms underlying the relationship between cognition and personality.

Biological relevance of acoustic signal affects discrimination performance in a songbird

The fee–bee song of the black-capped chickadee (Poecile atricapillus) is a two-note, tonal song that can be sung at different absolute pitches within an individual. However, these two notes are produced at a consistent relative pitch. Moreover, dominant birds more reliably produce songs with this species-typical interval, compared to subordinate birds. Therefore, we asked whether presenting the species-typical relative pitch interval would aid chickadees in solving pitch interval discriminations. We found that species-typical relative pitch intervals selectively facilitated discrimination performance using synthetic sine-wave stimuli. Using shifted fee–bee song notes from recordings of naturally produced songs, birds learned the discrimination in fewer trials overall compared to synthetic stimuli. These results may reflect greater generalization among stimuli that occur outside species-typical production parameters. In addition, although sex differences in performance are rarely observed in acoustic discriminations in chickadees, female chickadees performed more accurately compared to males.

Mechanisms of call note-type perception in black-capped chickadees (Poecile atricapillus): peak shift in a note-type continuum.

We report on operant conditioning and artificial neural network (ANN) simulations aimed at further elucidating mechanisms of black-capped chickadee chick-a-dee call note category perception. Specifically, we tested for differences in the speed of acquisition among different discrimination tasks and, in two selected discrimination groups, searched for evidence of peak shift. Earlier, unreported ANN data were instrumental in providing the motivation for the current set of studies with chickadees and are provided here. The ANNs revealed differences in the speed of learning among note-type discrimination groups that is related to the degree of perceptual similarity among the three note types tested (i.e., A, B, and C notes). In many respects, bird and network results were in agreement (i.e., in the observation of peak shift in the same group), but they also differed in important ways (i.e., all discrimination groups showed differences in speed of learning in simulations but not in chickadees). We suggest that the start, peak and end frequency of the chick-a portion of chick-a-dee call notes, which form a graded but overlapping continuum, may drive the peak shift observed.

Individual differences and repeatability in vocal production: stress-induced calling exposes a songbird's personality.

Recent research in songbirds has demonstrated that male singing behavior varies systematically with personality traits such as exploration and risk taking. Here we examine whether the production of bird calls, in addition to bird songs, is repeatable and related to exploratory behavior, using the black-capped chickadee (Poecile atricapillus) as a model. We assessed the exploratory behavior of individual birds in a novel environment task. We then recorded the vocalizations and accompanying motor behavior of both male and female chickadees, over the course of several days, in two different contexts: a control condition with no playback and a stressful condition where chick-a-dee mobbing calls were played to individual birds. We found that several vocalizations and behaviors were repeatable within both a control and a stressful context, and across contexts. While there was no relationship between vocal output and exploratory behavior in the control context, production of alarm and chick-a-dee calls in the stressful condition was positively associated with exploratory behavior. These findings are important because they show that bird calls, in addition to bird song, are an aspect of personality, in that calls are consistent both within and across contexts, and covary with other personality measures (exploration).

ZENK Activation in the Nidopallium of Black-Capped Chickadees in Response to Both Conspecific and Heterospecific Calls

Neuronal populations in the songbird nidopallium increase in activity the most to conspecific vocalizations relative to heterospecific songbird vocalizations or artificial stimuli such as tones. Here, we tested whether the difference in neural activity between conspecific and heterospecific vocalizations is due to acoustic differences or to the degree of phylogenetic relatedness of the species producing the vocalizations. To compare differences in neural responses of black-capped chickadees, Poecile atricapillus, to playback conditions we used a known marker for neural activity, ZENK, in the caudal medial nidopallium and caudomedial mesopallium. We used the acoustically complex ‘dee’ notes from chick-a-dee calls, and vocalizations from other heterospecific species similar in duration and spectral features. We tested the vocalizations from three heterospecific species (chestnut-backed chickadees, tufted titmice, and zebra finches), the vocalizations from conspecific individuals (black-capped chickadees), and reversed versions of the latter. There were no significant differences in the amount of expression between any of the groups except in the control condition, which resulted in significantly less neuronal activation. Our results suggest that, in certain cases, neuronal activity is not higher in response to conspecific than in response to heterospecific vocalizations for songbirds, but rather is sensitive to the acoustic features of the signal. Both acoustic features of the calls and the phylogenetic relationship between of the signaler and the receiver interact in the response of the nidopallium.

Dominance and geographic information contained within black-capped chickadee (Poecile atricapillus) song

In songbirds, male song is an acoustic signal used to attract mates and defend territories. Typically, song is an acoustically complex signal; however, the fee-bee song of the black-capped chickadee is relatively simple. Despite this relative simplicity, two previous studies (Christie et al., 2004b; Hoeschele et al., 2010) found acoustic features within the fee-bee song that contain information regarding an individual’s dominance rank; however each of these studies reported a different dominance-related acoustic cue. Specifically, the relative amplitude of the two notes differed between the songs of dominant and subordinate males from northern British Columbia, while the interval pitch ratio differed between the songs of dominant and subordinate males from eastern Ontario. In the current study, we examined six acoustic features within songs from both of the chickadee populations (northern British Columbia and eastern Ontario) examined in these previous studies and used bioacoustic analyses and discriminant function analyses to determine whether there is a consistent dominance-related acoustic cue across both, or in each of these populations. Consistent with the previous findings, the current results indicate that relative amplitude differs based on dominance status in the songs from British Columbia; however, our results failed to reach significance with songs from Ontario. These results suggest that acoustic cues that signal a male’s dominance in this species vary with geographic location. Furthermore, examining songs from these two locations and one additional location in northern British Columbia, we found that discriminant function analyses could correctly classify songs based on geographic location. Considering the broad extent of the species’ range, black-capped chickadee song is considered relatively invariant; however, our results suggest that there is geographic variation in songs, although the differences are subtle compared to geographic song variation in other species.

Acoustic mechanisms of a species-based discrimination of the chick-a-dee call in sympatric black-capped (Poecile atricapillus) and mountain chickadees (P. gambeli)

Previous perceptual research with black-capped and mountain chickadees has demonstrated that these species treat each others namesake chick-a-dee calls as belonging to separate, open-ended categories. Further, the terminal dee portion of the call has been implicated as the most prominent species marker. However, statistical classification using acoustic summary features suggests that all note-types contained within the chick-a-dee call should be sufficient for species classification. The current study seeks to better understand the note-type based mechanisms underlying species-based classification of the chick-a-dee call by black-capped and mountain chickadees. In two, complementary, operant discrimination experiments, both species were trained to discriminate the species of the signaler using either entire chick-a-dee calls, or individual note-types from chick-a-dee calls. In agreement with previous perceptual work we find that the D note had significant stimulus control over species-based discrimination. However, in line with statistical classifications, we find that all note-types carry species information. We discuss reasons why the most easily discriminated note-types are likely candidates to carry species-based cues.