Group size and social interactions are associated with calling behavior in Carolina chickadees (Poecile carolinensis).

The complexity of a social group may influence the vocal behavior of group members. Recent evidence in Carolina chickadees, Poecile carolinensis, indicated that one component of social complexity, group size, influenced the complexity of the "chick-a-dee" call, a vocalization functioning in social cohesion. Individuals in larger social groups used calls with greater information than did individuals in smaller social groups. Here, the authors review this earlier work, and describe a recent study indicating that social interactions between females and males within female-male pairs of chickadees were associated with rates of chick-a-dee call production in the males. Together, these studies suggest that the nature and complexity of social interactions among members of chickadee social groups influence chick-a-dee calling behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Open-ended categorization of chick-a-dee calls by black-capped chickadees (Poecile atricapilla).

The authors trained black-capped chickadees (Poecile atricapilla) in an operant discrimination with exemplars of black-capped and Carolina chick-a-dee calls, with the goal of determining whether the birds memorized the calls of conspecifics and heterospecifics or classified the calls by species. Black-capped calls served as both rewarded (S+) and unrewarded (S-) stimuli (the within-category discrimination), whereas Carolina chick-a-dee calls served as S-s (the between-category discrimination) in the black-capped chick-a-dee call S+ group. The Carolina call S+ group had Carolina calls as S+s and S-s (within-category) and black-capped calls as S-s (between-category). Both groups discriminated between call categories faster than within a call category. In 2 subsequent experiments, both S+ groups showed transfer to novel calls and propagation back to between-category calls. The results favor the hypothesis that the acoustically similar social calls of the 2 species constitute separate open-ended categories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acoustic Mechanisms of Note-Type Perception in Black-Capped Chickadee (Poecile atricapillus) Calls.

Acoustic communication in black-capped chickadees (Poecile atricapillus) has been studied intensively, the "chick-a-dee" call being among the most well described. This call consists of 4 note types; chickadees perceive these notes as open-ended categories and do so in a continuous manner, with As more similar to Bs and Bs more similar to Cs. Acoustic features contributing to the note-type differentiation are unknown. Recent analyses suggested that certain acoustic features may play a role in note-type classification. Here, the authors tested black-capped chickadees in an operant-conditioning paradigm to determine which features were controlling note-type perception. The results suggest that the note pitch and the frequency modulation in the initial portion of the note control the perception of note types. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Statistical classification of black-capped (Poecile atricapillus) and mountain chickadee (Poecile gambeli) call notes.

Both black-capped (Poecile atricapillus) and mountain chickadees (Poecile gambeli) produce a chick-a-dee call that consists of several distinct note types. In some regions, these 2 species live sympatrically, and it has been shown that 1 species will respond weakly to songs of the other. This suggests that chickadee song, and potentially other of their vocalizations, contains species-specific information. We tested the possibility that call notes were acoustically sufficient for species identification. Black-capped and mountain non-D notes were summarized as a set of 9 features and then analyzed by linear discriminant analysis. Linear discriminant analysis was able to use these notes to identify species with 100% accuracy. We repeated this approach, but with black-capped and mountain D notes that were summarized as a set of 4 features. Linear discriminant analysis was able to use these notes to identify species with 94% accuracy. This demonstrates that any of the note types in these chickadee calls possesses sufficient information for species classification. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuron Production, Neuron Number, and Structure Size Are Seasonally Stable in the Hippocampus of the Food-Storing Black-Capped Chickadee (Poecile atricapillus).

Neuronal recruitment in the black-capped chickadee (Poecile atricapillus) hippocampus occurs at a higher rate in the fall than at other times of the year. As a means of determining whether this increase in recruitment results from greater neuron production, chickadees were caught in the wild between October and March and injected with the cell-birth marker 5-bromo-2'-deoxyuridine. Two weeks later, birds were killed by overdose, and hippocampal neuron production, apoptosis, neuron number, and hippocampal volume were determined. Chickadees collected in October, November, January, February, and March did not differ in neuron production, apoptosis, hippocampal volume, or neuron number. These findings indicate that increases in neuronal recruitment in the chickadee hippocampus in the fall do not result from increased neuron production, but instead, enhanced survival of new neurons. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Song sequence discrimination in the black-capped chickadee (Parus atricapillus).

14 captive black-capped chickadees were presented with normal and altered versions of their species-specific "fee bee" song to determine how note type, number, and sequence affect recognition. Perch changes and vocalizations given in response to playback did not differ reliably as a function of song type, whereas latency to 1st vocalization after playback did. In Exp I, using 2-note songs, Ss vocalized sooner to songs beginning with fee than with bee and to fee bee than to fee fee. In Exp II, Ss were presented with single-note, normal, and 3-note songs each consisting of a single-note type. Habituation slowed responding to altered songs but not to fee bee over 3 test sessions. Results suggest that Ss distinguished (a) single fees and 3-note songs from normal song, (b) single fees from single bees, (c) 2-note songs from 3-note songs, and (d) normal song from altered songs. It is concluded that the internal representation of conspecific song in the chickadee distinguishes between fee and bee notes, contains information about note order, and is sensitive to note number. The pattern of responses is consistent with a model of recognition based on note-by-note integration of individual decisions about song structure. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Long-Term Memory for Spatial Locations in a Food-Storing Bird (Poecile atricapilla) Requires Activation of NMDA Receptors in the Hippocampal Formation During Learning.

Food-storing birds use a form of long-term memory to recover their hidden food caches that depends on the hippocampal formation (HF). The authors assessed whether food-storing birds' long-term memory for spatial locations requires N-methyl-D-aspartate receptor (NMDA-R)-dependent synaptic plasticity. Black-capped chickadees (Poecile atricapilla) were given bilateral infusions of the NMDA-R antagonist AP5 into the hippocampus, and their memory on a spatial reference memory task was assessed. NMDA-R inactivation during learning prevented formation of long-term spatial memories but did not affect short-term memory and retrieval processes. NMDA-R inactivation immediately following learning did not disrupt long-term memory formation. NMDA-R inactivation disrupted the learning of multiple serially encoded reward locations when a 180-min delay separated successive learning episodes, suggesting that NMDA-R activity has a role in the incorporation of new information into existing long-term memory, as well as in forming unitary long-term memories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of captivity and memory-based experiences on the hippocampus in mountain chickadees.

The complexity of an animal's physical environment is known to affect the hippocampus. Captivity may affect hippocampal anatomy and this may be attributable to the limited opportunities for memory-based experiences. This has tangential support, in that differential demands on memory can mediate changes in the hippocampus. What remains unclear is whether captivity directly affects hippocampal architecture and whether providing memory-based experiences in captivity can maintain hippocampal attributes comparable to wild-caught conspecifics. Using food-caching mountain chickadees (Poecile gambeli), we found that wild-caught individuals had larger hippocampal volumes relative to the rest of the telencephalon than captive birds with or without memory-based food-caching experiences, whereas there were no differences in neuron numbers or telencephalon volume. Also, there were no significant differences in relative hippocampal volume or neuron numbers between the captive birds with or without memory-based experiences. Our results demonstrate that captivity reduces hippocampal volume relative to the remainder of the telencephalon, but not at the expense of neuron numbers. Further, memory-based experiences in captivity may not be sufficient to maintain hippocampal volume comparable to wild-caught counterparts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)