Jill A. Soha

Potential trade-off between vocal ornamentation and spatial ability in a songbird

Bird song is hypothesized to be a reliable indicator of cognition because it depends on brain structure and function. Song features have been found to correlate positively with measures of cognition, but the relationship between song and cognition is complicated because not all cognitive abilities are themselves positively correlated. If cognition is not a unitary trait, developmental constraints on brain growth could generate trade-offs between some aspects of cognition and song. To further clarify the relationship between song and cognition in song sparrows (Melospiza melodia), we examined repertoire size and performance on a spatial task. We found an inverse relationship between repertoire size and speed of spatial learning and suggest that a developmental trade-off between the hippocampus and song control nuclei could be responsible for this relationship. By attending to male song, females may learn about a suite of cognitive abilities; this study suggests that females may glean information about a males cognitive weaknesses as well as his strengths.

URBAN NOISE PREDICTS SONG FREQUENCY IN NORTHERN CARDINALS AND AMERICAN ROBINS

ABSTRACT We examined the extent to which acoustic noise in urban environments influences song characteristics and singing behaviour of Northern Cardinals Cardinalis cardinalis and American Robins Turdus migratorius. We predicted that, in response to loud noise, birds would improve signal transmission by (1) increasing singing rate and (2) adjusting song characteristics such as pitch and length. From May—July 2006, 42 cardinals and 53 robins were recorded in forests located within four acoustic environments in central Ohio: rural, residential, commercial, and highway. Following each recording, we measured ambient noise level and recorded information describing location, weather, habitat, and conspecific presence within 75 m. As predicted, frequency range was positively correlated with noise level for both species, but neither song length nor rate was related to noise level for either species. These data support the idea that anthropogenic noise influences avian singing behaviour and acts as a selective force in urban areas.

The auditory template hypothesis: a review and comparative perspective

Studies of vocal development in the white-crowned sparrow, Zonotrichia leucophrys , and other songbirds led to Peter Marlers formulation of the auditory template hypothesis. According to this hypothesis, young songbirds possess an auditory template system that serves three functions in song learning: to focus attention on appropriate song models during the sensitive period, to facilitate memorization of these models, and later, to guide motor development of song during the sensorimotor phase. Marler postulated two types of innate templates: latent templates that require activation by external input, and preactive templates that do not. Here, I review experiments that examined the specifications of these templates in the white-crowned sparrow and suggest that this system also serves a fourth function, acting to shape the final repertoire at the end of song development. I then discuss the template system in a comparative context, first reviewing the influence of results from several species on the derivation of the auditory template hypothesis and then describing variation in several aspects of auditory templates across species. Finally, I address ways in which the template model can continue to be informative in the comparative study of song learning.

Early life conditions that impact song learning in male zebra finches also impact neural and behavioral responses to song in females: Developmental Stress in Female Songbirds

Early life stressors can impair song in songbirds by negatively impacting brain development and subsequent learning. Even in species in which only males sing, early life stressors might also impact female behavior and its underlying neural mechanisms, but fewer studies have examined this possibility. We manipulated brood size in zebra finches to simultaneously examine the effects of developmental stress on male song learning and female behavioral and neural response to song. Although adult male HVC volume was unaffected, we found that males from larger broods imitated tutor song less accurately. In females, early condition did not affect the direction of song preference: all females preferred tutor song over unfamiliar song in an operant test. However, treatment did affect the magnitude of behavioral response to song: females from larger broods responded less during song preference trials. This difference in activity level did not reflect boldness per se, as a separate measure of this trait did not differ with brood size. Additionally, in females we found a treatment effect on expression of the immediate early gene ZENK in response to tutor song in brain regions involved in song perception (dNCM) and social motivation (LSc.vl, BSTm, TnA), but not in a region implicated in song memory (CMM). These results are consistent with the hypothesis that developmental stressors that impair song learning in male zebra finches also influence perceptual and/or motivational processes in females. However, our results suggest that the learning of tutor song by females is robust to disturbance by developmental stress.

Song ontogeny in Nuttall’s white-crowned sparrows tutored with individual phrases

Behavioral ontogeny involves the interaction of innate predispositions and experience. In bird song learning, one approach to exploring this interaction is to examine the songs rehearsed by young birds whose exposure to tutor models has been carefully controlled. Here, I analyzed the rehearsed repertoire in Nuttalls white-crowned sparrows (Zonotrichia leucophrys nuttalli) tutored with individual phrases of conspecific and heterospecific songs. The proportions of phrase types rehearsed indicate that the learning biases evident in crystallized song are manifest early on, suggesting preferential memorization rather than preferential retention during attrition. The proportion of songs beginning with whistles increased during song rehearsal and phrase sequence variability decreased, consistent with the idea that innate syntax specifications guide song rehearsal. Single-phrase tutored birds overproduced phrases to the same extent previously observed in birds tutored with full, normal song but retained fewer phrase types in their crystallized repertoires. This suggests that in this subspecies, acquired syntax information does not affect the number of phrase types memorized and rehearsed but does affect repertoire attrition at the end of the sensorimotor phase. I discuss these results with a focus on the action of innate templates in song development and subspecies differences in this process.