Discrimination of acoustically similar conspecific and heterospecific vocalizations by black-capped chickadees (<Emphasis Type="Italic">Poecile atricapillus</Emphasis>)

Chickadees produce a multi-note chick-a-dee call in multiple socially relevant contexts. One component of this call is the D note, which is a low-frequency and acoustically complex note with a harmonic-like structure. In the current study, we tested black-capped chickadees on a between-category operant discrimination task using vocalizations with acoustic structures similar to black-capped chickadee D notes, but produced by various songbird species, in order to examine the role that phylogenetic distance plays in acoustic perception of vocal signals. We assessed the extent to which discrimination performance was influenced by the phylogenetic relatedness among the species producing the vocalizations and by the phylogenetic relatedness between the subjects’ species (black-capped chickadees) and the vocalizers’ species. We also conducted a bioacoustic analysis and discriminant function analysis in order to examine the acoustic similarities among the discrimination stimuli. A previous study has shown that neural activation in black-capped chickadee auditory and perceptual brain regions is similar following the presentation of these vocalization categories. However, we found that chickadees had difficulty discriminating between forward and reversed black-capped chickadee D notes, a result that directly corresponded to the bioacoustic analysis indicating that these stimulus categories were acoustically similar. In addition, our results suggest that the discrimination between vocalizations produced by two parid species (chestnut-backed chickadees and tufted titmice) is perceptually difficult for black-capped chickadees, a finding that is likely in part because these vocalizations contain acoustic similarities. Overall, our results provide evidence that black-capped chickadees’ perceptual abilities are influenced by both phylogenetic relatedness and acoustic structure.     

Odometry and backtracking: social and individual navigation in group foraging desert harvester ants (Veromessor pergandei)

Animal Cognition - Veromessor pergandei harvester ants are group foragers which use a combination of social cues (pheromone-marked columns) and individual cues (e.g., self-generated movement,...     

Bonhoeffer and Bultmann: Toward an Apocalyptic Rapprochement

In the 1950s and 1960s, the relation between Dietrich Bonhoeffer and Rudolf Bultmann was a topic of much dispute, with Gerhard Krause declaring the apparent opposition between them ‘resolved’ in 1964. Recent apocalyptic theology has reopened the divide between them by claiming Bonhoeffer as an apocalyptic thinker over against Bultmann. This article disputes that reading by arguing that the very conditions under which Bonhoeffer is rightly understood as apocalyptic open up the door for a new interpretation of Bultmann. The question of their relationship reveals the ambiguity surrounding the notion of apocalyptic. There is a pressing need for greater clarity regarding this notion as well as greater charity in relation to Bultmann.