Vocal traits of shorebird chicks are related to body mass and sex

Acoustic communication is critical during early life phases in precocial birds. For example, adult alarm calls can elicit antipredator behaviour in young, and chick vocalisations can communicate information to parents about chick identity, condition, location, sex, or age. We investigated whether chick calls of two species of Australian Charadriidae vary with sex or body mass. We handled Red-capped Plover Charadrius ruficapillus and Southern Masked Lapwing Vanellus miles novaehollandiae chicks for purposes of measurement, blood sampling, and banding. We opportunistically recorded their distress calls while in the hand, and analysed the calls to determine whether call structure is related to sex or body mass (a proxy for age). We measured five traits per call, plus time intervals between successive calls, for 26 plover chicks (2600 calls) and 95 lapwing chicks (6835 calls). In plovers, inter-call intervals were shorter in males and both inter-call interval and the dominant frequency range of calls decreased with increasing body mass. In lapwings, frequency modulation (computed as the range in the rate of change of the dominant frequency) was lower in male calls. The dominant frequency range of lapwing calls decreased with mass in both sexes, but the decline was greater in males, resulting in a lower dominant frequency range in males. Frequency modulation and entropy of lapwing calls also decreased with increasing body mass. Minimum dominant frequency did not change with body mass or sex in either species. Our study provides the first evidence for charadriid chicks of (a) a sexual difference in call structure and rate and (b) gradual growth-related changes in call structure and rate, across chicks. Studies on calls from a greater range of chick ages and from more species within this large and diverse family would be valuable. We provide a foundation for further studies of shorebird vocalisations during growth, which may elucidate the development and functional significance of such vocalisations.

Discrimination of Acoustic Stimuli and Maintenance of Graded Alarm Call Structure in Captive Meerkats

Animals living in human care for several generations face the risk of losing natural behaviors, which can lead to reduced animal welfare. The goal of this study is to demonstrate that meerkats (Suricata suricatta) living in zoos can assess potential danger and respond naturally based on acoustic signals only. This includes that the graded information of urgency in alarm calls as well as a response to those alarm calls is retained in captivity. To test the response to acoustic signals with different threat potential, meerkats were played calls of various animals differing in size and threat (e.g., robin, raven, buzzard, jackal) while their behavior was observed. The emitted alarm calls were recorded and examined for their graded structure on the one hand and played back to them on the other hand by means of a playback experiment to see whether the animals react to their own alarm calls even in the absence of danger. A fuzzy clustering algorithm was used to analyze and classify the alarm calls. Subsequently, the features that best described the graded structure were isolated using the LASSO algorithm and compared to features already known from wild meerkats. The results show that the graded structure is maintained in captivity and can be described by features such as noise and duration. The animals respond to new threats and can distinguish animal calls that are dangerous to them from those that are not, indicating the preservation of natural cooperative behavior. In addition, the playback experiments show that the meerkats respond to their own alarm calls with vigilance and escape behavior. The findings can be used to draw conclusions about the intensity of alertness in captive meerkats and to adapt husbandry conditions to appropriate welfare.

Addressing Transition to Practice: Assessing Perceived Effectiveness of a Competency Based Change to On-Call Responsibilities of Senior Cardiology Residents

Background There has been a paradigm shift in residency training over the last several years wherein Competency by Design (CBD) is being integrated to replace more traditional time-based models of training. The Residency Program Committee (RPC) for the Cardiology training program at Dalhousie University in Halifax, Canada addressed the Transition to Practice stage by approving a trial of adjusting the resident call responsibilities to reflect the transition to CBD curriculum. The goal of this adjustment was three-fold: i. Gradually increase accountability of the senior cardiology resident as they transition to practice; ii. Address a gap in training that allows the senior resident to have a gradual transition to the role of a practicing cardiologist while on call; iii. Allows further evolution of skills and abilities. Methods A survey was administered to the practitioners involved in this competency-based change to the call responsibilities. Surveys were distributed to the final year Cardiology Residents, Staff Cardiologists, and Senior Internal Medicine residents to assess their experience and opinions of the current, competency-based change of the on-call curriculum. The survey consisted of eleven questions, of which, four were assessed on a Likert scale and 3 were yes/no questions. Results Four PGY6 cardiology residents, five senior internal medicine residents and eleven staff cardiologists completed the survey. Amongst those who completed the survey there was agreement that the change to the on-call responsibilities improved cardiology residents’ skills, accountability and preparedness to practice. All groups felt the changes were useful for the cardiology training program. There was mild negative effect of perceived accountability by the internal medicine residents. Conclusion Overall the change in call structure led to improved perceived preparedness to practice amongst the cardiology residents and addressed a gap in the Transition to Practice phase of CBD training. This study provides some evidence to the potential benefit of CBD and specifically in the benefits towards transitioning to practice.

Acoustic deterrents influence foraging activity, flight and echolocation behaviour of free-flying bats

Acoustic deterrents have shown potential as a viable mitigation measure to reduce human impacts on bats, however, the mechanisms underpinning acoustic deterrence of bats have yet to be explored. Bats avoid ambient ultrasound in their environment and alter their echolocation calls in response to masking noise. Using stereo thermal videogrammetry and acoustic methods, we tested predictions that i) bats would avoid acoustic deterrents and forage and social call less in a ‘treated airspace’; ii) deterrents would cause bats to fly with more direct flight paths akin to commuting behaviour and in line with a reduction in foraging activity, resulting in increased flight speed and decreased flight tortuosity; iii) bats would alter their echolocation call structure in response to the masking deterrent sound. As predicted, overall bat activity was reduced by 30% and we recorded a significant reduction in counts of Pipistrellus pygmaeus (27%), Myotis spp. (probably M. daubentonii) (26%) and Nyctalus and Eptesicus spp. (68%) passes. P. pygmaeus feeding buzzes were also reduced by the deterrent in relation to general activity (by 38%), however social calls were not (only 23% reduction). Bats also increased their flight speed and reduced the tortuosity of their flight paths and P. pygmaeus reduced echolocation call bandwidth and start frequency of calls in response to deterrent playback, probably due to the masking effect of the sound. Deterrence could therefore be used to remove bats from areas where they forage, for example wind turbines and roads, where they may be under threat from direct mortality.

Imperfect mimicry of host begging calls by a brood parasitic cuckoo: a cue for nestling rejection by hosts?

Coevolutionary interactions between avian brood parasites and their hosts often lead to the evolution of discrimination and rejection of parasite eggs or chicks by hosts based on visual cues, and the evolution of visual mimicry of host eggs or chicks by brood parasites. Hosts may also base rejection of brood parasite nestlings on vocal cues, which would in turn select for mimicry of host begging calls in brood parasite chicks. In cuckoos that exploit multiple hosts with different begging calls, call structure may be plastic, allowing nestlings to modify their calls to match those of their various hosts, or fixed, in which case we would predict either imperfect mimicry or divergence of the species into host-specific lineages. In our study of the little bronze-cuckoo Chalcites minutillus and its primary host, the large-billed gerygone Gerygone magnirostris, we tested whether: (a) hosts use nestling vocalisations as a cue to discriminate cuckoo chicks; (b) cuckoo nestlings mimic the host begging calls throughout the nestling period; and (c) the cuckoo begging calls are plastic, thereby facilitating mimicry of the calls of different hosts. We found that the begging calls of little bronze-cuckoos are most similar to their gerygone hosts shortly after hatching (when rejection by hosts typically occurs) but become less similar as cuckoo chicks get older. Begging call structure may be used as a cue for rejection by hosts, and these results are consistent with gerygone defences selecting for age-specific vocal mimicry in cuckoo chicks. We found no evidence that little bronze-cuckoo begging calls were plastic.

Genetic, but Not Behavioral, Evidence Supports the Distinctiveness of the Mealy Amazon Parrot in the Brazilian Atlantic Forest

The presence of unidentified cryptic species within a species complex can obscure demographic trends of vulnerable species, impacting potential species conservation and management decisions. Previous work identified a taxonomic split between Central and South American populations of the mealy amazon (Amazona farinosa) that subsequently resulted in the elevation of these two populations to full species status (Amazona guatemalae and A. farinosa, respectively). In that study, however, a third, geographically disjunct population from the Brazilian Atlantic Forest was insufficiently sampled, limiting the ability of researchers to fully evaluate its genetic distinctiveness. Given that significant levels of biodiversity and endemism are found in this region, we aimed to use genetic and behavioral data to determine if the Atlantic Forest population of A. f. farinosa represents a third cryptic species within the complex. We sequenced 6 genes (4 mitochondrial and 2 nuclear introns) from the Atlantic Forest population of A. f. farinosa to measure the genetic relationships between this population and all other recognized species and subspecies of the mealy amazon. In addition, we use spectrographic cross-correlation and an analysis of 29 acoustic parameters to determine whether the taxa diverge in their learned contact call structure and if the degree of vocal differentiation correlates to genetic structure. We found that the Atlantic Forest population of A. f. farinosa was genetically distinct from that of the greater Amazon basin, but the degree of differentiation was less than that separating the Central and South American taxa. Acoustic analysis revealed substantial variation in contact call structure within each clade. This variation created substantial overlap in acoustic space between the clades. In all, the degree of call divergence between clades did not correspond to the degree of genetic divergence between the same clades. The results suggest that in taxa with substantial geographic variation in learned calls, such as the mealy amazon, vocalizations may not be a useful tool in the identification of cryptic species that are lifelong vocal learners. While these results do not support the elevation of the Brazilian Atlantic Forest population of the mealy amazon to full species status, given current trends of habitat loss in the Atlantic Forest as well as the imperiled status of large parrot species globally, we argue that this population nonetheless warrants special conservation and management consideration as a pool of unique genetic diversity within the southern mealy amazon species.

Born to sing! Song development in a singing primate

In animal vocal communication, the development of adult-like vocalization is fundamental to interact appropriately with conspecifics. However, the factors that guide ontogenetic changes in the acoustic features remains poorly understood. In contrast with a historical view of nonhuman primate vocal production as substantially innate, recent research suggests that inheritance and physiological modification can only explain some of the developmental changes in call structure during growth. A particular case of acoustic communication is the indris' singing behavior, a peculiar case among Strepsirrhine primates. Thanks to a decade of intense data collection, this work provides the first long-term quantitative analysis on song development in a singing primate. To understand the ontogeny of such a complex vocal output, we investigated juvenile and sub-adult indris' vocal behaviour, and we found that young individuals started participating in the chorus years earlier than previously reported. Our results indicated that spectro-temporal song parameters underwent essential changes during growth. In particular, the age and sex of the emitter influenced the indris' vocal activity. We found that frequency parameters showed consistent changes across the sexes, but the temporal features showed different developmental trajectories for males and females. Given the low level of morphological sexual dimorphism and the marked differences in vocal behavior, we hypothesize that factors like social influences and auditory feedback may affect songs' features, resulting in high vocal flexibility in juvenile indris. This trait may be pivotal in a species that engages in choruses with rapid vocal turn-taking.