Interspecific acoustic recognition in two European bat communities

Echolocating bats emit echolocation calls for spatial orientation and foraging. These calls are often species-specific and are emitted at high intensity and repetition rate. Therefore, these calls could potentially function in intra- and/or inter-specific bat communication. For example, bats in the field approach playbacks of conspecific feeding buzzes, probably because feeding buzzes indicate an available foraging patch. In captivity, some species of bats recognize and distinguish the echolocation calls of different sympatric species. However, it is still unknown if and how acoustic species-recognition mediates interspecific interactions in the field. Here we aim to understand eavesdropping on bat echolocation calls within and across species boundaries in wild bats. We presented playbacks of conspecific and heterospecific search calls and feeding buzzes to four bat species with different foraging ecologies. The bats were generally more attracted by feeding buzzes than search calls and more by the calls of conspecifics than their heterospecifics. Furthermore, bats showed differential reaction to the calls of the heterospecifics. In particular, Myotis capaccinii reacted equally to the feeding buzzes of conspecifics and to ecologically more similar heterospecifics. Our results confirm eavesdropping on feeding buzzes at the intraspecific level in wild bats and provide the first experimental quantification of potential eavesdropping in European bats at the interspecific level. Our data support the hypothesis that bat echolocation calls have a communicative potential that allows interspecific, and potentially intraspecific, eavesdropping in the wild

Traffic noise exposure depresses plasma corticosterone and delays offspring growth in breeding zebra finches.

The impact of human activity on the acoustic environment is overwhelming, with anthropogenic noise reaching even remote areas of the planet. The World Health Organization has identified noise pollution as one of the leading environmental health risks in humans, and it has been linked to a myriad of short- and long-term health effects in exposed individuals. However, less is known about the health effects of anthropogenic noise exposure on animals. We investigated long- and short-term effects of traffic noise on zebra finches breeding in small communal aviaries, using a repeated measures design. Birds bred in both noise and no-noise conditions, and we measured baseline plasma glucocorticoid levels before, during and after breeding. In addition, we assayed immune function, measured reproductive success and offspring growth and compared rates of extra-pair paternity of breeding adults. Breeding birds had significantly lower baseline plasma corticosterone levels when exposed to traffic noise than when they were not exposed to noise playback. In addition, the nestlings reared during noise exposure were lighter than nestlings of the same parents when breeding in control conditions. Our results suggest that traffic noise poses a more severe hurdle to birds at more vulnerable stages of their life history, such as during reproductive events and ontogeny. While chronic exposure to traffic noise in our birds did not, by itself, prove to be a sufficient stressor to cause acute effects on health or reproductive success in exposed individuals, it did result in disruptions to normal glucocorticoid profiles and delayed offspring growth. However, animals living in urban habitats are exposed to a multitude of anthropogenic disturbances, and it is likely that even species that appear to be thriving in noisy environments may suffer cumulative effects of these multiple disturbances that may together impact their fitness in urban environments

Effect of noise on vocal behaviour, physiological systems and reproductive success in birds

Urbanization is considered one of the biggest environmental challenges of our times. One of the consequences of the continuing growth in global urbanization is increasing noise pollution. Indeed, anthropogenic noise is predicted to rise considerably levels in the near future. The concern about an increase in anthropogenic noise is that it has been associated with a series of negative effects for humans and animals. For instance, noise is linked to cognitive and auditory problems in humans. In birds, it has been related to changes in vocal signal traits and changes in breeding and parental care behaviour, among others. Despite the relevance and the consequences of anthropogenic noise for humans and wildlife, the effects of noise on health and fitness of the urban fauna are still little known.In this thesis, I investigate how noise can impact birds through different mechanistic pathways by disrupting communication, by impacting physiological systems via stress, and by interfering with development. I choose birds as model organisms for this topic because many species of birds are common inhabitants of cities and have developed a variety of strategies to adapt to urban habitats. Thus, an investigation about the impact of noise on birds not only contributes to the advancement of basic science, but can have direct relevance for conservation actions aimed at maintaining or increasing biodiversity in urban landscapes. In addition, the similarities between humans and birds such as the effects of environmental conditions on physiological systems and the vocal learning process, may allow us to increase the understanding of the mechanism underlying effects of noise in people exposed to chronic noise.The disruption of vocal communication can have detrimental consequences for birds since they use acoustic signals for a variety of functions including mate attraction, territorial defense, kinship communication, maintenance of social cohesion, and information sharing about food sources and potential predators Environmental noise can cause such as disruption. Consequently, birds have developed strategies to overcome the challenge of communicating in noisy environments. One strategy is known as Lombard effect, in which in response to an increase in the background noise, a signaler increases its vocal amplitude. This effect is well-studied in human speech and has also been reported in other mammals and several bird species and is considered as a basic mechanism for maintaining communication in noise. In some cases, the Lombard effect is accompanied by additional changes in signal parameters, such as increased frequency. To date, only three out of eight major avian clades have been studied, therefore the evolution of the Lombard effect and other related vocal adjustments in birds are still unclear. In chapter I.1, I report the first evidence for the Lombard effect in an anseriform bird, the mallard duck (Anas platyrhynchos). Linked to the Lombard effect, ducklings also increased the peak frequency of their calls in noise, however, they did not change any of the others measured parameters. This evidence supports the hypothesis that all extant birds use the Lombard effect to solve the common problem of maintaining communication in noise. Thus, Lombard effect is an ancestral trait shared among all living avian taxa, which strongly suggests that it has evolved more than 70 million years ago within that group. At the same time, our data suggest that parameter changes associated with the Lombard effect follow more complex patterns, with marked differences between taxa, some of which might be related to proximate constraints. In addition to changing certain traits of the vocalizations, birds can also shift the time of singing behaviour in presence of noise. For instance, birds in cities start to sing earlier in the morning than birds in the rural areas. Some studies have attributed these temporal shifts to increased levels of light pollution, while other studies suggest that the shifts are linked to noise pollution. However, all previous studies have taken place in temperate zones. In contrast to temperate birds, tropical birds experience little seasonal variation in day length and may be less dependent on light intensity as a modifier for reproductive behaviours such as song. To test whether noise or light pollution has an impact on the dawn chorus of a tropical bird, in chapter I.2 I investigated the singing behaviour of rufous-collared sparrows (Zonotrichia capensis) in Bogota, Colombia, at two times during the year. The results show that birds start to sing earlier in places with high noise levels. On the other hand, light pollution did not have a significant effect on song timing. Birds may begin to sing earlier in noisy areas to avoid acoustic masking by traffic that peaks later in the morning. These results also suggest that some tropical birds may be less sensitive to variations in day length and thus less sensitive to light pollution.Noise not only can impact acoustic communication, it can also have an impact on short and longterm effects on health and fitness of wildlife. To test how chronic noise affects physiology and well-being of birds, I did a series of experiments in breeding zebra finches (Taenopygia guttata) and their offspring. In chapter II, I experimentally investigated the direct and cross-generational effects of traffic noise on telomeres at 21 and 120 days post-hatch. Telomere length is a measure of cellular ageing that is predictive of disease and longevity in humans and other organisms. Birds were exposed to traffic noise at different developmental stages (pre and post-fledging). Noise did not have a significant effect on telomeres when the birds were exposed pre-fledging. On the other hand, birds exposed to noise during the post-fledging stage exhibited faster telomere loss than pre-fledging exposed and control birds. In chapter III, breeding birds were exposed to noise during courtship and nestling period and I measured the impact of noise on the immune system, baseline corticosterone levels, reproductive success and extra-pair paternity as well as the growth rate of the offspring. Although I did not find significant differences in any of the traits measured in breeding birds, I did find that offspring of birds exposed to noise were smaller than offspring in control groups. These results suggest that traffic noise affects birds differently depending on which the developmental stage they were in when they were exposed.Taken together, the evidence of this thesis suggests that noise has a varying impact on traits related to fitness, such as vocal behaviour, longevity, reproductive success and growth rate in birds depending on species identity, ecological factors and developmental stages. The combination of laboratory and field approaches is necessary to understand how the different elements of urbanization, such as noise pollution, are impacting wildlife in the urban areas.publishe

Data from: Anthropogenic noise, but not artificial light levels predicts song behaviour in an equatorial bird

Birds in cities start singing earlier in the morning than in rural areas; commonly this shift is attributed to light pollution. Some studies have suggested that traffic noise has a stronger influence on singing activity than artificial light does. Changes in the timing of singing behaviour in relation to noise and light pollution have only been investigated in the temperate zones. Tropical birds, however, experience little seasonal variation in day length and may be less dependent on light intensity as a modifier for reproductive behaviours such as song. To test whether noise or light pollution has a stronger impact on the dawn chorus of a tropical bird, we investigated the singing behaviour of rufous-collared sparrows (Zonotrichia capensis) in Bogota, Colombia at two times during the year. We found that birds in places with high noise levels started to sing earlier. Light pollution did not have a significant effect. Birds may begin to sing earlier in noisy areas to avoid acoustic masking by traffic later in the morning. Our results also suggest that some tropical birds may be less sensitive to variations in day length and thus less sensitive to light pollution

Data from: Anthropogenic noise, but not artificial light levels predicts song behaviour in an equatorial bird

Birds in cities start singing earlier in the morning than in rural areas; commonly this shift is attributed to light pollution. Some studies have suggested that traffic noise has a stronger influence on singing activity than artificial light does. Changes in the timing of singing behaviour in relation to noise and light pollution have only been investigated in the temperate zones. Tropical birds, however, experience little seasonal variation in day length and may be less dependent on light intensity as a modifier for reproductive behaviours such as song. To test whether noise or light pollution has a stronger impact on the dawn chorus of a tropical bird, we investigated the singing behaviour of rufous-collared sparrows (Zonotrichia capensis) in Bogota, Colombia at two times during the year. We found that birds in places with high noise levels started to sing earlier. Light pollution did not have a significant effect. Birds may begin to sing earlier in noisy areas to avoid acoustic masking by traffic later in the morning. Our results also suggest that some tropical birds may be less sensitive to variations in day length and thus less sensitive to light pollution

Anthropogenic noise, but not artificial light levels predicts song behaviour in an equatorial bird.Data.

Onset time of the dawn chorus of rufous-collared sparrows, artificial light levels and noise levels of their territories in May-June and November-December in the city of Bogota (place 1 to 33) and rural areas in the Colombian Andes. The exact coordinates of the rural areas are unknown, the territories of rufous-collared sparrows were found in the surroundings of the village Nutrias that belong to the town Susa, Cundinamarca (5° 30′ 0″ N, 73° 50′ 0″ W)

Dorado-Correaetal.DATA.ducks.2017

Call characteristics of ducklings exposed to three different noise treatments