Dusk Choruses Research Articles

Natural Patterns in the Dawn and Dusk Choruses of a Neotropical Songbird in Relation to an Urban Sound Environment.

Urbanization is one of the more important phenomena affecting biodiversity in the Anthropocene. Some organisms can cope with urban challenges, and changes in birds' acoustic communication have been widely studied. Although changes in the timing of the daily organization of acoustic communication have been previously reported, there is a significant gap regarding possible variations in song structure between dawn and dusk choruses. Considering that urbanization imposes different soundscapes for dawn and dusk choruses, we postulate two hypotheses: (i) there are variations in song parameters between dawn and dusk choruses, and (ii) such parameters within the city will vary in response to urban noise. We studied urban and extra-urban populations of Chiguanco Thrush in La Paz, Bolivia, measuring in dawn and dusk choruses: song length; song sound pressure level; minimum, maximum, range and dominant frequency; and the number of songs per individual. The results support our two hypotheses: there were more songs, and songs were louder and had larger band widths at dawn than at dusk in urban and extra-urban populations. Urban Chiguanco Thrushes sing less, the frequency of the entire song rises, and the amplitude increases as compared with extra-urban Chiguanco Thrushes. Understanding variations between dawn and dusk choruses could allow for a better interpretation of how some bird species cope with urban challenges.

Melatonin duration gates photoperiodic vocal state change in a songbird.

Seasonally breeding animals concentrate courtship to a particular time of year such that their offspring will be reared in a favorable environment. In house sparrows, Passer domesticus, primary (gonads) and secondary (song, plumage, beak color, etc) sexual characteristics are expressed differentially depending on the photoperiod. Removal of the pineal gland (PINX) has no effect on seasonal rhythms in gonad size but alters the photostimulated increase in vocal rate and complexity. Administration of long durations of melatonin, indicative of short days of winter, prevents seasonal recrudescence of song control nuclei in photostimulated house sparrows. In this study, male PINX house sparrows were exposed to three durations of melatonin, while vocalization and locomotor behavior were recorded as they were transitioned from short photoperiod to equinoctial photoperiods of spring. Birds receiving short duration melatonin or vehicle control increased dawn and dusk choruses as well as call complexity. Long durations of melatonin prevented this expansion to a spring-like vocal state observed in birds receiving the short duration of melatonin or vehicle control. The daily distribution of locomotor activity, beak color, and testis size was unaffected by treatment. Vocal state change was defined by our measures in two capacities: (i) increased dawn and dusk choruses, and (ii) an increase in calls associated with territory and mate attraction compared to the winter-like "social song." We conclude that house sparrows use the calendar information provided by melatonin duration to control seasonal vocalization behavior, independent of effects on and of the gonads.

Diel and seasonal patterns of variation in the singing behaviour of Savannah Sparrows (Passerculus sandwichensis)

BackgroundThe vocalizations of birds are dynamic traits that often vary in output with time of day and time of year. By quantifying patterns of diel and seasonal variation in vocal output, we can gain insight into the ecology and evolution of birds and the function of their vocalizations. In this investigation, we quantified diel and seasonal variation in song output by studying a breeding population of Savannah Sparrows (Passerculus sandwichensis).MethodsWe used autonomous recorders to collect extensive recordings across the breeding season in a long-term, colour-marked study population of Savannah Sparrows in eastern Canada. We described diel and seasonal variation across five different breeding stages based on recordings of more than 50,000 songs from 34 males.ResultsDuring the pre-breeding stage, prior to female arrival, males sang a pronounced dawn chorus with a peak in song output during the early morning. During the breeding stage, in contrast, the dawn chorus was diminished and males instead exhibited a pronounced dusk chorus with a peak in song output during the evening. Across the breeding season, the highest levels of song output occurred in late April and early May, soon after males arrived on the breeding grounds, and the lowest levels occurred in August, prior to the departure of birds for the wintering grounds.ConclusionsThese patterns suggest that Savannah Sparrows’ early-season dawn choruses are directed at males and serve a territorial defense function. Later-season dusk choruses, in contrast, appear to play a role in attracting mates and possibly acoustic mate guarding.

Using soundscapes to detect variable degrees of human influence on tropical forests in Papua New Guinea.

There is global concern about tropical forest degradation, in part, because of the associated loss of biodiversity. Communities and indigenous people play a fundamental role in tropical forest management and are often efficient at preventing forest degradation. However, monitoring changes in biodiversity due to degradation, especially at a scale appropriate to local tropical forest management, is plagued by difficulties, including the need for expert training, inconsistencies across observers, and lack of baseline or reference data. We used a new biodiversity remote-sensing technology, the recording of soundscapes, to test whether the acoustic saturation of a tropical forest in Papua New Guinea decreases as land-use intensity by the communities that manage the forest increases. We sampled soundscapes continuously for 24 hours at 34 sites in different land-use zones of 3 communities. Land-use zones where forest cover was fully retained had significantly higher soundscape saturation during peak acoustic activity times (i.e., dawn and dusk chorus) compared with land-use types with fragmented forest cover. We conclude that, in Papua New Guinea, the relatively simple measure of soundscape saturation may provide a cheap, objective, reproducible, and effective tool for monitoring tropical forest deviation from an intact state, particularly if it is used to detect the presence of intact dawn and dusk choruses.

A methodology for analyzing biological choruses from long-term passive acoustic monitoring in natural areas

Long-term passive acoustic monitoring can provide important insights on the study of biological choruses, which represent a key component of natural environments. Nowadays, the development of methods for analysis and visualization of large acoustic datasets is an active area of research. In this context, the present paper addresses how the traditional computation of spectrograms and Sound Pressure Levels (SPL) could be used for analyzing large sound datasets. Additionally, a visualization tool named here as SPL-Gram and a method for automatic detection of trends in dawn and dusk choruses are presented. The dataset used as a case study represents 3months of underwater sound collected in a marine wildlife refuge in southern Brazilian coast. Results reveal events with strong daily periodicity, originated by fish choruses in the frequency band from 0.01–2kHz, and, in the higher frequencies, reflecting acoustic activity of crustaceans. The reported periodicities show a marked relation with sunrise and sunset through the studied period, thus revealing circadian cycles present in the monitored environment. The proposed methodology is not only easy for implementation, but also proves to be valuable in the description of daily and seasonal patterns of biological choruses in large acoustic datasets.

Information obtained from long-term acoustic recordings: applying bioacoustic techniques for monitoring wetland birds during breeding season

Digital acoustic recording devices allow for recording of vocal activity of animals over long time periods and therefore open new perspectives for monitoring. In this paper results of a bioacoustic monitoring of birds in a wetland restoration area in Mecklenburg-Western Pomerania in Northeastern Germany are presented. Ninety minutes of sound recordings were made daily from March 29 until May 30 2012 using a four-channel recording setup. The recording schedule was mainly designed for nocturnal birds but also included dawn and dusk choruses. By listening to the recordings, supported by spectrographic visualization, 61 bird species could be detected. Despite the fact that most of the recordings were made during the night, no period of absolute silence was detected. The occurrence data allow some conclusions on the state of the bird species, e.g., breeding bird, resting during migration, or guest only. The bioacoustic monitoring revealed the occurrence of rare nocturnal birds such as Little Crake (Porzana parva), Spotted Crake (Porzana porzana) and Short-eared Owl (Asio flammeus). For the Eurasian Bittern (Botaurus stellaris) data on vocal activity and population size could be obtained. The study has shown that automated acoustic recordings can be applied for long-term monitoring of bird populations in remote areas.

Owl dusk chorus is related to the quality of individuals and nest-sites

Dawn and dusk choruses represent one of the most investigated topics in avian vocal behaviour, but their underlying basis remains unclear. As with the dawn chorus in passerines, dusk chorus in owls seems to support the mate and rival assessment hypothesis and happens during the most constraining period, as individuals have not yet fed and, under the handicap principle, dusk chorus is likely to reveal inter‐individual differences in competitive ability, body condition and/or habitat quality. Here, a study of vocal displays at dusk of 14 Eurasian Eagle Owls Bubo bubo revealed a temporal succession in the order in which males began their vocalizations. The vocalization order appeared to be related to both the quality of the nesting territory (based upon mean number of fledged young and proportion of rats in the diet) and the male's individual quality, as revealed by haematocrit values and the brightness of the white throat patch.

Low cost (audio) recording (LCR) for advancing soundscape ecology towards the conservation of sonic complexity and biodiversity in natural and urban landscapes

Low cost (audio) recorders (LCRs) represent a new opportunity to investigate the sonic complexity of both natural and urban ecosystems. LCRs are inexpensive sampling audio recorders which have the external shape of a universal serial bus (USB) flash drive, and are composed of a microphone, an analog-to-digital converter, central processing unit with permanent internal non-volatile memory, rechargeable battery, and a USB connection. The reduced dimensions allow the device to be deployed inconspicuously within any environment, in any configuration and for an extended time period. This investigation tested a specific type of LCR (UR-09) with a spectral range of 8 kHz - sufficient to cover the acoustic range of most western Palearctic songbirds. The reliability of the UR-09, compared with other commercial recorders (Zoom H4 and Song Meter SM1) and based on the quality of recordings quantified by the Acoustic Complexity Index (ACI), was tested and confirmed. An example of the application of LCRs is presented in an evaluation of the audio patterns occurring during dawn and dusk choruses within a forested ecosystem. Results of this investigation are encouraging and a new generation of LCR devices is currently being designed with real-time acoustic data processing capabilities, timer programmability, a larger frequency range and wireless communication compatibility. LCRs are revealed to be ideal instruments to conduct surveys in fragile or protected areas and also in urban environments. Moreover, due to their low cost, they can be used to encourage research in soundscape ecology, especially within developing countries, where large areas can be monitored by professionals or incorporating citizen science models of data collection.

Visualization of temporal change in soundscape power of a Michigan lake habitat over a 4-year period

Soundscape Ecology is an emerging area of science that does not focus on the identification of species in the soundscape but attempts to characterize sounds by organizing them into those produced by biological organisms such as birds, amphibians, insects or mammals; physical environmental factors such as thunder, rainfall or wind; and sounds produced by human entities such as airplanes, automobiles or air conditioners. The soundscape changes throughout the day and throughout the seasons. The soundscape components that create the sound occur at different frequencies. A set of metrics termed soundscape power was computed and visualized to examine the patterns of daily and seasonal change in the soundscape.Automated recorders were used to record soundscape samples every half hour for one minute duration from six sites on an uninhabited island in Twin Lakes located near Cheboygan in Michigan's northern Lower Peninsula. Each recording was divided into 1kHz frequency intervals and visualization tools were used to examine the soundscape power in each interval during 48 half-hour time segments from April–October for four consecutive years. Daily patterns of soundscape power change were also examined during the seven month sample period. To synthesize the data set, three dimensional contour plots were used to visualize day of the year (x), time of day (y) and soundscape power (z) for several frequency intervals. A further synthesis was developed to visualize soundscape change using a Normalized Difference Soundscape Index (NDSI) which is a ratio of low to high frequencies.The visualization of the soundscape revealed discrete patterns in the soundscape including striking changes in the time of the occurrence of dawn and dusk choruses. The patterns in the soundscape were remarkably similar over the four-year investigation. Soundscape power in the lower frequency examined (1–2kHz) was a dominant feature of the soundscape at Twin Lakes and the low frequency soundscape power was negatively correlated with higher frequency sounds.The soundscape power metrics and the visualizations of the soundscape produced in this study should provide a means of rapidly synthesizing large numbers of recordings into meaningful patterns to examine soundscape change. This is especially useful because of the need to develop indices of ecological metrics based on soundscape attributes to assist resource managers in making decisions about ecosystem integrity. Visualization can also be of immense benefit to examine patterns in large soundscape time series data sets that can be produced by automated recording devices.

Neighbours' talk: interspecific choruses among songbirds

In territorial songbirds, duets between mates represent one of the best-known examples of communal display, with the main function being the defence of joint resources. In this study, we found evidence of a coordinated choral display performed by neighbouring heterospecific songbirds. In such choruses, most of the participating species perform a deliberate temporal overlap of songs, thus suggesting agonistic behaviour. However, they then utilize a complex form of behaviour to avoid signal jamming, making the aggressive purpose unlikely. We define these displays as “coordinated interspecific choruses”. We recorded dusk choruses of songbirds living in a mixed turkey oak wood in central Italy, and then carried out a niche overlap analysis using null models that were intended for investigations of concurrent emissions of songs, finding that species tend to sing concurrently instead of using the refractory period of another species. Among the species singing concurrently, about half used the same frequency range, but instead of finding considerable spectral overlap between their vocalizations, the number of real spectral overlaps was lower than would be expected by chance. We propose a tentative explanation for this, where such choruses are the expression of the existence of a neighbourhood of different species that has evolved a communal signal that is similar to that used by mates in a pair, i.e. coordinated vocalizations. As coordination requires experience of each other's songs, we propose that evolution has selected individuals that are more skilled at learning heterospecific songs.

Dawn and Dusk “Chorus” in Visually Communicating Jamaican Anole Lizards

A key hypothesis explaining the existence of dawn and dusk choruses in acoustically communicating animals centers on the need to advertise continued territorial occupancy after and before a period of nocturnal inactivity. If this hypothesis is correct, it follows that similar dawn and dusk choruses should occur in territorial animals exploiting other signal modalities. Adult male Anolis lizards defend territories by using elaborate head-bobbing displays and extensions of a throat fan or dewlap. Males are inactive at night and return to their territories at dawn, remaining there until dusk. I quantified the production of visual displays as a function of time of day for four species on the island of Jamaica: Anolis lineatopus, Anolis sagrei, Anolis grahami, and Anolis opalinus. All exhibited dawn and/or dusk peaks in display behavior. These patterns have remarkable parallels with the dawn and dusk choruses reported for many acoustically communicating animals.

Resonating sea urchin skeletons create coastal choruses

Ambient sound intensity in coastal waters typically increases by as much as 2 to 3 orders of magnitude (20 to 30 dB) immediately after sunset and before sunrise in what is known as a dawn and evening chorus. The dominant feature of the chorus is most often a dramatic increase in spec- trum level usually in a narrow frequency range of around 400 to 4000 Hz. While the sources of some choruses have been identified, the sources of many choruses remain unidentified. Here we confirm that in New Zealand, the sound is the feeding noises of sea urchins for which frequencies in the range of 800 to 2800 Hz are amplified by the ovoid calcareous skeleton, or 'test', of urchins acting as a Helmholtz resonator. Furthermore, the timing of the dawn and dusk choruses is related to the crepus- cular feeding activity of sea urchins. Underwater sound recordings from individual sea urchins of a range of sizes confirm earlier speculation that the urchin test acts as a Helmholtz resonance chamber capable of generating sufficient acoustic power to create these choruses. These results indicate the potential importance of coastal urchin populations as a major contributor to the underwater choruses, which appear to be important in assisting the larvae of key reef species, such as fishes, crabs, and lobsters, to locate suitable settlement sites.

Seasonal and diel budgets of song: a study of Savi’s warbler (Locustella luscinioides)

Seasonal and diel patterns of singing activity of Savi’s warblers (Locustella luscinioides) were studied in two areas of Central Europe 300 km apart, over a period of 18 years. We assess about 4,600 records of individuals singing. Males were found to exhibit similar singing activity in both study sites. They started to sing after arrival at the beginning of April and peaked from the end of April to the beginning of May. Thereafter, their singing activity was lower but more stable for a relatively long period from mid-May to mid-July. At the end of July, males sang only sporadically and singing activity ceased at the beginning of August. At the beginning and towards the end of the song-period males sang sporadically whereas in the period of the highest singing activity they sang over the entire 24-h period. During the whole song-period, there was a significant difference in singing activity between daylight and the dark (67.2 and 32.8%, respectively). However, the period of daylight was longer. Average singing activity showed similar levels in daylight and the dark with mean numbers of 5.9 and 6.6 males per hour, respectively. Major changes in singing activity were related to the twilight periods. There were distinctive dawn and dusk choruses. In the morning, Savi’s warblers exhibited similar levels of singing activity over 3 h of the dark before twilight, singing reached its highest level at twilight and 1 h after twilight. During the evening, singing activity reached its highest-level 1 h before twilight, while during twilight it was decreasing, with a considerable decline 1 h after nightfall.

Two explanations of the dawn chorus compared: how monotonically changing light levels favour a short break from singing

I used optimality modelling to compare two of the most plausible and general explanations for the dawn and dusk peaks in bird song output. Kacelnik's explanation is that foraging is inefficient in poor light, but that social interactions are less affected, making singing more worthwhile than foraging. McNamara et al.'s explanation is based on stochasticity in foraging success and overnight energy requirements; it has been extensively analysed with stochastic dynamic programming models. Both explanations are now incorporated into this sort of model. I used various functions to link success of foraging and singing to time of day, but assumed that above some light level there is no further effect. Kacelnik's explanation has as strong an effect as stochasticity in generating dawn and dusk choruses. It also predicts short pauses in the singing output just after the dawn chorus and before the dusk chorus. The former arises because birds delay foraging when it will become more profitable later, until foraging success reaches a plateau, when the energetic debt accumulated makes them forage. The principle of this see-saw double switch in behaviours may apply to other explanations for the dawn chorus, and to other shifts in behaviour when conditions change gradually. The model predicts that from day to day cloud cover determines when a dawn chorus starts, but that overnight temperature and wind strength have more effect on chorus intensity and duration. I discuss what sort of observational and experimental data on singing routines would better test this model. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.

The Functions of Advertising Song in the Sedge Warbler (Acrocephalus Schoenobaenus) and the Reed Warbler (a. Scirpaceus)

AbstractThe possible functions of male advertising song in the Sedge Warbler (Acrocephalus schoenobaenus) and the Reed Warbler (A. scirpaccus) were studied using both observational and experimental techniques in the field. The seasonal rhythms of advertising song in the populations over three years were found to be species-specific, and were related to male arrival, female arrival and pairing. Population song was also related to population breeding acivity as revealed by the seasonal pattern of egg-laying. When population song was more synchronised, population breeding activiy was more synchronised towards the start of the breeding season. The diurnal rhythms of advertising song in individual marked males were monitored before and after pairing. In Sedge Warbler males advertising song ceased completely after pairing, and only resumed if the female deserted. In Reed Warbler males, a vestige of the former diurnal rhythm remained after pairing, with groups of paired males performing dawn and dusk choruses of 'social song'. The interspecific differences were extended further, as both observations and play-back experiments confirmed that paired male Sedge Warblers did not utilise advertising song in territorial interactions, but performed visual 'threat' displays instead. Male Reed Warblers however utilised advertising song in territorial interactions both before and after pairing. A functional interpretation of advertising song is presented, based upon the observational and experimental evidence collected. It is suggested that the prime function of persistent advertising song in the unpaired male is sexual attraction of the female, and that intermittent advertising song from paired males functions in territorial defence. The precise function(s) of social song in paired males are not known, but some suggestions are discussed. The interspecific differences in the functional spectra of advertising song found in the Reed Warbler (sexual, territorial, social) and Sedge Warbler (sexual only,) are discussed in relation to habitat and social organisation. The Reed Warbler inhabits more dense, non-visual habitats, and the Sedge Warbler more open, visual ones. Thus the Sedge Warbler has developed comparatively more visual forms of advertisement, and the Reed Warbler more vocal forms which in the latter case is reflected particularly in the wider functional spectrum of advertising song. The only common function for which advertising song is utilised in both species is sexual attraction of the female. This, and other evidence discussed suggests that sexual attraction may be the most important and perhaps the most primitive function of advertising song in these species.