Flight Song Research Articles

Social Evaluation of Female Preferences in Birds’ Songs and Songs Function in Mating

The selection of a mate is influenced by bird songs, which are known for their complexity and diversity. This essay delves into the realm of female mate preferences within various avian species, presenting both supportive and contradictory evidence regarding the importance of larger song repertoires. It emphasizes the distinction between controlled laboratory settings and ecologically authentic field studies, revealing nuanced findings. Furthermore, it explores additional factors like individual variation, song complexity, cognitive abilities, and contextual adaptability to elucidate this mixed outcome, enriching our comprehension of avian communication dynamics. Male bird songs emerge as essential conduits for conveying vital information that enables females to make informed choices about potential mates. Through song types and tones, they transmit demographic information, social status, and physical condition, offering females a means of remote evaluation. The examination of distinct song behaviors, including duets, flight songs, and the dawn chorus, highlights their significance as indicators of partnership, strength, and commitment. The varied strategies employed by male birds and the selective decisions made by females underscore the profound role of avian songs in shaping relationships and ensuring the perpetuation of species. This marks a substantial contribution to our understanding of avian mate selection dynamics.

Vocalizations and song flight of Pink-billed Lark Spizocorys conirostris

Pink-billed Lark Spizocorys conirostris is an unobtrusive bird with a relatively low reporting rate of ~10% in the second South African Bird Atlas Project (SABAP2). Little is known about the species’ vocalizations and song flight, and published descriptions are vague or confus-ing. Here I provide a detailed description of vocalizations and song flights as recorded between 2012 and 2019 in Limpopo Province, South Africa. Vocalizations were recorded using a digital recorder for calls in flight and occasionally on the ground, or were obtained from a video camera placed near the nest to record vocalizations that would be impossible to record from a distance. Twelve categories of vocalizations were identified, eight of them described here for the first time. The majority of the eight newly described vocalizations were obtained from video footage. A more detailed description of the song flight is also provided and should clarify some of the confusing descriptions provided in the literature. Knowledge of the flight song of Pink-billed Lark is valuable to locate and identify the species and will be an asset for moni-toring programmes and SABAP2.

Novel ideas to further expand the applicability of rhythm analysis.

The temporal structure of animals’ acoustic signals can inform about context, urgency, species, individual identity, or geographical origin. We present three independent ideas to further expand the applicability of rhythm analysis for isochronous, that is, metronome‐like, rhythms. A description of a rhythm or beat needs to include a description of its goodness of fit, meaning how well the rhythm describes a sequence. Existing goodness‐of‐fit values are not comparable between methods and datasets. Furthermore, they are strongly correlated with certain parameters of the described sequence, for example, the number of elements in the sequence. We introduce a new universal goodness‐of‐fit value, ugof, comparable across methods and datasets, which illustrates how well a certain beat frequency in Hz describes the temporal structure of a sequence of elements. We then describe two additional approaches to adapt already existing methods to analyze the rhythm of acoustic sequences of animals. The new additions, a slightly modified way to use the already established Fourier analysis and concrete examples on how to use the visualization with recurrence plots, enable the analysis of more variable data, while giving more details than previously proposed measures. New methods are tested on 6 datasets including the very complex flight songs of male skylarks. The ugof is the first goodness‐of‐fit value capable of giving the information per element, instead of only per sequence. Advantages and possible interpretations of the new approaches are discussed. The new methods enable the analysis of more variable and complex communication signals. They give indications on which levels and structures to analyze and enable to track changes and differences in individuals or populations, for instance, during ontogeny or across regions. Especially, the ugof is not restricted to the analysis of acoustic signals but could for example also be applied on heartbeat measurements. Taken together, the ugof and proposed method additions greatly broaden the scope of rhythm analysis methods.

Activity patterns of the soprano pipistrelle Pipistrellus pygmaeus throughout the year in southern Norway

BackgroundMost temperate bats are regular hibernators in the winter. Knowledge about the length of their active season and how they adjust their nightly activity throughout the season, is critical to conservation. The characteristics of these are likely to vary with climate as well as latitude. This study investigated the flight activity of the soprano pipistrelle Pipistrellus pygmaeus in Frafjord, a small valley in the south-western corner of Norway (58° 50′N 6° 18′E) with an oceanic climate.ResultsActivity was recorded with an ultrasound recorder throughout April 2018 to June 2019 at one site, with supplemental recordings in March to June 2020, i.e., covering all months of the year. Recordings at other nearby sites were made in the summers (June–August) of 2016, 2017, 2019 and 2020, as well as some of the last days in December 2019 to the first days of January 2020. Overall, soprano pipistrelles were recorded flying in all months of the year, but very few in December–March. Regular activity was recorded from late April or early May until late October, and some recordings were also made in November. The highest numbers of recordings were made in August and September. Social calls, i.e. male song flights, were recorded from April to November, with the vast majority in August and September. Nearly all recordings were made between sunset and sunrise.ConclusionsThe soprano pipistrelle in this region showed regular activity through 6–7 months of the year. It adjusted its activity to the changing night length throughout the year, closely following sunset and sunrise. It was rarely recorded flying before sunset and almost never after sunrise. Most activity was recorded in the middle of the night, and social calls also followed this trend closely. Harems in late summer and autumn were confirmed in a bat box, which was also used for winter hibernation.

Seasonal and diel plasticity of song type use in individual ovenbirds (Seiurus aurocapilla)

AbstractAnimal communication is an important aspect of ecology across taxa, and there is a growing area of research that examines how animals plastically adjust their signals to account for both abiotic and biotic factors. Song type use and the temporal plasticity of song have been described in many bird species, but as of yet, few studies have examined how song type use may change across both seasonal and diel timeframes, and no studies have considered individual‐level variation in plasticity. Using a hierarchical framework, we examined temporal patterns of primary and flight song use in ovenbirds (Seiurus aurocapilla; N = 21 individuals). We recorded ovenbird songs (N = 99,259) with autonomous recorders over 24‐hr periods once per week across a breeding season near Sault Ste. Marie, Canada. As predicted, the occurrence and frequency of both song types significantly decreased over the season and showed temporal separation over diel periods. Primary songs peaked at dawn and declined throughout the day, while flight songs peaked at dusk and night. Our results support that primary songs have multiple functions as they remained more frequent during dawn and morning across the breeding season, while flight songs likely serve an intersexual function as they decreased similarly for all diel periods as mating opportunities decreased. Individuals were consistent in how frequently they sang their primary songs, but not their flight songs, suggesting that flight songs are more plastically expressed. We highlight the importance of examining plasticity in animal communication at the individual level as we show that males significantly differed in both their song behaviours (random intercepts) and the seasonal plasticity (random slopes) in these behaviours. Integrating themes such as song type use, temporal plasticity, and individual variation will be important for examining the evolutionary mechanisms that shape animal communication systems.

Characterising the flight song: repeatable individual variation of Ovenbird song features

ABSTRACT The songs of most passerines have been well described; however, songs from some species are more difficult to record and have yet to be characterised. The Ovenbird (Seiurus aurocapilla) flight song occurs rarely, is complex in its syllable composition, and its function is still not well understood. We examine the structure of the Ovenbird flight song using the largest sample of warbler flight songs to date (n = 396, 23 individuals) from autonomous recordings made in Sault Ste. Marie, Canada. We characterised the syllable repertoire of this song, examined song syntax, compared syllable sharing among males, and estimated repeatability of several song features. Syllable repertoires varied among males and they appeared to transition differently between syllables while singing, but we found no evidence for syllable sharing between neighbours. Male Ovenbirds were significantly repeatable in the syllable compositions of their flight songs, but repeatability estimates were lower for terminal compared to introductory segments. We find weak evidence of a negative relationship between song features at the within-individual level, suggesting that individuals also demonstrate considerable plasticity when singing. Understanding variation in the Ovenbird flight song will lead to a better understanding of the function(s) of this song type.

Understanding the function of nocturnal song in ovenbirds: males do not countersing at night

Many diurnal bird species vocalize at night, however the function of nocturnal song is, generally, still poorly understood. Previous research has suggested that nocturnal song may serve a social function and is influenced by environmental factors. To test whether males attend to the nocturnal song of conspecifics, we experimentally exposed ovenbirds Seiurus aurocapilla to nocturnal flight songs, and recorded their response both during the night and during the following dawn chorus. We compared latency to song and vocal output before and after playback exposure to determine if males altered their vocalizations in response to exposure to flight songs from an unknown male. We found no evidence of counter singing or change in nocturnal song output, nor a change in vocal output during the dawn chorus following playback exposure. Our results suggest that, in ovenbirds, nocturnal song does not serve as an intraspecific social function. Nocturnal song, through rare, may be significant in the mating systems of some diurnal bird species, and requires additional study.

The appearance of Lapland Buntings <em>Calcarius lapponicus</em> in song flight

The territorial song flight of Lapland Bunting Calcarius lapponicus males has been described in the literature as similar to that of pipits Anthus spp. Observations at Hardangervidda, S. Norway, show that the buntings sing over their territories while gliding about more or less horizontally, quite different from the steep ascending and descending flight trajectories of singing pipits. Also, the buntings’ body plan during song flight differs strikingly from that of pipits, potentially creating a very different visual signal.

Flight Phases in the Song of Skylarks: Impact on Acoustic Parameters and Coding Strategy

Skylarks inhabit open fields and perform an aerial song display which serves as a territorial signal. The particularly long and elaborate structure of this song flight raises questions about the impact of physical and energetic constraints acting on a communication signal. Song produced during the three distinct phases of the flight - ascending, level and descending phase could be subject to different constraints, serve different functions and encode different types of information. We compared song parameters during the ascending and the level phases. We found that the structure of the song varied with the phase of the flight. In particular, song had a higher tempo when skylarks were ascending which might be related to higher oxygen and energetic demands. We also explored which phase of the song flight might encode individuality. Earlier studies reported that skylarks reduced their territorial response to established neighbours if the neighbour song was broadcasted from the correct adjacent boundary, but reacted aggressively if the neighbour songs were broadcasted from an incorrect boundary (mimicking a displaced neighbour). Such differential response provides some evidence for individual recognition. Here, we exposed subjects to playback stimuli of neighbour song in which we had replaced either the song produced during the level or the ascending phase by the relevant song of the neighbour from the incorrect border. Singing response was higher towards stimuli in which the ‘level phase song’ was replaced, indicating that skylarks could be able to recognise their neighbours based on song of this phase. Thus, individuality seems to be primarily coded in the level phase of the flight song.

Proximate and ultimate factors that promote aggregated breeding in the Western Sandpiper.

We report that Western Sandpipers (Calidris mauri) on Alaska's Yukon-Kuskokwim River Delta exhibited aggregated breeding behavior at a relatively small spatial scale. Prior to clutch initiation, males performing song flight displays on a 36 ha plot were aggregated as were subsequent initial nesting attempts on the plot. We tested three hypotheses commonly invoked to explain aggregated breeding in territorial species (social mate choice, predation, and material resources hypotheses), and found support for the material resources hypothesis, as dispersed individuals were more often associated with tundra habitat patches, and aggregated individuals nested more often in undulating-tundra habitat patches compared to patch availability. The pattern of habitat occupancy conformed to an ideal despotic distribution with aggregated nesting birds in undulating-tundra patches experiencing lower reproductive success. On our study plot, older, more aggressive males solicited females more often, and defended larger, more dispersed sites in tundra habitat patches, compared to younger, less aggressive males that were aggregated in undulating-tundra habitat patches. Breeding aggregations are often concentrated on or near a critical resource. In contrast, Western Sandpiper breeding aggregations occur when dominant and/or older individuals exclude younger, subordinate individuals from preferred habitat. Although many taxa of non-colonial birds have been reported to aggregate breeding territories, this is the first quantitative report of aggregated breeding behavior in a non-colonial monogamous shorebird species prior to hatch.

MICRODIALECT AND GROUP SIGNATURE IN THE SONG OF THE SKYLARK ALAUDA ARVENSIS

ABSTRACT The Skylark Alauda arvensis is a territorial species of open landscape in which pairs settle in stable and adjacent territories during the breeding season. Due to the heterogeneity of the habitat, territories are gathered in patches spaced by a few kilometres, in which each male produces very long and complex flight songs as a part of the territorial behaviour. We showed that, in a given patch, all the males (neighbours) share some particular sequences of syllables in their songs, whereas males settled in different patches (strangers) have almost no sequences in common. Such a phenomenon is known as microdialect. To test the hypothesis that these shared sequences support a group signature, we made playback experiments with “chimeric” signals: songs of strangers where the sequences shared by neighbours were artificially inserted. Behavioural responses to playbacks indicated a neighbour-stranger discrimination consistent with the dear enemy phenomenon, i.e. a reduced aggression toward neighbours compared to strangers. Furthermore, the same level of responses, observed when a “chimeric” song and a neighbour song were broadcast, indicated that shared sequences are recognised and identified as markers of the neighbourhood identity.

Flight songs of Dusky Flycatchers: a response to bird-hunting raptors?

Flight-song displays usually include distinctive vocalizations and behaviors that are probably energetically expensive and also likely to attract the attention of aerial predators. We observed flight songs performed by Dusky Flycatchers (Empidonax oberholseri) in two breeding populations. During 15 yr at Tioga Pass, California, we observed the display twice and, during 9 yr at Steamboat Mountain, British Columbia, we observed 21 flight-song displays. These displays were generally observed later in the breeding season, suggesting that they were not used for courtship, mate attraction, or territory defense. However, for 83% of these displays, a raptor was observed to be present, usually either an American Kestrel (Falco sparverius) or a Sharp-shinned Hawk (Accipiter striatus). We hypothesize that these displays, like stotting or other pursuit-deterrent signals, may be directed at small raptors that represent a greater threat to Dusky Flycatchers and might deter attack by signaling awareness. However, because only males were observed performing flight-song displays, it is also possible that these displays serve to alert mates and offspring about the presence of an aerial predator and reduce their vulnerability to attack. RESUMEN La conducta de cantar mientras se vuela incluye vocalizaciones distintivas y conductas que probablemente son energeticamente costosas y que pudieran atraer la atencion de depredadores. Observamos cantos al volar en dos poblaciones del papamoscas Empidonax oberholseri. Durante 15 anos de estudios en Tioga Pass, California y nueve anos en Steamboat Mountain, Columbia Britanica, observamos la conducta previamente descrita observamos la conducta en dos y 21 ocasiones, respectivamente. Los cantos a vuelo fueron observados tardes en la epoca reproductiva, lo que sugiere que no fueron utilizados para el cortejo, atraer la atencion de parejas prospectivas o defender el territorio. Sin embargo, en el 83% de las ocasiones, se observaron tambien a individuos de Falco sparverius o de Accipiter striatus. Proponemos como hipotesis, que la conducta observada, al igual que otras conductas de proteccion, pueden ser dirigidas a rapaces pequenos que representan una amenaza a los papamoscas y que pudieran detener el ataque indicando precaucion. Sin embargo, dado el caso de que solo se observaron machos del papamoscas exhibiendo la conducta, es probable ademas que la conducta sirva para alertar a las parejas y pichones de los vocalizadores sobre la presencia de un depredador y de esta manera reducir su vulnerabilidad de ataque.

The advertisement song of Pipistrellus nathusii (Chiroptera, Vespertilionidae): a complex message containing acoustic signatures of individuals

Males of Nathusius’ pipistrelle (Pipistrellus nathusii) are well known for their complex acoustic advertisement behaviour performed either as songflight (SF) or sedentary display (SD). We analysed phonologic, syntactic and semantic characteristics of these calls based on 2,924 acoustic records obtained from individual males repeatedly occupying 33 roosts in southern Bohemia from 1999 to 2006. Both SF and SD calls are composed of three main phonologically contrasting motifs (A, B, C) and under specific contexts often supplemented with two accessory motifs (D, E). Besides the major syntagmatic string ABC we recorded further 15 syntagms containing the main motif A and 10 syntagms without this motif. At the peak of the mating season and with the SD, the complexity of the vocalisation increases (increased variation in syntagmatic structure and syllabic composition of particular motifs, as well as in length of syntagmatic strings). The motif A corresponds to advertisement calls of congeneric species and is related to agonistic vocalisation, and B, C, D are specific for P. nathusii. B and C exhibit the largest between-individual but low within-individual variation, and their combination provides an acoustic signature of an individual and uniquely identified each particular male. Motif D corresponds to calls of mother-young communication and shows the largest syllabic variation. Motif E is a series of steep FM signals evocative of the act of landing. The message of a complete advertisement call (ABCED) could be thus: ‘(A): Pay attention, here is a P. nathusii, (B, C): I am male X, (E): land here, (D): we share a common social identity and common communication pool’. The individual characteristics of the performance of B, C, and D motifs were found to be invariant both within a season and over a series of successive years.

Structure and Complexity of Perched and Flight Songs of the Tree Pipit (Anthus trivialis)

We analysed 2166 songs of 90 males of the tree pipit (Anthus trivialis; Passeriformes: Motacillidae) from five Czech localities to evaluate variation in song characteristics, the song structure and syntax rules, and differences between songs performed in flight and from perches. We measured temporal and spectral song characteristics; structure analysis was based on the identification of individual syllable units. There was a high among-population variation in the repertoire, suggesting substantial differences in local dialects. Flight and perched songs significantly differed in most analysed quantitative characteristics. While both types of songs are apparently used in territorial defence, trill elements within flight songs may also indicate male quality to potential mates. Characteristic bi-syllable repeats within songs were often unique for individual males and may function in individual recognition. Features of tree pipit songs make it a good species for studying song variation and function in birds with complex repertoires.

Male whitethroats, Sylvia communis, advertise their future contribution to parental care

Summary In altricial species participation of males in parental care enhances reproductive success of females. How does a female select a mate who will allocate time and energy to parental effort? In the whitethroat Sylvia communis, a socially monogamous bird, parental performance of males might be predicted on the basis of elaborated song flights displayed in courtship. The correlation analysis revealed that males which advertised intensively needed less time to attract a female and also their parental performance was better compared to males that produced cheaper signals. In the subsequent experiment, we handicapped males by increasing their body mass by 5% with a weight attached to tail feathers. Males in the treatment group reduced the proportion of showy song flights significantly more than controls and their mating success was significantly lower. We conclude that song flights in whitethroats honestly signal male quality and that the signalling system depends on a dynamic handicap trait which responds to a relatively small change in the male.

Flight Display Song of the Vermilion Flycatcher

A number of authors have qualitatively described the songs of Vermilion Flycatchers (Pyrocephalus rubinus) given during flight display, but no spectrograms or quantitative analyses are available. We present such a description based on displays of 14 different males. Our analysis confirms the impressions of earlier authors that the flight song is closely similar to that given by perched birds, but also revealed an important difference: most flight display songs also included an extra element known as the peent vocalization. The peent is also an alarm call, given during male-male and male-female interactions, as well as during foraging bouts. Besides reporting on the common use of peent vocalizations by perched Vermilion Flycatchers, we now describe the frequency and use of peent vocalizations in flight display songs.

Simulated courtship interactions elicit neighbour intrusions in the whitethroat, Sylvia communis

Animals often signal in communication network environments that include nonintended receivers that may constitute a risk to the signalling animals. Unpaired male songbirds, which sometimes intrude into neighbouring territories and interrupt courtship, may be an example of nonintended receivers of vocal courtship signals. We investigated this in the whitethroat, using dyads of unmated territorial males. Each dyad consisted of a resident male, who was part of the experimental treatment, and a neighbouring male, whose responses to the treatment stimuli were tested. Each dyad received two playback treatments: a courtship treatment in which the treatment male was induced to court a remotely controlled calling and jumping stuffed female, and a song duel treatment in which playbacks of male song were used to induce the focal male to countersing. The neighbours responded with more song flights to the courtship treatment than to the song duel treatment, perhaps to achieve an overview of the courtship activity or attract the female. Only the courtship treatment resulted in neighbouring intrusions and immediate chasing of the intruder by the treatment male. The males that suffered intrusions did not sing less than those that did not suffer intrusions. Reduced singing therefore may not be able to explain the intrusions. Every intrusion except one occurred after the first courtship vocalization, making it likely that the courtship per se caused the intrusions. This emphasizes the necessity of restricting the transmission range of courtship vocalizations in a network and therefore also explains why the courtship vocalizations of whitethroat males are relatively short ranging.

The application of a fuzzy‐rule‐based system in an exposition of the antecedents of sedge warbler song flight

Abstract: The utilization of a fuzzy aspect within data analysis attempts to move from a quantitative to a more qualitative investigative environment. As such, this may allow the more non‐quantitative researchers results they can use, based on sets of linguistic terms. In this paper an inductive fuzzy decision tree approach is utilized to construct a fuzzy‐rule‐based system for the first time in a biological setting. The specific biological problem considered attempts to identify the antecedents (conditions in the fuzzy decision rules) which characterize the length of song flight of the male sedge warbler when attempting to attract a mate. Hence, for a non‐quantitative investigator the resultant set of fuzzy rules allows an insight into the linguistic interpretation on the relationship between associated characteristics and the respective song flight duration.

Degradation of whitethroat vocalisations: implications for song flight and communication network activities

Abstract Transmission of acoustic signals through the habitat modifies the signals and may thus influence their use in communication. We investigated the transmission of five different types of whitethroat (Sylvia communis) vocalisations, three types of song and two calls. Typical examples were broadcast and re-recorded in a whitethroat habitat with hedgerows and open meadow. We used a complete factorial design with speaker and microphone placed in different natural sender and receiver positions including high perches and song flights. Sound degradation was quantified in terms of signal-to-noise ratio, excess attenuation, tail-to-signal ratio and blur ratio. The results suggest that sound degradation generally increased with distance along a hedgerow, which means that birds here potentially may use degradation in assessing the distance to a vocalising individual. This is unlike the open meadow where the change in degradation with distance was negligible. Surprisingly, song flight relative to perched singing seems not to facilitate transmission of own vocalisations or perception of vocalisations from other individuals, and song flight vocalisations do not transmit differently from other types of vocalisations during song flights. One purpose of song flights might therefore be visual location by potential receivers and surveillance by the territory owner. Source level and degradation differed between the five types of vocalisations in accordance with their functions. Motif song and song flight songs used in attraction of females and/or deterrence of males could transmit through neighbouring territories, whereas the calls and the courtship diving song where a specific individual within or near the territory is addressed had relatively short communication ranges.

Male singing behaviour and female presence in the territory in whitethroats Sylvia communis

Unmated male songbirds usually change their vocal behaviour when females enter their territories. Either the males court the females by changing the rate or pattern with which their normal long-ranging full songs are emitted, or they shift to special displays and long- or short-ranging vocalisations. In this study we quantified how female presence and behaviour affect the singing behaviour of male whitethroats. In the presence of a female the male frequently performed song flights, maybe to locate the female before it was courted, with sequences of diving-song displays. The courtship was interrupted by periods of perch songs. Female dscharp calls and short movements made the males initiate or resume courtship, whereas short horizontal jumps made the males intensify their courtship. Overall, the males changed their dual-function song activity in females' presence by emitting fewer perch songs and more flight songs. The quiet diving songs were only emitted during direct courtship of a female. The song types emitted immediately before, during, and after courtship are all highly variable, thus allowing for a quick assessment of the male's song repertoire. The courtship was also interrupted by periods of male woid calling, a call that is known to have a deterring effect on rival males. Bouts of woid calls were usually followed by song flights, again probably to locate the female that might have moved out of sight, or maybe to locate potential rival intruders. The latter was supported by an increased intrusion rate during female presence.