Flight Calls Research Articles

Discrete Variants of Evening Grosbeak Flight Calls

Abstract We describe four discrete variants of the frequency-modulated flight calls of Evening Grosbeaks (Coccothraustes vespertinus) in the United States and southwestern Canada. Each call type is aurally and spectrographically distinct, and individual birds appear to produce only one call type. The observed geographic distributions of these call types are roughly concordant with described subspecies ranges. The long-term geographic distribution patterns of these vocal forms, and of genetic, morphological, and plumage correlates of vocalizations, warrant further study. Variantes Discretas de las Llamadas de Vuelo de Coccothraustes vespertinus Resumen. Describimos cuatro variantes discretas de las llamadas de vuelo de frecuencia modulada de Coccothraustes vespertinus en los Estados Unidos y el sudoeste de Canadá. Cada tipo de llamada es auditiva y espectrográficamente distintivo, y un individuo dado parece emitir sólo uno de ellos. La distribución geográfica observada de estos tipos de llamadas concuerda de manera general con las distribuciones de las subespecies. Es necesario hacer más estudios sobre los patrones de distribución geográfica a largo plazo de estas formas vocales, y sobre qué caracteres genéticos, morfológicos y de plumaje se correlacionan con las vocalizaciones.

The distribution and habitats of crossbills Loxia spp. in Britain, with special reference to the Scottish Crossbill Loxia scotica

A study was carried out, primarily in northern Scotland, to relate bill and wing measurements to diagnostic calls of crossbill species, and thereby use the calls to describe the distributions and habitats of the different species. Bill depth and wing length measurements from museum specimens and live‐trapped birds were used to describe the size categories. Almost all measurements of crossbills from England were similar to measurements of Common Crossbills from Fennoscandia. Museum specimens showed that crossbills in northern Scotland between 1822 and 1990 were a combination of Common Crossbills, birds which were intermediate between Common and Parrot Crossbills (Scottish Crossbills), and perhaps a few Parrot Crossbills. However, catches of crossbills between 1995 and 2000 showed that Parrot Crossbills (based on bill and wing measurements) were present at some sites in the Highlands. Recordings of flight calls and excitement calls of birds of known bill sizes allowed a classification of crossbills according to call types. Four different flight calls (referred to here as types 1–4) and five excitement calls (types A–E) were recognized. A sample of small‐billed birds, thereby identified as Common Crossbills, indicated that there were three groups of Common Crossbills: those giving type 1 flight calls and type A excitement calls (1A), type 2 flight calls and type B excitement calls (2B), and type 4 flight calls and type E excitement calls (4E). Large‐billed birds identified as Parrot Crossbills gave mainly type 2 flight calls and type D excitement calls. Birds with intermediate bill depths (Scottish Crossbills) gave type 3 flight calls and type C excitement calls. Distributions based on calls showed that 1A Common Crossbills were widespread in Scotland but the other types of Common Crossbill were rare. Parrot Crossbills were found in a few localities in the Highlands, and Scottish Crossbills (defined as those giving type 3 flight calls and type C excitement calls) were restricted to the northern and eastern Highlands. Scottish Crossbills and 1A Common Crossbills had overlapping distributions, and overlapped greatly in the types of forests they used between January and March when the Scots Pine cones were still closed. However, Scottish Crossbills were more frequently associated with stands containing Scots Pine compared with Common Crossbills.

Seeing is believing: information about predators influences yellowhammer behavior

Behavioral decisions based on a trade-off between foraging and vigilance or hiding require information. I studied how the amount of information about predators influenced yellowhammers' (Emberiza citrinella) foraging delay and alert perching behavior. Yellowhammers were shown a flying sparrowhawk (Accipiter nisus) silhouette, which elicited alarm calls, or a square piece of wood (control), which elicited flight calls. Yellowhammers that could not see the sparrowhawk model, but heard the alarm calls, had less complete information about the predation risk than those that actually saw the sparrowhawk. Hearing alarm calls affected the behavior of yellowhammers. Birds with less complete information about the predator exhibited alert perching more often immediately after the encounter than did birds that saw the sparrowhawk model. Also, birds that saw the sparrowhawk resumed foraging earliest, while birds that heard the alarm calls resumed foraging latest. Although there was a tendency for a significant difference in body mass between dominant and sub-dominant individuals, there was no significant difference in foraging delay. Both the foraging delay and the increase in alert perching caused lost feeding opportunities. Completeness of information and its effect on decision-making may thus affect the fitness of an animal.

Nocturnal flight calls of Dickcissels and Doppler radar echoes over south Texas in spring

Abstract Recording flight calls of migrating birds with one or more microphones provides information on identity of some birds aloft over each microphone and on the time course of their migration, or at least their calling. Doppler surveillance radar observations, on the other hand, provide information on the numbers and sizes of flying animals aloft over a wide area and on speeds, directions of travel, and height in favorable circumstances. Comparison of calls of Dickcissels (Spiza americana) from sound recording stations across south Texas in spring with images from the KBRO NEXRAD (WSR-88D) radar operated by the National Weather Service showed a surprising correspondence between the two kinds of data, both temporally over the course of a night and geographically across about 115 km. Highly significant correlations between call rates and radar reflectivity were obtained for seven sound recording stations but not for two other stations that were too distant for the radar to receive echoes from birds migr...

Cultural Diversification in the Flight Call of the Ringneck Parrot in Western Australia

Abstract I investigated geographic variation in a parrot vocalization to obtain an understanding of cultural population differentiation and exchange between hybridizing taxa. The flight calls of Ringneck Parrots (Barnardius zonarius) were tape recorded in Western Australia within and outside the zone of overlap and hybridization between the Port Lincoln (B. z. zonarius) and Twenty-eight (B. z. semitorquatus) subspecies. Measured variables distinguished the Twenty-eight call from those in the overlap populations. Although birds in typical Twenty-eight plumage were present in the overlap zone, no Twenty-eight flight calls were found, suggesting convergence by immigrants. Populations within the hybrid zone also were acoustically differentiated as dialects associated with roosting areas. Observations on the social behavior of the birds indicated that this call functions in coordination of movements of the mated pair. Roost-specific dialects might aid pairs in finding each other in the event of separation during the day's foraging activity.

Cultural Diversification in the Flight Call of the Ringneck Parrot in Western Australia

I investigated geographic variation in a parrot vocalization to obtain an understanding of cultural population differentiation and exchange between hybridizing taxa. The flight calls of Ringneck Parrots (Barnardius zonarius) were tape recorded in Western Australia within and outside the zone of overlap and hybridization between the Port Lincoln (B. z. zonarius) and Twenty-eight (B. z. semitorquatus) subspecies. Measured variables distinguished the Twenty-eight call from those in the overlap populations. Although birds in typical Twenty-eight plumage were present in the overlap zone, no Twenty-eight flight calls were found, suggesting convergence by immigrants. Populations within the hybrid zone also were acoustically differentiated as dialects associated with roosting areas. Observations on the social behavior of the birds indicated that this call functions in coordination of movements of the mated pair. Roost-specific dialects might aid pairs in finding each other in the event of separation during the day's foraging activity.

CULTURAL DIVERSIFICATION IN THE FLIGHT CALL OF THE RINGNECK PARROT IN WESTERN AUSTRALIA

Abstract I investigated geographic variation in a parrot vocalization to obtain an understanding of cultural population differentiation and exchange between hybridizing taxa. The flight calls of Ringneck Parrots (Barnardius zonarius) were tape recorded in Western Australia within and outside the zone of overlap and hybridization between the Port Lincoln (B. z. zonarius) and Twenty-eight (B. z. semitorquatus) subspecies. Measured variables distinguished the Twenty-eight call from those in the overlap populations. Although birds in typical Twenty-eight plumage were present in the overlap zone, no Twenty-eight flight calls were found, suggesting convergence by immigrants. Populations within the hybrid zone also were acoustically differentiated as dialects associated with roosting areas. Observations on the social behavior of the birds indicated that this call functions in coordination of movements of the mated pair. Roost-specific dialects might aid pairs in finding each other in the event of separation duri...

Bird flight call discrimination using machine learning

The development of a software system which can detect and identify the flight calls of migrating birds is reported. The system first produces a spectrogram using a DFT. Calls are detected in the spectrogram using an ad hoc combination of local peak‐finding and a connectedness measure. Attributes are extracted both globally from the call and from a window moved incrementally through the call. Decision trees are then used to determine the bird species. These decision trees are induced from a training set using Quinlan’s C4.5 system [J. R. Quinlan, C4.5: Programs for Machine Learning, Morgan Kauffman (1993)]. The system has been tested on a set of 138 nocturnal flight calls from nine species of birds [W. R. Evans, personal communication]. Some calls are faint, and interfering insect noise is present in others. Tenfold resampling was used to classify the calls unseen. Seventy‐eight percent of calls were identified correctly, 4% incorrectly and 18% were placed in an ‘‘uncertain’’ category. Neural network‐based classifiers are commonly used in this general domain and would likely produce similar accuracy, but use of symbolic machine learning offers two important advantages: Training time is linear in the number of examples and the resulting classifier is less opaque. Both significantly ease classifier construction.

Automatic detection and classification of nocturnal migrant bird calls

Computer software was developed to detect the nocturnal flight calls of nine species of migrating warblers in digitized field recordings, and to classify the calls by species. The calls are frequency-modulated tones in the 5- to 9-kHz frequency band, and between 50 and 100 ms in duration. Detection was accompanied by locating temporal peaks in call band energy. Some false detections of insect calls were prevented by rejecting certain types of peaks. Classification is approached by tracking the frequencies of the calls over time and classifying the frequency tracks with an artificial neural network.

Sexual Differences in Flight Calls and the Cue for Vocal Sex Recognition of Swinhoe's Storm-Petrels

Previous studies have shown that the Flight Calls of Swinhoe's Storm-Petrels (Oceanodroma monorhis) differ clearly between the sexes in their frequency component and that birds can discriminate the calls of either sex with few errors (Taoka et al. 1989b). But the cue for sex recognition has not yet been identified. In this study, we quantitatively analyzed the calls of both sexes for call length, number of syllables, and duration and interval of syllables. We found some sexual differences in rhythmic components, but mean ? standard deviation overlapped in all syllables. In order to make synthetic calls for playback experiments, frequency and rhythmic components were systematically manipulated. Birds recognized the synthetic calls having the same harmonic structure as female calls but those without harmonic structure were recognized as male calls regardless of whether the rhythm was that of the female or the male. Therefore, we concluded that harmonic structure is the cue for sex recognition. The mechanism of vocal sex recognition was compared with that of the closely related species, the Leach's Storm-Petrel (0. leucorhoa).

Resolution of Cryptic Species in Appalachian Red Crossbills

Two distinct and sympatric forms of Red Crossbill (Loxia curvirostra) from breeding populations in Virginia and North Carolina were resolved using multivariate analysis of vocalizations and morphology. Five characters were used to describe individually distinctive flight calls of 135 adults which were also measured for a set of nine bill and body size characters. Call notes were bimodal for two characters, and a principal components plot separated birds into two clusters based on call note shape. Univariate distributions of morphological data showed some weak bimodalities and higher coefficients of variation than other passerine bird populations. Distributions along multivariate first principal component axes from morphological data (sexes in separate analyses) were bimodal, dividing fully grown adults into two distinct bill and body size classes. The vocal and morphological multivariate clusterings of individuals were entirely congruent, but no univariate character in either data set could completely separate the two forms. The matrix correlations between vocal and morphological interindividual distances were 0.441 for males and 0.423 for females and were highly significant using Mantel tests. However, within each hypothetical cryptic species, vocal and morphological characteristics were uncorrelated, showing a lack of pattern in the sample beyond the division into two nonreducible clusters. Other vocal differences between the two forms are described, and observations of ecological differences are summarized. The type specimens representing the two names which have been applied to Appalachian crossbills, L. c. pusilla (Gloger 1834) and L. c. minor (Brehm 1845), were compared to birds of known vocalizations. The type of pusilla matched the larger Appalachian form, but the type of minor was smaller than all adult males in the sample. The taxonomic problem of L. curvirostra is discussed, and an argument is made in favor of the species level for the two Appalachian vocal and morphological forms.

Social influences on foraging behaviour of the Red‐cheeked Cordon Bleu Uraeginthus bengalus Estrildidae

Red‐cheeked Cordon Bleus U. bengalus forage on bare patches of ground for fallen grass seeds and termites in particular home ranges. Foraging is confined to shaded areas in the middle parts of the day but birds exploit places exposed to the full sun in the early mornings and late afternoons. They mostly occur in pairs but often aggregate to form temporary foraging groups. Although birds in groups spend less time vigilant than those foraging alone, they react sooner than them to approaching danger. Birds foraging in pairs peck more rapidly than those in other situations and it is suggested that one advantage of forming permanent pair bonds is that paired birds forage more efficiently than unpaired ones in preparation for the coming breeding season. Flight calls, contact calls and alarm calls are given in specific behavioural contexts. Birds make contact calls when they become separated from their mates and evidently use them to re‐locate one another. It is shown experimentally that members of pairs can recognize one another's contact calls.

AUDITORY COMMUNICATION IN THE BLUE WAXBILLS URAEGINTHUS

Summary Cantrell, M. A. & Evans, S. M. 1981. Auditory communication in the blue waxbills Uraeginthus. Ostrich 52:104-107. Field observations on the function of calls in the Redcheeked Cordon Bleu Uraeginthus bengalus, the Bluecapped Cordon Bleu U. cyanocephalus, and the Purple Grenadier U. (=Granatina) ianthinogaster were made in Kenya, East Africa. Individuals of all three species were usually seen in male-female pairs, and distinct calls were used to synchronize movement. Flight calls were made in rapid succession on take-off, but less frequently during flight. When birds on or near the ground became separated, repeated contact calls were used to locate and rejoin the partner. Alarm calls were rarely heard in the field, but usually originated from perched birds in relatively safe positions. Laboratory experiments on the reactions of solitary caged birds to playback of calls were conducted using male U. bengalus. Separate playbacks of contact and flight calls both elicited a series of contact calls from ...

Call Form in Relation to Function in the Steller's Jay

Vocalizations of the Steller's Jay and of the scrub jay for comparison were recorded in the field and analyzed together with behavior to determine relationships between acoustic form and information conveyed. Call form is a combination of acoustic structures, selected and integrated by the requirements of each kind of information that the call conveys. 1. Location appears to be conveyed by calls with wide band structure, especially over far range, by calls with rapid, regularly repeated transient notes at moderate range, and possibly by Doppler effect in flight calls. Location apparently is concealed by diffuse onset combined with narrow band, by ventriloquism, and by quietness. 2. Threat calls are noisy or dissonant in tone, sustained in tempo, and stress a moderately narrow range of low frequencies. Assertive calls with varied social functions are noisy, rhythmic, and stress a wider range and higher frequencies than threat calls. Song, lacking a territorial function, is very quiet, primarily pure or resonant in tone, sustained or irregular in temporal character, and complexly melodic. 3. Appraisive information appears to be conveyed by continuous variation in rate of notes in at least one highly rhythmic call. It is suggested that appraisive information is conveyed by gradation in design features that convey motivation. 4. Between the Steller's jay and the scrub jay different features of form distinguish each of three calls that are probably homologous. The differences apparently are not species-isolating mechanisms yet do show the trends that call divergence may take to convey species identity. Features of form that can be used to convey species identity may be those that can change because they are not constrained by acoustic form requirements of other kinds of information the call must convey.

Call Learning in the Carduelinae: Ethological and Systematic Considerations

Call Learning in the Carduelinae: Ethological and systematic considerations. Syst. Zool. 28:270–283.—Experiments and field observations document vocal imitation in six cardueline species representing four genera. Flight call learning was found in all birds studied; learning of many other call types was observed in two genera. Additional evidence extends call learning to other carduelines bringing to eight the total number of genera in which call learning has been observed. Call learning is perhaps characteristic of subfamily Carduelinae, and the taxonomist should consider the possibility that learning may affect the patterns of all adult cardueline vocalizations. The taxonomic value of cardueline calls in particular and passerine calls in general is re-examined in light of this extensive call learning. It is suggested that the ontogenetic, learned modification in call pattern can be eliminated from the taxonomic analysis, and that calls may then be taxonomically valuable behavioral characters. The problem of homologizing behavior is discussed, with criteria for homology applied to two call types, both associated with call learning. Cardueline flight calls are autapoinorphic characters useful as species specific characters, while social/alarm calls are synapomorphic at the subfamilial level and can be used as taxonomic characters at the family level.

Specific distinctiveness in the calls of cordon bleus ( Uraeginthus spp.; estrildidae)

The structure of contact, flight and alarm calls of three species of cordon bleus, Uraeginthus spp., has been investigated by sonagraph analysis. In each species, contact and flight calls are similar in structure, but alarm calls are distinctively different from them. Each species reacts to play-back recordings of its own calls but shows less reaction to the calls of the other species.

An exploration study of vocalization areas in the brain of the redwinged blackbird (Agelaius phoeniceus).

The brain of the redwinged blackbird, a species of the suborder of songbirds, was explored for regions from which vocalization could be evoked by electrical stimulation. In all, 966 points in the brain were tested for evoked vocalizations in acute experiments with the bird restrained under local anesthesia in a stereotaxic instrument. Responsive regions were found mainly I) in the midbrain in and near the torus semicircularis in its non-auditory part, 2) in the hypothalamus and septal area, and 3) in the archistriatum. Responses of uncertain significance were also obtained from the hyperstriatum accessorium. Minimum thresholds for evoked vocalization were lowest in the torus and highest in the striatum. The evoked vocalizations were analyzed spectrographically. They included both normal and abnormal calls; male and female song and flight calls were not evoked. In most cases calls evoked from the midbrain were of the annoyance type. Calls evoked from the anterior brain stem were more variabe and also included Cheers and various other alarm calls. The neuroanatomical data are presented on sections which may be employed as a stereotaxic guide to the brain of the redwinged blackbird. The basic similarity between the neuroanatomical substrate of vocalization in birds and most mammals is pointed out.

Vocal Imitation and Individual Recognition of Finch Calls

American goldfinch females recognize individual males by their individually distinctive flight calls. Goldfinches and other cardueline finch species are also capable of learning new flight calls by imitation during pair and flock formation. Vocal imitation can occur between members of different species as well as between members of the same species. Learning of new flight calls differs in several respects from typical passerine song learning.

The Physiology and Geophysics of Bird Navigation

Radar observations often show nocturnal migrants well oriented under opaque layers of cloud, and perhaps even inside or between cloud layers. Some homing pigeons can orient towards home from unfamiliar territory under overcast skies. In searching for non-visual sensory capabilities of birds it is important to consider not only their sensory physiology but also the atmospheric ecology of migration when neither sky nor ground is visible. Either inertial naviation or orientation to the earth's magnetic field requires considerably greater sensitivity than any yet demostrated in birds. Natural or artificial sounds from the surface, or even ground echoes of flight calls, might facilitate orientation under some conditions. Birds communicating by flight calls might detect the differential wind drift experienced by upper and lower members of a flock, and thus determine the direction of wind shear. Under many meteorological conditions such patterns of air movement as roll vortices or internal gravity waves produce readily detectable updrafts capable of providing both lift and information about the direction of the wind or wind shear.

Evidence concerning the Function of Nocturnal Call Notes of Migratory Birds

Nearly all birds which migrate at night give characteristic flight calls, but only recently has any attempt been made to investigate these quantitatively. Ball (1952) and Vleugel (1954, 1960) relied on the unaided ear to register the notes of migrants aloft. Graber and Cochran (1959, 1960) have successfully recorded call notes with a parabola pointed skyward. A tape recorder automatically monitored a 112 minute portion of each 10-minute interval through the night. The data collected in these studies have been used to interpret the volume of migration, its species composition, and the conditions under which it takes place. The function of night calls has not been a major concern of these workers. There has been no lack of speculation concerning the significance of night calls, however. Some suggest that the calls are not adaptive. Ball (1952) supposed that the dawn surge of call notes of thrushes might be inspired by hunger and light from the oncoming dawn. Hudson (1923) postulated that the calls were an expression of fear in the unfamiliar night, an idea shared by a number of others. But it seems unlikely that a behavior pattern which is so frequent and characteristic is functionless. A frequently suggested function of the night calls is that they serve to hold flocks together. A corollary to this is the suggestion that young benefit from the experience of adults by travelling in their company (Brewster, 1886). Another related idea implies that the calls are mutually stimulating, each call urging flight partners onward (Tyler, 1916; others). Lowery and Newman (1955) suggest that the calls may serve an echosounding function, facilitating the landing process. This suggestion, while perhaps reasonable, is not considered here for lack of evidence. The evidence presented here is based on analysis of the calls of caged birds exhibiting migratory restlessness and calls given by free flying migrants. Both lines of evidence clearly indicate that for at least some passerine species the calls are communicatory.