8. REVIEWS AND NOMENCLATURAL NOTES

Greig-Smith, P. W. 1978. Behaviour of Woodland Kingfishers in Ghana. Ostrich, 49:67-75.

The behaviour of Woodland Kingfishers Halcyon senegalensis was studied during the breeding season. Inactive postures were dependent on alertness, perch height, and time of day. Prey was mainly grasshoppers, captured by diving from elevated perches. Breeding territories were near water, and were maintained by a long-range vocal display, a short-range visual display and attacks on intruders. Other bird species were also attacked. Courtship involved “duets”, display flights, and allofeeding. A late wet season in 1974 apparently caused delayed migration, and postponement of all breeding behaviour except inspection of nest-holes.     

Individual variation in pup vocalizations and absence of behavioral signs of maternal vocal recognition in Weddell seals (Leptonychotes weddellii)

Individually stereotyped vocalizations often play an important role in relocation of offspring in gregarious breeders. In phocids, mothers often alternate between foraging at sea and attending their pup. Pup calls are individually distinctive in various phocid species. However, experimental evidence for maternal recognition is rare. In this study, we recorded Weddell seal (Leptonychotes weddellii) pup vocalizations at two whelping patches in Atka Bay, Antarctica, and explored individual vocal variation based on eight vocal parameters. Overall, 58% of calls were correctly classified according to individual. For males (n= 12) and females (n= 9), respectively, nine and seven individuals were correctly identified based on vocal parameters. To investigate whether mothers respond differently to calls of familiar vs. unfamiliar pups, we conducted playback experiments with 21 mothers. Maternal responses did not differ between playbacks of own, familiar, and unfamiliar pup calls. We suggest that Weddell seal pup calls may need to contain only a critical amount of individually distinct information because mothers and pups use a combination of sensory modalities for identification. However, it cannot be excluded that pup developmental factors and differing environmental factors between colonies affect pup acoustic behavior and the role of acoustic cues in the relocation process.     

NEWS

ABSTRACT

Australian fur seals Arctocephalus pusillus doriferus are colonial breeding animals forming dense social groups during the breeding season. During this time, males establish and defend territories through physical conflicts, stereotyped posturing and vocalisations. While vocalisations are suggested to play an important role in male recognition systems, it has received little attention. Recordings of nine adult male Australian fur seals were made during the 2000 and 2001 breeding seasons at Kanowna Island (39° 10′S, 146° 18′ E), Bass Strait, Australia. The in-air bark vocalisations of territory-holding males were used to characterise the Bark Call and to determine whether males produce individually distinct calls, which could be used as a basis for vocal recognition. Seventeen frequency and temporal variables were measured from a total of 162 barks from nine individual males. The Bark Series was more reliably classified (83%) to the correct caller compared to the Bark Unit. This was assigned with less certainty (68%), although the classification was still relatively high. Findings from this study indicate that there is sufficient stereotypy within individual calls, and sufficient variation between them, to enable vocal recognition in male Australian fur seals.     

Vocal individuality,but not stability,in wild palm cockatoos (Probosciger aterrimus)

The ability to identify individuals within a population is often essential for a detailed understanding of the ecology and conservation of a species. However, some species, including large parrots, are notoriously difficult to catch and mark for individual identification. Palm cockatoos (Probosciger aterrimus) are a large, poorly understood species of parrot which are likely in severe decline within the eastern part – and possibly the western part – of their range on Cape York Peninsula, Australia. Here, we investigated whether three different palm cockatoo call types are sufficiently individually distinctive to function as a non-invasive “marker” for identifying individuals over time. Using Discriminant Function Analysis, overall identification accuracy among 12 putative individuals for all call types was 81% (i.e. 148 out of 183 calls were assigned to the correct individual) on the basis of multiple temporal, energy (amplitude) and frequency measurements on the spectrogram. For three different call types, individual identification accuracy among males and females ranged from 69 to 95%. However, based on a limited sample sizes of five putative individuals between years, our data suggest that individual call structure, as quantified by call parameters, was not stable between years. We discuss the applicability of these results for future studies of palm cockatoos and other parrot species.     

Individual Signature in a Lekking Species: Visual and Acoustic Courtship Parameters May Help Discriminating Conspecifics in the Houbara Bustard

Selection pressures acting on both intrasexual competition and intersexual relationships may lead to the emphasis of individual variation and might thus lead to the expression of individual signature. This is particularly true in lek mating systems, where providing information on identity and/or quality to potential mates or congeners of the same sex can be essential for individuals to optimize their reproductive success. Visual and acoustic signals produced during the courtship of the lekking North African Houbara bustard (Chlamydotis undulata undulata), based on field data from wild birds, are investigated here for the first time. Results show that the vocal signals, called booms, are characterized by a very low frequency, a rare phenomenon in birds which should allow booms to propagate over long distances. Results also show that both visual and acoustic signals are individualized and stereotyped between males. Using three methods of analysis, we highlight the acoustic parameters likely to support vocal individual signature and show that such information mainly relies on frequency parameters.     

Food niche segregation between the Malachite Kingfisher,Alcedo cristata,and the Pied Kingfisher,Ceryle rudis,at Lake Nokoué, Bénin

Several species of kingfisher occur on Lake Nokoué, southern Bénin, including Malachite (Alcedo cristata) and Pied Kingfishers (Ceryle rudis). Here, we compare their diet and estimate the degree of overlap in food niche by analysing contents of regurgitated pellets collected near nesting sites of Pied Kingfishers or inside the nest chambers of Malachite Kingfishers. Characteristic fish skull bones were identified using a reference collection of local fish skeletons. Malachite Kingfishers feed most frequently on fish that occur around floating vegetation, mainly Kribia sp. (56%), Hemichromis fasciatus (28%) and Sarotherodon melanotheron (8%). Important differences were found between different pairs, and between adults and nestlings, the latter being fed almost exclusively on Kribia sp. Larger fish are fed to nestlings than are eaten by the adults. Pied Kingfishers prey upon 14 different fish species, some of them being caught in the pelagic region of the lake, particularly clupeids taken by hovering. By comparison with Malachite Kingfishers, Pied Kingfishers feed on a wider diversity of prey, and take larger fish, so that the dietary overlap between the species is relatively low (O = 0.181).     

Individual identity coding depends on call type in the South Polar skua Catharacta maccormicki

In colonial birds, acoustic communication is essential for mate recognition. The South Polar skua (Catharacta maccormicki) lives in loose colonies and is highly territorial for feeding and breeding. We studied the potential of individual identity coding in the three main calls of the South Polar skua repertoire: the courtship, the contact and the alarm calls. We investigated parameters in both temporal and frequencial domains, i.e. amplitude modulation, frequency modulation and power spectrum density. For each parameter, the intra- and inter-individual variabilities were calculated. The ratio between these values represents the potential of individuality coding (PIC) of the considered feature. Low values of PICs for amplitude and frequency modulations show that both parameters may not be used for individual recognition. In contrast, high values of PIC for the power spectrum density indicate that the energy distribution among the frequency spectrum is likely to be an individual marker. PIC also varies according to the call type. Both courtship and contact calls have a higher potentiality of individual identity coding than the alarm call. The two former calls may allow individual recognition whereas the latter may not, and this last result can be extrapolated to many other species.     

INDIVIDUALITY IN THE VOICE OF FUR SEAL FEMALES: AN ANALYSIS STUDY OF THE PUP ATTRACTION CALL IN ARCTOCEPHALUS TROPICALIS

Like most otariids species, the Subantarctic fur seal breeds on land in large, dense colonies. Pups are confronted by the long and repetitive absences of their mother throughout lactation. At each mother's return, pups have to find her among several hundreds of congeners. This recognition process mainly relies on acoustic signals. We performed an acoustic analysis on 125 calls from 20 females recorded during the 1999–2000 breeding season on Amsterdam Island (Indian Ocean). Ten variables were measured in both temporal and frequency domains. To find the acoustic parameters supporting individual signature, we assessed the differences between individuals using Kruskall-Wallis univariate analysis of variance. For each variable, we also calculated the potential of individuality coding (PIC) as the ratio between the between-individual coefficient of variation and the mean value of the within-individual coefficients of variation. We found that the frequency spectrum, the characteristics of the frequency modulation of the initial and middle part of the call and the call duration exhibit an important individual stereotypy (PIC values ranging between 1.5 and 3), whereas features relative to amplitude and the frequency modulation of the final part of the call are weakly individualized (PIC values between 1 and 1.2).     

The first call note of the Anhui tree frog (Rhacophorus zhoukaiya) is acoustically suited for enabling individual recognition

The effective production of acoustic signals is critically important for intraspecific communication in vocal animals; however, it is also highly time-consuming, energetically demanding and likely to increase predation risks. Thus, we hypothesized that the biological significance of each component of complex acoustic signals would differ serving specific functions and that the first component of such signals would be most important for social signalling and exhibit unique acoustic characteristics because of the precedence effect. To test this hypothesis, we measured temporal and spectral acoustic parameters for each note in the advertisement calls of the Anhui tree frog (Rhacophorus zhoukaiya), a species in which males build mud burrows and call from within these nests. Multivariate analyses including hierarchical cluster analysis and multidimensional scaling were used, based on temporal and spectral acoustic parameters for each of 10 notes/call. These results show that the first call notes form one cluster while the other notes form a second cluster in multidimensional space when the parameters measured were normalized. Furthermore, the temporal and spectral sound attributes of the first call note provide sufficient information for discrimination between different individuals. Moreover, discriminant analysis showed that the fundamental frequency of the first note is sufficient to identify individuals when the data are not normalized. Taken together, these results indicate that the first call note is poised to play an important role in Anhui tree frog vocal communication insofar as the temporal and spectral features provide sufficient information for individual recognition.     

Using Shannon entropy on measuring the individual variability in the Rufous-bellied thrush Turdus rufiventris vocal communication

We applied the information theory concepts to notes repertoire characteristics combined with temporal parameters of the Rufous-bellied thrush Turdus rufiventris song, using this particular case to test a new method of analysing quantitatively complex animal communication systems. Like most Turdus thrushes, Rufous-bellied thrushes are remarkable for their long, varied and melodious songs. For the analysis of the species repertoire, we used recordings of 44 individuals from 24 localities covering its full geographical range. We measured the repertoire size, note duration and rhythm (frequency of note utterance), and combined these parameters with the Shannon entropy values calculated for each individual. Although individuals maintain species-specific recognition capacity, we find a large variation between their song parameters and show that the information theory can be useful to analyse large and varied animal vocal repertoires. We are introducing two new parameters, temporal average entropy (E(t)) and utterance frequency average entropy (E(f)), for measuring such communication systems.     

Sound or Silence: Call Recognition in the Temporal Domain by the Frog Allobates femoralis

Acoustic communication often mediates agonistic interactions in territorial species. Because both the reaction to potential intruders and the lack thereof are costly, mechanisms that allow recognition of conspecific signals should be evident in intrasexual communication systems. While the spectral domain of the recognition space of the frog Allobates femoralis appears asymmetrically shaped in a way that reduces masking interference by the often syntopic frog Ameerega trivittata, frequency alone does not appear to account for the correct identification of conspecific intruders (Amézquita et al., Animal Behaviour, 70, 2005: 1377). As signal recognition may rely on a combination of spectral and temporal parameters of the signal, we test here the subsequent prediction that the recognition space should be asymmetrical in the temporal domain as well. We conducted playback experiments with 80 synthetic calls on 30 males and modeled all‐or‐none responses to define unidimensional functions of the recognition space for two call parameters: note duration and internote interval. For both parameters, male maximal response matched very well the average values of the conspecific signal and decreased with concomitant deviations from these values. While the response curves exceeded the range of signal variation and were not asymmetrical for either call parameter, they differed in breadth. The highest male permissiveness to variation in internote interval, as evidenced by a broader response curve, coincided with the lower probability of between‐species overlap in this signal parameter. Together with previous studies, our data suggest that a combination of spectral and temporal parameters of the advertisement call is necessary for recognition of calling intruders in A. femoralis. Our results emphasize the importance of multidimensional approaches in understanding signal recognition mechanisms in acoustically complex environments.     

Individuality but not Stability in Marmoset Long Calls

Individually distinct communication signals (‘signatures’) have been documented in a variety of taxa across signal modalities and they serve a host of important functions. However, studies have rarely examined the temporal stability of these signals. Cooperatively breeding species, such as marmosets and tamarins, are characterized by long-term group membership, complex social organization, and high levels of interindividual coordination of behaviour. These social attributes may promote complex, individually distinct and stable acoustic signals to facilitate the expression of cooperative behaviour. In this study, the long calls of socially housed individual Wied's black tufted-ear marmosets, Callithrix kuhli, were examined for a ‘signature system’ potentially important in such interactions. Vocalizations were recorded at three different times (1993, 1995, 1996), digitized, and then measured by spectrographic analysis. Acoustic and temporal features of the calls were examined, including number of syllables, length of syllables, intersyllable interval, frequency range, start/stop frequency, peak frequency, and total call duration. A number of significant intra-individual changes in acoustic parameters were identified across the recording periods. Discriminant analysis revealed that many variables contributed to differentiation among individuals, and average classification accuracy for calls within a given year was high, ranging from 91.7% to 93.5%. However, reclassification accuracy for calls between-years was much poorer, averaging less than 50%. In addition, classification confidence was higher for within-year scores in contrast to the between-year values. Thus, tufted-ear marmosets have an individually distinct vocalization which is acoustically modified across time. Our finding suggests that to the extent that the vocalization is used for individual recognition, recognition mechanisms must be modified over time as well.     

How Does Individual Recognition Evolve? Comparing Responses to Identity Information in Polistes Species with and Without Individual Recognition

A wide range of complex social behaviors are facilitated by the recognition of individual conspecifics. Individual recognition requires sufficient phenotypic variation to provide identity information as well as receivers that process and respond to identity information. Understanding how a complex trait such as individual recognition evolves requires that we consider how each component has evolved. Previous comparative studies have examined phenotypic variability in senders and receiver learning abilities, although little work has compared receiver responses to identity information among related species with and without individual recognition. Here, we compare responses to identity information in two Polistes paper wasps: P. fuscatus, which visually recognizes individuals, and P. metricus, which does not normally show evidence of individual recognition. Although the species differ in individual recognition, the results of this study show that receiver responses to experimentally manipulated identity information are surprisingly similar in both species. Receivers direct less aggression toward identifiable individuals than unidentifiable individuals. Therefore, the responses necessary for individual recognition may pre‐date its evolution in the P. fuscatus lineage. Additionally, our data demonstrate the apparent binary differences in a complex behavior between the two species, such as individual recognition, likely involve incremental differences along a number of axes.     

Sex recognition in brown skuas: do acoustic signals matter?

Bird vocalisations are often essential for sex recognition, especially in species that show little morphological sex dimorphism. Brown skuas (Catharacta antarctica lonnbergi), which exhibit uniform plumage across both sexes, emit three main calls: the long call, the alarm call and the contact call. We tested the potential for sex recognition in brown skua calls of 42 genetically sexed individuals by analysing 8–12 acoustic parameters in the temporal and frequency domains of each call type. For every call type, we failed to find sex differences in any of the acoustic parameters measured. Stepwise discriminant function analysis (DFA) revealed that sexes cannot be unambiguously classified, with increasing uncertainty of correct classification from contact calls to long calls to alarm calls. Consequently, acoustic signalling is probably not the key mechanism for sex recognition in brown skuas.     

Advertisement Call Variation in the Golden Rocket Frog (Anomaloglossus beebei): Evidence for Individual Distinctiveness

Individual distinctiveness in acoustic signals can allow receivers to respond appropriately to different individuals. The aim of this research was to examine signal variation and to investigate the relative importance of different acoustic properties for coding individual distinctiveness in the advertisement calls of male golden rocket frogs (Anomaloglossus beebei). We examined patterns of within‐individual and among‐individual variability in 760 advertisement calls of 40 males as well as repeatability in 16 additional males that were recorded on two different occasions. We examined eight call properties, and all properties exhibited significant among‐individual variation and moderate to high repeatability across days. We employed discriminant function analysis to examine individual distinctiveness statistically. These analyses assigned 79% of calls to the correct individual. Fine temporal properties, including pulse duration, pulse rate, and pulse interval, as well as the spectral property of dominant frequency, contributed most toward discrimination among individuals. These results indicate that individual male golden rocket frogs can be distinguished statistically by their advertisement calls. We use these findings to evaluate results of previous playback studies in A. beebei and to generate testable predictions regarding the potential for specific call properties to function in mate selection and social recognition.     

PATTERNS OF VARIATION IN AQUATIC AMBYSTOMATID SALAMANDERS: KINEMATICS OF THE FEEDING MECHANISM

Patterns of variation in the feeding mechanism of three species of ambystomatid salamanders (Ambystoma dumerilii, A. mexicanum, and A. ordinarium) were studied to provide insight into the nature of variation in kinematic parameters of the jaw mechanism associated with prey capture. A nested analysis of variance design provided an assessment of the amount of variation in six kinematic variables (measured from 200 frames/sec films of feeding behavior) both among species and among individuals within species. For all six variables, a highly significant proportion of the variance was explained at the intraspecific level. Among species, the most robust discriminators were variables associated with movement of the hyoid. The variables reflecting gape and lifting of the head provided no significant discrimination among species and had large error variances. The hyoid apparatus is the most phylogenetically conservative component of the feeding mechanism in lower vertebrates and was the most stereotyped component of feeding behavior within the salamander species studied here.     

Genetic markers validate using the natural phenotypic characteristics of shed feathers to identify individual northern goshawks Accipiter gentilis

The recognition of individual animals is essential for many types of ecological research, as it enables estimates of demographic parameters such as population size, survival and reproductive rates. A popular method of visually identifying individuals uses natural variations in spot, stripe or scar markings. Although several studies have assessed the accuracy of these methods in mammals, crustaceans and fish, there have been few attempts to determine whether phenotypic characteristics are accurate when used for birds. Furthermore, even less is known about whether shed or moulted body parts can be reliably used to visually identify individuals. Here we assessed the accuracy of using phenotypic characteristics to identify avian individuals using a double‐marking experiment, whereby nine microsatellite genetic markers and natural markings on shed feathers were used to independently identify northern goshawks Accipiter gentilis. Phenotypic and genetic identification of individuals was consistent in 94.4% (51/54) comparisons. Our results suggest that the phenotypic characteristics of shed feathers can be reliably used as a non‐invasive and relatively inexpensive technique to monitor populations of an elusive species, the northern goshawk, without having to physically re‐capture or re‐sight individuals. We posit that using natural markings on shed feathers will also be a reliable method of identifying individuals in avian species with similar phenotypic characteristics, such as other Accipiter species.     

Songbirds tradeoff auditory frequency resolution and temporal resolution

Physical tradeoffs may in some cases constrain the evolution of sensory systems. The peripheral auditory system, for example, performs a spectral decomposition of sound that should result in a tradeoff between frequency resolution and temporal resolution. We assessed temporal resolution in three songbird species using auditory brainstem responses to paired click stimuli. Temporal resolution was greater in house sparrows (Passer domesticus) than Carolina chickadees (Poecile carolinensis) and white-breasted nuthatches (Sitta carolinensis), as predicted based on previous observations of broader auditory filters (lower frequency resolution) in house sparrows. Furthermore, within chickadees, individuals with broader auditory filters had greater temporal resolution. In contrast to predictions however, temporal resolution was similar between chickadees and nuthatches despite broader auditory filters in chickadees. These results and the results of a model simulation exploring the effect of broadened auditory filter bandwidth on temporal resolution in the auditory periphery strongly suggest that frequency resolution constrains temporal resolution in songbirds. Furthermore, our results suggest that songbirds have greater temporal resolution than some mammals, in agreement with recent behavioral studies. Species differences in temporal resolution may reflect adaptations for efficient processing of species-specific vocalizations, while individual differences within species may reflect experience-based developmental plasticity or hormonal effects.     

Individual Distinctiveness in the Fine Structural Features and Repertoire Characteristics of the Songs of White‐eared Ground‐sparrows

Communication between social animals is often more effective when signals facilitate individual recognition. Two critical requirements for individual recognition are the occurrence of characteristics that are unique to each individual, and the consistency of these characteristics through time. In some animals, characteristics of acoustic signals are known to vary over time due to changes in a variety of factors, including physiological and environmental features. Such temporal variation requires careful evaluation when exploring the individual distinctiveness of animal signals. In this study, we evaluate individual distinctiveness in the songs of male white‐eared ground‐sparrows Melozone leucotis and the persistence of distinctive characteristics over time. We collected focal recordings from populations of banded ground‐sparrows during two consecutive breeding seasons, including multiple recording sessions within each breeding season. We evaluated individual distinctiveness in fine structural acoustic features of songs. We also extended our analysis to repertoire characteristics, focusing on whether the relative frequency of song type use may provide cues to individual identity. We found that each male white‐eared ground‐sparrow sang individually distinctive songs, although their fine structural features varied between recording sessions. We found the frequency with which males sang different song types was also individually distinctive, and this feature varied little between recording sessions. Receivers may be able to use these distinctive characteristics to differentiate individuals over extended time periods; this may be especially important for species that engage in long‐term social interactions, such as tropical birds that defend territories against rival conspecific animals throughout the year.     

Sex determination of Pohnpei Micronesian Kingfishers using morphological and molecular genetic techniques

ABSTRACT.   Conservation-oriented studies of Micronesian Kingfishers ( Todiramphus cinnamominus ) have been hindered by a lack of basic natural history information, despite the status of the Guam subspecies ( T. c. cinnamominus ) as one of the most endangered species in the world. We used tissue samples and morphometric measures from museum specimens and wild-captured Pohnpei Micronesian Kingfishers ( T. c. reichenbachii ) to develop methods for sex determination. We present a modified molecular protocol and a discriminant function that yields the probability that a particular individual is male or female. Our results revealed that females were significantly larger than males, and the discriminant function correctly predicted sex in 73% (30/41) of the individuals. The sex of 86% (18/21) of individuals was correctly assigned when a moderate reliability threshold was set. Sex determination using molecular genetic techniques was more reliable than methods based on morphology. Our results will facilitate recovery efforts for the critically endangered Guam Micronesian Kingfisher and provide a basis for sex determination in the 11 other endangered congeners in the Pacific Basin.