Anna V. Klenova

Duet structure provides information about pair identity in the red-crowned crane (Grus japonensis)

We studied the acoustic features of the endangered red-crowned crane (Grus japonensis), and, specifically, whether or not the duets carry information about a mating pair identity. The population of this species in the wild is only approximately 2,000 individuals. In 2003–2006, we recorded 343 duets from eight captive and two wild pairs. All of the duets contained an introduction, an unordered alternation of pair mate calls, followed by the main part, representing the regular sequence of syllables, containing 1–2 male and 1–4 female calls per syllable. We subdivided the syllables into five types, by the number of male and female calls per syllable, and analyzed the occurrence of the different syllable types in the duets of the ten pairs. The analysis showed the sustainable pair-specific use of particular syllable types through the years. The discriminant analysis standard procedure, based on seven frequency and temporal parameters of male and female calls, showed 97.7% correct assignment to the pair, which is significantly higher than random values. The high pair specificity of the duet acoustic structures provides the basis for call-based censuses. This would enable the monitoring of the red-crowned crane mating pairs in their natural habitat.

Examination of pair-duet stability to promote long-term monitoring of the endangered red-crowned crane (Grus japonensis)

Acoustic-based monitoring has proved useful for many birds and seems promising for the endangered red-crowned crane. However, its validity in crane conservation is unclear in the absence of knowledge concerning the long-term stability of pair-specific duets. The red-crowned crane is monogamous and long-lived, with stable pair bonding both within and between years. Pair mates perform loud duets—a succession of male and female calls emitted with definite temporal coordination. We examined the stability of duets for five captive pairs over five years (2003–2007) on the basis of analysis of the syllables within the duets. MANOVA showed that the effect of pair identity on syllable characteristics was always stronger than the effect of the year of recording. Cross-validation of duets from 2004, 2005, 2006, and 2007 with discriminant analysis (DFA) functions derived, respectively, from pooled samples from 2003, 2003–2004, 2003–2005, and 2003–2006 resulted in comparably high percentages of correct classification into pairs. The pairs could be reliably identified by their duets and pair-specific differences in syllable characteristics were stable with time. These data suggest acoustic monitoring is a feasible alternative to more invasive methods of identification.

Voice breaking in adolescent red-crowned cranes ( Grus japonensis )

Summary Voice breaking is a process associated with puberty of human males that also occurs in adolescence in some birds. This study reports the jump-like vocal changes occurring during voice breaking in adolescent red-crowned cranes (Grus japonensis). We investigated acoustic parameters of chirp and trill calls during vocal ontogenesis from hatching to the age of 1.5 years in 17 male and 31 female captive red-crowned cranes and compared them with definitive calls of 5 male and 8 female conspecific adults. During voice breaking, trills and chirps of both sexes contained two non-overlapping independent fundamental frequencies: the upper one, representing the retained juvenile frequency, and the lower one, the newly attained adult frequency. Before voice breaking, the calls contained only the upper frequency, whereas after it only the lower one. Voice breaking occurred between the age of 7 and 11.5 months. We test whether sex, dates of birth and body mass gain are associated with voice breaking and speculate whether voice breaking triggers the disruption of the parent‐ chick bond or vice versa, or both events are driven by a third, yet unidentified trigger.

The variation in reliability of individual vocal signature throughout ontogenesis in the red-crowned crane Grus japonensis

Distinctiveness of chicks’ calls may arise in ontogenesis when parents can confuse their own and alien chicks, leaving their nests and forming crèches or flocks. It is unknown, however, whether the individual vocal signature retains further in ontogenesis or relaxes when the necessity in the parental care disappears. In this paper, we study the inter- and intra-individual variations of the acoustic parameters in chicks’ calls in the red-crowned crane Grus japonensis, the species with prolonged development enveloping three stages: territorial under parental care, in flocks under parental care and in flocks self-independently. We found, that discriminability of chicks’ calls increased significantly to the second stage, characterized by the maximum risk for parents to confuse the own and alien chicks, and significantly decreased to the third stage, when the needs in the parent–chick vocal recognition disappeared. Our data agree with a hypothesis that the individual distinctiveness decreases in the absence of necessity in accuracy of parent–chick recognition.

Individual and Sexual Differences in the Calls of the Monomorphic White-Faced Whistling Duck Dendrocygna viduata

Abstract. The White-faced Whistling Duck is a waterfowl species lacking any differences in ornamentation, coloration, size or behavior between the sexes. For distant communication, this species uses loud whistles. We analyzed 12 spectral parameters of 344 whistles from 23 captive adult ducks (14 males and 9 females). Discriminant analysis showed 94% correct assignment to an individual (N = 279 calls from 14 birds; 15–22 calls per bird). Separately for 8 males (162 calls) and for 6 females (117 calls), discriminant analysis showed 99% and 93% correct assignment to individuals respectively. Discriminant analysis for sex (N = 86; 3 calls from each of 14 males and 5 calls from each of 9 females) showed 100% correct assignment. Intersexual differences were governed by frequency parameters, the values of which were significantly higher in females than in males. Cluster analysis showed that differences between sexes were expressed significantly more strongly than the individual differences. The fact that the “acoustical keys” differed as regards the identification of individual birds or their sex may significantly enhance the reliability of acoustical recognition systems in the White-faced Whistling Duck. The data are discussed in the context of the biology of the White-faced Whistling Duck and significant intersexual differences in syringial and tracheal anatomy, which may be responsible for the sharp distinctions between the sexes in the calls of this species.

The vocal development of the Red-crowned Crane Grus japonensis

ABSTRACT Most studies on avian vocal ontogenesis have focused on taxa exhibiting some kind of vocal learning. This study provides a detailed analysis of vocal processes through early and late ontogenesis in 17 chicks of the Red crowned Crane Grus japonensis, a species lacking vocal learning. Three basic structural classes: trills, PE-chirps and PS-chirps and their transitional forms are described. Trends in call parameter values are presented for 10 age classes in the course of a period from birth to 9.5 months. We discuss our vocal classification with those reported for other crane species, relate the revealed stages of vocal ontogenesis in the Red-crowned Crane to biologically relevant life stages in this species and advance a hypothesis for the proposed function of retaining high juvenile frequencies in adolescent cranes for a prolonged period, up to voice breaking (a rapid significant decrease in fundamental frequency). We conclude, that voice breaking is universal for both sexes and that the retained high call frequencies may represent an infantile characteristic, essential in evoking care from the parents towards the growing chick and may also act as a mechanism to reduce aggression from conspecifics.

THE TECHNIQUE OF NONINVASIVE DISTANT SEXING FOR FOUR MONOMORPHIC DENDROCYGNA WHISTLING DUCK SPECIES BY THEIR LOUD WHISTLES

ABSTRACT Here we present an acoustic approach for reliable sexing in four whistling duck species from the genus Dendrocygna and compare it with molecular and cloacal inspection techniques. In the four examined species, the White-faced Whistling Duck D. viduata, Fulvous Whistling Duck D. bicolor, Cuban Whistling Duck D. arborea and Red-billed Whistling Duck D. autumnalis, sexes are indistinguishable by appearance. However all the four species show strong sexual differences in the structure of their species-specific loud whistles. For 59 examined birds, an acoustic-based sexing showed 100% accordance to the DNA PCR analysis, while the cloacal inspection showed only 89.8% accuracy. The results demonstrate that acoustic sexing represents a feasible alternative to the two traditional methods as a noninvasive tool for the distant sexing of the four whistling duck species both in captivity and in the wild.

Behavior of crested auklets (Aethia cristatella, Charadriiformes, Alcidae) in the breeding season: Visual and acoustic displays

The crested auklet, a highly social planktivorous bird species of the Northern Pacific, is an important component of marine ecosystems. Although visual and acoustic modalities play a major role in the communication of these birds, the available data on the repertoire of their vocal signals and postures are scarce and lack quantitative analysis. This study deals with visual and acoustic displays of crested auklets on their breeding grounds and the occurrence frequencies of certain forms of social behavior in male and female birds. The data were collected on Talan Island (the Sea of Okhotsk) in 1987–1991 and 2008. They show that the rate of contacts between birds is very high and sex-specific: on average, males initiate 1.13 contacts/min, compared to 0.65 contacts/min initiated by females. Directionality of ruff-sniff displays differs depending on the posture of the recipient bird. The duration of the trumpeting display in males depends on their social surroundings. However, the duration of either the trumpeting display or the mutual cackling display during courtship is independent of the behavioral context. Vocalization of crested auklets is characterized by two independent basic frequencies occurring either sequentially or simultaneously. The role of different communicative modalities in the behavior of the crested auklet is discussed.

Inter- and intra-season stability of vocal individual signatures in a social seabird, the crested auklet

Vocal plasticity due to changes of social context is well documented in passerine birds. In other bird species, the impact of social environment changes on the whole vocal structure and on individual specific signatures remains largely unexplored. Here, we assessed inter- and intra-season stability of specific features of individual signatures in advertising calls of crested auklet (Aethia cristatella) males and tested the effects of pair mate and territory changes on the stability of the calls. The crested auklet is a highly social seabird of the North Pacific that breeds in dense colonies, and its individuals switch pair mates and territories with probability of 25–54%. During summer 2008–2010, we recorded 464 trumpet calls from 21 individually marked males and determined their pair mates and positions of their displaying places on a breeding colony of Talan Island, Sea of Okhotsk. We found that strong individual specific features of crested auklet trumpet calls stay stable not only during one season but also from year to year. However, we failed to find any effects of pair mate or territory changes on individual signatures of crested auklet trumpet calls. Our results suggest that crested auklets can potentially use their individually specific trumpet calls to form long-term social bonds both between pair mates and between neighbors; however, future experimental studies should test whether this is indeed the case.

Vocal development and voice breaking in Demoiselle Cranes (Anthropoides virgo)

The vocal development of cranes (Gruidae) has attracted scientific interest due to a special stage, so-called voice breaking. During voice breaking, chicks produce both adult low-frequency and juvenile high-frequency vocalizations. The triggers that affect voice breaking are unknown. For the first time, we study the vocal development of the Demoiselle Crane (Anthropoides virgo). We describe the age and possible drivers of the onset of voice breaking. We analyse the calls of 21 Demoiselle Crane chicks, and compare them with the calls of six adult birds, noting the day when adult low-frequency calls are first recorded as the day when voice breaking begins. The age of voice breaking onset does not depend on hatching date, clutch order or chick body mass. Thus, there is no correlation between body growth and the onset of voice breaking for individual Demoiselle Crane chicks. However, there is a strong relationship between body mass and voice breaking among different crane species. Demoiselle Cranes stop intense body growth at the age of 2 months and start voice breaking at 70 ± 46 days. By way of comparison, Red-crowned Cranes finish the period of intense body growth at the age of 7 months and start voice breaking at 211 ± 60 days. Thus, we show that the Demoiselle Crane has a sudden vocal development, similar to other crane species, and we suggest that the end of intense body growth is the trigger for the onset of voice breaking in cranes.