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The Demoiselle Crane (Grus virgo L. 1758) occupies a vast breeding range in the Eurasian steppe zone. The birds follow several migration routes and share a number of wintering grounds. Although the Demoiselle Crane is distributed in many countries and has a long history of study, no efforts of assessing the population genetic structure of the species have been undertaken to date. We present the first results of the estimation of genetic diversity by sequencing the Control Region of mitochondrial DNA (1003 bp) and analyze spatial distribution of haplotypes on the northern edge of the species’ breeding range and genetic differentiation among territorial groupings. We studied 83 birds from six breeding groups in Europe (Azov-Black Sea, Caspian, Volga-Ural) and Asia (Trans-Ural, South Siberian, Transbaikal). Our research has revealed a high level of genetic diversity in all parts of the species’ range (Hd = 0.964) and showed the total genetic subdivision to be moderate (Wright’s FST = 0.075) with more differentiated European (FST = 0.128) and more homogenous Asian breeding groups (FST = 0.012). Genetic isolation of the territorial groupings seems to be incomplete suggesting substantial gene flow across the Demoiselle Crane breeding range that likely represents a formerly continuous breeding population fragmented just recently in Europe and only on its northern edge in Asia. At the same time, mitochondrial haplotype distribution and segregation of haplogroups specific to Europe and Asia may serve as evidence of an increasing genetic differentiation and reflect initial steps of the Demoiselle Crane gene pool structuring process.

Vocal-based monitoring is increasingly being used as a non-invasive method for identifying individuals within avian populations and is promising for the Siberian Crane, Leucogeranus leucogeranus. This is a poorly studied, long-lived, secretive and critically endangered bird species that breeds in the Arctic tundra of western and eastern regions of Siberia. We assessed between- and within-year stability of individual-specific vocal features in duets of Siberian Crane and tested the effect of pair-mate change on their stability. Previous findings showed that duets are specific to different pairs of birds; however, it is still unknown how long pair-specific traits of duets remain and if they change in the course of a year or when birds re-mate. We recorded duets of 15 reproductively active pairs in the Oka Crane Breeding Centre in 2003–2006 and 2013–2017. We found that pair-specific vocal signatures remained stable both within the year and across ~ 10 years. After a change of mate, most of the variables we measured in the call did not change in any of the birds. Our data suggest that the stability of the individually specific vocal features may enable Siberian Cranes to be reliably identified by their duets over the birds’ lifetime. We believe that our work can increase confidence in the use of acoustic recognition techniques for endangered crane monitoring programs. Our results also suggest that Siberian Cranes may use their duets to form long-term social bonds between neighbours.

Vocal development of cranes (Gruidae) has attracted scientific interest due to its special stage, voice breaking. During voice breaking, chicks of different crane species produce calls with two fundamental frequencies that correspond to those in adult low-frequency and juvenile high-frequency vocalizations. However, triggers that affect voice breaking in cranes are mainly unknown. Here we studied the voice breaking in the Siberian Crane (Leucogeranus leucogeranus) and test its relation to the body mass and testosterone level. We analyzed 5846 calls, 39 body mass measurements and 60 blood samples from 11 Siberian Crane chicks in 8 ages from 2.5 to 18 months of life together with 90 body mass measurements and 61 blood samples from 24 Siberian Crane adults. The individual duration of voice breaking and dates of its onset, culmination and completion depended neither on the body mass nor on the testosterone level at various ages. But we found correlation between the testosterone level and mean deltas of percentages of the high and low frequency components in Siberian Crane calls between the closest recording sessions. We also observed some coincidence in time between the mean dates of voice breaking onset and the termination of body mass gain (at 7.5 months of age), and between the mean dates of voice breaking completion and the start of a new breeding season. Similar relations have been shown previously for some other crane species. We also showed for the first time that the mean dates of voice breaking culmination correlated with the significant increase of the testosterone level (at 10.5 months of age). So, we suggest that voice breaking in cranes may be triggered by the end of chicks’ body growth, is stimulated by the increase of testosterone level and ends soon after adult cranes stop taking care of their chicks.

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.