Common Crane as a species indicating the conservation importance of wetlands

The relevance of the study is determined by the high importance of wetlands in the ecological frameworks of territories and the need for methodological approaches to identify wetlands of high conservation importance. The paper is aimed to demonstrate the indicator role of the Common crane to determine the conservation importance of wetlands on the example of the Nizhny Novgorod region. Objectives: to estimate the number of the common crane in existing and reserved protected areas; to analyze the presence of wildlife species listed in the Red Data Book of the Nizhny Novgorod region in these protected areas. The results of many years of surveys as well as data from the Red Data Book of Nizhny Novgorod region are analyzed. It is shown that within 93 protected areas of the total area 491870 ha 135598.4 ha of wetlands are protected, where 830 territorial pairs of cranes (about 60% of the regional population of the species) inhabit. Along with the common crane, these areas serve to protect almost all (91%) obligate wetland wildlife species listed in the Red Data Book of Nizhny Novgorod region, 82% of rare species associated with wetlands and 53% of species not associated with wetlands. Our calculations showed a high correlation of the number of rare wildlife species with the wetland area (correlation coefficient 0.75). The correlation of the number of rare species with the number of common crane was higher (correlation coefficient 0.82). Quantitative correlations of the number of rare wildlife species with the area of wetlands and the number of common cranes were also calculated. The obtained conclusions allow using the number of the common crane for substantiation of importance of wetlands for nature protection and establishment of protected areas.

What do we know about survival of Common cranes? An elementary introduction with Euring databank

The increase of the western populations of Common cranes (Grus grus) in the last five decades highlights the need to estimate survival rates. According to Euring databank (EDB), the oldest Common crane ever known was 27 years old in year 2017. This lifespan was obtained by means of 24,900 recoveries of 2,124 ringed cranes collected between years 1936 and 2017. Nearly all cranes were ringed and observed in the last 30 years, and therefore the elapsed time was not enough to reach the maximum longevity reported for the species in captivity (43 years, Mitchell 1911). Life expectancy was five years on average after the ring was attached. Here we provide some elementary analyses to calculate the annual apparent survival rate (ϕ = 0.85) and the annual encounter probability (p = 0.45) of Common cranes, as a first step to advance in the knowledge of the species' population dynamics. The great increase of breeding and wintering crane populations in western Europe in the last decades remains largely unexplained.

Circadian preferences of birdwatchers in Poland: do “owls” prefer watching night birds, and “larks” prefer daytime ones?

Birdwatching is a very popular and increasing leisure activity, and the study and observation of birds is more popular in the morning due to the greater activity among birds at that time of day. The aim of our study was to find out whether there was a relationship between the circadian preference of observers and their favourite bird species and whether it was influenced by such factors as professional status, age and gender. In an e-mail survey we asked a total of 433 Polish ornithologists (professionals) or birdwatchers (non-professionals) for their morningness–eveningness preferences (four categories) and favourite (open choice) bird species and received 143 responses. The temporal (circadian) preferences of respondents declined from early morning (35.7%) to evening/nighttime (11.4%). Circadian preference categories differed significantly by age, with early morning respondents significantly older. These preference categories did not differ significantly in terms of response time to the survey invitation or in the percentage of their favourite birds that were categorised as daytime birds. A total of 204 species were identified as favourite birds of which 34 species were mentioned by five or more respondents, with only two, the common crane Grus grus and the Eurasian pygmy owl Glaucidium passerinum mentioned by more than 10% of respondents. The white stork Ciconia ciconia was more popular with professionals than non-professionals and the swift Apus apus less popular. A significant gender × circadian preference interaction was detected for the percentage of favourite birds categorised as daytime birds, with fewer daytime birds among early morning female recorders. The presented results are obviously of a correlative nature, but open the door for further, more advanced study and suggest there may be a need to investigate temporal biases when analysing citizen-based data.

Grote trap en kraanvogel als historische broedvogel in Nederland

Great bustard Otis tarda and common crane Grus grus as historic breeding bird in The Netherlands For extinct breeding birds it is often difficult to establish when and why they got extinct. This can be done by comparing the pattern of extinction for different bird species. In this article great bustard and common crane are compared. They became extinct as a breeding bird in the same period and both stayed irregular dwellers in the centuries afterwards. For common crane archeozoological findings suggest they were widespread and common in the Netherlands until 1000 AD. Written sources on hunting from the 14th till 19th century show they were present in different parts of the country. But they were not common anymore. Several of these sources involve breeding birds. In western and southern parts of the Netherlands they became extinct as breeding birds from the 14th till the beginning of the 17th century. In eastern and northern parts they could survive longer as breeding birds. Possibly, in the province of Drenthe this was until the beginning of the 18th century. For great bustard archeozoological findings suggest they were scarce or absent until 1000 AD. Written sources on hunting from the 16th century on show they were present in the western part of the country. Some of these sources describe their status as breeding bird. The sources suggest they became extinct as breeding bird around 1600. Changing landscapes are for both species the main driver of their extinction. Their breeding habitats disappeared by reclamation, intensification of land use and a growing human population. One of the underlying factors was the economic upheaval of the Golden Age (1588-1702). The prosperity made big investments for reclamation possible. Both species were hunting bird and were protected by hunting laws. During the Dutch revolt (1568-1648) these laws could not always be enforced. Lack of protection could be an additional factor in their extinction. The presence of great bustard shows a relation to the Medieval Warm Period. The successive Little Ice Age, starting in the 16th century, may have been a factor in their disappearance.

SYNTHESIS OF STRUCTURAL SCHEMES OF LINKAGE MECHANISMS FOR PORTAL Gantry CRANE JIB SYSTEM

The most common crane structural scheme used in the practice includes 4-link guiding mechanism and 4-link balancing mechanism. Some special crane construction as such designed by Kranbau – Eberswalde contains a 6-link balancing mechanism with structural scheme obtained by conjunction of 2 consecutive 4-hinged units. Similar construction is a subject of research, related to synthesis of 6-links mechanism during designing of new crane constructions. Another paperwork presents an approach for development of jib system of existing gantry crane type. Such approach relates to keep both – jib and arm without changes in their mass, shape and loading conditions. Still another paperwork revealing an approach for synthesis of existing gantry crane allowing minor structural changes by addition of small-sized links to the scheme of balance mechanism without changes in the structure of jib, arm and frame. According Assur’s classification the number of links in each mechanism would be theoretically unlimited although it would cause significant difficulties during production of such systems. Practically, not any crane constructions designed with 8-link or 10-link structural scheme exists. At other side, increasing the number of links is a precondition to more accurate dimensional movement of balance unit. Structural schemes for plain linkage mechanisms appropriate for application in a portal crane are being synthesized. At the synthesis the limitations of the links must be no more than ten and they save the configuration of the crane’s mechanism that is mostly used in practice. Potential applications of 4 different structural schemes indicated as Н1У1, Н2У1, Н1У2 and Н2У2, synthesized by a practical example, are being appraised. Results for alteration of the reduced moment to jib from weights of links of jib system depending on the range of jib with and without useful load are obtained.