Occurrence of the birds of the Middle Volga Region (South-East of the European part of Russia)

Abstract Background Birds are the most numerous and widespread group of higher vertebrates. Due to the peculiarities of their biology, birds play an important role in nature and in human life. Ornithological studies described in this publication were conducted in seven regions of the Middle Volga Region (Chuvashia, Mordovia, Tatarstan, Samara, Nizhny Novgorod, Ulyanovsk and Penza Regions) from 1978 to 2021. Visual and acoustic methods were used to study the species composition during field studies. In total, 5065 birdoccurrences belonging to 157 species, 48 families and 19 orders were registered. All occurrences have a geographical reference. The large volume of data collected, the wide geographical coverage and the long-term nature of the observations determined the value of their inclusion in the GBIF and the need for publication in the Biodiversity Data Journal. New information We are publishing our original data on the coordinates of bird occurrences in the Middle Volga Region for the first time. Most of the original information about bird occurrences was contained in field diaries and was not available to a wide range of researchers. All 5065 occurrences are new to GBIF.


Introduction
Birds play an important role in natural complexes and in human life. They minimise outbreaks of harmful insects, regulate the number of rodents and dispersal of seeds of several plants (Raman 2001, Rey Benayas et al. 2017, Carvalho et al. 2020, Simonov and Matantseva 2020. They can serve as bioindicators for the state of the environment, since they respond to anthropogenic impact by changing the species composition of nesting avifauna and the number of various ecological groups (Bykov 2013, Lebedinskii et al. 2019, Kuznetsova 2021. In addition, birds make a significant contribution to the spread of parasites and transmissible diseases and can partially destroy grain crops (Girikaran et al. 2019, Stanković et al. 2019, Kucherenko et al. 2020. It shows the need for a comprehensive study of this animal group. The avifauna of the Middle Volga Region is quite well studied, but it is still relevant to conduct new research since there are migratory species and species expanding their range (Lebedeva 2017). Thus, over the past 20 years, the appearance of such new species as Phoenicurus ochruros (S. G. Gmelin, 1774) and S. decaocto (Frivaldszky, 1838) has been noted for the Samara Region, including cases of their nesting (Lebedeva 2017, Klenina et al. 2021). Streptopelia decaocto (Frivaldszky, 1838) and S. alba deepened their connection with the territory as, previously, they they were only registered (Lebedeva 2017, Klenina et al. 2021 (Simak et al. 2019). 5 species also being found in the Republic of Mordovia (Astradamov 2005).

Project description
Title: Occurrence of the birds of the Middle Volga Region (South-East of the European part of Russia)

Sampling methods
Sampling description: The dataset is based on original data obtained during field observations of birds in the period from 1978 to 2021 in the Middle Volga Region. The study of avifauna was carried out within the following administrative regions of the Russian Federation: the Republics of Chuvashia, Mordovia and Tatarstan; in the Samara, Nizhny Novgorod, Ulyanovsk and Penza Regions. The study of the species composition of birds was carried out in the course of field research, including in the framework of quantitative accounting for the number of birds. The number of birds according to the mating song of the male was recorded during the nesting period according to the standard method (Priednieks et al. 1986). Sometimes visual identification of the species belonging to a singing bird was carried out using a bird identifier (Flint et al. 1968). The species were identified on the basis of their vocalisation or by using a visual method with the help of the keys released at the time of observation (Promptov 1929, Ryabitsev 2008, Kalyakin and Voltzit 2020. If there were feather residues, an atlas for feather identification was used (Korepova 2016). In cases where it was difficult to determine a bird to a species in the field due to minor differences in plumage or vocalisation, we resorted to additional actions (for example, photographing and looking for nests). If the definition were impossible, it was not entered into the database. Some of the data were collected during special bird observations, during route surveys of birds of recreational forests (Bykov 2000, as well as during the study of the effectiveness of bird protection devices on power lines (Klenina and Bakiev 2014).
Step description: Field research included the determination of the species composition of birds of the region by audio-visual methods, with a record of the date of the meeting of the species and the coordinates of its habitat. To make the geographical reference, we fixed the coordinates of the location of the bird's occurrence using a GPS navigator or using Google maps. In all cases, the WGS-84 coordinate system was used with the accuracy of determining the coordinates up to the fourth digit. If the bird could not be detected visually, then its identification was made by listening to its voсalisation, the place of occurrence was then the place where the bird was heard. Since the bird class is one of the most geographically mobile from all the taxonomic groups of animals, this assumption seems insignificant. Subsequent processing of materials included entering data into an Excel spreadsheet and preparing a dataset in accordance with the Darwin core format, uploading the dataset to GBIF.
The field names of the dataset were chosen according to Darwin Core (Wieczorek et al. 2012).

Geographic coverage
Description: The dataset contains information about the occurrence of birds in seven administrative Regions of the Russian Federation: the Chuvash Republic, the Republic of Tatarstan, the Republic of Mordovia, Penza, Samara, Ulyanovsk and Nizhny Novgorod Regions. These Regions are located in the European part of Russia, which is designated by the Russian Bird Conservation Union as a key ornithological territory. It is used by birds as nesting sites, moulting, wintering and stopover sites (Sviridova and Zubakin 2000). Ornithological studies were conducted within the territory of such protected areas as the Mordovia State Nature Reserve (Republic of Mordovia), the national parks "Samarskaya Luka" (Samara Region) and "Smolny" (Republic of Mordovia).
The studied territory is in the south-east of the European territory of Russia in the middle course of the Volga River (Fig. 1).

Taxonomic coverage
Description: The dataset includes only occurrences of birds identified to the species level. In total, 157 species belonging to 48 families from 19 orders have been registered (Fig. 2). It is about a third of the species composition of the avifauna of the European territory of Russia (Kalyakin and Voltzit 2020). The noted species belong to 48 families from 19 orders (see Table of Taxa included below). According to our data, the most common in the Middle Volga Region are Fringilla coelebs (451 occurrences of 768 individuals), Dendrocopos major (381 occurrences of 578 individuals) and Parus major (260 occurrences of 459 individuals) (