Influence of meteorological parameters on the occurrence of grey partridge family groups in the Southern Cis-Ural region

Against the background of a steady increase in air temperature and a decrease in precipitation and humidification in the study area (Burtinskaya Steppe in the Orenburg Nature Reserve, southern Cis-Ural region, Russia) several dependences between the dates of sightings of the grey partridge family groups and meteorological parameters in different parts of the season were revealed. In total, during the period 1992-2019, 1332 sightings of grey partridges were recorded in Burtinskaya Steppe, in most cases they were broods with adult birds accompanying them (family groups). The increased average temperatures in May - June contributed to an earlier average and median date of sightings of family groups of partridges during the period until the end of autumn (June - November) until the end of the year (June - December) (maximum value of Spearman’s rank correlation coefficient: R = -0.55, р ˂ 0.01, n = 26). Increased precipitation in April - June led to a significant shift in the average and median dates of sightings of partridge family groups at a later date in the season (R = 0.59, р ˂ 0.01, n = 26). As in the case of precipitation, increased moisture in May - July resulted in a shift in the average and, to a lesser degree, the median date of family group sightings to a later period (R = 0.49, р ˂ 0.05, n = 26). There is also a weak tendency to expand the scope of family group sightings from June till November - December in the warmest years. This trend was manifested in a positive correlation of the scope of family group sightings on the route until the end of autumn (June - November) with the average air temperature for the same period (R = 0.46, р ˂ 0.05, n = 25), as well as in the linear regression of the scope of family group sightings on the route until the end of the calendar year and the average temperature for the same period (B = 0.44, R2 = 0.19, F(1,23) = 5.51, р ˂ 0.05, n = 25). The expansion of the scope of sightings in seasons with increased average air temperature is also confirmed by a reliable positive correlation between the number of family group sightings in June - July and temperatures in this and previous periods (R = 0.52, р ˂ 0.01, n = 27), as well as a correlation between the number of sightings in November - December and temperatures in this and previous periods (R = 0.44, р ˂ 0.05, n = 27). Increased precipitation in April - May led to a decrease in the number of partridge sightings in June - July (R = -0.43, р ˂ 0.05, n = 27), however, the amount of precipitation in autumn did not significantly affect the number of partridge sightings in November - December. The negative relationship of precipitation with the number of sightings increases in December, but remains unreliable. In addition, a linear dependence of the average and median date of sightings on time (the number of years of observations) was revealed, which increases when considering the intervals of the season in the direction June - November (until the end of autumn), June - December (until the end of the year), June - April (until the end of family group meetings) (B = 0.46, R2 = 0.21, F(1,23) = 6.07, р ˂ 0.05, n = 25). The reasons for all identified dependencies are discussed. It is suggested, in particular, that all the above linear relationships are associated with climate warming and the extension of the period of comfortable stay of partridges in the reserve. Warm weather and decreasing precipitation and humidification not only accelerate the appearance of family groups in June, but also contribute to the increasing delay of birds on the site until the end of the year and even the wintering of a small part of the birds in the reserve. This, in turn, apparently, is connected with the acceleration of the breeding process at the beginning of the season and with an increase in the availability of food in the autumn - winter season.