An Assessment of the Annual Mortality Rate and Population Demographics Status in Birds Based on Ring-Recovery Data

Abstract

A new method for assessing the annual mortality rate in bird populations is described. Ring recoveries from birds that died from various causes serve as the basis for such an assessment. The commonly accepted technique for such an assessment performed with the help of MARK software is laborious, yet fails to ensure a highly precise assessment. To calculate the mortality rate, we propose an exponential demographic model that is based on the geometric progression of a decrease in the annual numbers in some arbitrarily selected set of birds in a population. The equation of the model allows calculating the annual mortality rate of a bird population or even a species in a simple way, if the ringing data covers a vast area, for example, the territory of Russia. In addition, the proposed equation permits producing “a mortality pattern,” namely, to present a chart of interrelations between the theoretical and real rates of the decrease in numbers in a given cohort of birds. The interrelations between the theoretical and real annual mortality rates allow understanding the status of a bird population each year during a period of ringing and recovery collecting: this makes it possible to reveal the population trend about whether the population is stable or decreasing or increasing in numbers.