The Effect of Seasons on Total Antioxidant Capacity (TAC), Total Oxidant Capacity (TOC) and OSI (Oxidative Stress Index) Levels in Free-Living Blackbirds ( Turdus merula ) in Nature

The oxidative stress level of organisms is one of the best indicators of whether they are healthy or not. The increase in oxidative stress level in the cell can affect the longevity of the organism as well as cause some immune diseases. In this study, wing, tail, tarsus lengths, weights, muscle and fat scores, Total Antioxidant Capacity (TAC), Total Oxidant Capacity (TOC) and Oxidative Stress Index (OSI) levels of Blackbirds living in Sinop, Sarıkum Nature Protection Area were examined during all four seasons. A total of 55 Blackbirds were caught in autumn, winter, spring and summer. The highest weight was detected in females and males in autumn, and the lowest in summer. Although there was no statistical difference between the wing and tail lengths, they were slightly higher in the Spring. Total antioxidant levels were highest in both sexes in spring. TAC levels were statistically different only in males, and OSI levels in both sex. The season with the highest OSI levels for both sexes is autumn. This situation was closely related to seasonal conditions and whether they were in the breeding period or not. This study shows that total antioxdant levels and oxidative stress index can easily change in Blackbirds.