The population trend of the red-backed shrike, Lanius collurio, is declining in its range. We studied the breeding biology of this species in the 2011 and 2012 breeding seasons in the north of Turkey. Our study site was an area of approximately 650 ha in the Kizilirmak Delta. Population density was 2.4 breeding pairs (bp)/10 ha and 2.7 bp/10 ha in 2011 and 2012, respectively. Blackberry bushes were used most frequently as nest sites (66%). The mean height of the nests from the ground was 125 +/- 39 cm. The mean height of nest plants was 224 cm +/- 76 cm. Nest height and nest plant height were positively correlated. We present an inequality of breeding parameters in the two successive breeding seasons. In 2011, the red-backed shrikes arrived at their breeding sites later, began to breed later, laid smaller clutches, and were less productive than in 2012. The main factor of the nest failures was nest predation in the study area. We detected normal second broods (six pairs) and it seems that this case was not exceptional. The Kizilirmak Delta is an important breeding area of the red-backed shrike population and more comprehensive studies are required.