Survival probabilities of first and second clutches of blackbird (Turdus merula) in an urban environment

The breeding success of blackbirds was investigated in April and June 2008 and 2009 in the Botanical Garden of the University of Pecs, with a total of 50 artificial nests at each of the four sessions (with 1 quail egg and 1 plasticine egg placed in every nest). In all four study periods of the two years, 2 nests (4%) were destroyed by predators. Six nests (12%, of the nests) were not discovered in either of the cases. The survival probability of artificial nests was greater in April than in June (both years), but the difference was significant only in 2008. Nests placed into a curtain of ivy (Hedera helix) on a wall were located higher up than those in bushes, yet their predation rates were quite similar. The predation values of quail vs. plasticine eggs did not differ in 2008. In the year 2009, however, significantly more quail eggs were discovered (mostly removed), than plasticine eggs. Marks that were left on plasticine eggs originated mostly from small mammals and small-bodied birds, but the disappearance of a large number of quail and plasticine eggs was probably caused by larger birds, primarily jays.