Breeding Density, Nest Sites, Clutch Size and Egg Dimensions of the Magpie (pica Pica) in Nw Croatia

Between 1997 and 1998 the breeding density, nest sites, clutch size and egg dimensions of the magpie (Pica pica) was investigated in a 7 km2 area in the Krapina river valley. We recorded a high breeding density of 4.79 pairs/km2 (during both years). The nests were situated at a height of 1–16 m above ground (mean = 6.74 m). Magpie nests were found in at least 9 species of bushes and trees. We recorded 3–8 eggs in the first clutch (mean = 5.91 eggs). Egg length averaged 33.43 mm, egg breadth 23.35 mm, egg volume 9.288 cm3, egg shape index 1.433 and egg weight 9.22 g. There were no significant differences in egg dimensions between 1997 and 1998 (length: F = 1.79, p = 0.10; breadth: F = 1.41, p = 0.34; volume: F = 1.27, p = 0.52; shape index: F = 1.10, p = 0.78). The positive correlation between egg volume and egg breadth, egg volume and egg length, egg length and egg shape index as well as between egg length and egg breadth were statistically significant. So was the negative correlation between egg breadth and egg shape index. The correlation coefficient (r) between egg volume and egg shape index was near 0.