Variability of daily nest survival and breeding success in relation to characteristics of Eurasian magpie (Pica pica) nests

Abstract

Size and structure of birds’ nests can arise from evolutionary trade-offs between benefits, such as insulation from unfavourable conditions, maintenance of eggs or chicks, security against predation, and costs, such as energy spent in construction of the nest and the risk of predation in more visible nests. The relationships between nest characteristics and breeding success and survival probabilities of Eurasian magpie (Pica pica) eggs and nestlings were studied in Baghbadaran, central Iran during the 2008 and 2010 breeding seasons. Nesting success was modelled to assess the relationships between nest parameters and the probability of daily nest survival. Mean clutch and brood size, hatching, fledging and breeding success did not vary significantly between the two years. Mean internal diameter, external diameter, distance to feeding location and distance to open areas varied significantly between the two study years. Daily nest survival rate for both years (2008 and 2010) was 0.98 ± 0.002. Nest size and status of nests, defined as old or newly established nests, were the best factors predicting probabilities of nest survival. Nests with small internal diameters had higher overall nest productivity. Nest height was positively correlated with both fledging success and breeding success. Our results agree with previous findings that have shown that magpie pairs with large nests provided their nestlings with higher quality food compared with pairs with smaller nests and so nest size was an indicator of parental ability. Nest height is also recognized as an important determinant of nest predation, mostly because it may affect nest detectability and accessibility.