Is there a trade-off between clutch size and egg volume in Magpie Pica pica in northwestern Croatia?

Abstract

A negative relationship, or trade-off, between egg size (egg volume or egg mass) and clutch size is a central component of life-history theory. This paper presents evidence for a relationship between clutch size and egg volume (egg size) of the Magpie (Pica pica). Magpies are common and sedentary birds in study area. Egg characteristics were recorded in Mokrice rural area (46°00'N, 15°55'E), northwestern Croatia; carried out during the breeding season (April-May) in the year 2012. I have not detected any negative correlation (trade-off) between mean estimated egg volume (egg size) and clutch size in the Magpie. The results indicate that, in researched Magpie population, in northwestern Croatia, there is a positively significant correlation between clutch size and egg volume. It can probably be explained by good environmental conditions and/or good quality females, which other authors offer as a plausible explanation. In conclusion, these results do not seem to support the prediction based on the theory of optimal egg/clutch size concerning the inverse relationship between egg size and clutch size.

Contribution to the oology of the Eurasian wryneck Jynx torquilla

“…Saches-Lafuente 2004) and some positive (e.g. Dolenec, 2016b). Clutch size and egg size (volume) values of the Eurasian wryneck in this study are similar to the results collected in other European countries.…”

No evidence for trade-off between egg dimensions and clutch size in first, second and third clutches of the Tree Sparrow Passer montanus

“…According to Hõrak et al (1995), "being hatched from a large egg could potentially be beneficial of the laying female, however, high investment into egg quality (size) might conflict with her own energetic demands and willingness to produce more offspring". Studies have found negative (Martin et al 2006, Bańbura et al 2018, positive (Aslan & Yavuz 2010, Dolenec 2016) and no significant correlations (Dolenec 2011, Bao et al 2020 between egg size and clutch size. Negative relationships between egg volume (or egg mass) and clutch size is consequence of compromise between egg size and clutch size with females laying numerous small or few large eggs (e.g.…”