Clutch and egg size variation in the Marsh Harrier Circus aeruginosus in eastern Poland

Marcin Polak

doi:10.34080/os.v20.22638

Abstract

The main aim of this study was to examine how clutch size and season influenced egg size in a population of Marsh Harriers Circus aeruginosus in eastern Poland. The Marsh Harriers nested in small, isolated patches of reed belts surrounding fish ponds. A total of 328 eggs from 70 clutches were measured during four nesting seasons (2005–2008). Average clutch size was 4.69 ± 0.71 eggs and did not vary between years; the modal clutch size was 5 eggs. Mean values of the egg dimensions were: egg length = 48.60 ± 1.78 mm; egg breadth = 38.36 ± 1.13 mm; egg volume = 36.53 ± 2.99 cm3. There was a strong correlation between egg length and egg breadth. The number of eggs in a clutch had no effect on the egg size.

Highlights

In birds, egg size is of major importance for individual reproductive success (Blackburn 1991, Nager & Zandt 1994)
In many studies special attention has been given the adaptive significance of intra-clutch egg size variability, since egg size may influence the condition of the chick at hatching time and its survival (Custer & Frederick 1990; Swennen & van der Meer 1992)
The Marsh Harrier Circus aeruginosus is a medium-sized raptor species, almost exclusively breeding on the ground, mostly in flooded emergent vegetation, and in arable fields (Glutz et al 1979, Stanevicius 2004). This short paper describes the variation in size of Marsh Harrier eggs and examines the effect of clutch size and season on egg size variation

Summary

Introduction

Egg size is of major importance for individual reproductive success (Blackburn 1991, Nager & Zandt 1994). In many studies special attention has been given the adaptive significance of intra-clutch egg size variability, since egg size may influence the condition of the chick at hatching time and its survival (Custer & Frederick 1990; Swennen & van der Meer 1992). The Marsh Harrier Circus aeruginosus is a medium-sized raptor species, almost exclusively breeding on the ground, mostly in flooded emergent vegetation, and in arable fields (Glutz et al 1979, Stanevicius 2004) This short paper describes the variation in size of Marsh Harrier eggs and examines the effect of clutch size and season on egg size variation

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