KLEEFSTRA R (2005) Do Purple Herons Ardea purpurea dump eggs in nests of conspecifics?. LIMOSA 78 (3): 107-112.

The breeding success of a small population of Purple Herons was studied in 2001-05 in a peat swamp in central Friesland, The Netherlands. The regular clutch size was 4-5 eggs. However, in 2004 and 2005, single clutches of respectively 9 and 13 eggs were recorded in nests built in presumably the same Willow Salix cinerea. Both clutches failed to hatch. The clutch of 13 eggs was incubated for at least 59 days. These exorbitant clutch sizes are explained by intra-specific egg dumping. This behaviour is known for Squacco Heron Ardeola ralloides and Reddish Egret Egretta rufescens, but information on intra-specific egg dumping in Purple Herons is very scarce. Because Purple Herons in general are very attentive and the individual female of the clutch with 13 eggs specifically, was breeding firmly, it is suggested that the large clutch sizes might not be the result of brood parasitism but that two or more females were cooperating. Based on their volume, three sets of eggs could be recognized in the clutch of 13 eggs, suggesting that up to three females could have been laying eggs in this nest. Based on a large dataset of more than 1000 clutches in The Netherlands, it is concluded that intra-specific egg-dumping might occur more often in Purple Herons but is a rare phenomenon. Purple Heron Ardea purpurea

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