Formation and growth of a heronry in a managed wetland in Doñana, southwest Spain

Abstract

Capsule A newly created wetland has been beneficial for the breeding of five heron species and for the settlement and expansion of Glossy Ibises in the region.

Aim To determine whether created wetland would lead to the establishment of a heron and ibis breeding colony, and if so, to determine its effects on the distribution of these species in the wider region.

Methods Number of pairs breeding at the new wetland and in the region were estimated annually from 1996 to 2008. We investigated whether the growth of the new colony was explained by redistribution of breeding pairs within the region.

Results Purple Herons, Squacco Herons and Glossy Ibises colonised the new wetland in 1996. Black‐crowned Night Herons settled in 1998, while Cattle and Little Egrets were the last species to establish in the mixed colony in 2001. The population increase was particularly marked for Glossy Ibises (which had bred in Doñana only sporadically through the 20th century). Our findings suggest that simple redistribution of pairs does not explain the formation and growth of the new colony. Since the first year of establishment numbers of Glossy Ibises and Purple Herons have shown a significant growth trend at both the new colony and in Doñana.

Conclusion The creation and management of a new wetland has been successful for the conservation of heron and egret species and promoted the expansion of the Glossy Ibis population across the western Mediterranean region.

ACKNOWLEDGEMENTS

This study was possible thanks to the Doñana Biological Station Monitoring Team. In particular, we thank Luis García, Rubén Rodriguez, Fernando Ibañez, José Luis Arroyo, José Luis del Valle, Alfredo Chico and Hector Garrido. Thanks also to Carlos Urdiales, María Dolores Cobo and Juan Manuel Espinar for valuable information. We are especially grateful to the Laboratory of GIS and Teledetection (LAST‐EBD) for providing data on marshes, flooded area and other information. SS is supported by a JAE pre‐doctoral grant from CSIC (co‐funded by FEDER Program). Our research has been funded by the Regional Government of Andalusia (Junta de Andalucía) via the project ‘Las aves acuáticas de Doñana y el cultivo del arroz: la interacción entre la agricultura y la conservación de las zonas húmedas’.