Do breeding site characteristics influence breeding performance of the purple heron Ardea purpurea in the Camargue?

The breeding biology of the Purple Heron, Ardea purpurea, was studied in 19 97-1998 in the Camargue delta complex in southern France. The mean laying d ate differed significantly between colonies in only one of the two years wh ile clutch size remained constantly low (2.9-3.4) and showed no significant inter-colony or inter-annual differences. Chick mortality was similar amon g colonies the same year but was significantly higher in 1997 than in 1998. Brood size, hatching rank order and laying date had a significant effect o n chick growth. Analyses of food regurgitated by chicks revealed a large va riety of prey categories and surprisingly few fish. Ringing data provided e vidence on several occasions that young herons can colonize foreign nests t o improve their conditions. Future studies should focus on the feeding ecol ogy and on factors affecting the availability of suitable nest sites.