The Purple Heron population in southern France suffered a 46% decline between 1981 and 1994. A study of breeding biology was instigated in 1997 in order to examine potential changes in the main breeding parameters between the early 1980s and the late 1990s. Here, we present data on the breeding biology and diet of breeding Purple Herons in the Camargue, southern France, collected from 1997 to 1999. These results were compared with those from a similar study conducted between 1979 and 1982. No difference in first spring arrival date on breeding grounds was noted between these two periods. Mean first egg date was 22 April during 1979â82, in contrast to 6 May during 1997â99. Mean colony size was c. 118 breeding pairs during 1979â82, but only c. 59 during 1997â99. For broods of three and four chicks, linear growth rates for rank A (first hatched) chicks were higher during 1979â82 than during 1997â99. For broods of four chicks linear growth rates were also higher for rank B (second hatched) chicks and tended to be higher for rank C (third hatched) but lower for rank D (fourth hatched) chicks. During 1979â82 nestling diet (determined from regurgitates) was dominated by fish (85.4% by biomass). There was an increase in the proportion of insects from 12.8% during 1979â82 to 21.7% in 1998 (from regurgitates), whereas the proportion of fish was 61.3% in 1998. Diet was determined from pellets in 1999 and indicated that 42.6% of the biomass was insects whereas 33.8% was fish. No difference was found between 1979â82 and 1997â99 for clutch size and hatchling mass. Results suggest that birds needed more time to initiate breeding during 1979â82 than during 1997â99. Possible causes for the observed differences in the Purple Heron breeding biology and diet between both study periods are discussed.