Breeding Success of Western Reef Heron in Hara Biosphere Reserve, Persian Gulf

Breeding success of the Arabian/Indian race of the Western Reef Heron Egretta gularis schistacea was studied in the Hara Biosphere Reserve, Persian Gulf, during 2008 and 2009, with 103 and 137 nests studied, respectively. Marked nests were checked at least twice a week to note egg-laying date, clutch size, brood size, egg loss and chick mortality. Also, hatching and breeding success were estimated. Egg-laying was from 21 March to 17 April in 2008 and from 28 March to 28 April in 2009. Mean clutch size in the two years combined was 3.4 ± 0.05 and significantly greater in 2009 (3.5 ± 0.07) than 2008 (3.2 ± 0.07). Mean brood size was 2.0 ± 0.1 for all clutches and was greater in 2008. The internal diameter of nests, the height of nests from the ground and the distance of nests from the mangrove forest border were important factors influencing breeding success. The percentage of successful nests varied significantly between the two years (80% in 2008 and 51% in 2009). Overall, approximately 64% of nests were successful in producing at least one fledgling. Mean hatching and breeding success were 0.6 ± 0.02 and 0.5 ± 0.02, respectively. Both measures of success were lower in 2009 than in 2008, probably due to weather and egg predation by the Black Rat Rattus rattus which was responsible for about 50% of nest failures in the two years of the study. Mechanical control methods are suggested to reduce the negative effects of this rodent on breeding colonies of Western Reef Heron.