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1 December 2017 Long-Term Changes in Food Intake by Grey Herons (Ardea cinerea), Black-Crowned Night-Herons (Nycticorax nycticorax) and Little Egrets (Egretta garzetta) Foraging in Rice Fields in Italy
Elisa Cardarelli, Mauro Fasola, Adriano Martinoli, Daniele Pellitteri-Rosa
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Abstract

In northwestern Italy, traditional rice cultivation using permanent flooding has been replaced by cultivation that uses a reduced water depth and a shortened submersion period. Prey availability for the numerous herons and egrets using this intensive rice cultivation region changed as well, with a diminution of amphibians and an increase of crayfish (Procambarus clarkii) and oriental weatherfish (Misgurnus anguillicaudatus). The prey intake in 2014 was compared with data available for 1987 for the three most common species of waterbirds that forage in the paddies. Total biomass intake by Grey Herons (Ardea cinerea) feeding in the paddies decreased from 28 g dry mass/min in 1987 to 7 g in 2014, and by Black-crowned Night-Herons (Nycticorax nycticorax) from 8 g to 5 g, while the intake by Little Egrets (Egretta garzetta) remained similar (12 and 13 g in 1987 and 2014, respectively). The observed levels of prey intake allowed breeding Grey Herons to meet their energy needs by feeding exclusively in the rice paddies in 1987, but not in 2014. The other two study species could not meet their daily requirements for successful breeding by feeding in the paddies only, either in 1987 or 2014. Yet the three species bred successfully in the study area, and their reproductive output remained stable both in 1987 and 2014. Successful breeding was probable by the three species foraging in other habitats, such as rivers, small natural wetlands and irrigation canals, in the region.

Elisa Cardarelli, Mauro Fasola, Adriano Martinoli, and Daniele Pellitteri-Rosa "Long-Term Changes in Food Intake by Grey Herons (Ardea cinerea), Black-Crowned Night-Herons (Nycticorax nycticorax) and Little Egrets (Egretta garzetta) Foraging in Rice Fields in Italy," Waterbirds 40(4), 344-352, (1 December 2017). https://doi.org/10.1675/063.040.0406
Received: 15 February 2017; Accepted: 1 May 2017; Published: 1 December 2017
KEYWORDS
Ardea cinerea
Black-crowned Night-Heron
Egretta garzetta
Energy budget
food intake
Grey Heron
Little Egret
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