Ardea
Official journal of the Netherlands Ornithologists' Union

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Gilbert G., Tyler G. & Smith K.W. (2003) Nestling diet and fish preference of Bitterns Botaurus stellaris in Britain. ARDEA 91 (1): 35-44
The first assessment of both nestling diet composition and selection of fish prey by Bitterns Botaurus stellaris in Britain. We provide quantitative information on the diet of nestling Bitterns, examine the factors influencing diet composition and determine whether adult females are choosing particular species and size of prey. Sixty regurgitate samples from 44 broods were examined during visits to Bittern nests made at nine sites in England from 1996 to 2001. Compositional analysis was used to assess influence of age, season and year effects on diet. The fish component of the diet was compared with species found to be generally available within each site from electro fishing data. Eel Anguilla anguilla and Rudd Scardinius erythrophthalmus made up the greatest proportion of biomass of the diet and this proportion did not significantly change with the age of the chicks. The amount of Eel in the diet changed during the season and the amount of Rudd between years. From those fish species available, female Bitterns preferred to feed chicks on Nine-spined Sticklebacks Pungitius pungitius, Eels (0-40g). Three-spined Sticklebacks Gasterosteus aculeatus and Rudd (0-20g). It is likely that female Bitterns feeding young in Britain have a limited prey choice. To optimise food availability we need better understanding of the seasonal habitat requirements of key fish species within reedbed-dominated sites


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