Non-fish prey in the diet of an exclusive fish-eater: the Common Kingfisher Alcedo atthis

Abstract

Capsule Non-fish prey constitutes an important component of the diet of many fish-eating birds.Aims In the present study, the role of non-fish prey in the diet of the Common Kingfisher Alcedo atthis was evaluated.Methods The species and size spectrum of prey in the diet was studied at 15 nest sites on 6 trout streams, 1 river and 1 reservoir in the Czech Republic, using the analysis of the nest sediment.Results 16 933 individual prey items were identified (99.93% fish and 0.07% non-fish prey). European Perch Perca fluviatilis, Roach Rutilus rutilus and Bleak Alburnus alburnus dominated the diets on the reservoir; Gudgeon Gobio gobio, European Chub Squalius cephalus and Roach those on the river; and Gudgeon, European Chub, Bullhead Cottus gobio, Roach, Bleak and Brown Trout Salmo trutta m. fario those in the trout streams. The sizes of their fish prey ranged from 16 to 134 mm in total length (LT) with an average size of 66 mm. The remains of non-fish prey were detected in only 5 of 30 nest sediments. The non-fish prey were mostly composed of large aquatic insect larvae: dragonflies Anax sp. and Aeshna sp., Common Club-tail Gomphus vulgatissimus and Great Diving Beetle Dytiscus marginalis. Kingfishers also took Spiny-cheek Crayfish Orconectes limosus, Newt Triturus sp. and a Lizard Lacerta sp. The estimated sizes of the non-fish prey ranged from 30 to 90 mm.Conclusion The catch of non-fish prey appears to be accidental, and is more likely a result of target misinterpretation (fish-like body and fish-like movement) than a Kingfisher regularly switching to prey other than fish. The unique finding of a Lizard is the first record of an amniotic vertebrate in the diet of Common Kingfisher.