Acta Oecologica 108 (2020) 103608 Contents lists available at ScienceDirect Acta Oecologica journal homepage: www.elsevier.com/locate/actoec The impact of a catastrophic flood on species and size composition of the T diet of fish-eating birds ∗ Alena Hadravováa, , Pavel Čechb, Martin Čecha,c a Institute for Environmental Studies, Faculty of Science, Charles University, Benátská 2, 128 01, Prague, Czech Republic b Czech Union for Nature Conservation, 02/19 ZO ČSOP Alcedo, Blanická 1299, 258 01, Vlašim, Czech Republic c Biology Centre of the Czech Academy of Sciences, Institute of Hydrobiology, Na Sádkách 7, 370 05, České Budějovice, Czech Republic ARTICLE INFO ABSTRACT Keywords: Floods in June 2013 affected significant portions of the Czech Republic (total damages amounted ~600 millions Common kingfisher (Alcedo atthis) of euro). This study examines the impact of catastrophic flood on the species composition and size of fish prey in Diagnostic bones the diet of the common kingfisher (Alcedo atthis), a fish-eating bird, nesting and hunting on Botič stream (Prague, Diet composition Czech Republic) in 2013. Hundred and forty years water (flow 74.5 3m s−1) caused considerable damage to Regurgitated pellets property and it is likely that the character and size composition of biota, especially fish, changed. This should be Nesting sediment reflected naturally in the diet of resident kingfishers. The diet of kingfishers before and after the flood were Floods investigated from the mass of regurgitated pellets, which were collected from the nest tunnel and chamber immediately after the successful breeding period before and after the flood event. Before the flood (normal 3 −1 situation; flow 0.4–1.5 m s ), the average length of fish caught was 6.5 cm LT (total length), average weight 2.6 g, and the index of food diversity was 1.58. After the flood, the average length of fish caught was 7.5 cmL T, weight 4.1 g, and the index of the food diversity was 1.36. It was evident that after the flood kingfishers were forced to hunt significantly larger prey. Six fish species (Gobio gobio, Squalius cephalus, Perca fluviatilis, Scardinius erythrophthalmus, Rutilus rutilus, Pseudorasbora parva) which were hunted both before and after the flood com- posed 96.5 and 99.8% of the catch (by numbers). Surprisingly, the impact of floods may not always be reflected in the species composition of the diet of fish-eating birds, it mostly depends on the presence of fish broadly occurring in the stream, natural stability of the fish stock and on the composition of the fish assemblage in the upstream catchment area. 1. Introduction diversity and distribution of aquatic organisms, particularly fish (Čech and Čech, 2004; Čech et al., 2007). Such changes could then be re- Floods are extreme hydrological events, which are usually short flected even in the diet of fish-eating predators (diet composition, term and sharply delineated (Lake, 2000). Their impacts are reflected in hunting success etc.; Luz-Agostinho et al., 2008; Čech and Čech, 2011, both natural and urban environments. They have effects on both the 2013). abiotic and biotic components of streams, rivers and reservoirs (Lake, Čech and Vejřík (2011) have shown the impact of the flood on the 2000; Čech et al., 2007; Lugeri et al., 2010). Floods have a pre- hunting success of great cormorant (Phalacrocorax carbo). During the dominantly negative impact on organisms, primarily lead to a decline in high flow, some individuals were not able to hunt, some hunted but body condition (Reiley et al., 2017), fecundity, species richness (Chiu failed to catch the amount of fish corresponding to their daily dose. et al., 2013), and may lead to a population decline (Jurajda et al., 2006; Similarly, Prigioni et al. (2006) have shown the impact of floods on the Kubín et al., 2018; Maxwell et al., 2018). They can change habitat hunting success of Eurasian otter (Lutra lutra). Even in this fish-eating availability and structure (Breck et al., 2003; Wilson and Peach, 2006; predator, the increasing water turbidity and water flow significantly Yamanakaa et al., 2019) and cause changes of ecosystem processes reduced the ability to catch a fish. Otters and cormorants pursue their (Reich and Lake, 2015). Fast-flowing flood water has a strong potential prey underwater and although they are predominantly visual predators, to create material (Romanescu and Nistor, 2011) and nutrient losses they also use tactile cues (Prigioni et al., 2006; Grémillet et al., 2012). (Pecqueur et al., 2011). Floods cause significant changes to the In contrast, the common kingfisher (Alcedo atthis) uses diving/ ∗ Corresponding author. E-mail addresses: [email protected] (A. Hadravová), [email protected] (P. Čech), [email protected] (M. Čech). https://doi.org/10.1016/j.actao.2020.103608 Received 19 January 2020; Received in revised form 3 June 2020; Accepted 15 June 2020 1146-609X/ © 2020 Elsevier Masson SAS. All rights reserved. A. Hadravová, et al. Acta Oecologica 108 (2020) 103608 floods in 2002, that affected the entire territory of the Czech Republic (only 20 × higher flow in a particular stream; at some middle sized and large rivers, however, a thousand years flood estimated; total damages in the country amounted to 3 billions of euros). The floods had an effect on species composition in the diet of kingfisher: fewer fish species and different fish species were found in the sample collected after the cat- astrophic flash flood in 2001. The floods in 2002 were much less de- vastating to the aquatic biota of that particular stream and, on the contrary, led to an increase in the number of species in the diet of kingfishers compared to the normal situation (at that time Štěpánovský stream served as a refuge for fish, they migrated into the stream from the heavily swollen, larger Sázava River; Čech and Čech, 2004, 2011). Kingfisher (Fig. 1) has limited digestion abilities. It means that only the soft tissues can be digested from the caught prey, and the residues – bones, scales, eye lenses etc. - are regurgitated in a form of a compact pellet (Cramp, 1990; Reynolds and Hinge, 1996; Čech and Čech, 2011, 2015). During the breeding period, the mass of regurgitated pellets Fig. 1. Female (right) and male (left) of common kingfisher (Alcedo atthis) at forms nesting sediment, which is located in the nest chamber of the Botič stream (Prague, Czech Republic). Photo: A. Hadravová. kingfisher. From the analysis of regurgitate pellets, one can gain qua- litative and quantitative information about the diet of the kingfisher (Vilches et al., 2012; Čech and Čech, 2015, Čech and Čech, 2017a; Novčić and Simonović, 2018) and subsequently reconstruct even the harpooning to catch the prey (i.e. exclusively a visual predator). This impact of floods on the local ichthyofauna (Čech and Čech, 2011, bird identifies fish or aquatic invertebrates based on their movement 2013). and shape, when sitting on a low perch or when hovering above the The aim of the present study is to focus on the qualitative and water (Cramp, 1990; Čech and Čech, 2011; Vilches et al., 2013b). quantitative parameters of the diet of a kingfisher from the nesting site The kingfisher hunts fish from the entire water collum (Hallet, on Botič stream (Prague, Czech Republic) during a normal situation and 1977; Reynolds and Hinge, 1996; Campos et al., 2000; Čech and Čech, after the catastrophic flash flood in June 2013. This study represents 2011, 2013; Vilches et al., 2013a). During the normal river/stream si- the first, unique observation of the impact of a drastic natural event on tuation, the diet of kingfishers is composed of either benthic species like the diet composition of a fish-eating predator during one breeding gudgeon (Gobio gobio) or bullhead (Cottus gobio), sub-surface species season at one single stream (identical nesting locality, occupied by one like European chub (Squalius cephalus) or bleak (Alburnus alburnus), or pair of kingfishers). The main questions were: 1) Does the food diversity mid-water species (occurring mostly in the middle of the water column) index changed after the catastrophic flood? 2) Does the size of fish like European perch (Perca fluviatilis), roach (Rutilus rutilus) or stone caught by a kingfisher differ before (normal situation) and after the moroko (Pseudorasbora parva) (Čech and Čech, 2013, Čech and Čech, catastrohic flood? It is hypothesized that the catastrophic flood will 2017a). At most sites, a kingfisher prefers cyprinid species (Cyprinidae; have crucial effect on the size/weight of hunted fish (larger after the Raven, 1986; Vilches et al., 2012; Čech and Čech, 2015; Novčić and flood; the smallest fish washed out from the system) as well as the effect Simonović, 2018). It chooses its prey by size (Hallet, 1977; Reynolds on the broadness of the diet spectrum (wider after the flood; newly and Hinge, 1996; Čech and Čech, 2013, 2015) and body shape (Cramp, established “Monte Carlo” community from resident fish and fish ori- 1990), particularly prefering slender fish (Zając and Dobrowolska, ginating from the catchment area lacking any very dominant species to 2007; Čech and Čech, 2011). Kingfishers hunt fish ranging in size (LT, focus on). total length) from 1.5 to 12 cm (Čech and Čech, 2011, 2015). These small fish are more theatened by floods than fish of larger sizes 2. Methods (Schlosser, 1985; Cattanéo et al., 2001; Freeman et al., 2001; Jurajda et al., 2006) – they are washed out, which should be immediately re- 2.1. Study area and the catastrophic flood event flected in the diet of kingfishers. In the former study, Bunzel and Drüke (1989) have found that the The study was carried out on the Botič stream in the Czech Republic. kingfisher was unable to hunt during the flood.