Frequent Prey Items Research Articles

Prey targeted by lactating Weddell seals (Leptonychotes weddellii) in Erebus Bay, Antarctica

AbstractFemale Weddell seals (Leptonychotes weddellii) display a mixed capital-income breeding strategy, losing up to 40% of their body mass between birthing and weaning their pups. How and when they regain energy stores, however, remains to be fully explored. To better understand the foraging by lactating Weddell seals, we fitted time-depth recorders and head-mounted cameras on 26 seals in Erebus Bay, Ross Sea, for ~ 5 days in November and December 2018 and 2019. We aimed to (1) identify prey species and foraging depth and (2) investigate relationships between seal physiology and demographics and probability of foraging. We recorded 2782 dives, 903 of which were > 50 m, maximum depth was 449.3 m and maximum duration was 31.1 min. Pup age likely contributes to the probability of a lactating Weddell seal foraging (Est. = 1.21 (SD = 0.61), z = 1.97, p = 0.0484). Among 846 prey encounters, the most frequent prey items were crustaceans (46.2%) and Antarctic silverfish (Pleuragramma antarcticum, 19.0%); two encounters were observed with juvenile Antarctic toothfish (Dissostichus mawsoni, 0.2%). We identified substantial variability in foraging behaviour, individually and between locations, and found that lactating seals target many species and some may specialise on certain prey groups.

Mysis segerstralei, an unexpected but important prey for resident Arctic charr (Salvelinus alpinus) in a Svalbard lake

Mysis segerstralei is distributed over a wide geographic area and in habitats with a variety of salinity conditions, including marine and brackish waters around Svalbard. The species has seldom been found in freshwater lakes, and the discovery of M. segerstralei in Lake Pulmankijärvi at the border between Northeastern Norway and Finland, may represent the single known freshwater occurrences in western Europe. Svalbard lake systems are characterized by very low water temperatures, long-term ice cover, and low levels of nutrients. Food is thus limited, and chironomids generally dominate the stomach contents in Arctic charr, the only freshwater fish species on Svalbard. Based on several surveys in more than 30 of Svalbard lakes over many decades, M. segerstralei has only been found as food for Arctic charr in Lake Vårfluesjøen. In a later fishery survey, we studied the diet of Arctic charr in this lake. The stomach contents from Arctic charr sampled in the profundal habitats were dominated by M. segerstralei, but the species was also among the most frequent prey items in the littoral and pelagic habitats. This unexpected occurrence of M. segerstralei demonstrates the high importance of mysids even in a low-productive, High Arctic lake.

Is the population increase of an invasive portunid crab (Charbydis hellerii) a concern? The effect on native prey

Biological invasions have the potential to change the local marine biodiversity through increasing predation pressure and interactions among species. Charybdis hellerii is a swimming crab native to the Indo-West Pacific, it was first collected in the Atlantic Ocean in 1987 and is currently found in high abundance in coastal areas of southeastern Brazil. We evaluated the presence of the invasive crab C. hellerii from the coast of São Paulo state, Brazil, analyzing the stomach contents and performing laboratory-based feeding experiments. In crabs with stomachs full enough to be analyzed (N = 19), mussels (30%) and brachyuran crabs (14.21%) were the most frequent prey items found. Based on these data, we experimentally tested how different densities and life stages (adults and juveniles - differentiated by carapace width - CW) of the invasive crab affected feeding patterns. Results indicated that predator density effects on the predation pressure were dependent on the prey type. Mussels were consumed highest at medium predator densities (30 crabs/m3), whereas crabs were consumed highest at high predator densities (60 crabs/m3). There was no influence of the life stage on prey consumption, suggesting that adults (CW = 57.12–67.59 mm) and juveniles (CW = 39.77–43.18 mm) exhibit similar predation. Charybdis hellerii is an important consumer of benthic native prey, having the potential to change food webs through predation pressure on bioengineers and associated fauna. As the removal of C. hellerii from the environment is difficult, the next step toward is to understand the effect of the invasive crab on the native trophic web.

Assessing Asiatic cheetah’s individual diet using metabarcoding and its implication for conservation

Knowledge on diet composition allows defining well-targeted conservation measures of large carnivores. Little is known about ecology of critically endangered Asiatic cheetah, especially the overall diet and its possible regional differences. We used cheetah scats, metabarcoding technique and microsatellite markers to assess the individual and overall diet composition of the species across its entire range in Asia. Cheetahs were primarily predating on mouflon; following by ibex, cape hare and goitered gazelle. Despite their high availability, small-sized livestock was never detected. Goitered gazelles were only detected in an area where the habitat is mainly flatlands. In hilly areas, mouflon was the most frequent prey item taken. Ibex was typically taken in rugged terrain, but mouflon was still the most frequently consumed item in these habitats. High consumption of mouflon in comparison to goitered gazelle suggests that human pressure on lowland habitats has possibly forced Asiatic cheetahs to occupy suboptimal habitats where gazelles are less abundant. The protection of flatlands and the removal of livestock from them are needed to ensure the long-term survival of Asiatic cheetah. The laboratory and bioinformatics pipelines used in this study are replicable and can be used to address similar questions in other threatened carnivores.

Trophic ecology of the Hubb's octopus Octopus hubbsorum (Cephalopoda: Octopodidae) in the central Mexican Pacific

ABSTRACT The diet of the Hubb's octopus Octopus hubbsorum along the coast of Acapulco, Guerrero, Mexico, was determined by analysing the stomach contents of 413 individuals collected monthly between February 2017 and March 2018. Most stomachs (74.3%) presented contents, while 25.7% were empty. Sixty prey items were identified and grouped into 16 categories. The most frequent prey items were Petrolisthes sanfelipensis, Clastotoechus diffractus, Petrolisthes hians and Alpheus spp. Smith's index indicated that O. hubbsorum follows a generalist diet for each hydroclimatic season, sex and size class (1: juvenile; 2: young adult; 3: mature adult). Cannibalism was frequent among males, less so among females. Pianka's index revealed a higher overlap among the three size classes of both sexes during the dry season, while during the rainy season the overlap was reduced for size classes 2 and 3 in both sexes. The average isotopic values overall were δ13C −14.96‰ (±0.08) and δ15N 13.02‰ (±0.09). A significant difference (P = 0.005) was observed in δ13C among hydroclimatic seasons (rainy and dry) and size classes, while for δ15N a significant difference (P = 0.013) was observed between seasons. Stomach content analysis gave values of the trophic position of O. hubbsorum ranging from 3.57 to 3.72, whereas the values obtained using stable isotope analysis, using δ15N, ranged from 3.52 to 3.86. Variation was observed in isotopic niche size and Layman's metrics among hydroclimatic seasons. A higher isotopic niche overlap was observed between size classes 2 and 3 during the dry season. The rocky shore ecosystem has been heavily exploited by artisanal fisheries (fish and invertebrates). A more integrated, ecosystem-based management of these fisheries requires an understanding of their trophic structure.

FEEDING HABITS OF THE STYGIAN OWL (ASIO STYGIUS) AND THE SHORT-EARED OWL (A. FLAMMEUS) IN THE SOUTHWEST OF BOGOTÁ SAVANNA, CUNDINAMARCA, COLOMBIA

This study quantitively compares the diets of the Stygian Owl (Asio stygius) and the Short-eared Owl (A. flammeus) in the south-west of the Bogotá Savanna, Colombia. We identified 130 prey items from 111 A. stygius pellets and 579 prey items from 149 A. flammeus pellets. In terms of the numbers of preys, the diet of A. stygius consisted of the following: 88.1% birds, mainly pigeons, rails and cuckoos; and a smaller proportion of beetles (11.4%). In the diet of A. flammeus, insects were the most frequent prey item (59.8%), followed by rodents (39.8%), and birds (0.5%). In terms of biomass contribution, the main preys in the diet of A. stygius were Eared Doves (Zenaida auriculata) (54%) and Purple Gallinules (Porphyrio martinica) (19.3%), while the diet of A. flammeus consisted mainly of House Mice (Mus musculus) (65.2%). Diet diversity varied between the owl species: A. flammeus was more selective in its hunting habits, while A. stygius was more of an opportunistic predator. It is important to quantify the ecosystem services these owls provide not only by controlling M. musculus, Z. auriculata, and Shiny Cowbird (Molothrus bonariensis) populations, which can affect human well-being and threatened species populations, but also through secondary seed dispersion and birdwatching opportunities.

Aproximación a la dieta de Thalassoma lucasanum (familia Labridae) en el arrecife coralino de La Azufrada, isla Gorgona, Pacífico Oriental Tropical

El arcoíris de Cortés, Thalassoma lucasanum, es un pez arrecifal abundante en el Pacífico Oriental Tropical (POT). A diferencia de otras especies del género Thalassoma que son reconocidas por ser limpiadoras, en T. lucasanum este comportamiento es poco frecuente, ya que se alimenta principalmente de invertebrados mediante forrajeo. No obstante, la información sobre la ecología trófica de esta especie es limitada, especialmente en el POT. En este estudio se caracterizan los hábitos alimentarios de T. lucasanum en la isla Gorgona (POT) a partir del análisis de su contenido estomacal y se calcula su nicho trófico. Los moluscos fueron el principal recurso alimentario de T. lucasanum, siendo este el ítem de presa más importante y frecuente al ser encontrado en 100 % de los estómagos analizados (n = 5). En términos de biomasa, los crustáceos presentaron la mayor contribución a la dieta, con lo cual se posicionaron como el segundo ítem alimentario más importante. Otras presas incluyeron poliquetos, partes de peces y material calcáreo. Este estudio contribuye al conocimiento de la dinámica trófica de los ecosistemas arrecifales del POT.

Limited evidence of zebra mussel (Dreissena polymorpha) consumption by freshwater drum (Aplodinotus grunniens) in Lake Winnipeg

Freshwater drum (Aplodinotus grunniens) may be a predator of the invasive zebra mussel (Dreissena polymorpha), which established in Lake Winnipeg in 2013. In this study, the diets, trophic position, and growth of 51 freshwater drum collected in 2019 (six years post-zebra mussel invasion) were compared to 64 freshwater drum sampled in 2000. Benthic insect larvae were the dominant food items in both years. Although mollusks occur in high densities in Lake Winnipeg, they were only consumed by a few freshwater drum in either sample year. Zebra mussels were not a frequent prey item in 2019 as they were only consumed by four of the sampled freshwater drum. Stable isotope analysis of white muscle tissue yielded similar δ13C and δ15N values in both years and were consistent with a benthic, insectivorous diet. Length-at-age data derived from otoliths revealed that the 2019 population had at least an equal growth rate to the 2000 population. Weight-at-length data suggested that fish condition was greater in 2019 than in 2000, which coincided with increased benthic macroinvertebrate density in Lake Winnipeg. Based on these findings, Lake Winnipeg freshwater drum continue to feed predominantly on insect larvae and not zebra mussels.

Diet composition of the electric eel Electrophorus voltai (Pisces: Gymnotidae) in the Brazilian Amazon region.

The diet composition of the electric eel Electrophorus voltai was studied in specimens collected from the River Jari, state of Amapá, eastern Amazon region, Brazil. Analysis on their stomach contents revealed that fish, especially Megalechis thoracata, were the most frequent prey item, whereas arthropods and plant material were the least frequent intakes. This is the first stomach content analysis on E. voltai, and it corroborates that electric eel species are piscivorous.

Diet composition of an opportunistic predator from an upwelling area in the Southeastern Pacific

AbstractThe aim of this study was to use scat analysis to analyse the dietary composition of the South American sea lion (SASL, Otaria byronia) over a short temporal scale and in different but closely located colonies in the Humboldt Current System of northern Chile. Scat samples were collected at Arica (18°34′S), Iquique (20°48′S) and Mejillones (23°04′S) during the summer (January to March) and winter (July) of 2015. A total of 16 595 individual prey items from nine species were found in 194 of the 215 scat samples. In general, squat lobster (Pleuroncodes monodon) was the most important prey item for the sea lion diet, both by number and according to the index of relative importance (%IRI), followed by anchovy (Engraulis ringens), which was the most frequent prey item in the scats and the most important by weight. Patagonian squid (Loligo gahi) ranked third in importance in the sea lion diet. However, some spatiotemporal variations in the consumption of prey were found. Squat lobster was the most important prey for sea lions in Arica and Iquique, while anchovy was the dominant prey in Mejillones. Regarding seasonal variation, squat lobster was more important in winter than in summer in the three localities, while anchovy was also more important during winter, except in Mejillones where the levels of consumption of this prey were similar in both seasons. These results show that SASL adjust their dietary preferences, modifying the contribution of different prey both spatially and temporally. Spatiotemporal variations in the SASL diet can be explained by temporal changes in the distribution and abundance of their prey.

Nesting Behavior of the Mongolian Ground Jay (Podoces hendersoni) in the Gobi Desert of Southern Mongolia

The Mongolian ground jay is a species of least concern globally, but is of vulnerable in Mongolia mainly due to habitat fragmentation and habitat loss. There have been limited studies focused on the natural behaviors of the parent Mongolian ground-jays. We monitored a family of ground jays in the Southern Gobi, and studied the parental behaviors using a camera trap. This paper details the post-incubation parental behaviors of one ground jay family—that is, two parents and three young—for 19 days in May 2018. During the 19 days, we accumulated 869.6 hours of behavioral observations. Through monitoring their behaviors, we discovered that the female feeds the male when the chicks are vulnerable and featherless, while the male spends more time covering the chicks for insulation and protection. We also found correlations between temperature and the bird’s activity levels. We reported on the amount and type of food brought to nestlings, and found that the most frequent prey items were toad-headed agama and unidentified small insects.

Dietary Partitioning in Two Co-occurring Caecilian Species (Geotrypetes seraphini and Herpele squalostoma) in Central Africa.

SynopsisTrophic interactions among fossorial vertebrates remain poorly explored in tropical ecosystems. While caecilian species can co-occur, whether and how sympatric species partition dietary or other resources are largely unknown. Based on specimens collected during field surveys in southern Cameroon, we conducted a dietary analysis of two co-occurring caecilian species, Geotrypetes seraphini and Herpele squalostoma. We find a negligible overlap in the adult diets of these two species. Earthworms dominated the diet of adult G. seraphini, whereas we found that mole crickets were the most frequent prey items in adult H. squalostoma. The dietary breadth of adult G. seraphini is smaller than that of H. squalostoma, which consumes a variety of hard-bodied prey including mole crickets, cockroaches, beetles, and crabs. Juvenile diets were similar between these species and mostly contained earthworms and ants. We did not detect significant ontogenetic dietary shifts in either species, though adults generally consumed a broader diversity of prey. As adults, G. seraphini and H. squalostoma may partition prey categories by consuming soft-bodied and hard-bodied prey, respectively. Because most caecilians are likely opportunistic predators, we expect that sympatric species partition dietary resources either by preference for different soil layers or ability to consume different prey categories.

Feeding habits during migration of the Atlantic bonito Sarda sarda (Bloch, 1793) to the Black Sea

ABSTRACTInformation about food web dynamics is crucial for the success of ecosystem-based management. In order to collect such information, it is necessary to establish the dietary contents of species in the food chain. In this study, the diet of Atlantic bonito Sarda sarda (Bloch, 1793), one of the most important species in the Black Sea ecosystem, has been examined. The aim of this study was to investigate the prey preferences of Atlantic bonito over an eleven-year period during their feeding migration to the Black Sea. Sampling was carried out by commercial purse seine and gill nets along the Turkish Black Sea coast during migration of the Atlantic bonito from 2005 to 2016. Stomach contents were identified to the lowest possible taxonomic level. Atlantic bonito dietary composition was analyzed by fishing season, sex and size classifications. Results revealed a Vacuity Index value (V %) of 67% while 33% of individuals sampled had at least one prey species in their stomach content. Since S. sarda predominantly feed on small fish species, stomach contents contained mainly Engraulis encrasicolus, Trachurus mediterraneus, Sprattus sprattus, Mullus barbatus, Gobius niger, Merlangius merlangus, Pomatomus saltatrix, Alosa immaculata, Parablennius tentacularis and small unidentified prey items (tissue particles, … etc.). The most frequent prey item was E. encrasicolus with a percentage occurrence of 94%. In conclusion, the main prey species was determined as E. encrasicolus and statistical analyses of X2 was found significant (P < 0.005) according to year, sex and size.

HÁBITO ALIMENTAR DO BEIJUPIRÁ EM PERNAMBUCO, NORDESTE DO BRASIL

O hábito alimentar do beijupirá, Rachycentron canadum, foi descrito ao longo da costa do Estado de Pernambuco, Nordeste do Brasil. Foram capturados 110 exemplares entre fevereiro/2004 e agosto/2006, com comprimento furcal ou zoológico variando entre 40,0 e 137,0 cm (média e desvio padrão: 85,8±18,0 cm) e peso total entre 0,4 e 29,8 kg (7,5±4,4 kg). Foi avaliada a importí­¢ncia de cada item alimentar na dieta utilizando o í­­ndice de importí­¢ncia relativa (IIR). Dentre os 110 estômagos analisados (52 fêmeas e 58 machos), 92 (83,6%) com algum item alimentar e 18 (16,4%) vazios. Os peixes ósseos foram os principais itens consumidos na dieta alimentar (IIR = 98,7%), entre os quais a mariquita (Holocentrus adscensionis) e o baiacu (Diodon sp.) foram as presas mais consumidas (IIR = 30,7% e 8,2%, respectivamente). A dieta foi composta, ainda, por elasmobrí­¢nquios, crustáceos e cefalópodes (IIR &lt;1% cada). Não foram encontradas diferenças na dieta entre os sexos e classes de tamanho (&lt; ou â"°¥ 69,8 cm de comprimento furcal, L50 estimado para a espécie). Os dados analisados demonstram que, na costa de Pernambuco, o beijupirá é um predador carní­­voro com preferência por peixes ósseos demersais, independente do tamanho e sexo dos indiví­­duos analisados.

Prey selectivity by feral cats at central Australian rock-wallaby colonies

Threatened warru, or black-footed rock-wallaby (Petrogale lateralis MacDonnell Ranges race), populations in northern South Australia continued to decline despite baiting for foxes (Vulpes vulpes), which improved their short-term conservation status elsewhere. To investigate whether feral cats (Felis catus) also represent a risk to warru we compared frequencies of prey occurrence in 103 feral cat and 14 fox stomachs shot near warru colonies in northern South Australia during 2001–17 with measures of prey abundance from pitfall trapping and opportunistic searches. We hypothesise that one fresh adult warru kill and the presence of warru remains in four other cats suggests predation by cats on adult and juvenile warru. Small reptiles and invertebrates were the most frequently recorded prey of cats in summer, whereas rodents and small dasyurids were the most frequent prey items in winter. Small mammals, small snakes and pygopodid lizards were over-represented in the diet of cats compared with estimated encounter frequencies, whereas fast-running dragons, knob-tailed geckoes (Nephrurus) and echidnas (Tachyglossus aculeatus) were not recorded from cat stomachs despite being relatively abundant. Rabbits (Oryctolagus cuniculus), rodents and fruits were the most frequently recorded items in fox stomachs. This study reinforces that targeted management of feral cat populations should be considered in concert with control of canids in sustainable recovery programs for warru and other cat-vulnerable species.

Diet composition and prey diversity of Tengmalm’s owl Aegolius funereus (Linnaeus, 1758; Aves: Strigidae) in central Serbia during breeding

Annual variation in the diet, composition, and prey diversity of Tengmalm's owl Aegolius funereus (Linnaeus, 1758) was investigated in high-mountain coniferous forests of Mt. Kopaonik (central Serbia) during 3 consecutive years. Prey remains and decomposed pellets (detritus) were collected at the bottom of nest-boxes during 2 separate periods: during mating and after nesting. Prey remains such as maxillae, mandibles, beaks, or feathers were used for prey identification. In total, 438 prey items were separated and identified. Small mammals represented the most numerous class of prey (87.23%). The most frequent prey item was bank vole Myodes glareolus (23.29%). During the nesting season the proportion of voles eaten was significantly higher in comparison with the mating period. The mean prey weight was 20.74 g. In the study area, according to diversity index calculations, prey diversity was high and it seems that the number of breeding attempts by Tengmalm's owl showed dependence on the annual abundance of small rodents, but further research is needed to confirm this assertion.

English

The diet composition of the African clawless otter (Aonyx capensis) was studied by analyzing of 440 spraint samples collected during January, 2014 and December, 2015 in both dry and wet seasons from eight sites in and around Lake Tana, North West Ethiopia. Percentage frequency of occurrence and relative percentage frequency of diet items in the spraint samples were calculated.The statistical analysis was conducted using chi-square and one-way ANOVA tests.The number of diet categories per spraint ranged from 1 to 4 with a mean of 1.42 ± 0.591. Fish was the dominant prey item in all sites with an overall frequency of occurrence of 84.77% and a relative percentage frequency of 59.68%. Labeobarbus spp. was the most frequent fish prey (35.45%). Crabs were the second most frequent prey items with percentage frequency of 33.41% and a relative percentage frequency of 23.52%, while small mammals and birds were the least frequent dietary items with percentage frequency of 0.45 and 0.23%, respectively. Other identified diet items and the respective percentage frequency were plant matter (6.17%), insects (5.68%), amphibians (5%), mollusks (2.5%) and unidentified items (3.86%). Variation on fish and crab prey items were observed between seasons and sites, while no variation was observed for other prey items. The results suggested a dietary flexibility and shift in the African clawless otter from crabs to fish that can be explained by availability and accessibility. Key words: African clawless otter, Aonyx capensis, food items, Lake Tana.

The impact of amur sleeper (Perccottus glenii Dybowsky, 1877) on the riverine ecosystem: food selectivity of amur sleeper in a recently colonized river

Abstract The presented study aimed at comprehensive assessment of the Perccottus glenii (Amur sleeper) impact on the aquatic ecosystem. Our objective was to analyze the diet, the characteristics of the prey and the feeding behavior of the Amur sleeper. Fish (349 individuals) were captured by electrofishing in autumn 2012. To estimate the dietary importance of each prey category, we calculated the percentage or proportion of each food item and its frequency of occurrence. The Costello graphical method was applied to describe the feeding strategy and prey importance. A total number of 55 taxa of benthic macroinvertebrates were identified, amounting to a total of 2448 individuals. The digestive tract was empty in 48 individuals of the Amur sleeper. The most frequent prey items of the Amur sleeper were Asellus aquaticus L, Baetis spp., the Chironomidae family which was represented by 22 taxa identified to the genus and species levels, Corixa spp. and Physa acuta Drap. Depending on the frequency of prey items, two categories of size classes with specific diet compositions in the Amur sleeper populations were determined. Feeding strategy, cluster indicators of the size classes and traits of macroinvertebrates were the main aspects covered by our study of the Amur sleeper feeding behavior.

Diet Composition of Royal Tern (Thalasseus maximus) and Sandwich Tern (Thalasseus sandvicensis) at Isles Dernieres Barrier Island Refuge, Louisiana, USA

The Isles Dernieres Barrier Island Refuge in Louisiana, USA, constitutes a major colonial waterbird breeding site, and several restoration projects have been undertaken to sustain waterbird populations on the refuge. However, very little is known about food resources that colonial waterbirds depend on in the Gulf of Mexico. Royal (Thalasseus maximus) and Sandwich (T. sandvicensis) tern diet composition was investigated to determine important food resources during the breeding period. Regurgitated prey items in the 2013 and 2014 breeding seasons were used to compare diet composition, prey item frequency, and prey item mass among four groups: Royal Tern adults, Royal Tern chicks, Sandwich Tern adults, and Sandwich Tern chicks. The two most frequent prey items were Atlantic croaker (Micropogonias undulatus) and bay anchovy (Anchoa mitchilli). Royal Tern adults consumed significantly more Sciaenids than any other tern group, and Sandwich Tern adults consumed more Engraulids than any other tern group. Royal and Sandwich tern adults partitioned food resources by prey species and prey size, while chick diet showed more overlap in prey species composition. Royal and Sandwich tern diet closely reflected the species composition of trawls from nearby waters, suggesting opportunistic prey selection. The diets of both tern species contained a variety of demersal prey items indicating use of discards from local fisheries activities. Interactions between breeding waterbirds and fisheries in coastal Louisiana may be an important conservation consideration with profound implications on breeding abundance and breeding success of waterbirds.

Diet of Baillon's CrakesZapornia pusilla: Assessing Differences in Prey Availability and Consumption during the Breeding Season in the Senegal River Delta, West Africa

The Baillon's Crake Zapornia (Porzana) pusilla is considered as one of the least known Rallidae species of the Palaearctic. Very little information exists about its ecological requirements and knowledge on diet refers to very few observations. Based on the analysis of faecal samples (N = 59) from two study sites in Djoudj National Park (NW Senegal), we describe the major diet components and examine how seasonal and environmental factors influence its dietary composition. All faeces contained remains of invertebrates. Coleopterans were the most frequent prey items with an occurrence in 95% of the samples. Other important food items were: Odonata (82%), Aranaea (78%), Nematocera (59%), and Brachycera (44%). Remains of gecko skin were the only evidence for vertebrate prey. 75% of the faeces contained plant matter, especially seeds of Eleocharis mutata which constituted in some individuals > 90% of the sample content. Generalized linear models (GLMs) were used to assess whether occurrence of prey items was an effect of selection or environmental variation, considering both consumed items as well as prey availability. Sweep netting was used to provide an estimate of relative abundance of potential invertebrate prey.Despite pronounced seasonal changes in temperature and humidity, models revealed a lower influence of meteorological variables on prey composition and availabilty. Rather we found water level, date and site having the highest impact in the models. In contrast to decreasing diversity of available food items in the course of the season, diversity in the faeces remained constant indicating Baillon's Crakes prey less selectively when resources diminish. Furthermore, diversity of Baillon's Crakes' diet was lower at higher water levels, suggesting stronger selectivity when prey abundances are high as implied by positive relationships of several invertebrate groups with water level. Despite the rapidly declining water levels and decreasing abundances of e.g. Nematocera, Odonata and Mollusca in the course of the season, we found no clear shift from aquatic to a more terrestrial dominated composition of taxa in the birds' diet. This might be due to the selection of profitable prey such as araneans or molluscs but could also be explained by better accessibility due to physical changes in the habitats e.g in the case of consumed Odonata and Saltatoria. High disintegration of invertebrates in the faeces rendered quantification of prey items impossible. Biomass estimates could support the assessment of specialization of the Baillon's Crakes as well as the detection of seasonal succession of the wetlands' biotic communities.