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River–floodplain ecosystems play a crucial role in connecting landscape patches through hydrological connectivity, but they are among the most threatened ecosystems. Floodplains provide important habitat for amphibians by connecting aquatic and terrestrial habitats. Modifications to floodplain hydrology can impact amphibian communities, yet few studies have examined amphibian metacommunities in floodplain wetlands.In this study, we assessed patterns in amphibian breeding abundance in one of the largest floodplains of the Danube River, Hungary, relative to hydrological connectivity and multi‐scale variables at 30 waterbody sites. Our aim was to determine whether these patterns aligned with the pond‐permanence gradient hypothesis, where breeding amphibian abundance is predicted to be highest in ephemeral ponds without large predatory fish. We used Bayesian hierarchical modelling to estimate multi‐species abundance from repeated survey (count) data collected over one breeding season.We detected the eggs and larvae of four amphibian species. The best model of abundance included covariates describing two principal component axes associated with waterbody hydrology and landscape composition within a 500‐m radius of a site. There was a positive relationship between mean community abundance at a site and hydrological disconnection from the main river channel; however, the common toad (Bufo bufo) was associated with hydrologically connected waterbodies. There was a positive relationship between mean community abundance and a high proportion of forest cover and low cover of agricultural land within a 500‐m radius around a site, although this relationship was clear for only two species. There was no support for models containing the number of large predatory fish species detected at a site.Although our results showed that amphibian abundance declined with hydrological connectivity, based on model selection we could not ascribe this relationship to an increased number of large predatory fish species detected in waterbodies close to the main river channel. Differences in life history and habitat requirements are likely to have explained interspecific responses to hydrological connectivity. Our results underscore the importance of addressing amphibian abundance at multiple spatial scales in floodplain wetlands, as landscape composition partly explained patterns in abundance.Application of multi‐species abundance modelling allowed us to investigate environmental relationships for common and infrequently detected species. Habitat restoration programmes in floodplains should provide waterbodies disconnected from main river channels as potential amphibian breeding sites and protect or restore forest as terrestrial habitat. [ABSTRACT FROM AUTHOR]

This study examined the size‐dependent scavenging behaviour of black bullheads Ameiurus melas under laboratory conditions, using common bleak Alburnus alburnus and pumpkinseed Lepomis gibbosus carcasses. Video camera observations showed that the activity of A. melas was higher at night, but substantial daytime activity was also recorded. Larger A. melas were more active than their smaller conspecifics, especially at night. All size classes exhibited a well‐defined sequence of consuming different parts of the carcasses independent of size, but larger individuals tended to consume carcasses more efficiently. Carcasses of the softer‐bodied A. alburnus were consumed more readily than those of the bonier L. gibbosus, independent of size. This scavenging behaviour of A. melas might facilitate the invasion success of the species. [ABSTRACT FROM AUTHOR]

Fish carcass decomposition can generate fluxes of nutrients to the water column at levels comparable to other major nutrient sources. However, relatively little is known about the biological processes modulating fish decay or the rates at which carcass‐bound nutrients are made available to the biota.This study focused on quantifying scavenger‐mediated phosphorus (P) recycling, because the availability of this essential element can regulate the trophic state of aquatic ecosystems.To explore the role of some important macroscopic aquatic scavengers in P recycling, laboratory experiments were conducted where carcasses of two fish species (common bleak Alburnus alburnus; pumpkinseed Lepomis gibbosus) were offered to two size classes of black bullhead (Ameiurus melas) and two crustacean species (spiny‐cheek crayfish Faxonius limosus; narrow‐clawed crayfish Astacus leptodactylus).Our results show that the black bullhead and the two crayfish species are highly efficient macroscopic decomposers as the P contents of scavenged carcasses were reduced at significantly higher rates compared to those of microbially decomposed (control) carcasses.Pumpkinseed carcasses proved to be more resistant to rapid decomposition, as they typically lost lower proportions of their P content than bleak carcasses during the course of the experiments.Scavengers sequestered a relatively large fraction (up to 33% in black bullhead and 36% in crayfish) of total carcass P in their bodies. This suggests that the consumer species used in this study can transfer/return considerable quantities of carcass‐derived nutrients directly to higher trophic levels incorporated into their own tissues, and may serve as an additional, short‐term sink of these nutrients. [ABSTRACT FROM AUTHOR]

Urban animals often take more risk toward humans than their non‐urban conspecifics do, but it is unclear how urbanization affects behavior toward non‐human predators. Responses to humans and non‐human predators may covary due to common mechanisms enforcing a phenotypic correlation. However, while increased tolerance toward humans may be advantageous for urban animals, reduced vigilance toward non‐human predators that can pose actual threat may be costly. Therefore, urban animals may benefit from showing specific responses to different threat levels, such as humans versus non‐human predators, or hostile versus non‐hostile humans. To test these alternatives, we compared responses (latencies to return to nest) of urban and forest‐breeding great tits (Parus major) to familiar hostile and unfamiliar humans as well as one of their common predators, the sparrowhawk (Accipiter nisus). We found that urban birds were more risk‐taking toward both humans and sparrowhawk than forest birds. However, responses to sparrowhawk did not correlate with responses to humans either within or across habitats. This suggests that higher risk‐taking of urban compared to forest‐dwelling great tits toward sparrowhawk may be threat‐specific response to lower predation risk rather than a spillover effect of increased tolerance to humans. Furthermore, birds responded similarly to unfamiliar and familiar (potentially dangerous) humans in both habitats, suggesting that great tits may not adjust their risk‐taking to the threat represented by individual humans. These findings indicate that urban birds may flexibly adjust their risk‐taking to certain, but not all, types of threat. [ABSTRACT FROM AUTHOR]

Abstract: Urbanization can have marked effects on plant and animal populations’ phenology, population size, predator–prey, interactions and reproductive success. These aspects are rarely studied simultaneously in a single system, and some are rarely investigated, e.g., how insect phenology responds to urban development. Here, we study a tri‐trophic system of trees, phytophagous insects (caterpillars), and insectivorous birds (Great Tits) to assess how urbanization influences (1) the phenology of each component of this system, (2) insect abundance, and (3) avian reproductive success. We use data from two urban and two forest sites in Hungary, central Europe, collected over four consecutive years. Despite a trend of earlier leaf emergence in urban sites, there is no evidence for an earlier peak in caterpillar abundance. Thus, contrary to the frequently stated prediction in the literature, the earlier breeding of urban bird populations is not associated with an earlier peak in caterpillar availability. Despite this the seasonal dynamics of caterpillar biomass exhibited striking differences between habitat types with a single clear peak in forests, and several much smaller peaks in urban sites. Caterpillar biomass was higher in forests than urban areas across the entire sampling period, and between 8.5 and 24 times higher during the first brood's chick‐rearing period. This higher biomass was not associated with taller trees in forest sites, or with tree species identity, and occurred despite most of our focal trees being native to the study area. Urban Great Tits laid smaller clutches, experienced more frequent nestling mortality from starvation, reared fewer offspring to fledging age, and their fledglings had lower body mass. Our study strongly indicates that food limitation is responsible for lower avian reproductive success in cities, which is driven by reduced availability of the preferred nestling diet, i.e., caterpillars, rather than phenological shifts in the timing of peak food availability. [ABSTRACT FROM AUTHOR]

In group-living animals, individuals may benefit from the presence of an innovative group-mate because new resources made available by innovators can be exploited, for example by scrounging or social learning. As a consequence, it may pay off to take the group-mates' problem-solving abilities into account in social interactions such as aggression or spatial association, for example because dominance over an innovative group-mate can increase scrounging success, while spatial proximity may increase the chance of both direct exploitation and social learning. In this study, we tested whether the individuals' innovation success influences their social interactions with group-mates in small captive flocks of house sparrows ( Passer domesticus). First, we measured the birds' actual problem-solving success in individual food-extracting tasks. Then, we manipulated their apparent problem-solving success in one task (by allowing or not allowing them to open a feeder repeatedly) while a new, unfamiliar group-member (focal individual) had the opportunity to witness their performance. After this manipulation, we observed the frequency and intensity of aggression and the frequency of spatial associations between the focal individuals and their manipulated flock-mates. Although flock-mates behaved according to their treatments during manipulations, their apparent problem-solving success did not affect significantly the focal individuals' agonistic behaviour or spatial associations. These results do not support that sparrows take flock-mates' problem-solving abilities into account during social interactions. However, focal individuals attacked those flock-mates more frequently that had higher actual problem-solving success (not witnessed directly by the focal individuals), although aggression intensity and spatial association by the focal birds were unrelated to the flock-mates' actual success. If this association between flock-mates' actual innovativeness and focal individuals' aggression is not due to confounding effects, it may imply that house sparrows can use more subtle cues to assess the group-mates' problem-solving ability than direct observation of their performance in simple foraging tasks. [ABSTRACT FROM AUTHOR]