Search results for "PREDATION"
showing 10 items of 589 documents
Predation on artificial ground nests in relation to forest fragmentation, agricultural land and habitat structure
1996
The impacts of forest fragmentation, agricultural land and habitat structure on depredation of artificial ground nests were studied in the cultivated area in central Finland and in the forest dominated area in Finnish Lapland. The overall predation rate did not differ between the regions. The overall predation rate was also independent of landscape characteristics forest patch size and the distance to patch edge. However, nest predation was clearly affected by the agricultural land since the robbing rate in forest edges was higher near farmlands than further away. This effect was caused by avian predators which proportional importance in predation was higher in the agricultural landscape th…
Short communication: Landscape and season effects on the diet of the Goshawk
2009
There are two general effects of habitat loss and frag-mentation of mature boreal forests (Schmiegelow &Monkkonen 2002). First, fragmentation by farmlandcreates stable structures such as permanent edge zoneswith enrichment of species diversity and density(Andren 1992, Berg & Part 1994). Secondly, modernforestry with clear-cuts creates sharp, unstable bound-aries between forest and open areas, usually with lesspronounced edge effects (Helle 1983, Schmiegelow &Monkkonen 2002). Considering the vast array of stud-ies on the effects of habitat loss and fragmentation onbird populations, relatively little attention has beenpaid to the role of predators, other than nest preda-tors, across different…
Mercury and chlorinated hydrocarbons in the food chain of Lake Paijanne, Finland
1978
The sediments and various organisms in Lake Paijanne were examined for contaminants. The average mercury content of water plants was 9, of plankton 14, of sediment 114, of zoobenthic predators 83, of fish 332–1510 and of birds 240–13685 μg kg−1 (wet weight). The average PCB content of plants was 3, of plankton 21, of the zoobenthos 44, of fish 36-117 and of birds 219–13490 μg kg−1. The average ΔDDT content of plants was 0.5, of plankton 6, of the zoobenthos 14, of fish 7–42 and of birds 144-8262 μg kg−1. Regional differences in mercury content were most pronounced in sediment and fish. PCB concentration was highest near a town. ΔDDT was quite evenly distributed. Water plant species did not …
Host-Plant Selection and Predation Risk for Offspring of the Parent Bug
1995
Herbivores, especially specialists, must adapt to characteristics of their host to survive and reproduce successfully (Hardin and Tallamy1992). If offspring survival among different hosts varies, natural selection should lead females to choose egg-laying sites where performance of the progeny will be highest. This is especially true when newly hatched larvae cannot move to another host (Singer 1986), or when searching for new hosts would cause heavy mortality (Singer and Mandracchia 1982). A number of studies have shown that females that search for oviposition sites respond to plant characteristics that are correlated with the nutritional quality of plants for their offspring (e.g., Myers 1…
Food Habits of the Javelin Sand Boa Eryx jaculus (Linnaeus 1758; Serpentes, Erycidae) in Sicily, Italy
2021
The Javelin Sand Boa, Eryx jaculus, is reported to be a predator of mammals, lizards and their eggs, and occasionally of birds and invertebrates, but data on its diet are scarce and fragmentary. Here we describe some aspects of the feeding behavior of E. jaculus on the Mediterranean island of Sicily. A total of 132 individual snakes were examined. Prey remains were found in 43% of them, both in their feces (82.5%) and gut contents (17.5%). The number of snakes observed and their feeding rate decreased in August, probably as a result of the relatively higher temperatures. Feeding rate increases were observed in adult females in September, perhaps to enhance body reserves before hibernation. …
Wintering habitats of Eleonora's FalconsFalco eleonoraein Madagascar
2012
[Capsule]: Eleonora's Falcons wintering in Madagascar selected degraded humid forests and cultivated areas close to pristine humid forest. [Aims]: To identify the habitat preferences of Eleonora's Falcon Falco eleonorae on their wintering grounds in Madagascar, and to use this information to gain insights into the conservation priorities of this species. [Methods]: A total of 11 Eleonora's Falcons were captured in Spain in 2007 and 2008 and equipped with solar-powered satellite transmitters. We obtained information on five complete wintering events for three birds, two of them tracked for two consecutive years. Data were analyzed using geographic information system-based cartography. [Resul…
Predatory habits of the grasshopper-hunting waspStizus continuus(Hymenoptera: Crabronidae): diet preference, predator–prey size relationships and for…
2009
In a coastal salt-marsh of Spain, the digger wasp Stizus continuus primarily hunted for grasshoppers of the genus Heteracris, revealing (at least in the period of the study and in this area) this wasp to be almost monophagous. In contrast, grasshoppers of the genus Acrotylus were ignored by the wasps in spite of their high abundance in the environment. We hypothesize that this bias occurred because Acrotylus is found more often on the soil and on grasses, while Heteracris is nearly only found on Sarcocornia bushes, which probably represent the habitat mostly exploited by the wasps for hunting. The greater variance in size of the prey collected by larger females produced weak wasp–prey size …
Dialipsis villahermosaeHumala & Selfa n. sp. (Hymenoptera: Ichneumonidae), the second European species of the genus, with biological notes and a …
2009
Abstract The small genus Dialipsis Forster 1869 (Hymenoptera: Ichneumonidae) includes two known species, of which one is common in Central and Northern Europe. Here we describe the male and female of a new species, Dialipsis villahermosae Humala & Selfa, which was reared from mushrooms collected in Eastern Spain. The host fungus gnat, Mycetophila blanda Winnertz, is a new record for the whole genus, while the rate of parasitism seems very low. Based on environmental data of the collection localities and data available for other two species it is suggested that Dialipsis species occur preferably in cool temperatures habitats. A key of identification of the two known Palaearctic species is pr…
Manipulation of fish host by eye flukes in relation to cataract formation and parasite infectivity
2005
Trophically transmitted parasites may predispose infected hosts to predation by altering host behaviour, which can be either an adaptation of the parasites to enhance transmission to the next hosts in the life cycle or a nonadaptive side-effect of infection. In an experimental study, we investigated host manipulation by Diplostomum spathaceum (Trematoda), an eye fluke of fish, to evaluate its adaptive value as a parasite strategy to increase transmission efficiency to bird hosts. The parasite induces cataract formation in the lenses of fish eyes, and predisposes fish to predation by reducing their escape response. We examined the effect of developmental stage and the number of parasites on …
Predator Mixes and the Conspicuousness of Aposematic Signals
2003
Conspicuous warning signals of unprofitable prey are a defense against visually hunting predators. They work because predators learn to associate unprofitability with bright coloration and because strong signals are detectable and memorable. However, many species that can be considered defended are not very conspicuous; they have weak warning signals. This phenomenon has previously been ignored in models and experiments. In addition, there is significant within- and among-species variation among predators in their search behavior, in their visual, cognitive, and learning abilities, and in their resistance to defenses. In this article we explore the effects of variable predators on models th…