Search results for "Passer"
showing 10 items of 122 documents
Specific color sensitivities of prey and predator explain camouflage in different visual systems
2004
In situations of aggressive mimicry, predators adapt their color to that of the substrate on which they sit for hunting, a behavior that is presumed to hide them from prey as well as from their own predators. Females of few crab-spider species encounter such situations when lying on flowers to ambush pollinators. To evaluate the efficiency of spider camouflage on flowers, we measured by spectroradiometry adult female Thomisus onustus and marguerite daisies, Leucanthemum vulgare. We compared chromatic contrast (color used for short-range detection) of each pair of spider and flower to detection thresholds computed in the visual systems of both Hymenopteran prey and passerine bird predator. W…
Habitat quality is more important than matrix quality for bird communities in protected areas
2018
Protected areas are meant to preserve native local communities within their boundaries, but they are not independent from their surroundings. Impoverished habitat quality in the matrix might influence the species composition within the protected areas through biotic homogenization. The aim of this study was to determine the impacts of matrix quality on species richness and trait composition of bird communities from the Finnish reserve area network and whether the communities are being subject of biotic homogenization due to the lowered quality of the landscape matrix. We used joint species distribution modeling to study how characteristics of the Finnish forest reserves and the quality of t…
Costs and Benefits of Experimentally Induced Changes in the Allocation of Growth versus Immune Function under Differential Exposure to Ectoparasites
2010
Background Ecological immunology has focused on the costs of investment in immunocompetence. However, understanding optimal resource allocation to immune defence requires also identification of its benefits, which are likely to occur only when parasites are abundant. Methodology We manipulated the abundance of parasitic hen fleas in blue tit (Cyanistes caeruleus) nests, and supplemented their hosts, the nestlings, with methionine (a sulphur amino acid enhancing cell-mediated immunity) during day 3–6. We found a significant interaction between these two experimental factors on the development of immune defences and growth rates. Only in parasitized nests did methionine supplementation boost …
Active hiding of social information from information-parasites
2014
Background: Coevolution between pairs of different kind of entities, such as providers and users of information, involves reciprocal selection pressures between them as a consequence of their ecological interaction. Pied flycatchers ( Ficedula hypoleuca ) have been shown to derive fitness benefits (larger clutches) when nesting in proximity to great tits ( Parus major ), presumably because they this way discover and obtain information about nesting sites. Tits suffer from the resulting association (smaller clutches). An arms race between the tits (information host) and the flycatchers (information parasite) could thus result . Great tits often cover eggs with nesting material before, but no…
Social learning within and across predator species reduces attacks on novel aposematic prey
2020
Abstract To make adaptive foraging decisions, predators need to gather information about the profitability of prey. As well as learning from prey encounters, recent studies show that predators can learn about prey defences by observing the negative foraging experiences of conspecifics. However, predator communities are complex. While observing heterospecifics may increase learning opportunities, we know little about how social information use varies across predator species.Social transmission of avoidance among predators also has potential consequences for defended prey. Conspicuous aposematic prey are assumed to be an easy target for naïve predators, but this cost may be reduced if multipl…
Seasonal changes in some thermoregulatory variables of the house sparrow (Passer domesticus L.)
1975
Abstract 1. The body weight, plumage, insulation, oxygen consumption and body lipids were studied seasonally in the house sparrow, Passer domesticus L. 2. The weights of body and plumage were greater in autumn and winter than in summer. 3. The insulative property of the plumage was better in autumn and winter birds than in summer birds. 4. The oxygen consumption of young birds was higher than that of plucked and adult birds. 5. The amount of subcutaneous depot fat tissue and its lipid content was greatest in autumn. The C18-unsaturated fatty acids were most prominent in the subcutaneous fat. Palmitic acid was the most prevalent fatty acid in the liver. The relative amount of C18-unsaturated…
“La passerella? Si può fare” in GIORNALE DI SICILIA del 23 ottobre 2007 (cronaca di Agrigento).
2007
Parere sulla realizzazione di una passerela pedonale tra l'area del tempio di Ercole e quella del tempio di Zeus nel parco archeologico di Agrigento
REPRODUCTIVE SUCCESS OF EURASIAN TREECREEPERS,CERTHIA FAMILIARIS,LOWER IN TERRITORIES WITH WOOD ANTS
1999
Few studies have considered the effects of interspecific competition between distantly related taxa on the reproductive success of individuals. We compared the food supply, laying date, clutch size, and breeding success of a small double-brooded passerine bird, the Eurasian Treecreeper (Certhia familiaris) between territories with or without col- onies of red wood ants (Formica rufa group) during four years. Both the wood ants and Eurasian Treecreepers forage on tree trunks and utilize the same food resources. It has been shown that the wood ants are able to depress the available food supply for the treecreepers and interfere with their foraging behavior. We found that food abundance was lo…
Polygyny and Breeding Success of Pied Flycatchers Nesting in Natural Cavities
1990
Many hole-nesting passerine birds accept, or even prefer, nest boxes. Hence most of our knowledge about the breeding biology, population dynamics, life-history evolution and so forth of such species comes from nest box studies. This, in some cases, might lead to erroneous conclusions. For example, breeding density in nest box areas may often be much higher than in the natural situation (e.g. von Haartman, 1971), possibly leading to unnatural density dependent effects. Furthermore, the use of nest boxes may reduce predation risks (e.g. Nilsson 1975, 1984 a,b, Moller 1989), while the routine procedure of cleaning boxes after each breeding season may reduce the number of parasites, thus affect…
Variation in clutch size in relation to nest size in birds
2014
© 2014 The Authors. Nests are structures built to support and protect eggs and/or offspring from predators, parasites, and adverse weather conditions. Nests are mainly constructed prior to egg laying, meaning that parent birds must make decisions about nest site choice and nest building behavior before the start of egg-laying. Parent birds should be selected to choose nest sites and to build optimally sized nests, yet our current understanding of clutch size-nest size relationships is limited to small-scale studies performed over short time periods. Here, we quantified the relationship between clutch size and nest size, using an exhaustive database of 116 slope estimates based on 17,472 nes…