Search results for "SONGBIRDS"
showing 10 items of 55 documents
Different Scales of Spatial Segregation of Two Species of Feather Mites on the Wings of a Passerine Bird
2011
The "condition-specific competition hypothesis" proposes that coexistence of 2 species is possible when spatial or temporal variations in environmental conditions exist and each species responds differently to those conditions. The distribution of different species of feather mites on their hosts is known to be affected by intrinsic host factors such as structure of feathers and friction among feathers during flight, but there is also evidence that external factors such as humidity and temperature can affect mite distribution. Some feather mites have the capacity to move through the plumage rather rapidly, and within-host variation in intensity of sunlight could be one of the cues involved …
Evolution and genetic structure of the great tit (Parus major) complex
2003
The great tit complex is divided into four groups, each containing several subspecies. Even though the groups are known to differ markedly on morphological, vocal and behavioural characters, some hybridization occurs in the regions where they meet. The great tit has often been referred to as an example of a ring species, although this has later been questioned. Here, we have studied the genetic structure and phylogenetic relationships of the subspecies groups to clarify the evolutionary history of the complex using control region sequences of the mitochondrial DNA. The subspecies groups were found to be monophyletic and clearly distinct in mitochondrial haplotypes, and therefore must have h…
Predator experience on cryptic prey affects the survival of conspicuous aposematic prey.
2001
Initially, aposematism, which is an unprofitable trait, e.g. noxiousness conspicuously advertised to predators, appears to be a paradox since conspicuousness should increase predation by naive predators. However, reluctance of predators for eating novel prey (e.g. neophobia) might balance the initial predation caused by inexperienced predators. We tested the novelty effects on initial predation and avoidance learning in two separate conspicuousness levels of aposematic prey by using a 'novel world' method. Half of the wild great tits (Parus major) were trained to eat cryptic prey prior to the introduction of an aposematic prey, which potentially creates a bias against the aposematic morph. …
Selection for cryptic coloration in a visually heterogeneous habitat.
2001
We studied selection by predators for cryptic prey coloration in a visually heterogeneous habitat that consists of two microhabitats. It has been suggested that the probability of escaping detection in such habitats might be optimized by maximizing crypsis in one of the microhabitats. However, a recent model indicates that a coloration that compromises the requirements of different microhabitats might sometimes be the optimal solution. To experimentally study these hypotheses, we allowed great tits (Parus major L.) to search for artificial prey items in two different microhabitats (background boards): small patterned and large patterned. On each board there was one prey item that was either…
Multiple benefits of gregariousness cover detectability costs in aposematic aggregations
2001
Understanding the early evolution of aposematic (warning) coloration has been a challenge for scientists, as a new conspicuous morph in a population of cryptic insects would have a high predation risk and would probably die out before local predators learnt to avoid it1,2,3,4. Fisher5 presented the idea of aggregation benefit through the survival of related individuals; however, his theory has been strongly debated6,7,8 as the mechanisms that favour grouping have never been explored experimentally with the incorporation of detectability costs. Here we create a comprehensive ‘novel world’ experiment with the great tit (Parus major) as a predator to explore simultaneously the predation-relate…
Range size: Disentangling Current Traits and Phylogenetic and Biogeographic Factors
2006
The range size of a species can be determined by its current traits and by phylogenetic and biogeographic factors. However, only rarely have these factors been studied in combination. We use data on the geographic range sizes of all 26 Sylvia warblers to explicitly test whether range size was determined by current species-specific traits (e.g., body size, dispersal ability), phylogenetic factors (e.g., age of the lineage), or environmental, biogeographic factors (e.g., latitudinal position of the range). The results demonstrated that current traits and phylogenetic and biogeographic factors were interrelated. While a number of factors were significant in simple regression analyses, only one…
Effects of forest patch size on physiological stress and immunocompetence in an area-sensitive passerine, the Eurasian treecreeper ( Certhia familiar…
2004
We manipulated the primary brood size of Eurasian treecreepers (Certhia familiaris) breeding in different sized forest patches (0.5-12.8 ha) in moderately fragmented landscapes. We examined the effects of brood size manipulation (reduced, control, enlarged) and forest patch size on physiological stress (heterophil-lymphocyte ratios; H/L), body condition and cell-mediated immunocompetence (phytohaemagglutinin test). Nestlings' H/L ratios were negatively related to forest patch area in control and enlarged broods, whereas no effects were found in reduced broods. The effects of forest patch area were strongest in enlarged broods, which had, in general, twofold higher H/L ratios than control an…
Dissemination of wine-related yeasts by migratory birds.
2013
The present work was undertaken to evaluate the contribution of migratory birds in the environmental dissemination of yeasts. Four sites (Mazara del Vallo, Lampedusa, Ustica and Linosa), representing the main stop-over points in Sicily, were analysed during spring and autumnal bird migration and 349 birds (belonging to 10 families) were ringed and analysed for yeast presence. A total of 125 yeasts were isolated and identified by a multiple genotypic approach, consisting of restriction fragment length polymorphism (RFLP) of 5.8S rRNA gene and 26S rRNA and sequencing of D1/D2 domain of the 26S rRNA gene, which resulted in the recognition of 18 species, including the technological relevant Sac…
THE EFFECT OF ALTERNATIVE PREY ON THE DYNAMICS OF IMPERFECT BATESIAN AND MÜLLERIAN MIMICRIES
2004
Both Batesian and Müllerian mimicries are considered classical evidence of natural selection where predation pressure has, at times, created a striking similarity between unrelated prey species. Batesian mimicry, in which palatable mimics resemble unpalatable aposematic species, is parasitic and only beneficial to the mimics. By contrast, in classical Müllerian mimicry the cost of predators' avoidance learning is shared between similar unpalatable co-mimics, and therefore mimicry benefits all parties. Recent studies using mathematical modeling have questioned the dynamics of Müllerian mimicry, suggesting that fitness benefits should be calculated in a way similar to Batesian mimicry; that i…
Heterospecific female mimicry in Ficedula flycatchers
2014
Mimicry is a widespread phenomenon. Vertebrate visual mimicry often operates in an intraspecific sexual context, with some males resembling conspecific females. Pied flycatcher (Ficedula hypoleuca) dorsal plumage varies from the ancestral black to female-like brown. Experimental studies have shown that conspecific and heterospecific (collared flycatcher, F. albicollis) individuals of both sexes respond, at least initially, to brown individuals as if they were female. We quantified the perceptual and biochemical differences between brown feathers and found that brown pied flycatcher males are indistinguishable from heterospecific, but not from conspecific, females in both aspects. To our kno…