Search results for "Great Tits"
showing 10 items of 13 documents
Predator mimicry, not conspicuousness, explains the efficacy of butterfly eyespots
2015
Large conspicuous eyespots on butterfly wings have been shown to deter predators. This has been traditionally explained by mimicry of vertebrate eyes, but recently the classic eye-mimicry hypothesis has been challenged. It is proposed that the conspicuousness of the eyespot, not mimicry, is what causes aversion due to sensory biases, neophobia or sensory overloads. We conducted an experiment to directly test whether the eye-mimicry or the conspicuousness hypothesis better explain eyespot efficacy. We used great tits ( Parus major ) as model predator, and tested their reaction towards animated images on a computer display. Birds were tested against images of butterflies without eyespots, wi…
The role of partial incubation and egg repositioning within the clutch in hatching asynchrony and subsequent effects on breeding success
2019
The main mechanism to achieve hatching asynchrony (HA) for incubating birds is to start heating the eggs before clutch completion. This might be achieved through partial incubation and/or early incubation. Even in the absence of incubation behaviour during the laying phase, clutches still experience a certain degree of asynchrony. Recent studies have shown that eggs located in the centre of the nest receive more heat than peripheral ones during incubation. As eggs receiving more heat would develop faster, we hypothesized that HA should be shorter in nests where eggs were moved homogeneously along the centre–periphery space during incubation than in those nests where eggs repeatedly remained…
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…
Seeing red? Colour biases of foraging birds are context dependent.
2020
Funder: Suomen Kulttuurirahasto; doi: http://dx.doi.org/10.13039/501100003125
Predators' consumption of unpalatable prey does not vary as a function of bitter taste perception
2020
Many prey species contain defensive chemicals that are described as tasting bitter. Bitter taste perception is, therefore, assumed to be important when predators are learning about prey defenses. However, it is not known how individuals differ in their response to bitter taste, and how this influences their foraging decisions. We conducted taste perception assays in which wild-caught great tits (Parus major) were given water with increasing concentrations of bitter-tasting chloroquine diphosphate until they showed an aversive response to bitter taste. This response threshold was found to vary considerably among individuals, ranging from chloroquine concentrations of 0.01 mmol/L to 8 mmol/L.…
Interaction of climate change with effects of conspecific and heterospecific density on reproduction
2020
We studied the relationship between temperature and the coexistence of great tit Parus major and blue tit Cyanistes caeruleus, breeding in 75 study plots across Europe and North Africa. We expected an advance in laying date and a reduction in clutch size during warmer springs as a general response to climate warming and a delay in laying date and a reduction in clutch size during warmer winters due to density-dependent effects. As expected, as spring temperature increases laying date advances and as winter temperature increases clutch size is reduced in both species. Density of great tit affected the relationship between winter temperature and laying date in great and blue tit. Specifically…
Connecting the data landscape of long-term ecological studies: the SPI-Birds data hub
2021
The integration and synthesis of the data in different areas of science is drastically slowed and hindered by a lack of standards and networking programmes. Long-term studies of individually marked animals are not an exception. These studies are especially important as instrumental for understanding evolutionary and eco-logical processes in the wild. Furthermore, their number and global distribution provides a unique opportunity to assess the generality of patterns and to address broad-scale global issues (e.g. climate change).
Social transmission of avoidance among predators facilitates the spread of novel prey.
2018
Warning signals are an effective defence strategy for aposematic prey, but only if they are recognized by potential predators. If predators must eat prey to associate novel warning signals with unpalatability, how can aposematic prey ever evolve? Using experiments with great tits (Parus major) as predators, we show that social transmission enhances the acquisition of avoidance by a predator population. Observing another predator’s disgust towards tasting one novel conspicuous prey item led to fewer aposematic than cryptic prey being eaten for the predator population to learn. Despite reduced personal encounters with unpalatable prey, avoidance persisted and increased over subsequent trials.…
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 …
Social information use about novel aposematic prey is not influenced by a predator’s previous experience with toxins
2019
Aposematism is an effective antipredator strategy. However, the initial evolution and maintenance of aposematism are paradoxical because conspicuous prey are vulnerable to attack by naive predators. Consequently, the evolution of aposematic signal mimicry is also difficult to explain. The cost of conspicuousness can be reduced if predators learn about novel aposematic prey by observing another predator's response to that same prey. On the other hand, observing positive foraging events might also inform predators about the presence of undefended mimics, accelerating predation on both mimics and their defended models. It is currently unknown, however, how personal and social information combi…