Bio: Will Cresswell is an academic researcher from University of St Andrews. The author has contributed to research in topics: Population & Foraging. The author has an hindex of 46, co-authored 162 publications receiving 7110 citations. Previous affiliations of Will Cresswell include University of Oxford & University of Edinburgh.
Papers published on a yearly basis
TL;DR: Anti-predator behaviour in overwintering redshanks on an estuary in south-east Scotland was studied in the context of a very high mortality rate due almost entirely to predation by raptors.
TL;DR: This review draws attention to the problem that fitness consequences of antipredation behaviors cannot be determined without considering the potential for reduction of predation risk, or increased reproductive output, through other compensatory behaviors than the behaviors under study.
Abstract: Any animal whose form or behavior facilitates the avoidance of predators or escape when attacked by predators will have a greater probability of surviving to breed and therefore greater probability ...
TL;DR: The trade-off approach allows us to predict better how changes in predator density will impact on population and community dynamics, and how animals perceive and respond to predation risk, when non-lethal effects decouple the relationship between predator density and direct mortality rate.
Abstract: Predators can affect individual fitness and population and community processes through lethal effects (direct consumption or ‘density’ effects), where prey is consumed, or through non-lethal effects (trait-mediated effects or interactions), where behavioural compensation to predation risk occurs, such as animals avoiding areas of high predation risk. Studies of invertebrates, fish and amphibians have shown that non-lethal effects may be larger than lethal effects in determining the behaviour, condition, density and distribution of animals over a range of trophic levels. Although non-lethal effects have been well described in the behavioural ecology of birds (and also mammals) within the context of anti-predation behaviour, their role relative to lethal effects is probably underestimated. Birds show many behavioural and physiological changes to reduce direct mortality from predation and these are likely to have negative effects on other aspects of their fitness and population dynamics, as well as affecting the ecology of their own prey and their predators. As a consequence, the effects of predation in birds are best measured by trade-offs between maximizing instantaneous survival in the presence of predators and acquiring or maintaining resources for long-term survival or reproduction. Because avoiding predation imposes foraging costs, and foraging behaviour is relatively easy to measure in birds, the foraging–predation risk trade-off is probably an effective framework for understanding the importance of non-lethal effects, and so the population and community effects of predation risk in birds and other animals. Using a trade-off approach allows us to predict better how changes in predator density will impact on population and community dynamics, and how animals perceive and respond to predation risk, when non-lethal effects decouple the relationship between predator density and direct mortality rate. The trade-off approach also allows us to identify where predation risk is structuring communities because of avoidance of predators, even when this results in no observable direct mortality rate.
TL;DR: The increased proportion of synchronized nests in recent years probably resulted in increased chick output: a greater proportion of recent nests successfully fledged all of the chicks that hatched and the number of young fledged per successful nest also increased in recentyears.
Abstract: Summary 1. Breeding birds increase their fitness by synchronizing their production of chicks with a peak of food abundance. Synchronization is primarily achieved by varying first egg date, but yearly temperature variations may delay or accelerate the food peak after the first egg has been laid. We tested the extent to which great tits ( Parus major L.) can strategically change their synchronization of hatch date with the food peak after the first egg has been laid by changing clutch size, laying interval and the amount of incubation. We also tested whether these possible synchronization change mechanisms resulted in changes in breeding success, because if the food peak is late relative to first egg date, we would predict more of the population to have larger clutches and/or a hatch date synchronous with the food peak date. 2. Great tits modified synchronization strategically by varying clutch size and the onset of incubation after clutch completion. When first egg date was early but then followed by cold weather so that the food peak was late, clutch sizes were larger, and when first egg date was late and temperatures were low, mean incubation periods were shorter if the food peak was early. 3. Over the 39-year period of the study, the period between the first egg date and food peak increased significantly by 1·7 days more than the period between the food peak and hatch date. Great tits have maintained synchronization by significantly increasing their incubation period. 4. Overall, the proportion of nests that had synchronous hatch dates depended on the yearly temperature pattern: the decline in variance between date of clutch completion and hatch was significantly greater in years where prelaying temperatures were higher (i.e. early first egg dates) and has therefore increased in recent years because of climate change. In warm early seasons (and more often in recent years) more of the great tits that laid relatively late had sufficient time to complete their clutches before having to start incubation in order to hatch in time for the food peak. 5. The increased proportion of synchronized nests in recent years probably resulted in increased chick output: a greater proportion of recent nests successfully fledged all of the chicks that hatched and the number of young fledged per successful nest also increased in recent years. These changes may have arisen because the proportion of nests with disadvantageous asynchronous hatching and/or smaller clutches has decreased. As the proportion of great tits that start nesting too late to synchronize has declined so selection for early laying has also declined in recent years.
TL;DR: Differences in geography and so average migration distance, migrant species composition and history of anthropogenic change in the two areas may account for the differences in the strength of the importance of phenology mismatch on migrant declines in the Nearctic and Palaearctic.
Abstract: 1. Migrant bird populations are declining and have been linked to anthropogenic climate change. The phenology mismatch hypothesis predicts that migrant birds, which experience a greater rate of warming in their breeding grounds compared to their wintering grounds, are more likely to be in decline, because their migration will occur later and they may then miss the early stages of the breeding season. Population trends will also be negatively correlated with distance, because the chances of phenology mismatch increase with number of staging sites. 2. Population trends from the Palaearctic (1990-2000) and Nearctic (1980-2006) were collated for 193 spatially separate migrant bird populations, along with temperature trends for the wintering and breeding areas. An index of phenology mismatch was calculated as the difference between wintering and breeding temperature trends. 3. In the Nearctic, phenology mismatch was correlated with population declines as predicted, but in the Palaearctic, distance was more important. This suggests that differential global climate change may be responsible for contributing to some migrant species' declines, but its effects may be more important in the Nearctic. 4. Differences in geography and so average migration distance, migrant species composition and history of anthropogenic change in the two areas may account for the differences in the strength of the importance of phenology mismatch on migrant declines in the Nearctic and Palaearctic.
TL;DR: For the next few weeks the course is going to be exploring a field that’s actually older than classical population genetics, although the approach it’ll be taking to it involves the use of population genetic machinery.
Abstract: So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to
TL;DR: In this article, the authors present a document, redatto, voted and pubblicato by the Ipcc -Comitato intergovernativo sui cambiamenti climatici - illustra la sintesi delle ricerche svolte su questo tema rilevante.
Abstract: Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.
TL;DR: In this paper, a test based on two conserved CHD (chromo-helicase-DNA-binding) genes that are located on the avian sex chromosomes of all birds, with the possible exception of the ratites (ostriches, etc.).
TL;DR: Meta-analysis is used to ask whether different types of behaviours were more repeatable than others, and if repeatability estimates depended on taxa, sex, age, field versus laboratory, the number of measures and the interval between measures.
TL;DR: Researchers with long-term datasets on phenology are urged to link their data with those that may serve as a yardstick, because documentation of the incidence of climate change-induced mistiming is crucial in assessing the impact of global climate change on the natural world.
Abstract: Climate change has led to shifts in phenology in many species distributed widely across taxonomic groups. It is, however, unclear how we should interpret these shifts without some sort of a yardstick: a measure that will reflect how much a species should be shifting to match the change in its environment caused by climate change. Here, we assume that the shift in the phenology of a species’ food abundance is, by a first approximation, an appropriate yardstick. We review the few examples that are available, ranging from birds to marine plankton. In almost all of these examples, the phenology of the focal species shifts either too little (five out of 11) or too much (three out of 11) compared to the yardstick. Thus, many species are becoming mistimed due to climate change. We urge researchers with long-term datasets on phenology to link their data with those that may serve as a yardstick, because documentation of the incidence of climate changeinduced mistiming is crucial in assessing the impact of global climate change on the natural world.