Summary1. It is widely accepted that the arrival order of migratory birds is correlated with the condition of the birds, which leads to high quality individuals occupying prime sites. However, the theoretical backgrounds for this argument have been lacking. A simple game-theoretic model of arrival timing is provided which investigates the evolutionary stability of condition-dependent arrival order in territorial migrant birds. 2. Competition for territories or other priority-dependent bene®ts can lead to arrival dates far preceding the cost-minimizing date (the optimum date in the absence of competition) for all but the weakest individuals. Increasing the number of competitors can generate a`cascading' competition for early arrival, which advances arrival dates further apart from the individual optimum dates for the onset of breeding. 3. At equilibrium, arrival order corresponds strictly to condition order only if marginal costs of advancing arrival are always larger for individuals in lower condition. If spring mortality vacates territories for later-arriving birds, the criterion for`honest' arrival order becomes still stricter: dierential survival costs should exist, but survival dierences among individuals (or, alternatively, territory quality dierences) should not be very large. 4. If the habitat is saturated so that there is a risk of not obtaining a territory at all, or if worst territories are of much lower value than the rest, competition may lead to the majority of the population arriving within a fairly short interval, followed by a much later¯oating fraction. This synchrony in the arrival of breeders imposes an increasing cost for the lesser ®t breeding birds. Thus, arrival costs paid are not necessarily highest for earliest arriving individuals, but for those who have the most to lose if they drop a few steps in the arrival order. 5. Competition for high quality territories can also lead to partial migration, in which case birds in good condition are expected to be most likely to remain resident.

Summary Fundamental ecological research is both intrinsically interesting and provides the basic knowledge required to answer applied questions of importance to the management of the natural world. The 100th anniversary of the British Ecological Society in 2013 is an opportune moment to reflect on the current status of ecology as a science and look forward to high‐light priorities for future work. To do this, we identified 100 important questions of fundamental importance in pure ecology. We elicited questions from ecologists working across a wide range of systems and disciplines. The 754 questions submitted (listed in the online appendix) from 388 participants were narrowed down to the final 100 through a process of discussion, rewording and repeated rounds of voting. This was done during a two‐day workshop and thereafter. The questions reflect many of the important current conceptual and technical pre‐occupations of ecology. For example, many questions concerned the dynamics of environmental change and complex ecosystem interactions, as well as the interaction between ecology and evolution. The questions reveal a dynamic science with novel subfields emerging. For example, a group of questions was dedicated to disease and micro‐organisms and another on human impacts and global change reflecting the emergence of new subdisciplines that would not have been foreseen a few decades ago. The list also contained a number of questions that have perplexed ecologists for decades and are still seen as crucial to answer, such as the link between population dynamics and life‐history evolution. Synthesis. These 100 questions identified reflect the state of ecology today. Using them as an agenda for further research would lead to a substantial enhancement in understanding of the discipline, with practical relevance for the conservation of biodiversity and ecosystem function.

Sexual reproduction is associated with the evolution of anisogamy and sperm-producing males and egg-laying females. The ensuing competition for mates has led to sexual selection and coevolution of the sexes. Mathematical models are extensively used to test the plausibility of different complicated scenarios for the evolution of sexual traits. Unfortunately, the diversity of models is now itself equally bewildering. Here we clarify some of the current debate by reviewing evolutionary explanations for the relationship between anisogamy, potential reproductive rates, parental care, sex roles, and mate choice. We review the benefits females might gain by mating with certain males rather than others. We also consider other forms of selection that can make females mate nonrandomly. One way empiricists can contribute to resolving theoretical disputes is to quantify the cost of expressing mating biases in the appropriate life-history currency.

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Estimation of individual fitness -i.e. description of the extent to which an individual's genes are represented in future generations -is a feature central to most evolutionary studies. Lifetime reproductive success (LRS) is a commonly used estimate of individual fitness, but because it is rate-insensitive (i.e. timing of reproductive events is not incorporated), it may give a biased estimate of fitness when reproductive timing is an important component of fitness. A review of all empirical studies which have used a recently derived, rate-sensitive estimate of individual fitness, k ind revealed that k ind ranks the fitness of phenotypes differently from LRS, and that this difference may lead to different conclusions about strength of selection acting on phenotypic traits. However, although k ind may be a better estimate of individual fitness than LRS in certain situations (e.g. in growing populations), its application is not always unproblematic. For instance, in contrast to rate-insensitive estimates of individual fitness, the k ind is sensitive to the age at which offspring are censused and there is little consensus among published studies on when offspring should be counted. Further, rate-sensitivity does not necessarily improve a fitness estimate in spatio-temporal variable environments. We suggest that the ultimate test on the applicability of k ind vs. LRS as practical measures of individual fitness in quantifying selection should come from studies which correlate these estimates with actual number of descendants left more than one generation further in future.