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The arrival‐time hypothesis of partial seasonal migration proposes that over‐winter residence is driven by reproductive benefits of early presence on the breeding grounds. Thus, it predicts increased occurrence of residence at reproductive age. In contrast, the body size hypothesis proposes age‐independent benefits of residence for large individuals, who should exhibit greater winter tolerance. Despite different expectations in age patterns for the two hypotheses in long‐lived partially migrant species, there is little empirical work investigating the ontogeny of migratory phenotypic expression, that is the expression of residence or migration.We investigated the influence of age, sex and body size on migratory phenotype throughout ontogeny (from first year to early adulthood) in a long‐lived partially migrant species, the red kite Milvus milvus. We GPS‐tracked 311 individuals tagged as juveniles and 70 individuals tagged as adults over multiple years, yielding 881 observed annual cycles. From this data, we estimated age‐dependent probabilities of the transition to residence and of survival in migrants and residents using a Bayesian multistate capture‐recapture model, as well as the probability of resuming migration once resident. We then calculated the resulting proportion of residents per age class.In both sexes, almost all juveniles migrated in their first winter, after which the probability of becoming resident gradually increased with age class to approximately 0.3 in adults (>3 calendar years). A size effect in third calendar year females suggests that large females adopt residence earlier in life than small females. The transition from residence back to migration only occurred with a probability of 0.15 across all resident individuals. In addition, survival was notably reduced in adult male migrants compared to adult male residents. These results are largely consistent with the arrival‐time and body size hypotheses, simultaneously.Our results reveal a plastic, yet primarily directional within‐individual change in migratory phenotype towards more residence with increasing age, varying between sexes and between individuals of different size. This study highlights that different individual characteristics can jointly shape the ontogeny of migratory behaviour and result in complex within‐population patterns and persistence of migratory phenotypes. [ABSTRACT FROM AUTHOR]

Wind energy production has expanded to meet climate change mitigation goals, but negative impacts of wind turbines have been reported on wildlife. Soaring birds are among the most affected groups with alarming fatality rates by collision with wind turbines and an escalating occupation of their migratory corridors. These birds have been described as changing their flight trajectories to avoid wind turbines, but this behaviour may lead to functional habitat loss, as suitable soaring areas in the proximity of wind turbines will likely be underused.We modelled the displacement effect of wind turbines on black kites (Milvus migrans) tracked by GPS. We also evaluated the impact of this effect at the scale of the landscape by estimating how much suitable soaring area was lost to wind turbines.We used state‐of‐the‐art tracking devices to monitor the movements of 130 black kites in an area populated by wind turbines, at the migratory bottleneck of the Strait of Gibraltar. Landscape use by birds was mapped from GPS data using dynamic Brownian bridge movement models, and generalized additive mixed modelling was used to estimate the effect of wind turbine proximity on bird use while accounting for orographic and thermal uplift availability.We found that areas up to approximately 674 m away from the turbines were less used than expected given their uplift potential. Within that distance threshold, bird use decreased with the proximity to wind turbines. We estimated that the footprint of wind turbines affected 3%–14% of the areas suitable for soaring in our study area.We present evidence that the impacts of wind energy industry on soaring birds are greater than previously acknowledged. In addition to the commonly reported fatalities, the avoidance of turbines by soaring birds causes habitat losses in their movement corridors. Authorities should recognize this further impact of wind energy production and establish new regulations that protect soaring habitat. We also showed that soaring habitat for birds can be modelled at a fine scale using publicly available data. Such an approach can be used to plan low‐impact placement of turbines in new wind energy developments. [ABSTRACT FROM AUTHOR]

For many species, there is evidence that breeding performance changes as an individual ages. In iteroparous species, breeding performance often increases through early life and is expected to level out or even decline (senesce) later in life. An individual's sex and conditions experienced in early life may also affect breeding performance and how this changes with age.Long‐term monitoring of individuals from reintroduced populations can provide unique opportunities to explore age‐related trends in breeding performance that might otherwise be logistically challenging.We used a unique dataset from a reintroduced population of white‐tailed eagles Haliaeetus albicilla in Scotland, which has been intensively monitored since their initial reintroduction in 1975, to study age‐ and sex‐specific trends in two measures of breeding performance. This monitoring provided data on the breeding performance of known individuals ranging in age from 3 to 26 years. We also explored changes in breeding performance in relation to early life experience (i.e., whether they were released or fledged in the wild).Breeding performance increased with age in early life in a similar manner for both sexes. We found stronger evidence for senescence in breeding performance in males than females. However, late‐life female breeding success was associated with early life experience, while male senescent trends were not apparently impacted by conditions experienced during early life.Sexual differences in senescence mean that older males are less likely to breed successfully compared to older females, and this may influence females' mate changes later in life. This difference may suggest a linked sexual difference in survival rates or the possibility of proactive partner change by females in later life in this typically monogamous biparental species. This article uses a unique individual‐based long‐term dataset derived from the reintroduction of white‐tailed eagles in Scotland to examine sex‐specific trends in reproductive senescence. Male white‐tailed eagles age faster than females, possible evidence for toy‐boy relationships in later life. [ABSTRACT FROM AUTHOR]

Intraguild predation ( IGP) is a commonly recognized mechanism influencing the community structure of predators, but the complex interactions are notoriously difficult to disentangle. The mesopredator suppression hypothesis predicts that a superpredator may either simultaneously repress two mesopredators, restrain the dominant one and thereby release the subdominant mesopredator, or elicit different responses by both mesopredators., We show the outcome arising from such conditions in a three-level predator assemblage (Eurasian eagle owl Bubo bubo L., northern goshawk Accipiter gentilis L. and common buzzard Buteo buteo L.) studied over 25 years. In the second half of the study period, the eagle owl re-colonized the study area, thereby providing a natural experiment of superpredator introduction. We combined this set-up with detailed GIS analysis of habitat use and a field experiment simulating intrusion by the superpredator into territories of the subdominant mesopredator, the buzzard., Although population trends were positive for all three species in the assemblage, the proportion of failed breeding attempts increased significantly in both mesopredators after the superpredator re-colonized the area., We predicted that superpredator-induced niche shifts in the dominant mesopredator may facilitate mesopredator coexistence in superpredator-free refugia. We found significant changes in nesting habitat choice in goshawk, but not in buzzard. Since competition for enemy-free refugia and the rapid increase in population density may have constrained niche shifts of the subdominant mesopredator, we further predicted behavioural changes in response to the superpredator. The field experiment indeed showed a significant increase in aggressive response of buzzards towards eagle owl territory intrusion over the course of 10 years, probably due to phenotypic plasticity in the response towards superpredation risk., Overall, our results show that intraguild predation can be a powerful force of behavioural change, simultaneously influencing habitat use and aggressiveness in predator communities. These changes might help to buffer mesopredator populations against the negative effects of intraguild predation. [ABSTRACT FROM AUTHOR]

1. We analysed time-series data from populations of red kangaroos (Macropus rufus, Desmarest) inhabiting four areas in the pastoral zone of South Australia. We formulated a set ofa priorimodels to disentangle the relative effects of the covariates: rainfall, harvesting, intraspecific competition, and domestic herbivores, on kangaroo population-growth rate.2. The statistical framework allowed for spatial variation in the growth-rate parameters, response to covariates, and environmental variability, as well as spatially correlated error terms due to shared environment.3. The most parsimonious model included all covariates but no area-specific parameter values, suggesting that kangaroo densities respond in the same way to the covariates across the areas.4. The temporal dynamics were spatially correlated, even after taking into account the potentially synchronizing effect of rainfall, harvesting and domestic herbivores.5. Counter-intuitively, we found a positive rather than negative effect of domestic herbivore density on the population-growth rate of kangaroos. We hypothesize that this effect is caused by sheep and cattle acting as a surrogate for resource availability beyond rainfall.6. Even though our system is well studied, we must conclude that approximating resources by surrogates such as rainfall is more difficult than previously thought. This is an important message for studies of consumer-resource systems and highlights the need to be explicit about population processes when analysing population patterns.Journal of Animal Ecology(2005)74, 22–30doi: 10.1111/j.1365-2656.2005.00915.x [ABSTRACT FROM AUTHOR]

Journal of Animal Ecology (2004) 73, 342–352 [ABSTRACT FROM AUTHOR]

Summary 1. We performed an extensive statistical modelling study on the population fluctuations and population growth rates of 15 raptor species in the Kalahari desert in South Africa. 2. The correlation pattern between rainfall and population abundance changed systematically with raptor body weight and diet type. The abundance of heavier raptors feeding on larger prey-items had lower correlations with rainfall than lighter raptors feeding on small prey-items. Whereas raptor species feeding on small prey-items were more affected by immediate rainfall, species feeding on large prey-items were more affected by rainfall in the previous year. 3. Population abundances were explained most parsimoniously by direct and delayed density dependence and rainfall during the current and previous breeding season. Interspecific competition was never a predictor variable. Population abundances of species best described by rainfall fed on larger prey-items than population abundances of species best described by density dependence. 4. Population growth rates were always best described by direct density dependence. The strength of density dependence was positively correlated with reproduction rate, due mainly to Falconiform species having higher reproduction rates than Accipitrid species. 5. Shifting from the species to the guild level, we found that abundance and biomass shares of feeding guilds did not vary significantly over time, supporting the hypothesis of guild constancy. [ABSTRACT FROM AUTHOR]