No abstract

In the summer of 2016, Belgium, France, Germany and the Netherlands reported widespread Usutu virus (USUV) activity based on live and dead bird surveillance. The causative USUV strains represented four lineages, of which two putative novel lineages were most likely recently introduced into Germany and spread to other western European countries. The spatial extent of the outbreak area corresponded with R0 values > 1. The occurrence of the outbreak, the largest USUV epizootic registered so far in Europe, allowed us to gain insight in how a recently introduced arbovirus with potential public health implications can spread and become a resident pathogen in a naïve environment. Understanding the ecological and epidemiological factors that drive the emergence or re-emergence of USUV is critical to develop and implement timely surveillance strategies for adequate preventive and control measures. Public health authorities, blood transfusion services and clinicians in countries where USUV was detected should be aware of the risk of possible USUV infection in humans, including in patients with unexplained encephalitis or other neurological impairments, especially during late summer when mosquito densities peak.

Summary1. Long-term effects of conditions during early development on fitness are important for life history evolution and population ecology. Using multistrata mark-recapture models on 20 years of data, we quantified the relation between rearing conditions and lifetime fitness in a long-lived shorebird, the oystercatcher ( Haematopus ostralegus ). We addressed specifically the relative contribution of short-and long-term effects of rearing conditions to overall fitness consequences. 2. Rearing conditions were defined by differences in natal habitat quality, in which there is a clear dichotomy in our study population. In the first year of life, fledglings from high-quality natal origin had a 1·3 times higher juvenile survival. Later in life (age 3-11), individuals of high-quality natal origin had a 1·6 times higher adult prebreeder survival. The most striking effect of natal habitat quality was that birds that were reared on high-quality territories had a higher probability of settling in high-quality habitat (44% vs. 6%). Lifetime reproductive success of individuals born in high-quality habitat was 2·2 times higher than that of individuals born in low-quality habitat. This difference increased further when fitness was calculated over several generations, due to a correlation between the quality of rearing conditions of parents and their offspring. 3. Long-term effects of early conditions contributed more to overall fitness differences as short-term consequences, contrary to common conceptions on this issue. 4. This study illustrates that investigating only short-term effects of early conditions can lead to the large underestimation of fitness consequences. We discuss how long-term consequences of early conditions may affect settlement decisions and source-sink population interactions.

Climate warming challenges animals to advance their timing of reproduction [1], but many animals appear to be unable to advance at the same rate as their food species [2, 3]. As a result, mismatches can arise between the moment of largest food requirements for their offspring and peak food availability [4-6], with important fitness consequences [7]. For long-distance migrants, adjustment of phenology to climate warming may be hampered by their inability to predict the optimal timing of arrival at the breeding grounds from their wintering grounds [8]. Arrival can be advanced if birds accelerate migration by reducing time on stopover sites [9, 10], but a recent study suggests that most long-distance migrants are on too tight a schedule to do so [11]. This may be different for capital-breeding migrants, which use stopovers not only to fuel migration but also to acquire body stores needed for reproduction [12-14]. By combining multiple years of tracking and reproduction data, we show that a long-distance migratory bird (the barnacle goose, Branta leucopsis) accelerates its 3,000 km spring migration to advance arrival on its rapidly warming Arctic breeding grounds. As egg laying has advanced much less than arrival, they still encounter a phenological mismatch that reduces offspring survival. A shift toward using more local resources for reproduction suggests that geese first need to refuel body stores at the breeding grounds after accelerated migration. Although flexibility in body store use allows migrants to accelerate migration, this cannot solve the time constraint they are facing under climate warming.