vacancies Wendt Müller

One of the most exciting findings in contemporary behavioral ecology is that natural selection favors the evolution of multiple consistent responses to the same environmental conditions, resulting in discrete personality types within animal populations. How personalities are shaped during early life, and how they affect adult life-history strategies, however, remains virtually unstudied in free-living animals. To advance this field, we aim to apply concepts and tools from behavioral and spatial ecology, ecotoxicology, physiology and experimental psychology on an exceptionally well-studied long-lived migratory bird, the Lesser black-backed gull. Within this framework, we will study how parental food provisioning strategies affect pollutant loads in their chicks, such as of methyl mercury by marine feeders or pesticides by terrestrial ones, and how these toxic components interfere with the development of the gut microbiome. Through field observations and controlled experiments in outdoor aviaries, we will further study how diets, pollutants and gut microbiota jointly shape behavioral traits related to exploration and competition in developing chicks. Finally, by releasing juveniles with known physiology and personalities and tracking them with state-of-the-art GPS technology, we will study how food provisioning during early life shapes personalities and life-history strategies across an individual’s life cycle. The integration of captivity experiments with monitoring of wild-breeding and free-ranging individuals is expected to make a significant contribution to avian life-history theory within the context of anthropogenic effects and global change.

Individual variation is increasingly recognized as an important driver of eco-evolutionary dynamics at population, community and ecosystem level. Animal personality and foraging specialization constitute important dimensions of such ecologically-relevant individual trait variation, and have therefore been increasingly implemented in ecological studies. However, in contrast to spatial consistency, individual variation in timing of responses to environmental change has received much less attention, despite the fact that environments vary both at spatial and temporal scale. Within a second research framework, we therefore aim to quantify to what extent adult Lesser black-backed gulls vary in consistency in timing of their activities, and how this shapes life history strategies throughout their annual cycle. To advance this field, we aim to apply concepts from chronobiology, behavioral ecology and spatial ecology, and we will capitalize on recent advances in GPS tracking technology that opened up unprecedented opportunities to combine spatial, temporal and behavioral data streams across life-history stages at high temporal resolution. We believe that such integrated approach will significantly advance our understanding of the ecological consequences and evolutionary implications of individual variation in temporal consistency.

A central tenet in evolutionary biology is that populations adapt to their environment with every generation through the process of natural selection. In long-lived species such as gulls (Larus spp.), environmental changes may however also occur at timescales much shorter than generations, which is the timeframe over which evolution acts. Individuals should therefore benefit from being able to (partly) adjust their physiology or behavior to environmental changes throughout their lifetime. However, such adjustments are believed to be costly in terms of time or energy, and may hence jeopardize an organism’s reproduction or survival. Individuals must therefore benefit when they are able to assess the reliability of environmental cues and the extent to which current adjustment costs may be offset by future benefits. Yet, current ecological theory generally assumes that individuals exhibit a constant degree of plasticity throughout their lifetime, tracking environmental changes to the best of their ability, irrespective of the entailed costs. Within this framework, we elaborate further on this theory by assessing to what extent two co-occurring gull species, Lesser black-backed and Herring gulls, adjust their foraging strategies throughout their lifetime in response to (a)biotic environmental cues, how such plasticity in foraging niche use may trade off with other life-history traits, and how individual differences in niche plasticity may therefore persist over evolutionary timescales.

Worldwide human population growth has dramatic effects on wildlife and biodiversity. It continuously causes habitat destruction and habitat degradation. Nowadays anthropogenic change increasingly affects wildlife that initially adapted to (sub)urban conditions and man-made habitats, because urban areas are currently one of the main hotspots of habitat change. Population declines of wild animals inhabiting urban environments thus dismayingly concern species that were considered to be highly efficient in the exploitation of new, anthropogenic resources. Lesser black-backed gulls (Larus fuscus) are a prime example of such an opportunistic species that once successfully adapted to human-induced feeding opportunities, but what has for long been a success story is looming to switch completely. All landfill areas were decommissioned and at long last a fishery discard ban has been implemented so that lesser black-backed gulls inhabiting the southern North Sea will have to adapt to new, likely man-made resources in order to survive. This will potentially place them even further in a conflict zone with humans, as it can be expected that these opportunities are searched for and found in the urban environment. The transition to new foraging behaviors may, however, be hampered by the fact that (a) foraging in an anthropogenic context is highly competitive (b) anthropogenic food is suboptimal for reproduction and (c) not all individuals will be able to adapt to the change in environmental conditions. How and why individuals of the same species differ in their responses to environmental conditions is actually a central question for our understanding of population dynamics. In case of the lesser black-backed gulls it will determine how many gulls will still be able to fulfill their nutritional needs as well as the demands of their progeny in the near future.

This project has as main objective to improve our understanding about consequences of variation of individual foraging behaviour in Herring Gulls (Larus argentatus). This species is a widespread generalist that opportunistically forages within marine and terrestrial habitats that are increasingly altered by humans. The first part of the project will focus on the costs and consequences of urban resource use, assessing space use and timing of movements in relation to the availability of anthropogenic food resources, whether the timing of anthropogenic food availability may constrain reproduction, which may ultimately explain why  gulls that feed on urban areas are less successful than breeding gulls that feed on non-urban areas. The latter may on the one hand also relate to higher levels of plastic debris ingested and transferred to the chicks within an urban and industrialised areas. On the other hand, a lot of Herring Gulls feed on mussels along the breakwaters at the coast, which may be a major source of microplastics. It will also be investigated whether there is the variation of environmental chemical pollutants across different foraging strategies. Finally, breeding gulls feeding on anthropogenic food resources might have more diverse composition of gut microbiota (attributed to the contamination or parasitism of an animal), and therefore are prone to acquire parasites, natural infections, and other physiological stressors from urban habitats.