Colonial breeding in a rapidly changing world

The world is witnessing unprecedented rates of habitat degradation due to anthropogenic activities, especially urbanisation. Yet, some species are commonly believed to have successfully adapted to breed in urban areas. However, we have still a poor understanding of the actual fitness consequences. The fact that animals are attracted to an urban environment might conceal that urban landscapes can act as ecological traps, since even highly opportunistic species might have difficulties to keep up with the high rate of environmental change. This dissertation tackles this question by exploring the capacities to breed in changing environments along with in depth studies on the drivers of territoriality and on the role of the early life social environment for the offspring in order to deduce potential consequences of reproducing in urban landscapes. To this end, a colonial breeding seabird species, the lesser black-backed gull (Larus fuscus), which is thought to thrive in highly anthropogenic environments, is used as model species. First, I explored whether nesting site relocations, as frequently occurring in rapidly changing urban environments, impact on reproductive success, and I could show that individuals that lost their breeding site due to anthropogenic activities laid smaller eggs and that the likelihood of skipping a breeding season increased. In a next step and by using GPS tracking devices, I then showed that investing time in territoriality imposes a carry-over effect on reproductive investment. While not measured explicitly, it can be assumed that time costs increase after a relocation and might be the cause of the observed negative reproductive investment in relocated birds. Moreover, we currently lack a profound understanding of the importance of a territory for the chicks, even though it is known that the social early-life environment can shape an individual’s (behavioural) phenotype. This is particularly relevant in lesser black-backed gulls, because here chicks experience high levels of aggression when crossing into a neighbouring territory. I indeed found that chicks raised in dense areas where territories are closer together showed the lowest exploration activity. In a final step, I deployed a novel tracking technology to study the movement behaviour of the chicks in the colony, and I could show that the social environment also affected the movement activity, territory size and social associations among chicks from neighbouring nests.

Jaar van publicatie:2023

Trefwoorden:Doctoral thesis

Toegankelijkheid:Embargoed