Urbanization of Blue Tits
It is known that urbanisation affects ecological communities. However, much less is known about how interspecific interactions such as those between predator and preys are impacted. Davide Dominoni and colleagues at MVLS, Glasgow are interested to investigate how urbanisation modifies a classic tritrophic interaction between cavity nesting songbirds (blue tits and great tits), their main caterpillar preys and the plants' leaves upon which caterpillars feed. Isotope measurements were funded by the NEIF.
Preliminary work (Pollock et al 2017) has shown that in urban blue tits, reduced breeding success is linked to poor nestling diet and in particular to an underabundance of caterpillars, their preferred nestling food. Thus the blue tits have to rely on alternative diets to feed their offspring. Thus this has severe implications for offspring physiology and survival.
The study compared rural nesting areas around Loch Lomond with city parks in Glasgow. Prey counts showed that caterpillars were much reduced in Glasgow, and stable isotope analysis of blood samples of blue tits and also their eggs, confirmed that the urban chicks had access to much fewer caterpillars.
In 2023 we hosted Ana Beatriz Navarro from the University of São Paulo on a 6-month FAPESP funded exchange visit to help us process the samples from the latest field study in 2023, encompassing a larger number of field locations over a longer urbanisation gradient.