As an eco-physiologist, I am interested in how different environments influence the physiology and behaviour of animals. I study, for example, whether birds behave differently and have different hormone levels in tropical and temperate environments.
We humans have a huge impact on the habitats in which animals live. We transform whole landscapes to suit our purposes. In this process, we rarely think about the consequences these changes will have on the animals therein.
In the tropics, fast growing human populations and an increased need for agricultural land clash with the need to protect biodiversity hotspots. Often nature loses out and pristine habitats become fragmented and gradually degraded. How does this affect the animals that have roamed these landscapes before humans started to exploit them? Can they cope with these changes?
I am trying to find answers to this question by studying placid greenbuls (Phyllastrephus placidus) a bird species inhabiting the cloud forests of the Taita Hills – a biodiversity hotspot located in the Taita-Taveta County in southeastern Kenya.
Once covering most of the Taita Hills, these cloud forests have been reduced to 12 fragments in recent decades. Only three larger fragments remain, most of the other fragments are small to tiny (1-8ha) and most of the fragments are used for collection of fire wood and timber.
Placid greenbuls still breed in most of these fragments, but as forest specialists that depend on indigenous forest for breeding they may face serious problems because of these changes. Placid greenbuls are not endemic to the Taita Hills – they also occur in other regions in East Africa – and are not vulnerable to extinction.
However, other bird species, such as the Taita thrush and the Taita apalis that are found exclusively in the Taita Hills face an uncertain future.
Using placid greenbuls as a model system, I study how habitat fragmentation and degradation affects the behaviour and physiology of birds during breeding. I am still collecting data in the field and I don’t have any answers yet.
However, the cloud forests of the Taita Hills and its inhabitants have already cast a spell over me. Let me share some impressions from deep within the forests.
Entering the forest is like stepping into a different world – inside it is cool and moist even when outside the sun is burning hot. It is like entering the coolness of an ancient cathedral during a hot summer day. The dense canopy allows only few rays of sun to reach the forest floor.
The forest floor is covered by many centimetres of leaves in varying states of decay. You might tug at some twig and end up by holding a whole branch in your hand. You might step on a fallen tree trunk and end up stuck with your foot inside. Everything is covered by fungi, lichens and mosses. At the same time there is life everywhere.
Leaf-litter frogs call from hidden places underneath the leaves. Cicadas, barely distinguishable from the bark, stridulate without a break in their song. Squirrels run up and down the tree stems. Hordes of blue monkeys jump from tree to tree, barking to each other. For those with eyes for them, nests of birds can be found everywhere– adorned with rotting leaves, they look like debris caught up between the twigs of a bush.
Life and death are just two sides of the same coin.
I am very grateful to the funding bodies that are supporting this project (National Geographic Society (#NatGeoExplorers), the Alexander von Humboldt Foundation, German Ornithologists’ Society, Gesellschaft für Tropenornithologie (GTO), The Linnean Society of London). I am also grateful to the National Museums of Kenya, the Kenyan Wildlife Service, the Kenyan Forest Service and the Technical University of Munich for their support.