Bird builders: diversity of avian architecture

bowerbird nest

Photo credit: Jim Bendon

From ornate archways surrounded by colourful plastic gardens to the labyrinths of tunnels built inside towering termite mounds, animal architecture is a source of some of the most awe-inspiring natural wonders. These structures reveal the ability of animals to refine their habitat to meet their own needs, often for mating and raising their offspring. But as the atmosphere warms and changes the climate, architects have to adapt to the new conditions and vegetation of their ecosystem, and researching construction behaviour is important for determining the conservation status of these animals.

Ornate animal dwellings are not just important for the sake of their creators because many structures change the ecosystem in important ways for all the other animals. Hamerkops build some of the largest nests in the avian kingdom, hollow palaces constructed of around 8000 sticks and weighing several hundred times the weight of its builder. Hamerkops have a habit of building nests they don’t need for breeding, and often the empty nests are taken over by lucky individuals such as snakes, genets and birds who can fit through the mud-plastered entrance and tunnel, and other birds such as weavers will attach their nests to the outside.

Hamerkops also occasionally customise their nests using colourful decorations, often using plastic wrappers if there are towns or houses nearby, which is an increasingly common practise seen in birds which may help males attract mates or display dominance to rivals. One of the most striking examples is that of male bowerbirds, who build romantic archways and surround them with coloured decorations. Males will dumpster-dive for plastic wrappers, pick flowers and steal from rivals to design bowers which will cater to the local females’ aesthetic preferences.

The question of how female choice can direct males’ construction behaviour is hard to answer. Some females, like the bowerbirds, have elaborate selection procedures not unlike the rounds of X Factor- the first round the female conducts secret assessments of her contestants’ bowers, the second the males audition by displaying with their bowers, and often the female will consequently build her (rather more practical) nest nearby her finalists’ bowers, and finally she conducts a final round of her suitors before choosing her winner.

Investigating how flexible construction behaviour is to female choice gives us a good idea of how adaptable it could be to the challenges of climate change. As global temperatures rise, plants and animals face the choice of migrating to chase the temperatures they are accustomed to towards the poles or up mountains, or remaining where they are and adapting to the new conditions. Unfortunately some species adapt or migrate faster than others, and as the niche of every living thing is intricately woven into the ecosystem, those that cannot evolve fast enough can be left behind- and lagging means extinction. So being able to adapt to the environment- whether that means designing a nest which appeals to local females, or choosing the best nesting materials as the vegetation composition changes with the climate- is a key skill for avian architects to survive the upcoming challenges.

Recent research has found that bird nests are not built by simple genetically determined rules, and actually show remarkable learning curves as they gain more experience. A study on young weaverbird males found that they begin to weave from an early age, and have the genetic toolkit to begin weaving even if raised without a normal nest or nest building materials, but their first attempt is a loosely woven mess compared to the neat, tight nests built by more experienced males. The ability for birds to remember their previous attempts and learn from their mistakes may be crucial for them to develop flexibility in their construction behaviour.

The intricate nests of avian architects hold greater environmental importance than attracting mates and providing a place to incubate, protect and feed offspring, as many builders have keystone importance to the environment and help sustain other species in the ecosystem.

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