How do birds ‘know’ how to build a nest?

My name is Alexis Breen and for my PhD at the University of St Andrews I am trying to get a better understanding of how birds understand what nest to build. Indeed, despite the wide-spread occurrence of nest building, little is known about how birds learn to build such impressive structures.

Humans build many different kinds of shelters, ranging from tipi tents to massive skyscrapers. The same is true for birds: many bird species build nests to raise their young, but these nests vary substantially in size, shape, material etc. A bird’s choice of nest material is crucial for its building success. But how do birds tell if, for example, a certain twig works well for building? Some materials are easier to manipulate while others might be more supportive.

In my research I study the nest-building behaviour of zebra finches (Taeniopygia guttata); more specifically, of the males—because they build the nest! Male zebra finches build nests at any time during the year and with (pretty much) any kind of material (e.g., pieces of coloured paper or cotton string), which makes these orange-cheeked birds ideal for looking at how different kinds of experiences might influence nest building. To be able to control the different influences, I study zebra finches in the laboratory and analyse video recordings.

One way a bird might choose material is by using information from previous building experience. In order to test this I gave male zebra finches the opportunity to build a nest with one of four different types of nest material (long-stiff, long-flexible, short-stiff and short-flexible). After this building experience, I presented the same birds with all four kinds of material again and looked at which one they preferred for their second nest. Strikingly, birds overwhelmingly preferred material the longer, and stiffer it was regardless of which one they built their first nest with—but why? It turns out that building with the flexible and/or shorter types of string required more work, either in terms of the number of pieces used to build a nest or the number of nest-building attempts made. The birds’ behaviour showed two important things: (1) birds pay attention to nest material features (in this case, length and rigidity); and (2) they can learn to avoid choosing material that makes nest building difficult – a form of learning known as ‘associative learning’.

But birds might not need to have previously built a nest to have an idea of what to do. Indeed, another way a bird could go about nest building is to build one just like its parents – a learning process called ‘imprinting’. To examine this possibility I am currently looking at whether material colour influences male zebra finches’ first-time nest-building decisions. For example, do males raised in nests built out of pink string prefer this colour material for their first nest, or do they instead prefer the orange string each was able to ‘interact’ with as a ‘teenager’? Do these aspects of early-life experience matter at all? Maybe they are in fact learning from watching others (‘social learning’)? I hope that by the end of my PhD I can provide answers to some of these intriguing aspects of bird nest building.

To read more about what nest-building birds can teach us, here is our latest review paper and you can also visit my website!

 

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