Birds are amazing architects that can build intricate nests using various materials.
But how do they choose the right materials for different parts of their nests? And do their beak shape have anything to do with it?
A recent study by researchers from the University of Bristol and the University of Lincoln sheds some light on these questions.
The link between beak shape and nest material use
The researchers used a new global database of nest materials used by 5,924 species of birds and analyzed the relationship between beak shape and these materials, as per Phys.org.
They found that beak morphology, together with species diet and access to materials, can predict nest-material use above chance and with high accuracy (68% to 97%).
This means that birds with similar beaks tend to use similar materials for their nests, and that these materials are also influenced by what they eat and what is available in their environment.
For example, birds with long, thin beaks may prefer to use soft and flexible materials, such as feathers or grasses, while birds with short, thick beaks may prefer to use hard and rigid materials, such as twigs or bones.
However, the researchers also found that much of this relationship is driven by phylogenetic signal and sampling biases.
This means that some of the patterns are due to the shared evolutionary history of birds and the uneven distribution of data across different regions and habitats.
Therefore, the link between beak shape and nest material use is not as straightforward as it may seem, and other factors may also play a role.
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The structural properties of nest materials
Another study by researchers from the University of Lincoln examined the structural properties of nest materials from four species of thrushes (Turdidae) and two species of finches (Fringillidae) that all constructed nests made of woody stems.
They measured the diameter, mass, rigidity and bending strength of the materials used in different parts of the nest: the cup lining, the upper part of the outer nest and the lower part of the outer nest.
According to the study, the placement of materials in the nest was non-random in all species. The materials used in the outer part of the nest were thicker, stronger and stiffer than those materials found in the cup lining.
This makes sense, as the outer part of the nest needs to provide more support and protection than the inner part.
They also found that both strength and rigidity strongly positively correlated with the diameter of the piece of material.
The researchers hypothesized that birds are not directly aware of the structural properties of the material per se but rather assess diameter and mass of the material when they pick it up by the bill.
Using this information, they decide on whether the piece is suitable for that appropriate stage of nest construction.
These studies showed that birds are selective when it comes to choosing materials for their nests, and that their choices are influenced by their beak shape, diet, environment and structural properties of the materials.
However, these factors are not independent from each other, and more research is needed to understand how they interact and vary across different species and habitats.
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