Design principles of biologically fabricated avian nests

Hadass R Jessel,Sagi Chen,Sol Efroni,Daniel Rittel,Ido Bachelet,Shmuel Osovski

doi:10.1038/s41598-019-41245-7

Hadass R Jessel, Sagi Chen + Show 4 more

Open Access

https://doi.org/10.1038/s41598-019-41245-7

Copy DOI

Abstract

Materials and construction methods of nests vary between bird species and at present, very little is known about the relationships between architecture and function in these structures. This study combines computational and experimental techniques to study the structural biology of nests fabricated by the edible nest swiftlet Aerodramus fuciphagus on vertical rock walls using threaded saliva. Utilizing its own saliva as a construction material allows the swiftlets full control over the structural features at a very high resolution in a process similar to additive manufacturing. It was hypothesized that the mechanical properties would vary between the structural regions of the nest (i.e. anchoring to the wall, center of the cup, and rim) mainly by means of architecture to offer structural support and bear the natural loads of birds and eggs. We generated numerical models of swiftlet nests from μCT scans based on collected swiftlet nests, which we loaded with a force of birds and eggs. This was done in order to study and assess the stress distribution that characterizes the specific nest’s architecture, evaluate its strength and weak points if any, as well as to understand the rationale and benefits that underlie this natural structure. We show that macro- and micro-scale structural patterns are identical in all nests, suggesting that their construction is governed by specific design principles. The nests’ response to applied loads of birds and eggs in finite element simulations suggests a mechanical overdesign strategy, which ensures the stresses experienced by its components in any loading scenario are actively minimized to be significantly smaller than the tensile fracture strength of the nests’ material. These findings highlight mechanical overdesign as a biological strategy for resilient, single-material constructions designed to protect eggs and hatchlings.

Highlights

Avian nests have a high degree of design variation across families which is translated to multiple functionalities
The nest’s section where the eggs are positioned was essentially stress-free in all scenarios, effectively insulated from stresses imposed by the adult birds themselves due to the fibers conducting and geometrically distributing the stresses in the horizontal direction (Fig. 3B)
A remarkable feature of the studied nests was the similarity in their macroscopic and microscopic properties, highly suggesting that the nests are constructed according to the same specific design principles

Summary

Introduction

Avian nests have a high degree of design variation across families which is translated to multiple functionalities As they primarily serve as a location and apparatus for incubation of eggs[1,2,3] and a safe place for offspring to develop[4], nests’ are hypothesized to integrate parts with specific physical and mechanical properties, evolutionarily selected to provide comfort[5], sexual signalling[6,7], defense from parasites or pathogens[6,8], and thermoregulation[9,10]. This control enables some species to achieve mechanical diversity by modulating the biosynthesis and composition of the same material during construction[23,24], a capability shared by contemporary human additive manufacturing technologies such as 3D printing[25]

Methods

Results

Conclusion