Birds use structural properties when selecting materials for different parts of their nests

Abstract

Bird nests can have various roles but all act as the location for incubation, so at least have to serve to hold and support the incubating bird and its clutch of eggs. Nest construction is species specific and the use of materials varies between different parts of the nest. At present we know very little about the role that these materials play in the structural characteristics of the nest. This study examined materials from deconstructed nests from four species of thrush (Turdidae) and two species of finch (Fringillidae) that all constructed nests made of woody stems. It was hypothesised that structural properties would vary within the different regions of a nest, with thicker and stronger materials being found in parts of the nest needing the most support. Secondly, it was predicted that structural properties would vary little between nests of members of the same family, but would be quite different between nests of different families. Nests were deconstructed to quantify the materials used in the cup lining, and the upper and lower parts of the outer nest. The 20 thickest pieces of material were selected from each nest part and for each piece, and their diameter and mass quantified. Each piece was then subjected to a three-point bending test using an Instron universal testing machine to determine its rigidity and bending strength. 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. The extent to which these structural properties varied between families depended on where the material was taken from the nest. Both strength and rigidity strongly positively correlated with the diameter of the piece of material. We hypothesise 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. Keywords

Construction materials affect the hydrological properties of bird nests

“…It is unclear why this was the case, but the results may reflect differences in the arrangement of materials. In nests, the materials are placed by the bird in specific parts of the structure (Biddle, Deeming & Goodman, , ; Biddle, Goodman & Deeming, ) and often air gaps are present within the walls (Deeming & Biddle, ). Isolated materials placed in the sieve may have lacked structural complexity and air gaps observed in a nest wall; these may have aided in drainage in the nest.…”

“…The insulative properties of feathers, grass, moss and wool have all been found to decrease when wet, whereas the cooling rate of feathers increased rapidly when wet (Hilton et al, 2004). Therefore, although a bird's choice of materials may relate to the thermal or structural properties of the materials (Britt & Deeming, 2011;Bailey et al, 2014;Biddle et al, 2015Biddle et al, , 2017Biddle et al, , 2018bBotero-Delgadillo et al, 2017), more research is required in different habitats across a range of different environments to help provide a clearer explanation of the factors affecting the use of materials.…”

Geographical location affects size and materials used in the construction of European Pied Flycatcher (Ficedula hypoleuca) nests

“…Avian nests are complex structures that represent extended phenotypes and are the place of incubation for all bird species and the site of nestling rearing for many species, particularly passerines (Deeming 2016). Nests exhibit considerable inter-specific (Deeming and Mainwaring 2015;Biddle et al 2018a) and intra-specific variation in size and composition (Britt and Deeming 2011;Crossman et al 2011;Briggs and Deeming 2016;Taberner Cerezo and Deeming 2016;Biddle et al 2018a, b), which can impact upon their functional properties (Biddle et al 2017(Biddle et al , 2018b. For instance, insulatory values of the walls of Common Blackbird (Turdus merula) nests significantly correlated with the amount of grass within the cup lining (Mainwaring et al 2014).…”

Elevation has contrasting effects on avian and mammalian nest traits in the Andean temperate mountains

“…A broad spectrum of materials is used in avian and mammalian nests, and the use of specific materials can vary within and among species based on their function (Biddle et al . ,). Green nest materials such as leaves, vines, and bryophytes can contain volatile secondary compounds and a pH that restricts the development of pathogens in the nest (Wimberger ; Clark & Mason ; Dubiec et al .…”