Chaffinch and Hawfinch nests, by Charles Deeming
RESEARCH | Thermal properties of nests
A Chaffinch nest (left) showing the clearly defined cup lining and the more substantial outer nest walls of moss and grass. The outer walls of a Hawfinch nest (right) are dominated by woody stems with lichens and the cup lining is mainly roots.
Nests inside out Over the past few years, research at the University of Lincoln has sought to better understand how songbird nests function as places for incubation. To achieve this, researchers have relied heavily on the generous cooperation of nest recorders who have monitored nests and then carefully collected, packed and posted them to the University. In this article, Charles Deeming, Adrian Goodman and Lucia Biddle report on what they have been doing with the nests. Bird nests are complex bio-engineered
CONSTRUCTION Nest construction behaviour is not random and the birds seem to have an ability to select materials for key roles in different parts of the nest. We think that this involves the beak feeling the materials but further research is needed. We can now predict how we think that these species should build their nests, which can be tested by observation or experiment.
30 – LIFECYCLE
structures that can have a range of roles, but all are constructed during reproduction so that they can be used for incubation. Nest structures range from simple scrapes on the ground through to the complex woven nests produced by weaverbirds, and sizes range from the tiny nests of hummingbirds to colossal platforms constructed by birds of prey over many years. Research has shown that nest building is not a fixed behaviour and the same species can vary its nests between locations, often according to prevailing climatic conditions. Bird nests are very familiar but, although structure and location are often species-specific, it is remarkable how little we know about how nests are constructed and how they can fulfil their different roles. The research team at the University of Lincoln has been involved with projects that have formed part of several undergraduate dissertation projects, an MSc and a PhD research programme. Nests studied were built by finches, thrushes, warblers, wagtails, pipits, Old World flycatchers and Dunnock. We have focussed on three main areas of study: the mechanical properties of nest
materials, the thermal properties of nests, and the hydrological properties of whole nests, all of which have been supported by work that deconstructed the nests to quantify their composition. As a result, over the past three to four years, we have doubled the number of species for which data are available for nest composition (it is still only 30 species worldwide). Such data are useful because they will allow us to start to investigate how nest complexity evolved; they have already proved invaluable in enhancing our understanding of how nests function. We have published much of this work already with a few papers still in the pipeline – if you are interested in reading these please get in touch. In meantime, we summarise our findings below. NEST STRUCTURE
For most songbirds, the nest’s structure has to support the clutch and the sitting parent during incubation. Working with ‘twiggy’ nests of Bullfinches and Hawfinches, as well as nests of four breeding species of thrush, mechanical testing revealed the sophistication of the structures that birds can create. Bullfinches nest out on tree Winter 2020
