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A corrugated bituminised roofing felt ‘tree tin’ originally provided to serve as a bat roost was adopted on a regular basis by Eurasian Treecreepers as nest sites. Data on nest construction under ‘...

Avian incubation relies on maintenance of the appropriate temperature and humidity within the nest. Previous studies suggested that conductance of the nest wall to water vapour was relatively low, albeit greater than the conductance of the eggshell, but no empirical studies confirmed this. In this study hygrometer loggers were used to measure water vapour inside and outside nest cups to determine conductance of the nest wall. Average water vapour conductance values for nine species of passerine ranged from 479 mgH2O·day-1·Torr-1 for Common Chaffinch Fringilla coelebs nests to 712 mgH2O·d-1·Torr-1 for Eurasian Reed Warbler Acrocephalus scirpaceus nests. Generally, water vapour conductance values were two orders of magnitude higher than that of published values for the eggshell for these species, although humidity in the nest cup were comparable to published data for passerine nests. These results indicate that in the study species the nest wall was not an effective barrier to water vapour loss. Reconsideration of high values for nest wall conductance, nest attentiveness and sources of water to create humidity, have led to a new approach that deals with nest humidity as part of the water budget during the incubation period. Over time the amount of water vapour required to raise nest humidity far exceeds that released by the eggs. It is proposed that nest humidity is driven by cutaneous water loss from the incubating bird, rather than water vapour lost from the eggs, in order to counter loss of humidity through the nest wall and during incubation recesses.

Increasing nestbox size affects mass of whole nests and the moss component but not proportions of nest materials except for feathers, which are inversely correlated with nestbox floor area.

Capsule: The use of woody material in the outer nest is significantly associated with heavier passerine species, whereas the use of grass, moss or leaves is unrelated to body mass.

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.

Bird nests represent an extended phenotype of individuals expressed during reproduction and so exhibit variability in composition, structure and function. Descriptions of nests based on qualitative observations suggest that there is interspecific variation in size and composition but there are very few species in which this has been confirmed. For these species, data of the amounts of different materials indicate that nest construction behaviour is plastic and affected by a variety of factors, such as prevailing temperature, geographic location, and availability of materials. The lack of data on nest composition is hampering our understanding of how nests achieve their various functions and how different species solve the problem of building a nest that will accommodate incubation and allow successful hatching of eggs. This study deconstructed nests of four species of the Turdidae, four species of the Muscicapidae, and six species of the Fringillidae and quantified the size of the nests and their composition. These data were used to test: (1) whether nest size correlated with adult bird mass; (2) whether it was possible to distinguish between species on the basis of their nest composition; and (3) whether, within a species, it was possible to distinguish between the cup lining and the rest of the nest based on composition. Most but not all nest dimensions correlated with bird mass. Principal component analysis revealed species differences based on nest composition and discriminant analysis could distinguish cup lining from the outer nest based on material composition. Intraspecific variation in composition varied among species and in general fewer types of material were found in the cup lining than the outer nest. These data provide insight into how nests are constructed by the different species and in conjunction with studies of the mechanical, thermal and hydrological properties of a nest, will begin to reveal how and why individual species select particular combinations of materials to build a nest.

Capsule: Air movement over a nest increases the rate of cooling within the nest cup but the walls provide good thermal insulation. Aims: This study compared nests of six bird species of the families Fringillidae and Motacillidae to investigate the insulative properties in still and moving air treatments. It was hypothesized that differences in nest size and moving air would differ between species and would have a significant effect on insulatory values of the nests. Methods: Nest dimensions were measured for a total of 35 nests from six species. Thermal properties of the nests were recorded using temperature loggers within nests placed in a wind tunnel under still and moving air conditions. Results: Insulatory values and internal nest cooling rates were significantly increased by moving air. There was no significant difference between species for the thermal properties of nests but nest mass correlated with greater insulatory values and a lower rate of cooling within the nest cup. Nest wall thickness had no significant effect on the thermal characteristics of the nests. Conclusion: The use of a constructed nest mitigated the effects of air movement but the differences between species reflected difference in nest mass rather than wall thickness.

The field of comparative psychology has traditionally focussed on investigating the cognitive abilities of a small number of mammal and bird species, but in order to understand the evolution of cognition, it is essential to examine cognitive abilities across a large range of vertebrates. Reptiles are particularly interesting in this context as they represent a key amniotic Class that do not develop under high, stable temperatures, which can produce phenotypic variation in the population. As their patterns of development differ substantially from those of birds and mammals reptiles can be used to investigate fundamental questions relating to factors shaping cognition; questions that cannot be asked in mammals and birds. In this review, we highlight some of these areas of interest and consider how the emerging field of reptile cognition can address crucial questions in cognitive science.

After laying their eggs, oviparous reptiles are reliant on the external environment to provide the required incubation conditions for successful embryonic development. Egg incubation temperature can impact the behaviour of various species of reptiles, but previous experiments have focused on the impact of incubation environment on hatchlings, with only a limited number of studies focussing on the longer-term behavioural consequences of incubation environment. This study investigated the effects of developmental environment on bearded dragon lizards (Pogona vitticeps) that were incubated at different temperatures within the natural range; half of them were incubated at a ‘hot’ temperature (30 ± 3 oC) and half at a ‘cold’ temperature (27 ± 3 oC). The growth and foraging behaviour of the lizards was then compared over 18 weeks of development. Although the lizards incubated at cooler temperatures grew more quickly, those incubated at the hotter temperature completed the foraging task more often and had significantly faster running speeds than those incubated at the cooler temperature. These results show that egg incubation temperature impacts the foraging behaviour of juvenile lizards and suggest a potential trade-off between growth and foraging speed, which could influence an animal’s life history trajectory.

Capsule Pied Flycatchers use different materials to construct their nests according to localised habitat and geographical location. Aims This study tested the hypotheses that birds would use the leaves they normally encountered within their breeding territories and that nest composition varied between geographical locations. Methods In Lancashire, Pied Flycatcher nests were collected from nestboxes built in locations dominated by different tree species and were deconstructed to determine which materials were used. Results Materials found in nests generally reflected the localised habitat around the nest rather than showing evidence of active collection from distant sources of material. Nests from Lancashire were significantly different in composition when compared with published data for nests from north Wales and central Spain. The use of moss was dominated by the use of one species in all but two nests. Conclusion Pied Flycatchers exhibit plasticity in nest construction behaviour because they were opportunistic in their choice of most nesting materials although they may be selective in their choice of moss.

Personality traits, defined as differences in the behavior of individual animals of the same species that are consistent over time and context, such as ‘boldness,’ have been shown to be both heritable and be influenced by external factors, such as predation pressure. Currently, we know very little about the role that early environmental factors have upon personality. Thus, we investigated the impact of incubation temperature upon the boldness on an oviparous reptile, the bearded dragon (Pogona vitticeps). Eggs, from one clutch, were incubated at two different average temperatures within the normal range. After hatching the lizards were raised under the same environmental conditions. Novel object and novel environment tests were used to assess personality. Each test was repeated in both the short term and the long term. The results revealed that incubation temperature did impact upon ‘boldness’ but only in the short term and suggests that, rather than influencing personality, incubation temperature may have an effect on the development of behavioral of oviparous reptiles at different stages across ontogeny.

The various roles that birds’ nests play are widely discussed and there is increasing interest in developing a better understanding of how they achieve these roles. The insulatory properties of nests have been investigated in a variety of songbird species and can vary with temperature and latitude. However, data are only available for a limited number of species. Here, we study the variations of the insulatory properties of European Robin ( Erithacus rubecula) nests in conjunction with the morphology of the nests and composition of the materials used in construction. As well as quantifying the materials used to construct these nests for the first time, we test the hypothesis that there is a latitudinal effect on nest insulation. Robin nests have a cup structure that is quite distinct, and easily separated, from the nest's base. Although the cup and nest's base shared similar construction materials discriminant analysis showed that they can be distinguished on the basis of their differing proportions of leaves. Insulatory values correlated with the mass of leaves in the cup but not latitude. Unlike other songbirds of comparable size that nest in nestboxes, European Robins appear to be able to use plant-derived materials rather than animal-derived materials to effectively insulate their nests.

Several methods have been used to determine the thermal properties of nests and in the last few years small iButton® temperature loggers have been used to determine an insulatory value. A recent study on Common Bullfinch ( Pyrrhula pyrrhula) nests used a different method, namely infrared (IR) thermography, to study nest wall insulation because pushing temperature loggers into the nest wall materials would have destroyed their structural integrity and probably adversely affected the insulatory value. Here, we compared the insulatory values of Common Linnet ( Carduelis cannabina) nests determined using temperature loggers (to record cooling rates in °C 20 s−1) with the temperature differences (ΔT in °C) across the nest wall as measured with IR thermography when the inside of the nest was heated under a steady state. Insulatory values were more variable than ΔT but there was no correlation between these two proxy measures of insulation. Despite being within the same family, Common Linnets build nests with very different materials from Common Bullfinches but ΔT values measured using IR thermography suggested that the nest wall of Common Linnet nests offered better insulation than the walls of Bullfinch nests. Our results suggest that comparative studies need to use the same methodologies but more research is needed to better understand the limitations of different methods in determining nest wall insulation.

Birds’ nests exhibit a considerable amount of plasticity in their size and construction. Indeed, several studies have shown that geographical location can affect this plasticity because local climatic conditions appear to affect nest-construction behaviours. This study examined nests collected in the UK and housed either at the University of Lincoln or at the British National Nest Reference Collection at the Hunterian Museum, University of Glasgow. Our aim was to increase the species diversity and the sample sizes for each species, over and above published studies. Mass and linear dimensions were recorded from nests of five finch species and two thrush species together with longitude and latitude for the nest site locations. An effect of species was shown for all finch nest dimensions measured but only for particular thrush dimensions. Latitude (range from 50.4 to 57.8°N) had no effect on nest measurements taken for thrush or finch species. However, while longitude (range from 6.8°W to 1.1°E) had no effect on thrush nests, it had a significant effect on the nest mass of finches, with nests constructed in the west being lighter in mass than those from the east. Previous studies examining the effects of latitude have used nests collected from different locations and built in a single year, which suggests that climatic conditions will be broadly comparable between locations. We found that museum collections have nests from a range of years and this rather limits their value in studies trying to ascertain the effects of location. Across different years there may be many unknown factors contributing to the patterns observed. We suggest that any future studies of the effects of climate on nest construction will have to rely on materials especially collected rather than using museum collections.

The behaviour of the incubating bird should be linked with the functional characteristics of its nest because they could minimise the incubation period that will reduce the risk of predation. Incubation attentiveness (percentage of daylight hours) in small passerines is a highly variable behaviour that is unrelated to egg mass. The thermal characteristics of nests are known to vary but whether they correlate with attentiveness, i.e. high attentiveness could reflect poorly insulated nests, has yet to be investigated. In this study, insulatory values were determined using temperature loggers for five species of British songbird in order to supplement equivalent data for six species from published sources. Attentiveness values for each species were determined from the literature. There was a significant negative correlation between attentiveness and insulatory values, which was unaffected by phylogeny. By contrast, attentiveness did not correlate with female body mass. That the avian incubation behaviour correlates with the functional properties of bird nests supports the concept of a bird–nest incubation unit, where reproductive success depends on both the bird and the nest structure. Further research should be directed towards a better understanding of this relationship for more species and, given the observed plasticity exhibited in nest composition and function, within species.

Thermal properties of nests have been investigated using a variety of techniques. Infrared (IR) thermography has the advantage of being a non-invasive technique allowing the integrity of the nest wall to be retained during measurement. This study investigated the insulative properties of nests of the Eurasian Bullfinch (Pyrrhula pyrrhula), the Common Blackbird (Turdus merula) and the Song Thrush (Turdus philomelos) using IR thermography. Nests were inverted over a heat source and the temperature of the external nest surface was recorded. Bullfinch nests were less insulated than thrush nests. Including foil inside the nest cup decreased the amount of convection through the open walls of Bullfinch nests. Removal of the outer nest and cup lining of thrush nests only slightly decreased the degree of insulation offered by the nest indicating an important insulative role for the substantial 'mud cup' in these nests. The results suggested that the nest wall is not sealed and convection currents may a play a significant role in nest insulation. In conjunction with a steady-state heat source IR thermography is useful in assessing the insulative properties of bird nests.

Testudines exhibit considerable variation in the degree of eggshell calcification, which affects eggshell conductance, water physiology of the embryos, and calcium metabolism of embryos. However, the underlying reason for different shell types has not been explored. Phylogenetically controlled analyses examined relationships between egg size, shell mass, and clutch size in ∼200 turtle species from a range of body sizes and assigned by family as laying either rigid- or pliable shelled eggs. Shell type affected egg breadth relative to pelvic dimensions, egg mass, and relative shell mass but did not affect size, mass, or total shell mass of the clutch. These results suggest that calcium availability may be a function of body size and the type of shell may reflect in part the interplay between clutch size and egg size. It was further concluded that the eggshell probably evolved as a means of physical protection. Differences in shell calcification may not primarily reflect reproductive parameters but rather correlate with the acidity of a species’ nesting environment. Low pH environments may have thicker calcareous layer to counteract the erosion caused by the soil and maintain the integrity of the physical barrier. Limited calcium availability may constrain clutch size. More neutral nesting substrates expose eggshells to less erosion so calcification per egg can be reduced and this allows larger clutch sizes. This pattern is also reflected in thick, calcified crocodilian eggs. Further research is needed to test whether eggshell calcification in the testudines correlates with nest pH in order to verify this relationship.

Recent work exploring the relationship between early environmental conditions and cognition has shown that incubation environment can influence both brain anatomy and performance in simple operant tasks in young lizards. It is currently unknown how it impacts other, potentially more sophisticated, cognitive processes. Social-cognitive abilities, such as gaze following and social learning, are thought to be highly adaptive as they provide a short-cut to acquiring new information. Here, we investigated whether egg incubation temperature influenced two aspects of social cognition, gaze following and social learning in adult reptiles ( Pogona vitticeps ). Incubation temperature did not influence the gaze following ability of the bearded dragons; however, lizards incubated at colder temperatures were quicker at learning a social task and faster at completing that task. These results are the first to show that egg incubation temperature influences the social cognitive abilities of an oviparous reptile species and that it does so differentially depending on the task. Further, the results show that the effect of incubation environment was not ephemeral but lasted long into adulthood. It could thus have potential long-term effects on fitness.

The pelvic girdle provides physical support and attachment for the hind limb musculature. In birds there is variability in pelvic morphology across different orders and this has been used as evidence for various types of locomotion. However, the morphological variation of pelvic bones has yet to be studied systematically in birds. Therefore, we investigated basic allometric relationships among female body mass (as a size proxy) and various pelvic measurements in a phylogenetic context. We also examined in detail the inter-relationships among various pelvic measurements. Also considered were the effects of broader taxonomic relationships at the level of order, with further examination of the influence of style of terrestrial locomotion on the allometric relationships. Positive relationships were initially found among all pelvic linear measurements and female body mass (FBM). The relationships among measures of pelvic width and FBM were isometric, whereas those between pelvic length and FBM showed positive allometry. Also, FBM explained more of the variance in pelvic length than in width. Similarly, the angle of the pelvis had a significant negative relationship, but FBM only explained a very low proportion of the variation in pelvic angles. In general terms, ancova showed that the effect of FBM was smaller than the effect of locomotor style in this species set. Both the synsacrum and pelvic girdle play roles in weight support and therefore scale in proportion to body weight accordingly. All three parts of the pelvis (ilium, ischium and pubis) are attached around the acetabulum and also provide muscle attachment points, so it might be expected for them to scale in a similar manner. Increased angulation of the pelvis is linked to orders which employ their hind limbs in feeding, perching and running, although FBM also explains a very low proportion of the variation in pelvic angle. Muscle attachment and the confines on morphology presented by locomotion explain much of the variation exhibited by the relationships among pelvic measurements.

Numerous new fossils have driven an interest in reproduction of early birds, but direct evidence remains elusive. No Mesozoic avian eggs can be unambiguously assigned to a species, which hampers our understanding of the evolution of contact incubation, which is a defining feature of extant birds. Compared to living species, eggs of Mesozoic birds are relatively small, but whether the eggs of Mesozoic birds could actually have borne the weight of a breeding adult has not yet been investigated. We estimated maximal egg breadth for a range of Mesozoic avian taxa from the width of the pelvic canal defined by the pubic symphysis. Known elongation ratios of Mesozoic bird eggs allowed us to predict egg mass and hence the load mass an egg could endure before cracking. These values were compared to the predicted body masses of the adult birds based on skeletal remains. Based on 21 fossil species, we show that for nonornithothoracine birds body mass was 187% of the load mass of the eggs. For Enantiornithes, body mass was 127% greater than the egg load mass, but some early Cretaceous ornithuromorphs were 179% heavier than their eggs could support. Our indirect approach provides the best evidence yet that early birds could not have sat on their eggs without running the risk of causing damage. We suggest that contact incubation evolved comparatively late in birds.

Recent fossil finds in China and Argentina have provided startling new insights into the reproductive biology and embryology of pterosaurs, Mesozoic flying reptiles. Nineteen embryos distributed among four species representing three distinct clades have been described and all are assumed to be at, or near, term. We show here how the application of four contrasting quantitative approaches allows a more precise identification of the developmental status of embryos revealing, for the first time to our knowledge, the presence of middle and late developmental stages as well as individuals that were at term. We also identify a predicted relationship between egg size and shape and the developmental stage of embryos contained within. Small elongate eggs contain embryos at an earlier stage of development than larger rounder eggs which contain more fully developed embryos. Changes in egg shape and size probably reflect the uptake of water, consistent with a pliable shell reported for several pterosaurs. Early ossification of the vertebral column, limb girdles and principal limb bones involved some heterochronic shifts in appearance times, most notably of manus digit IV, and facilitated full development of the flight apparatus prior to hatching. This is consistent with a super-precocial flight ability and, while not excluding the possibility of parental care in pterosaurs, suggests that it was not an absolute requirement.

Numerous studies over the past 90 years have described the various bird egg shapes in mathematical terms but few studies have considered the underlying reasons for such interspecifi c egg shape variability. Th is study investigated how the size and composition, i.e. proportions of shell, yolk and albumen, were associated with egg shape. Geometric morphometrics were used to generate principal components, which were analysed in relation to taxonomy (i.e. avian order) and degree of neonatal developmental maturity, which correlates with egg composition. Th e analysis confi rmed previous results that most of the variation in shape is associated with degree of elongation (i.e. length divided by breadth) and asymmetry (i.e. position of the broadest part of the egg away from the mid-point of the egg ’ s length). Egg shape refl ected avian order but not developmental maturity. Th e degree of elongation of an egg is related to absolute egg mass and the proportion of yolk. By contrast, the degree of asymmetry is related to the proportion of shell and the mass of the egg relative to female body mass. Although signifi cant, the models explained little of the variation in egg shape and so it was concluded that other factors, such as pelvis size and shape, could be more important in determining egg shape in birds.

Previous studies have suggested that birds and mammals select materials needed for nest building based on their thermal or structural properties, although the amounts or properties of the materials used have been recorded for only a very small number of species. Some of the behaviours underlying the construction of nests can be indirectly determined by careful deconstruction of the structure and measurement of the biomechanical properties of the materials used. Here we examined this idea in an investigation of Bullfinch (Pyrrhula pyrrhula) nests as a model for open-nesting songbird species that construct a “twig” nest, and tested the hypothesis that materials in different parts of nests serve different functions. The quantities of materials present in the nest base, sides and cup were recorded before structural analysis. Structural analysis showed that the base of the outer nests were composed of significantly thicker, stronger and more rigid materials compared to the side walls, which in turn were significantly thicker, stronger and more rigid than materials used in the cup. These results suggest that the placement of particular materials in nests may not be random, but further work is required to determine if the final structure of a nest accurately reflects the construction process.