Bird nests as botanical time capsules: DNA barcoding identifies the contents of contemporary and historical nests

Bird nests in natural history collections are an abundant yet vastly underutilized source of genetic information. We sequenced the nuclear ribosomal internal transcribed spacer to identify plant species used as nest material in two contemporary (2003 and 2018) and two historical (both 1915) nest specimens constructed by Song Sparrows (Melospiza melodia) and Savannah Sparrows (Passerculus sandwichensis). A total of 13 (22%) samples yielded single, strong bands that could be identified using GenBank resources: six plants (Angiospermae), six green algae (Chlorophyta), and one ciliate (Ciliophora). Two native plant species identified in the nests included Festuca microstachys, which was introduced to the nest collection site by restoration practitioners, and Rosa californica, identified in a nest collected from a lost habitat that existed about 100 years ago. Successful sequencing was correlated with higher sample mass and DNA quality, suggesting future studies should select larger pieces of contiguous material from nests and materials that appear to have been fresh when incorporated into the nest. This molecular approach was used to distinguish plant species that were not visually identifiable, and did not require disassembling the nest specimens as is a traditional practice with nest material studies. The many thousands of nest specimens in natural history collections hold great promise as sources of genetic information to address myriad ecological questions.

Wax, Wings, and Swarms: Insects and Their Products as Art Media

Every facet of human culture is in some way affected by our abundant, diverse insect neighbors. Our relationship with insects has been on display throughout the history of art, sometimes explicitly but frequently in inconspicuous ways. This is because artists can depict insects overtly, but they can also allude to insects conceptually or use insect products in a purely utilitarian manner. Insects themselves can serve as art media, and artists have explored or exploited insects for their products (silk, wax, honey, propolis, carmine, shellac, nest material), body parts (e.g., wings), and whole bodies (dead, alive, individually, or as collectives). This review surveys insects and their products used as media in the visual arts and considers the untapped potential for artistic exploration of media derived from insects. The history, value, and ethics of insect media art are relevant topics at a time when the natural world is at unprecedented risk. Expected final online publication date for the Annual Review of Entomology, Volume 67 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Who stole my nest? Weaver nests used as nest lining

Birds stealing nest material from a neighbour’s nest is well known, but stealing entire nests is less well known. This has been reported nine times for raptors and waterbirds taking the domed nests of weaverbirds. Three waterbird species and five raptor species are involved. Nests of four weaver species were identified. Three records were from Kwa-Zulu Natal in South Africa, and the rest from elsewhere in Africa. Weaver nests included green nests, but most were old nests, and at least one occupied nest (with eggs). Since green nests were not the norm, the weaver nests were probably taken as a source of plant material, rather than for any specific benefit relating to weaver nests.

Birds using artificial plants as nesting material

Here we present the first cases of birds using artificial plants as nest material. We report our findings for the common coot (Fulica atra) from Leiden, the Netherlands, in 2019. This is the first population of freshwater birds studied for its use of anthropogenic nest materials, and together with another report from the same year, the earliest case of an entire bird population with plastic in all nests. We also report the first artificial plants used as nesting material by birds, and discuss the implications of their usage as such.

Klein_2021_Wax_wings_swarms-preprint_complete

Every facet of human culture is in some way affected by our abundant, diverse insect neighbors. Our relationship with insects has been on display throughout the history of art, sometimes explicitly, but frequently in inconspicuous ways. This is because artists can depict insects overtly, but they can also allude to insects conceptually, or use insect products in a purely utilitarian manner. Insects themselves can serve as art media, and artists have explored or exploited insects for their products (silk, wax, honey, propolis, carmine, shellac, nest material), body parts (e.g., wings), and whole bodies (dead, alive, individually, or as collectives). This review surveys insects and their products used as media in the visual arts, and considers the untapped potential for artistic exploration of media derived from insects. The history, value, and ethics of “insect media art” are topics relevant at a time when the natural world is at unprecedented risk.

Egg covering in cavity nesting birds may prevent nest usurpation by other species

Some birds cover their eggs with nest material when they leave to forage. It has been suggested that such egg-covering aids thermoregulation or prevents predation but here we present a new hypothesis, that secondary cavity-nesting species cover their eggs to prevent nest usurpation by other birds. When the bottom of the cavity is dark, as when eggs are covered by nest material, it may be difficult for a prospecting competitor to see whether a defending nest owner or a predator is hiding inside the cavity. Competitors may therefore hesitate to enter dark cavities. We filmed 21 great tit (Parus major) nests during the egg-laying period and found that the female spent bouts of highly variable length outside the nest box (range 0.3–250 min, n = 51), so prospecting small passerines would have difficulty predicting whether an aggressive tit owner was in the box or would soon return. We presented prospecting male pied flycatchers (Ficedula hypoleuca) with a dyad of boxes (n = 93), each containing a great tit nest but only one with visible eggs. Flycatchers hesitated more to enter a nest box with no visible tit eggs than a box with exposed eggs. This was most evident for nest boxes with dark versus light interior paint, supporting the idea that better interior illumination makes prospecting birds more confident about entering an unfamiliar cavity. The usurpation and predation hypotheses are not mutually exclusive because both competitors and small predators may hesitate to enter dark, enclosed spaces if visibility is low. Significance statement Some birds deposit a layer of material on top of the eggs when they leave the nest. Several hypotheses have been proposed for such egg covering, for example that it may insulate the eggs and reduce the risk of nest predation. We propose a new hypothesis, namely that secondary hole-nesting birds cover their eggs when they leave the nest to prevent usurpation of the cavity by other birds. Great tits that we filmed at the nest during the egg-laying period could be absent for long periods. To test the hypothesis, we presented male pied flycatchers, potential nest competitors, with a dyad of nest boxes, each containing a great tit nest but only one with visible tit eggs. In support of the prediction, prospecting flycatchers hesitated to enter dark cavities with dark floors relative to boxes with exposed, reflective eggs.

Dynamics of Microbial Communities on Eggshells and on Nest Materials During Incubation in the Oriental Tit (Parus Minor)

Eggshell microbial communities may affect hatching success and nestling’s condition. Nest materials are in direct contact with the eggshells, but the relationships with the eggshell microbiome during incubation have not been fully elucidated. Here, we characterize eggshell and nest-material microbial communities and their changes during incubation in the Oriental Tit (Parus minor). Microbial communities on the nest material were relatively stable and remained distinct from the eggshell communities, and had higher diversity and greater phylogenetic clustering compared to the eggshell communities from the same nest, resulting in lower phylogenetic turnover rate of nest material microbiome during incubation than expected by chance. While the species diversity of both communities did not change during incubation, we found significantly greater changes in the structure of microbial communities on the eggshell than on the nest material. However, eggshell microbiome remained distinct from nest material microbiome, suggesting independent dynamics between the two microbiomes during incubation. We detected an increase in the relative abundance of several bacterial taxa on the eggshell that likely come from the bird’s skin, feathers or cloaca/intestine, which suggests some exchange of bacteria between the incubating bird and the eggshell. Furthermore, incubation appeared to promote the abundance of antibiotic producing taxa on the eggshell, which may hypothetically inhibit growth of many bacteria including pathogenic ones. Our results suggest that the future studies should focus on simultaneous monitoring of absolute abundance as well as relative abundance in communities on eggshells, nest materials and the incubating bird’s body.