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.

Song characters as reliable indicators of male reproductive quality in the Savannah Sparrow (Passerculus sandwichensis)

Bird song may provide female birds with signals of male quality. To investigate this potential for sexual selection via female choice, we assessed the relationships between male song variation and male mating and reproductive success of the Savannah Sparrow (Passerculus sandwichensis (J.F. Gmelin, 1789)) over 3 years (2001–2003) in a population of Savannah Sparrows near London, Ontario, Canada. We measured song rate, as well as temporal and frequency attributes of song structure, as possible predictors of male quality, and then related these measures to attributes of male reproductive performance (mating and breeding success and territory size of males). We found significant correlations between male reproductive performance and several song features, such that the combined effects of two trill sections could potentially play an important role: males possessing such songs arrived and paired earlier and had higher fledging success. The results suggested that the trill segments of the song may signal important aspects of male quality. Possible reasons for significant roles of such songs in open-habitat birds are discussed.