Samuel D. Hill

Using plumage and behavioural development to age New Zealand fantail nestlings

Accurate estimations of nestling ages are often required for studies of life history traits and breeding strategies of avian species. Yet detailed information on species-specific developmental patterns of chicks is scarce. In this study, we present comprehensive data on plumage and behavioural development of New Zealand fantail (Rhipidura fuliginosa placabilis) chicks during the nesting period. We also provide an illustrated guide to ageing New Zealand fantail nestlings using visual traits, based on the daily development characteristics of 15 broods. This study contributes towards understanding the life history of this species as well as forming a foundation for future comparative studies on avian life history.

It's complicated: the association between songbird extrapair paternity and within-song complexity

Many songbird species are socially monogamous while exhibiting varying extrapair paternity frequencies. Song complexity, often subject to sexual selection, similarly varies across songbird taxa. Some species form highly complex songs whereas others produce simple songs. The basis of this variability, however, is unresolved. Because selection pressures generally favour the evolution of sexually selected characteristics reflecting male quality, such as song complexity, it should be subject to extrapair mate selection. We therefore predicted a positive association between extrapair paternity frequency and songbird song complexity. In addition, we predicted that broadcast (long-range) rather than interactive songs (short-range) would be more likely to contain sexually selected characteristics, such as higher complexity, especially in species with high extrapair paternity frequencies. This was tested using tui, Prosthemadera novaeseelandiae , a species with high extrapair paternity frequency. First, analyses on 78 songbird species indicated a significant positive association between extrapair paternity frequency and within-song complexity (the level of complexity within a species-specific song) but not between-song complexity (size of species-specific song or syllable repertoire), while no phylogenetic trait conservation was found. Additionally, our results suggested tui broadcast songs had higher song complexity than interactive songs. The findings in this study indicate extrapair mate selection may play a role in the evolution of within-song complexity in songbirds.

Avian biodiversity across Auckland’s volcanic cone reserves

ABSTRACT Auckland, a city with a population of approximately 1.7 million, is located directly on the Auckland Volcanic Field, a late Quaternary-era monogenetic field. There are at least 53 volcanoes across the field, many of which are of geological, cultural and ecological significance, such as for being reserves for native species; however, few assessments of the richness of avian biodiversity across the volcanoes have been made. To address this data shortfall, we conducted avian biodiversity surveys using stationary point counts within nine of Aucklands volcanic cone reserves. Thirty-eight species were detected across the sites, of which 18 were native. Our estimates of relative species abundances and detection probabilities revealed that the most common native birds within these reserves were silvereyes, tui and southern black-backed gulls, while common mynas, house sparrows, Eurasian blackbirds and eastern rosellas were the most common introduced species. In addition to tui and silvereyes, the presence of other natives critical to the functioning of native ecosystems, such as New Zealand fantails, grey warblers and New Zealand pigeon, suggest that the volcanoes possess a diverse native avifauna supported by native flora that warrant continued and intensified restoration efforts. We discuss several feasible strategies for improving faunal and floral biodiversity across the volcanic cone reserves. Continued avian biodiversity surveys are also of critical importance as they will enable us to further evaluate and prioritise restoration projects within Aucklands multitude of diverse volcanic cone reserves.

So much for the city: Urban-rural song variation in a widespread Asiatic songbird

Song plays a fundamental role in intraspecific communication in songbirds. The temporal and structural components of songs can vary in different habitats. These include urban habitats where anthropogenic sounds and alteration of habitat structure can significantly affect songbird vocal behavior. Urban-rural variations in song complexity, song length and syllable rate are not fully understood. In this study, using the oriental magpie-robin (Copsychus saularis) as a model, we investigated urban-rural variation in song complexity, song length, syllable rate, syllable length and inter-syllable interval. Comparing urban and rural songs from 7 countries across its natural Asiatic range (Bangladesh, India, Malaysia, Nepal, Singapore, Sri Lanka and Thailand), we found no significant differences in oriental magpie-robin song complexity. However, we found significant differences in temporal song variables between urban and rural sites. Longer songs and inter-syllable intervals in addition to slower syllable rates within urban sites contributed the most to this variance. This indicates that the urban environment may have driven production of longer and slower songs to maximize efficient transmission of important song information in urban habitats.

Higher song complexity and intruder pressure at dawn in a vocally complex songbird

ABSTRACT Dawn is a critical period for vocal displays in songbirds. At dawn, songbirds intensify their vocalisations, for example increasing their singing rates in response to increased intruder pressure at this time, and for mate guarding. However, little is known about diurnal variations in song complexity, a sexually selected vocal trait associated with mate choice and territorial defence. We compared song complexity in 17 territorial male Tui (Prosthemadera novaeseelandiae) between dawn, solar noon and dusk. In addition, we investigated whether song complexity correlated directly with rival intrusion rate. Our results indicated that song complexity and intrusion rate were significantly higher at dawn than dusk. Analyses also suggested that higher entropy (spectral complexity) and syllable rate, in addition to shorter song duration, were associated with reduced intrusion rate into the singer’s territory. Males with higher song complexity may be perceived as stronger competitors and therefore would attract lower rival intrusion. Our study presents evidence of both diurnal changes in Tui song complexity and associations between song complexity and intrusion rate. These findings support the theory that dawn is important for songbird vocal communication in terms of territory assertion.

Avian biodiversity in the coastal wetlands of the Okahukura Peninsula

The Tapora Landcare Group, operating on the Okahukura Peninsula, has the long-term goal of making this region predator fenced. The aim of this study was to obtain information on the current status of avian biodiversity and the bird community across the band of coastal wetlands on the Okahukura Peninsula. Bird counts were conducted and playback lures used to detect three cryptic wetland species: fernbirds (Bowdleria punctata); spotless crakes (Porzana tabuensis); and banded rails (Gallirallus philippensis). Fernbirds and banded rails were detected at seven of the eight wetland sites sampled whereas spotless crakes were detected at two sites. The native species with the highest relative abundance across the eight sites were silvereyes (Zosterops lateralis) and South Island pied oystercatchers (Haematopus finschi). Changes in avian biodiversity over time in the region can now be monitored, and comprehensive long-term data on the status of avian biodiversity over time obtained.