Kevin A. Parker

The effects of translocation‐induced isolation and fragmentation on the cultural evolution of bird song

Understanding the divergence of behavioural signals in isolated populations is critical to knowing how certain barriers to gene flow can develop. For many bird species, songs are essential for conspecific recognition and mate choice. Measuring the rate of song divergence in natural populations is difficult, but translocations of endangered birds to isolated islands for conservation purposes can yield insights, as the age and source of founder populations are completely known. We found significant and rapid evolution in the structure and diversity of bird song in North Island saddlebacks, Philesturnus rufusater, in New Zealand, with two distinct lineages evolving in < 50 years. The strong environmental filters of serial translocations resulted in cultural bottlenecks that generated drift and reduced song variability within islands. This rapid divergence coupled with loss of song diversity has important implications for the behavioural evolution of this species, demonstrating previously unrecognised biological consequences of conservation management.

CONTEMPORARY CULTURAL EVOLUTION OF A CONSPECIFIC RECOGNITION SIGNAL FOLLOWING SERIAL TRANSLOCATIONS

The divergence of conspecific recognition signals (CRS) among isolated populations facilitates the evolution of behavioral barriers to gene flow. The influence of CRS evolution on signal effectiveness in isolated populations can be assessed by testing the salience of changes in CRS from surviving ancestral populations but founder events are rarely detected. The population history of the North Island (NI) saddleback Philesturnus rufusater is absolutely known following conservation translocations which increased the number of populations from 1 to 15. With one exception there is no gene flow between these populations. The translocations have generated interisland divergence of male rhythmical song (MRS), a culturally transmitted CRS. We conducted an experimental test of behavioral discrimination in NI saddlebacks exposed to familiar and unfamiliar MRS and found that responses were significantly stronger for familiar MRS, consistent with a model of contemporary cultural evolution leading to discrimination between geographic song variants. Significantly, this result demonstrates the rapid tempo with which discrimination of CRS might evolve within isolated populations and supports both bottleneck and cultural mutation hypotheses in CRS evolution. The evolutionary implications of contemporary cultural evolution in the production and perception of CRS merit debate on the time frames over which conservation management is evaluated.

Size dimorphism and avian‐perceived sexual dichromatism in a New Zealand endemic bird, the whitehead Mohoua albicilla

Sex differences in behavior, morphology, and physiology are common in animals. In many bird species, differences in the feather colors of the sexes are apparent when judged by human observers and using physical measures of plumage reflectance, cryptic (to human) plumage dichromatism has also been detected in several additional avian lineages. However, it remains to be confirmed in almost all species whether sexual dichromatism is perceivable by individuals of the studied species. This latter step is essential because it allows the evaluation of alternative hypotheses regarding the signaling and communication functions of plumage variation. We applied perceptual modeling of the avian visual system for the first time to an endemic New Zealand bird to provide evidence of subtle but consistent sexual dichromatism in the whitehead, Mohoua albicilla. Molecular sexing techniques were also used in this species to confirm the extent of the sexual size dimorphism in plumage and body mass. Despite the small sample sizes, we now validate previous reports based on human perception that in male whiteheads head and chest feathers are physically brighter than in females. We further suggest that the extent of sexual plumage dichromatism is pronounced and can be perceived by these birds. In contrast, although sexual dimorphism was also detectable in the mass among the DNA‐sexed individuals, it was found to be less extensive than previously thought. Sexual size dimorphism and intraspecifically perceivable plumage dichromatism represent reliable traits that differ between female and male whiteheads. These traits, in turn, may contribute to honest communication displays within the complex social recognition systems of communally breeding whitehead and other group‐breeding taxa. J. Morphol., 2010.

Parasite management in translocations: lessons from a threatened New Zealand bird

Awareness of parasite risks in translocations has prompted the development of parasite management protocols, including parasite risk assessment, parasite screening and treatments. However, although the importance of such measures seems obvious it is difficult to know whether the measures taken are effective, especially when working with wild populations. We review current methods in one extensively researched case study, the endemic New Zealand passerine bird, the hihi Notiomystis cincta . Our review is structured around four of the 10 questions proposed by Armstrong & Seddon ( Trends in Ecology & Evolution , 2008: 23, 20–25) for reintroduction biology. These four questions can be related directly to parasites and parasite management and we recommend using this framework to help select and justify parasite management. Our retrospective study of recent disease and health screening in hihi reveals only partial overlap with these questions. Current practice does not focus on, or aim to reduce, the uncertainty in most steps of the risk assessment process or on evaluating whether the measures are effective. We encourage targeted parasite management that builds more clearly on available disease risk assessment methodologies and integrates these tools within a complete reintroduction plan.

Corticosterone responses and post-release survival in translocated North Island Saddlebacks (Philesturnus rufusater) in New Zealand

Abstract The translocation of wild birds, commonly conducted as part of management of threatened and endangered populations, is a potentially stressful procedure that may have an impact on their subsequent survival. Corticosterone is the main avian stress hormone, and we examined the relationship between the corticosterone response to initial capture and handling, change in mass during a short period of captivity between capture and release, and subsequent survival after release during a translocation of North Island Saddlebacks (Philesturnus rufusater), an endemic New Zealand bird. In common with other birds, Saddlebacks had marked corticosterone responses to capture and handling. Saddlebacks confined in aviaries for 1–2 days between initial capture and release lost mass, but those confined for 3 days gained mass. The change in mass of birds after one night of confinement was not correlated with the initial corticosterone response. Survival after release to one year was high (70%) relative to four other monitored North Island Saddleback translocations (mean 53%, range 41–71%) but was not related to corticosterone response. The absence of a relationship between corticosterone response and survival may reflect benign conditions at the translocation site as suggested by this high rate of survival. The relationship between this acute corticosterone response and chronic stress and whether these physiological responses may potentially predict how individuals cope with these protocols warrants further investigation.

Population census of Cook's Petrel Pterodroma cookii breeding on Codfish Island (New Zealand) and the global conservation status of the species

Summary Codfish Island is the southernmost breeding location for Cook’s Petrel (Pterodroma cookii), endemic to the New Zealand archipelago. To provide a population estimate and indication of population growth following introduced predator eradications we conducted an island-wide survey of Codfish Island within two a priori defined strata. Plot surveys revealed only five burrows within forest habitats from 175 plots surveyed and the locations of these and other burrows observed incidentally were used to identify three key areas of Cook’s Petrel breeding activity that were subsequently surveyed using line transects. Within these areas, 42 burrows were counted with burrow densities ranging from 0.0003 to 0.002 burrows m 22 . Burrow densities in conjunction with the three-dimensional surface areas of the surveyed locations suggested a minimum of 6,194 i 956 burrows present and equated to approximately 5,000 (95% CI 3,000–6,000) breeding pairs, using a burrow occupancy estimate of 80%. The Cook’s Petrel population on Codfish Island appears to have increased markedly since Weka (Gallirallis australis ) and Pacific Rat (Rattus exulans) were eradicated in 1980 and 1998 and is consistent with a recent upwards revision of the species’ world population size of approximately 1,300,000 (900,000–1,800,000) individuals. Revised population data, and ongoing protection of Cook’s Petrel’s major breeding sites may now qualify the species for a revised conservation status moving from Endangered to Vulnerable under IUCN criteria.

Differences in vocalisations, morphology and mtDNA support species status for New Zealand saddleback Philesturnus spp

Appropriate definitions of species limits are critical for scientific study and conservation management. Many subspecies of birds are defined on the basis of phenotypic variation. However, it has been suggested that following close examination many of these subspecies will be recognised as good species. North Island (NI) (Philesturnus rufusater) and South Island (SI) saddlebacks (P. carunculatus) differ in plumage and apparent vulnerability to introduced predators and, until recently, were considered subspecific. Here, we formally compare vocalisations, morphology and mtDNA between NI and SI saddlebacks. We show significant differences in male song and chatter calls which are fundamental saddleback vocalisations. A discriminant analysis correctly allocated 90% of birds based on significantly larger tarsus, weight and wing measurements in SI saddlebacks relative to NI saddlebacks. Finally, molecular data show c. 5% sequence divergence in mtDNA between the two groups. We concur with previous work elevating NI and SI saddleback to full species.

Avian reintroduction biology: current issues for science and management

S TO SPOKEN PRESENTATIONS Developing the science of reintroduction biology

Inter-island differences in the corticosterone responses of North Island Saddlebacks (Philesturnus rufusater) in New Zealand do not suggest selective effects of translocation

Abstract North Island Saddlebacks (Philesturnus rufusater) have been the subject of a well-documented sequence of translocations to isolated islands around New Zealand. We measured corticosterone stress responses in North Island Saddlebacks derived from the ancestral population and from a series of three sequential translocations. Each translocation might impose a selective pressure on the founder populations of North Island Saddleback. This selective filter might favour a particular corticosterone response linked through an associated coping ability. Evidence of selection would be reflected in a progressive shift in the mean corticosterone response related to the number of sequential translocations. Mean corticosterone responses to a standardised stressor were highest in birds descended from a population subject to two sequential translocations. However, responses measured at localities representing the original source population and populations derived from one and three sequential translocations were not significantly different from each other. Accordingly, our data suggest that translocations do not necessarily cause directional selection on the stress responses of these vulnerable populations of birds.

Morphometric and genetic sexing in the Gough Moorhen Gallinula comeri

To develop an accurate, low-cost method for sexing Gough Moorhens Gallinula comeri using morphometric measurements, twelve measurements were taken from 59 birds and validated against genetic sexing. The classification accuracy of variables was determined and discriminant analysis was used to test whether multiple variables improved accuracy. Males were larger than females in all dimensions. Head length reliably differentiated male and female Gough Moorhens. A threshold of 64 mm correctly classified 92% of the sample birds; adding other variables did not improve accuracy. Gough Moorhens can be sexed with an acceptable level of accuracy using a single morphometric variable, but genetic sexing is needed to confirm the sex of individuals that fall within the overlap zone (62–66 mm).