Importance of Montane Riparian Forest and Influence of Wildfire on Nest-Site Selection of Ground-Nesting Birds

Abstract: We studied breeding populations of 2 coexisting ground-nesting birds, the red-faced warbler (Cardellina rubrifrons) and yellow-eyed junco (Junco phaeonotus), in high-elevation (>2,000 m) forested drainages of the Santa Catalina Mountains, Arizona, USA. From 2004 to 2005, we 1) estimated density and nesting success of breeding populations of red-faced warblers and yellow-eyed juncos, 2) identified nest-site characteristics for each species (i.e., used sites vs. random plots), 3) compared nest-site characteristics between the 2 species, and 4) examined effects of a recent (2003) wildfire on distribution of nests of both species. In addition, we estimated the areal extent of montane riparian forest (the preferred breeding habitat of both species) within high-elevation forests of the Santa Catalina Mountains. We found that red-faced warblers and yellow-eyed juncos were the 2 most common ground-nesting birds within our study area with an average density of 2.4 and 1.4 singing males/ha, respectively, along drainage bottoms. Compared to random plots, most red-faced warbler and yellow-eyed junco nests were located close (≤30 m) to drainage bottoms within a strip of montane riparian forest characterized by abundant brush, small woody debris, ferns, and forbs (both species), high number and diversity of saplings and small trees (red-faced warblers), and abundant shrubs and downed logs and less canopy cover (yellow-eyed juncos). Although both species nested in close proximity within montane riparian forest, nest-site characteristics differed between the 2 species, especially at finer spatial scales. For example, most yellow-eyed juncos nested adjacent to grass (principally Muhlenbergia spp.), whereas red-faced warblers nested adjacent to a variety of plant species, including grass, bigtooth maple (Acer grandidentatum), white fir (Abies concolor), and Douglas-fir (Pseudotsuga menziesii). Both red-faced warblers and yellow-eyed juncos avoided nesting in areas burned during a recent wildfire. In addition, nesting success was low for red-faced warblers (13%) and yellow-eyed juncos (19%) following the wildfire, suggesting an indirect negative effect of fire on breeding populations in the short-term. Montane riparian forest appears to provide important breeding habitat for red-faced warblers and yellow-eyed juncos. However, little research or conservation planning has been directed toward montane riparian forest in the region, even though this forest type is limited in its areal extent (<11% of high-elevation forest in the Santa Catalina Mountains) and increasingly threatened by disturbance. Results from our study can be used to facilitate the management and conservation of breeding populations of red-faced warblers and yellow-eyed juncos in high-elevation forests of the southwestern United States.     

Recent postglacial range expansion drives the rapid diversification of a songbird lineage in the genus Junco

Pleistocene glacial cycles are thought to have played a major role in the diversification of temperate and boreal species of North American birds. Given that coalescence times between sister taxa typically range from 0.1 to 2.0 Myr, it has been assumed that diversification occurred as populations were isolated in refugia over long periods of time, probably spanning one to several full glacial cycles. In contrast, the rapid postglacial range expansions and recolonization of northern latitudes following glacial maxima have received less attention as potential promoters of speciation. Here we report a case of extremely rapid diversification in the songbird genus Junco as a result of a single continent-wide range expansion within the last 10 000 years. Molecular data from 264 juncos sampled throughout their range reveal that as the yellow-eyed junco (Junco phaeonotus) of Mesoamerica expanded northward following the last glacial maximum, it speciated into the dark-eyed junco (Junco hyemalis), which subsequently diversified itself into at least five markedly distinct and geographically structured morphotypes in the USA and Canada. Patterns of low genetic structure and diversity in mitochondrial DNA and amplified fragment length polymorphism loci found in dark-eyed juncos relative to Mesoamerican yellow-eyed juncos provide support for the hypothesis of an expansion from the south, followed by rapid diversification in the north. These results underscore the role of postglacial expansions in promoting diversification and speciation through a mechanism that represents an alternative to traditional modes of Pleistocene speciation.     

Investigating food limitations in wild fisheries: the attendance and growth responses of fish at an anthropogenic feeding station within a temperate estuary

To investigate whether wild fish populations are food limited, this study explored whether the provision of supplementary food had a positive effect on the abundance, condition and growth characteristics of estuarine fish assemblages in New Zealand. Feed (7690 kg) was delivered from an anthropogenic feeding station over a 60-week period to a naturally occurring assemblage of wild fish. Yellow-eyed mullet (Aldrichetta forsteri) of juvenile, sub-adult and newly matured size classes were the dominant species actively foraging at the feeding station throughout its operation, whereas larger piscivorous species visited and foraged from the feed station over the summer period only. Other species were present in the wider area of Nelson Haven, but not at the feed station. No obvious changes in the condition factor of yellow-eyed mullet were observed across the period of monitoring, and no changes in their catchability were detected – although marked seasonal variation in catch rates was observed. Results from tag-recapture data identify that the length-based growth rates of yellow-eyed mullet recaptured near the feed station were higher than those of tagged individuals recaptured at a nearby comparison site, and were higher than the growth rates observed in natural populations of yellow-eyed mullet in the wider region. Shifts in the median size of fish, as observed by acoustic observations, agreed with the tag-recapture data. Although some of the results identified were not amenable to statistical analyses, the attendance of yellow-eyed mullet at the feeding station, in combination with the improved estimates of growth by most of the techniques employed, indicates that yellow-eyed mullet are food limited in their natural environment and that the growth performance of these fish can be positively affected by the increased availability of food.     

Avian malaria parasites (

There is concern that avian malaria may be partly responsible for fluctuations in yellow-eyed penguin (Megadyptes antipodes) populations in New Zealand. Recent findings, however, have provided no evidence of avian malaria parasites infecting yellow-eyed penguins on the Otago Peninsula, raising questions as to whether this area is currently free of such parasites. To test this possibility we collected blood samples from 109 individuals of five non-native bird species known to carry malarial parasites elsewhere in New Zealand. Molecular screening by polymerase chain reaction revealed 6% of the sampled birds were positive for malarial parasites, indicating that a local reservoir of infection is present. Sequence data revealed a generalist strain of Plasmodium is present, one that infects a number of native and non-native bird species elsewhere in the country. The absence of this generalist strain in yellow-eyed penguins, some of which were sampled during the same period as the current study, may be due to low levels of mosquito vectors of disease during the study period, low densities of non-native birds around yellow-eyed penguin colonies, or infected penguins dying before they could be sampled. Continued monitoring of mosquito populations and the factors that affect their densities should be included in the future management of native birds in this area.     

Comparison of population numbers of yellow-eyed penguins,

During a comprehensive survey in 1999, 2000 and 2001, we investigated the number of breeding yellow-eyed penguin pairs on Stewart Island, where cats are present, and on adjacent cat-free islands. We found 79 pairs of yellow-eyed penguin breeding in 19 discrete locations on Stewart Island (4.2 pairs per location), and 99 pairs breeding in 10 discrete locations on all cat-free islands (9.9 pairs per location). Large-scale humaninduced habitat modifications have not occurred on Stewart Island, nor on any of its adjacent offshore islands. While the extensive coastline of Stewart Island (673 km) offers potentially large areas of breeding habitat for penguins, the highest number of breeding pairs were found on the smaller, predator-free Codfish Island (25 km coastline), where a total of 61 breeding pairs were recorded. On Stewart Island, where mustelids do not occur, only feral cats can pose a serious threat to penguin offspring. Results from this study suggest that feral cats may prey on yellow-eyed penguins on Stewart Island. Further work is necessary to investigate whether the observed low numbers of yellow-eyed penguins on Stewart Island are caused by feral cat predation. If so, it may be possible to develop appropriate measures to protect this penguin species from a population decline.     

γ-Radiation studies of two strains of Trichoplusia ni: Sensitivity of the compound eye and induced sterility

The visual response of laboratory-reared wild-type and yellow-eyed mutant (lacking pigments) cabbage loopers, Trichoplusia ni, was studied by standard electroretinogram (ERG) techniques. The ERG waveform, time to dark-adapt, maximum sensitivity, and flicker fusion frequency (FFF) of both strains and sexes were compared with those of moths treated with 15 and 30 krad of γ-radiation. From the rate of dark adaptation, yellow-eyed moths were initially more sensitive than wild-type moths, but no significant differences were apparent in the ERG waveform, total time to dark-adapt, and FFF between strains, sexes, or treatment groups. However, both sexes of both strains exhibited increased sensitivity (required less light to evoke a threshold response when fully dark-adapted) to light stimulus when they had been treated with 15 krad of γ-radiation.A comparison of the effects of irradiation on the fertility and fecundity of the two strains showed no significant differences between the number of eggs oviposited by inseminated females. However, the lower egg hatch by yellow-eyed females at most dose levels indicated reduced egg viability for the yellow-eyed genotype. Thus, a significant dose × strain interaction was found when the percentage of egg hatch of the two strains was compared.     

When close neighbours become good friends: plasticity of behavioural traits in sympatric fishes that form mono- and mixed-species groups

Like mono-species fish groups, formation of mixed-species assemblages is likely driven by trophic influences and interspecific behavioural traits. Our aim was to identify how sympatric estuarine species of differing phenotypes form mixed-species group associations, and to identify changes to group structure of fish that migrate between mono- and mixed-species groups. We used sympatric yellow-eyed mullet (Aldrichetta forsteri), kahawai (Arripis trutta), and Australian snapper (Chrysophrys auratus), representing different phenotypes for the mixed-species group, and yellow-eyed mullet for the mono- and mixed-species comparison. Group formation and structure was quantified in predator and foraging treatment groups. We used previous research in mono-species yellow-eyed mullet to compare behavioural plasticity with the current study. Our novel results suggest similar behavioural traits in mono- and mixed-species fish groups have beneficially co-evolved and importantly, behavioural plasticity is necessary for migration between groups. Overall, our observations highlight key behavioural responses associated with mixed-species fish formations in estuarine ecosystems.     

Straight Line Foraging in Yellow-Eyed Penguins: New Insights into Cascading Fisheries Effects and Orientation Capabilities of Marine Predators

Free-ranging marine predators rarely search for prey along straight lines because dynamic ocean processes usually require complex search strategies. If linear movement patterns occur they are usually associated with travelling events or migratory behaviour. However, recent fine scale tracking of flying seabirds has revealed straight-line movements while birds followed fishing vessels. Unlike flying seabirds, penguins are not known to target and follow fishing vessels. Yet yellow-eyed penguins from New Zealand often exhibit directed movement patterns while searching for prey at the seafloor, a behaviour that seems to contradict common movement ecology theories. While deploying GPS dive loggers on yellow-eyed penguins from the Otago Peninsula we found that the birds frequently followed straight lines for several kilometres with little horizontal deviation. In several cases individuals swam up and down the same line, while some of the lines were followed by more than one individual. Using a remote operated vehicle (ROV) we found a highly visible furrow on the seafloor most likely caused by an otter board of a demersal fish trawl, which ran in a straight line exactly matching the trajectory of a recent line identified from penguin tracks. We noted high abundances of benthic scavengers associated with fisheries-related bottom disturbance. While our data demonstrate the acute way-finding capabilities of benthic foraging yellow-eyed penguins, they also highlight how hidden cascading effects of coastal fisheries may alter behaviour and potentially even population dynamics of marine predators, an often overlooked fact in the examination of fisheries’ impacts.     

Diet of feral house cats Felis catus, ferrets Mustela furo and stoats M. erminea in grassland surrounding yellow-eyed penguin Megadyptes antipodes breeding areas, South Island, New Zealand

Spring and summer diets of feral house cats ( Felis catus ), ferrets ( Mustela furo ) and stoats ( M. erminea ) were studied in grassland surrounding breeding areas of yellow-eyed penguins ( Megadyptes antipodes ), a regionally threatened native species. All three predator species ate large numbers of young rabbits ( Oryctolagus cuniculus ) and birds. Stoats also relied heavily on mice ( Mus musculus ). Use of rabbits increased in rank order of increasing predator size, and male stoats ate more lagomorphs than female stoats. Diet differences may reflect character displacement as a result of exploitation competition, but interference competition or predation may force the smaller species to exploit micro-habitats with increased ground cover and consequent increased availability of smaller prey. Reduction of predation of native species like yellow-eyed penguins by decreasing or increasing staple mammal prey numbers of the introduced predators may provide lasting conservation benefits, but could also trigger diet changes that increase risk to endangered wildlife.     

Hormonal correlates of parental behavior in yellow-eyed penguins (Megadyptes antipodes)

Penguins show varying degrees of brood reduction behavior, from obligate brood reducers to brood maximizers, and we hypothesize that this is associated with differences in prolactin secretion. To address this hypothesis, we determined the breeding season prolactin profile of the yellow-eyed penguin (Megadyptes antipodes) for comparison with those of other penguin species found in the literature. We also measured sex steroid plasma concentrations to better characterize the reproductive cycle of the species. Plasma concentrations of prolactin increased from early in the season, reaching a peak during late incubation, and remained elevated up to the guard period. This general pattern was similar to that of other penguins for which we have corresponding data. However, we found that throughout the laying period, prolactin titers in yellow-eyed penguins remained elevated while they fell to basal levels after the laying of the first egg in macaroni penguins, which corresponds to differences in incubation behavior during this time. We conclude, therefore, that differences in the brood reduction behavior in penguins, may be reflected in the pattern of PRL concentrations around the time of egg laying.     

Patterns of nest relief during incubation,and incubation period variability in the yellow-eyed penguin (Megadyptes antipodes)

Abstract

Daily nest checks were used to determine the yellow-eyed penguin’s pattern of nest relief during incubation, and to examine the inter-pair variability in incubation period. Nests at two breeding areas on the Otago Peninsula were visited between September and December in 1985 and 1986. At each visit, status of the nest and the identity and behaviour of the sitting bird was recorded. Incubation is shared between the sexes, with males tending to sit longer than females. Incubation spells ranged from 1–7 days with a mode of 1–2 days. Records of lone incubation following mate death show the yelloweyed penguin to be capable of 15 day unrelieved spells at the nest The incubation period of the yellow-eyed penguin ranges from 39–51 days and is the most variable of all penguins. This variability is because of the failure of some individuals to adequately cover the clutch until up to 5 days after the laying of the second egg.     

Yellow-eyed piranhas produce louder sounds than red-eyed piranhas in an invasive population of Serrasalmus marginatus

Serrasalmus marginatus is a piranha species native from the lower Paraná River basin and has been invasive in the upper Paraná River basin since the 1980s. In piranhas, sounds of different species have different features. The aim of this study was to investigate if the sounds produced by this species could be used to distinguish two morphotypes: red- and yellow-eyed S. marginatus from the Araguari River (upper Paraná River basin). All the temporal and frequency features of the sounds were equivalent in both groups of eye colour; it corresponds to the species-specific signature described for S. marginatus. Nonetheless, the amplitude features were all statistically different between red- and yellow-eyed piranhas. Yellow-eyed specimens produced louder sounds. In different fish species, colour change in eyes can be due to the absence or the presence of a dominant allele. It can also be involved in social rank or during reproduction. Different hormones and neuropeptides can modulate vocal features. It is hypothesized that a mutation or different hormonal concentrations could explain both sound amplitude and eye colour playing a role in animal communication in S. marginatus.     

Multilocus assignment analyses reveal multiple units and rare migration events in the recently expanded yellow-eyed penguin (Megadyptes antipodes)

The identification of demographically independent populations and the recognition of management units have been greatly facilitated by the continuing advances in genetic tools. Managements units now play a key role in short-term conservation management programmes of declining species, but their importance in expanding populations receives comparatively little attention. The endangered yellow-eyed penguin ( Megadyptes antipodes ) expanded its range from the subantarctic to New Zealand's South Island a few hundred years ago and this new population now represents almost half of the species' total census size. This dramatic expansion attests to M. antipodes' high dispersal abilities and suggests the species is likely to constitute a single demographic population. Here we test this hypothesis of panmixia by investigating genetic differentiation and levels of gene flow among penguin breeding areas using 12 autosomal microsatellite loci along with mitochondrial control region sequence analyses for 350 individuals. Contrary to our hypothesis, however, the analyses reveal two genetically and geographically distinct assemblages: South Island vs. subantarctic populations. Using assignment tests, we recognize just two first-generation migrants between these populations (corresponding to a migration rate of < 2%), indicating that ongoing levels of long-distance migration are low. Furthermore, the South Island population has low genetic variability compared to the subantarctic population. These results suggest that the South Island population was founded by only a small number of individuals, and that subsequent levels of gene flow have remained low. The demographic independence of the two populations warrants their designation as distinct management units and conservation efforts should be adjusted accordingly to protect both populations.     

Effects of artificial social stimuli on the reproductive schedule and hormone levels of yellow-eyed penguins (Megadyptes antipodes)

The effects of social stimuli on avian reproductive behaviors such as breeding schedules and courtship behaviors are well known due to numerous field studies. However, studies that have simultaneously examined the effects of social stimuli on reproductive behavior and the mediating endocrine mechanisms have been largely restricted to captive populations, which may not be representative of free-living populations. This study, conducted over two breeding seasons, aimed to simultaneously measure the effects of experimentally increasing auditory stimuli on the breeding schedule and endocrinology (levels of total androgen, estradiol, progesterone and prolactin) on free-living yellow-eyed penguins (Megadyptes antipodes). The yellow-eyed penguin is the least colonial of all penguins, nesting far apart from each other under dense vegetation, and, therefore, is presumed to experience much lower levels of social stimuli than other penguins. Egg laying was significantly more synchronous and tended to be earlier when birds were exposed to playbacks of the calls of conspecifics in 1 year of the study. We also found that levels of total androgen and estradiol of males in 1 year, and prolactin in another year, were proportionally higher among treated birds compared control birds that received no artificial auditory stimuli. These results show that even among supposedly solitary nesters, social stimuli could still play a role in influencing reproductive behavior and physiology. For the first time in free-living seabirds, we have demonstrated that behavioral responses to increased social stimuli are associated with hormonal changes.     

An empirical demonstration of risk-sensitive foraging preferences

We report laboratory experiments with yellow-eyed juncos (Junco phaeonotus) revealing that the birds' foraging preferences for variable rewards respond not only to the mean, but also the variance, of food rewards. The nature of their preferences for variable rewards is related to their expected daily energy budget. We summarize the birds' preferences in utility functions for energetic rewards. Since mean reward size is inadequate to predict their behaviour, we believe that foraging models should consider environmental stochasticity and an animal's response to this variation.     

A new location-scale test based on a combination of the ideas of Levene and Lepage

Lepage's test combines the Wilcoxon rank-sum and the Ansari-Bradley statistics. We propose to replace the latter statistic by a Wilcoxon rank-sum calculated after Levene's transformation. We use the medians for this transformation, i.e. absolute deviations from sample medians are calculated. The new location-scale test can be carried out as a permutation test based on permutations of the original observations, the Levene transformation has to be applied for each permutation in an intermediate step to calculate the test statistic. Simulations indicate that the new test can be more powerful than an O'Brien-type test and Lepage's test, the latter is the standard nonparametric location-scale test. The new test is illustrated using real data about colony sizes of yellow-eyed penguins and an SAS program to perform the test is freely available.     

Analysis of a recessive mutation on the Y chromosome of the fly Caliphora erythrocephala

Summary In a strain of the mutantw (yellow eye colour, sex-linked and sex-limited to the females) ofCalliphora erythrocephala yellow-eyed males have been found. In connexion with the mechanism of sex-determination in this fly, their origin is explained by an alteration on the Y-chromosome (one of the III^rd large chromosomes) in form of either a pre-meiotic cross-over or a spontaneous mutation on thew ⁺-locus. For being recessive, it can become manifest only in thew strain.     

Lateralisation of visual function in yellow-eyed mullet (Aldrichetta forsteri) and its role in schooling behaviour

Lateralisation of cognitive function is a common phenomenon found throughout the animal kingdom. In fish, lateralisation is involved in visually mediated behaviours such as schooling, predator avoidance and foraging. This study sought to quantify visual laterality in yellow-eyed mullet (Aldrichetta forsteri), to determine visual asymmetries and the significance of lateralisation, and the factors which influence functional behaviours in schooling fish. Tank-based experiments investigated individual and population level lateralisation, schooling behaviour, and optic lobe asymmetry. Variation in direction and strength of lateralisation in individuals was found in juveniles, but at a population level significant bias was found in adults. Right eye biased fish had a larger right optic lobe than control fish. Strongly lateralised fish showed a tendency to occupy positions of safety within the school more frequently than control fish. In combination with observed differences in schooling behaviour, the possibility of ontogenetic plasticity in behavioural lateralisation and optic lobe morphology is suggested.     

The use of approximate Bayesian computation in conservation genetics and its application in a case study on yellow-eyed penguins

The inference of demographic parameters from genetic data has become an integral part of conservation studies. A group of Bayesian methods developed originally in population genetics, known as approximate Bayesian computation (ABC), has been shown to be particularly useful for the estimation of such parameters. These methods do not need to evaluate likelihood functions analytically and can therefore be used even while assuming complex models. In this paper we describe the ABC approach and identify specific parts of its algorithm that are being the subject of intensive studies in order to further expand its usability. Furthermore, we discuss applications of this Bayesian algorithm in conservation studies, providing insights on the potentialities of these tools. Finally, we present a case study in which we use a simple Isolation-Migration model to estimate a number of demographic parameters of two populations of yellow-eyed penguins (Megadyptes antipodes) in New Zealand. The resulting estimates confirm our current understanding of M. antipodes dynamic, demographic history and provide new insights into the expansion this species has undergone during the last centuries.     

Lagomorph abundance around yellow-eyed penguin (

Predation of yellow-eyed penguin (Megadyptes antipodes) chicks may be reduced by removing stock around penguin breeding sites because long grass may reduce lagomorph abundance and hence small mammal predators. This study tests this hypothesis in the South Island, New Zealand. The abundance of lagomorph faeces (mainly rabbit Oryctolagus cuniculus, but some European hare Lepus europaeus) was used as an index of relative abundance of lagomorphs at 16 penguin breeding sites in winter 1991 and 37 sites in 1992/93. There was no evidence that lagomorph pellet abundance was reduced where vegetation was ungrazed. Lagomorph sign was widespread throughout ungrazed areas indicating that the entire ungrazed area and not merely the edge was used by lagomorphs. Lagomorph pellet abundance was higher on sand dunes than elsewhere. Retirement from grazing by stock may help protect and provide nesting habitat for penguins, but does not decrease lagomorph abundance close to nesting sites. Iris not yet known whether high lagomorph abundance leads to increased or decreased predation on penguin chicks. The habitat should not be modified ostensibly to reduce lagomorph abundance until the effect on predation is known.