Estimating site occupancy and detectability of the threatened partridge pigeon (Geophaps smithii) using camera traps

Since European settlement, many granivorous birds of northern Australia's savanna landscapes have declined. One such example, the partridge pigeon (Geophaps smithii), has suffered a significant range contraction, disappearing from at least half of its pre‐European range. Multiple factors have been implicated in this decline, including the loss of traditional Aboriginal burning practices, grazing by large exotic herbivores and predation by feral cats (Felis catus). While populations of partridge pigeon on the Tiwi Islands may be particularly important for the long‐term persistence of this species, they too may be at risk of decline. However, as a reliable method to detect this species has not yet been developed and tested, we lack the ability to identify, at an early stage, the species' decline in a given location or region. This severely limits our capacity to make informed management decisions. Here, we demonstrate that the standard camera trapping approach for native mammal monitoring in northern Australia attained an overall probability of detecting partridge pigeon greater than 0.98. We thus provide a robust estimate of partridge pigeon site occupancy (0.30) on Melville Island, the larger of the two main Tiwi Islands. The information presented here for the partridge pigeon represents a critical first step towards the development of optimal monitoring programmes with which to gauge population trajectories, as well as the response to remedial management actions. In the face of ongoing biodiversity loss, such baseline information is vital for management agencies to make informed decisions and should therefore be sought for as many species as possible.     

SHIFTS IN BILATERAL ASYMMETRY WITHIN A DISTRIBUTION RANGE: THE CASE OF THE CHUKAR PARTRIDGE

Abstract Three major types of bilateral asymmetry (fluctuating asymmetry, directional asymmetry, and antisymmetry) have long been recognized in the literature. Little, however, is known about transitions between asymmetry types, especially in natural populations. It is often assumed that directional asymmetry and antisymmetry have a larger genetic basis than fluctuating asymmetry. This leads many scientists to exclude traits or populations showing either directional asymmetry or antisymmetry from developmental instability studies, focusing attention on fluctuating asymmetry alone. This procedure may bias the findings and thus our understanding of patterns of bilateral asymmetry and the factors influencing it. To examine changes in bilateral asymmetry across the distribution range of a species, I studied the length of the third toe in 11 chukar partridge (Alectoris chukar) populations across a steep environmental gradient of 320 km within the species' range in Israel. This trait was selected due to its adaptive value in the chukar, a species that spends much of its activity walking, and due to its high measurement repeatability. Moving from the core toward the very extreme periphery of the range, the following four trends are detected: (1) the expression of the directional asymmetry component significantly increases; (2) the frequency of symmetrical individuals in the population significantly decreases, with a sharp decline at the steepest part of the climatic and environmental gradient studied, within the Mediterranean‐desert ecotone; (3) mean asymmetry levels, as estimated using the unsigned difference between the right and left toe, significantly increases; and (4) the range of asymmetry increases such that the most asymmetrical individuals originate from the very edge of the range. These findings provide primary evidence that substantial shifts in asymmetry may occur across short geographical distances within a species' distribution range. They show a continuum between asymmetry types and support the notion that all three types of asymmetry can reflect developmental instability. Further studies of developmental instability should be designed so that they enable detection of transitions between asymmetry types across natural populations. Such a procedure may partly resolve some of the contradictions seen in the literature regarding the relationship between bilateral asymmetry and environmental stress.     

Cytochrome P450 enzyme activity in five herbivorous,non-passerine bird species

We examined hepatic cytochrome P450 activity in wild and hand-reared grey partridges (Perdix perdix), capercaillies (Tetrao urogallus) and ring-necked pheasants (Phasianus colchicus), as well as the enzyme activity in a variety of tissues of hand-reared Japanese quails (Coturnix coturnix japonica) and pigeons (Columba livia). Post-mortem decrease in hepatic enzyme activity in the grey partridge was measured. Hepatic 7-ethoxyresorufin-O-deethylase activity was similar in wild and hand-reared grey partridges and pheasants, but the activity was significantly lower in wild than in hand-reared capercaillies, probably resulting from their phenolic-rich diet. In the tissues of both quails and pigeons 7-ethoxycoumarin-O-deethylase exhibited the highest and 7-pentoxyresorufin-O-deethylase the lowest activity. Hepatic enzyme activity was significantly higher than that in other tissues. In the small intestine some activity could be found, reflecting some intestinal detoxication capacity. Enzyme activity decreased by 34-69% during the 30-min sampling period, which confirmed the importance of equalising sampling time to obtain comparable data. Because the hand-reared birds in this study were fed the same commercial diets, we assumed that the enzyme activity values detected reflect species differences without any induction by dietary secondary compounds.     

Introgression of chukar genes into a reintroduced red-legged partridge (Alectoris rufa) population in central Italy

Insight regarding the genetic origin and composition of the studied population of the red-legged partridge (Alectoris rufa) is likely to provide general and critical information for the appropriate management and possible conservation of the species. The reintroduced population of red-legged partridges living in Pianosa Island (National Park Tuscany Archipelago) has proven to be sustainable: captive-bred individuals, morphologically assigned to the taxon A. rufa, were released to the island approximately 20 years ago, establishing an apparently well-adapted population. We have investigated this population by means of 10 microsatellite loci in order to shed light on its genetic structure. Considering that A. rufa is known to crossbreed with A. chukar, the Pianosa Island population was compared at the molecular level with a red-legged partridge breeding stock (Aulla, MS) as well as with a population of pure A. chukar. Our results indicate that the red-legged partridge population from Pianosa, morphologically identified as A. rufa, is actually partly introgressed with A. chukar, questioning its genetic purity and the possible use of this population as a starting stock for future reintroductions elsewhere.     

What happens to translocated game birds that 'disappear'?

The ultimate goal of most translocation efforts is to create a self-sustaining wild population of a species deliberately moved from one part of their range to another. As follow-up of a translocation attempt is often difficult, causes for failure are relatively unknown. Dispersal away from the release site is one potential source of failure because it decreases the likelihood of the released population establishing itself post-translocation. In this study, we used chukar Alectoris chukar as a surrogate for translocated game birds in order to conduct a large-scale experimental study. We observed that these desert-adapted birds demonstrate a strong fidelity for specific water sources. We also report the propensity for the translocated individuals to either disperse and return to their original water source site or remain at the release site. During two field seasons, we observed opposing behaviors such that the proportion of individuals returning to the capture site, versus those remaining at the release site, shifted between years. We analyzed this change between the years as well as within the years to assess the potential underlying causes such as translocated distance, differences in rainfall between seasons and water source type. We concluded that homing behavior was strong in this non-migratory bird species and that strength of this homing behavior varied, potentially due to conditions surrounding the limiting resource, water availability. The large-scale, original data presented here may help to explain why some releases result in a successfully established population while other releases result in widely dispersed individuals.     

Field evidence for apparent competition mediated via the shared parasites of two gamebird species

Although apparent competition mediated via shared parasites is potentially an important force influencing community structure, there is limited evidence to demonstrate its occurrence in the field. Here we show that the intensity of infection by the caecal nematode Heterakis gallinarum picked up by naive grey partridges, both maintained in pens and released on six gamebird estates in the UK, is significantly correlated with the intensity of infection recorded in the previous year from pheasants on those estates. Furthermore, the worm burdens picked up appeared to be sufficient to negatively influence host condition. These results provide evidence that infection from pheasants determines the worm burdens of partridges in the field, supporting the hypothesis that parasite-mediated apparent competition with the pheasant may be a factor influencing the decline and subsequent recovery of wild grey partridges.     

四川山鹧鸪繁殖期的鸣声行为特征

2005年4—12月在四川老君山自然保护区,通过计算机声谱分析技术,对四川山鹧鸪(Arborophilarufipectus)雄性的鸣声行为特征进行了研究,其结果表明,雄性单音节鸣声出现在啼叫、保护领域和求偶中,这些鸣声持续时间差异明显,主峰值差异不明显;雄性双音节鸣声出现在啼叫、保护领域、竞争雌体和求偶中,这些鸣声第一音节时间、第二音节时间、音节间隔时间和主峰值差异极显著,全句时间差异不明显;雄性多音节鸣声出现在保护领域、警戒和惊吓中。雄性亚成体多音节鸣声出现在惊吓和警戒中;雄性成体和亚成体警戒鸣叫的音节持续时间、音节间隔时间和主峰值差异均不明显,全句持续时间差异明显;雄性亚成体和雄性成体的惊吓鸣叫音节持续时间、音节间隔时间、全句持续时间和主峰值差异均不明显。四川山鹧鸪表现出的各种鸣声行为是为了保护配偶和防止天敌,使该种群更好地繁衍。     

鹧鸪胃的动脉分布

为了研究鹧鸪腺胃和肌胃的动脉分布状况,本实验用血管铸型法对10只鹧鸪胃的动脉分支和分布情况进行了详细的解剖观察。结果表明,鹧鸪的腺胃由腺胃背侧动脉和腺胃腹侧动脉供应营养,肌胃由胃左动脉和胃右动脉供应,肌胃背侧动脉是胃右动脉的一末端分支,肌胃腹侧动脉由胃左动脉分出。