Beach-foraging behaviour of Forest Ravens Corvus tasmanicus and an Australian Magpie Gymnorhina tibicen at Wilsons Promontory, Victoria

Observations are presented of Forest Ravens Corvus tasmanicus, and an Australian Magpie Gymnorhina tibicen, foraging by gleaning the sand on a beach.

Climatic variation and breeding in the Australian magpie (Gymnorhina Tibicen) : a case study using existing data

To anticipate the effects of climate change on Australia’s avifauna, it is first necessary to understand the current effects of climate (including climate variability) on life histories, and to examine the scope and nature of existing data that may provide the necessary historical context to anticipate the effects of climate change. This study examines naturally occurring geographical gradients (altitude, latitude) and the Southern Oscillation Index (SOI) as integrated measures of climate. These are then compared with the timing and ‘amount’ of breeding recorded for the Australian Magpie (Gymnorhina tibicen) using data from Birds Australia’s Nest Record Scheme and Atlas of Australian Birds, the NSW Bird Atlassers Inc.’s NSW Bird Atlas, and the Canberra Ornitholgists Group’s Garden Bird Survey. For this common, easily identified species, these data suggest links between Australian Magpie breeding and all three environmental variables. Breeding became later as altitude increased, the proportion of breeding records increased from north to south, and years of high SOI corresponded to more (and earlier) breeding in this species. That annual climatic fluctuations have a direct, immediate and substantial effect on breeding in the Australian Magpie, particularly on the amount of breeding that occurs, implies that longer term changes in climate will have substantial impacts on populations. Results were not solely temperature-driven, which makes predicting climate change impacts difficult. For rainfall, predictions are far less precise and regional variation is higher. The results also highlight the potential and limitations of current survey techniques for documenting the impacts of climate change on birds; in particular, the Nest Record Scheme does not measure the amount of breeding that occurs, but a useful index of this can be derived from bird atlassing data

Effects of artificial foods on the blood chemistry of the Australian magpie

Bird feeding on residential property is a popular activity throughout Western countries. Advocates insist the practice is beneficial, while opponents maintain that it can result in a wide range of negative outcomes including malnutrition. The biological effects of 'backyard feeding' were studied in Australian magpies Gymnorhina tibicen during the non-breeding season in 1999 in the Greater Brisbane and the Lockyer Valley regions, south-east Queensland, Australia. Six magpie populations were selected and 70 birds were individually tagged for identification. The birds were provided with processed foods, 20-40 g per bird daily. To monitor the effects of the food, blood chemistry and body mass (BM) were used as indices. Significant effects were observed in BM and plasma cholesterol (PC), showing strong sensitivity to food provisioning. Significant effects on PC and uric acid were found only when birds were fed dog sausage. Results suggest that blood PC levels in magpies are readily influenced by, probably, the lipids present in food, and that the type of food can affect blood PC levels. These effects may occur widely among fed magpies if the influence that we demonstrated at plasma level can be generalized. Following the free-ranging study, six magpies were captured and subjected to a 6-day captive experiment to determine whether the selected foods had the potential to alter the birds' blood chemistry. It was found that all of the foods, when provided ad libitum, influence at least two of the three blood parameters (PC and non-esterified fatty acids). Due to its popularity, wildlife feeding will continue. To make wildlife-feeding activities truly sustainable, there is a need for further studies. This study clearly demonstrated that the physiology of wild magpies can be affected by 'backyard feeding'.

Attacks on humans by Australian Magpies (Cracticus tibicen): Territoriality, brood-defence or testosterone?

Attacks on humans by Australian Magpies (Cracticus tibicen) are a significant human-wildlife conflict in Australia, especially in suburban environments. Remarkably little is known about the phenomenon. In this study, we explored three common hypotheses - territoriality, brood-defence and testosterone - as potential and non-exclusive explanations for aggression directed at people by Magpies living in suburban areas of Brisbane, south-eastern Queensland. The response of 10 pairs of aggressive Magpies to natural levels of human intrusion was compared with that of 10 non-aggressive pairs. Behavioural observations strongly supported the contention that attacks on humans resemble brood-defence and did not support an association with territoriality. The study also found no support for the suggestion that testosterone levels correlated with aggressiveness towards humans: male testosterone peaked immediately before laying and was significantly lower during the maximum period of attacks directed at people. Moreover, there were no differences in the testosterone levels of aggressive and non-aggressive male Magpies. The pattern of testosterone production over a breeding cycle closely resembled that of many other songbirds and appeared not to influence Magpie attacks on humans. © Royal Australasian Ornithologists Union 2010.

Population structure and reproductive period of the tropical hermit crab Calcinus tibicen (Decapoda : Diogenidae) in the region of Ubatuba, São Paulo, Brazil

The population of the hermit crab Calcinus tibicen in the Ubatuba region was studied with emphasis on seasonal abundance, seasonal size-frequency distribution, sex-ratio, and reproductive period based on the percentage of ovigerous females. The animals were collected at 2-month intervals for 2 consecutive years (from January 1993 to November 1994). Total mean animal size in shield length was 5.14 +/- 1.23 mm for males, 4.23 +/- 0.79 mm for females, and 4.53 +/- 0.60 for ovigerous females. A discontinuity in reproduction was observed, with an absence of ovigerous females in July (winter) and a high incidence from September to May (spring to autumn). Calcinus tibicen is sexually dimorphic in relation to size, with a higher growth rare in males. The sex-ratio pattern changes with season, indicating that it is more a function of season or habitat than of size.

Morphometry and sexual maturity of the tropical hermit crab Calcinus tibicen (Crustacea, Anomura) from Brazil

Ontogenetic changes in relative growth were studied in the hermit crab Calcinus tibicen in order to determine its growth phases with sexual maturity. Specimens were collected at 2-month intervals for two consecutive years. A total of 570 individuals was collected and analysed. Total mean animal size in terms of shield length was 5.14±1.23mm for males, 4.23±0.79mm for females and 4.53±0.60mm for ovigerous females. Sexual dimorphism in chela dimensions was stronger in males than in females. Differences between males and females were found in left propodus length (LPL) and height (LPH) versus shield length (SL) and wet weight (WW) versus SL relationships. Males showed a high positive allometry, while juveniles and adult females were isometric for the LPL/SL relationship. Negative allometry was observed in adult females in the LPL/SL relationship. The size at which a differentiation occurred in the growth of the chelipeds and in the weight gain of males and females was between 3.0 and 3.2mm SL, suggesting that sexual maturity occurs in small-sized individuals in the life cycle of C. tibicen.