Predator feeding ecology on Patagonian rocky outcrops: implications for colonies of mountain vizcacha (Lagidium viscacia)

On 10 rocky outcrops with mountain vizcacha colonies, diets and trophic relations of five predator species were analyzed to evaluate their impact in vizcacha populations. Diets included 17 prey items of which mammals represented 97% of biomass. Lagomorphs were the most important prey, followed by sigmodontines, tuco-tucos, and mountain vizcachas. The Barn Owl was a specialized predator, while the culpeo and lesser grison were generalized consumers. Predation of mountain vizcacha by Magellanic Horned Owls and culpeo foxes could increase vizcacha vulnerability because vizcacha populations are small and fragmented, and females produce only one offspring per year.     

The accumulation of trehalose in nodules of several cultivars of common bean (Phaseolus vulgaris) and its correlation with resistance to drought stress

Nine cultivars of common bean were grown in the presence of a natural microflora without exogenous rhizobial inoculation. Nodules were harvested 30 days post planting (early flowering stage) and the presence of trehalose determined. Amounts present varied according to cultivar and were between 0.20 and 1.63 mg g⁻¹ nodule dry weight. Rhizobial strains were isolated from the nodules of three selected cultivars (Canario 101, Flor de Mayo Bajio and Flor de Mayo 38). Trehalose levels in nodules produced after either mixed strain reinfection, or after axenic homologous reinfection or after axenic cross‐reinfection could be manipulated by applying drought stress. Mixed reinfection nodules from stressed plants accumulated between two and six times the trehalose concentration found in non‐stressed control plants. After axenic cross‐reinfection up to 48‐fold increases in nodule trehalose content were recorded during drought stress. Those cultivars exhibiting high nodule trehalose levels and/or a high degree of trehalose stimulation in response to drought stress also exhibited a high leaf relative water content and were also the most drought resistant. During drought stress nodule trehalase levels rose only slightly.     

Dietary shifts,niche relationships and reproductive output of coexisting Kestrels and Long-eared Owls

Summary Food samples of breeding Kestrels (Falco tinnunculus) and Long-eared Owls (Asio otus) were collected in the peak and low phase of their preferred prey (Microtus voles) in western Finland. Diets of pairs that bred as neighbours (1 km) with interspecifics were compared with those of non-neighbours. In both species, neighbouring pairs fed less on Microtus voles and more on alternative prey than did non-neighbours. Competition theory predicts that diet overlap should be lower during prey shortage and that diet similarity should be especially reduced in neighbouring pairs. Observations were consistent with expectations: diet similarity was lower in the low vole years and neighbouring pairs showed less diet overlap that non-neighbours. Differences in habitat composition and prey availability at the sample sites should not confuse the results. In addition to the high diet similarity, hunting habitats and nest sites of the species overlapped almost completely; they only showed clear temporal segregation in hunting. Probably because of food competition, the neighbouring pairs of both species produced significantly fewer young than the non-neighbours. These results contrast with the view that the diet composition and dietary shift of rodent-feeding predatory birds can be interpreted in terms of simple opportunistic foraging. In the breeding season, interspecific competition for food seems to be an important factor that affects the niches of these species, especially in northern areas, where the seasonal low phase of voles in spring and the number of alternative prey are lower than in more southern areas.     

Comparative analysis of avian BMAL1 and CLOCK protein sequences: a search for features associated with owl nocturnal behaviour

Animals differ widely in the phasing of their daily rhythms with respect to daily environmental rhythms. While birds are predominantly day-active, nocturnal activity is a characteristic feature of the order Strigiformes (owls). To study the evolution of owl night-activity cDNA sequences encoding the circadian core oscillator (CCO) proteins BMAL1 and CLOCK were obtained from barn owl (Tyto alba). The predicted proteins showed high sequence identity with their Galliform homologues (BMAL1: 99%; CLOCK: 95.6%). A computer-predicted chicken BMAL1 casein kinase-1 phosphorylation site is absent from T. alba BMAL1, but also absent from homologues of other six bird species (5 orders) (night-active (n=2), day-active (n=4)) indicating no evolutionary association with night activity. Sequence differences between T. alba and Galliform CLOCK frequently involved serine and threonine residues suggesting potential differences in their phosphorylation. The length of a poly-glutamine string in the CLOCK C-terminus varied between and within 25 species (6 orders) examined, however, no discernible feature distinguishing day and night active species was found. No differences were found between day (n=5) and night (n=7)-active species (12 species, 6 orders) in a region of the PER2 protein implicated in altered rhythm phasing in humans. In conclusion the avian CCO components examined showed strong evolutionary conservation. Molecular evolution associated with owl night-activity may have involved alterations in the CCO relationship with ‘output’ genes rather than in the molecular structure of the CCO itself.     

北朱雀、燕雀和白腰朱顶雀的能量代谢特征和体温调节

本实验采用封闭式流体压力呼吸计 ,测定了环境温度在 5 - 34℃范围内北朱雀 (Carpodacusroseus)、燕雀 (Fringillamontifringilla)和白腰朱顶雀 (Acanthisflammea)的耗氧量、热传导、体温等指标 ,探讨了其代谢产热特征。结果表明 :在环境温度 (Ta)为 5 - 30℃的范围内 ,北朱雀的体温基本维持恒定 ,平均体温为4 0 4 6± 0 1 0℃ ,热中性区为 2 2 5 - 2 7 5℃ ,基础代谢率为 4 30± 0 0 8mlO2 /(g·h) ;环境温度在 5 - 2 0℃范围内 ,代谢率 (MR)与Ta 呈负相关 ,回归方程为MR [mlO2 /(g·h) ]=9 34- 0 2 1Ta (℃ ) ;在此范围内 ,北朱雀的热传导率最低且基本保持恒定 ,平均为 0 2 4± 0 0 0mlO2 /(g·h·℃ )。在环境温度为 5 - 34℃的范围内 ,燕雀的体温基本保持稳定 ,为 4 0 4 0± 0 1 1℃ ,热中性区为 2 5 - 30℃ ,基础代谢率为 4 1 9± 0 0 5mlO2 /(g·h) ;环境温度在 5 - 2 5℃范围内 ,MR与Ta 的回归方程为 :MR [mlO2 / (g·h) ]=1 1 6 4 - 0 2 9Ta (℃ ) ;在 5- 30℃内 ,燕雀的热传导最低 ,平均为 0 2 9± 0 0 1mlO2 / (g·h·℃ )。白腰朱顶雀的热中性区为 2 5 - 2 8℃ ,平均体温为 4 0 4 8± 0 1 1℃ (5 - 34℃ ) ,最低代谢率为 4 4 5± 0 1 4mlO2 / (g·h) ,最低热传导为 0 3     

Variation partitioning for range expansion of an introduced species: the common waxbill Estrilda astrild in Portugal

The common waxbill Estrilda astrild was first introduced to Portugal, from Africa, in 1964, from where it has spread to much of the country and to Spain. We modelled the expansion of this species on a 20×20-km UTM grid in 4-year periods from 1964 to 1999. Colonisation process on a grid was modelled as a function of several biophysical and spatio-temporal variables through the fitting of several multiple logistic equations. Variation partitioning confirmed the importance of the spatial-temporal component, explaining 33% of the total variation, followed by the combined effects of both environmental and spatial-temporal variables (around 25%). Only 11% of the total variation can be attributed strictly to the considered environmental factors.     

Parental investment and its sensitivity to corticosterone is linked to melanin-based coloration in barn owls

Behavioral and physiological responses to unpredictable changes in environmental conditions are, in part, mediated by glucocorticoids (corticosterone in birds). In polymorphic species, individuals of the same sex and age display different heritable melanin-based color morphs, associated with physiological and reproductive parameters and possibly alternative strategies to cope with variation in environmental conditions. We examined whether the role of corticosterone in resolving the trade-off between self-maintenance and reproductive activities covaries with the size of melanin-based spots displayed on the ventral body side of male barn owls. Administration of corticosterone to simulate physiological stress in males revealed pronounced changes in their food-provisioning rates to nestlings compared to control males. Corticosterone-treated males with small eumelanic spots reduced nestling provisioning rates as compared to controls, and also to a greater degree than did corticosterone-treated males with large spots. Large-spotted males generally exhibited lower parental provisioning and appear insensitive to exogenous corticosterone suggesting that the size of the black spots on the breast feathers predicts the ability to cope with stressful situations. The reduced provisioning rate of corticosterone-treated males caused a temporary reduction in nestling growth rates but, did not affect fledgling success. This suggests that moderately elevated corticosterone levels are not inhibitory to current reproduction but rather trigger behavioral responses to maximize lifetime reproductive success.     

Cats and seabirds: effects of feral Domestic Cat Felis silvestris catus eradication on the population of Sooty Terns Onychoprion fuscata on Ascension Island, South Atlantic

The population of Sooty Terns Onychoprion fuscata breeding on Ascension Island in the Atlantic Ocean was monitored over 17 years (1990–2007). This period spanned the programme of feral Domestic Cat Felis silvestris catus eradication from the island, which commenced in 2001 with the last Cat recorded in 2004. We report on the abundance of Sooty Terns and Black Rats Rattus rattus before and after Cat eradication. The Sooty Tern breeding population in the 1990s averaged 368 000 and Cats were killing Terns at an average rate of 33 adults per night. Following Cat eradication, adult Terns are no longer predated. However, egg predation by both Rats and Common Mynas Acridotheres tristis has continued with Mynas destroying more eggs than Rats. Unexpectedly, we observed a change in Rat predatory behaviour. Following Cat eradication, Rats have become a major predator of Sooty Tern chicks. Despite this change, the Tern population has shown a season-on-season increase since Cat eradication, 48.8% in 2005, 8.2% in 2006 and 6.1% in 2007, and the breeding population increased to 420 000 birds in 2007. Incubation success improved from 66.0 to 84.4% during Cat eradication, before dropping down again to 67.9% after Cats were eradicated and Rat control measures were introduced. Index traplines were set for Rats and Rat numbers fluctuated widely immediately after Cats were eradicated but there were no significant differences that could be attributed to changes in Cat numbers. Ascension Island Sooty Terns breed every 9.6 months and juveniles defer breeding for seven seasons. Hence 2008 is the first year in which an increase in the breeding Sooty Tern population directly attributable to Cat eradication is likely to be detected. We conclude that long-term monitoring is essential to guide conservation practice even in this relatively simple predator–prey system.     

Antiphonal call timing in marmosets is behaviorally significant: interactive playback experiments

Studies of primate vocal communication systems have generally focused on vocalizations and the information they convey to conspecifics. But the vocalizations are not the only sources of information. Aspects of each species vocal behaviors are likely to be communicatively rich as well. During vocal interactions, for example, the latency delay between the calls could communicate an important message to the signal receiver, such as an interest and willingness to socialize. Here we employed novel, interactive playback software to address this issue in the antiphonal calling behavior of common marmosets. In these experiments, we parametrically varied the latency delay of antiphonal call stimuli and measured its effects on subjects’ resultant vocal behavior. Results showed that marmosets produced successively fewer antiphonal call responses during test conditions with increasing latency delays. Moreover, although subjects produced significantly more antiphonal than spontaneous calls in conditions with antiphonal call timing delays up to 9 s, a longer delay resulted in a significant decline in calling. These data suggest that antiphonal call timing is a salient cue for maintaining antiphonal calling interactions and may be used by marmosets to determine whether a subsequent call is produced in response to or independently of their own.