Are avian predators effective biological control agents for rodent pest management in agricultural systems?

Worldwide rodent pests are of significant economic and health importance. Controlling rodent pests will, therefore, not only benefit food security but also human and animal health. While rodent pests are most often chemically controlled, there is increased interest in biological control through avian predation. A rich body of research has addressed the impact of avian predators on wild rodent populations, but little is known about the effectiveness of avian predators as biological control agents of rodent pests in agricultural systems. In this study, we systematically reviewed research that investigated different aspects of avian predation on rodent pest populations in order to increase our understanding of the impact and effectiveness of avian predation on rodent pests. Several avian predators (Tyto alba, Elanus axillaris Falco tinnunculus, F. cenchroides, Bubo bengalensis, Buteo rufinus) were commonly cited in the biological control of rodents; however, barn owls (T. alba) are the most cited species (86% of studies). We found some support that the use of avian predators produced positive, measurable effects where increased presence of avian predators tended to lower rodent pest numbers, resulting in lower crop damage. However, our review highlighted several shortcomings related to research on avian predation of rodent pests. First, research concerning rodent pest control through avian predation was limited (1.86 articles per year). Secondly, we found that studies lack statistical rigor to detect and measure change in rodent pest species abundance. Finally, the majority of studies were short term and therefore not able to evaluate long term sustainable rodent pest population suppression. We suggest that current shortcomings could be adequately addressed with control-treatment studies that quantitatively investigate the effects of avian predation on rodent pest populations and agricultural impact. Such research could help develop recommendations regarding the use of avian predators in rodent pest management

The impact of forestry, agriculture, and cattle grazing activities on the quality of landscape in a transect of southern Chile

This study is centered on the concept of 'visual landscape', based upon two central factors, aesthetics and the observer's capacity of perception of the landscape. The landscape in southern Chile has been transformed over the past centuries, and particularly in recent decades. This transformation is a product of forestry, agriculture and cattle grazing activities; this study attempts to evaluate the landscape quality in a north-south transect of 587 km, along Chile's 5 South highway extending from Cabrero to Puerto Montt. Landscape Units (Unidades de Paisaje, UP) were established, quantified and evaluated by a mixed method with direct valuation of the representative subjectivity and subsequent indirect analysis, with analysis of components. A total of 1,702 Landscape Units (UP) were analyzed, concluding that the most frequent macro-units are: Visual Obstruction, Native Vegetation, Agriculture Cultivation, and Artificial Plantations. The general average was 11.57 VP (SD = 5.01), considered acceptable in the Fines scale. The macro-units of highest value were: Native Vegetation and Agriculture Cultivation, and those with lowest value were: Visual Obstruction and Artificial Plantations. Information was compiled about the frequency of the macro-units per sector and the evaluation of 42 sub-units of landscape value, 22 Landscape Units (UP) and four macro-units. This paper discusses the different valuations, the historical evolution of landscapes in southern Chile, and alternative propositions of mitigation in Landscape Units of low evaluation. This evaluation may be compared with future evaluations in order to quantify losses (or gains) of landscape, its destructive agents and mitigating measures

Diet of Lycalopex griseus (Gray, 1837) (Mammalia : Canidae) in the intermediate depression of southern Chile

A study about food habits of chilla (Lycalopex griseus) was done in a sector of the intermediate depression of southern Chile, called Predio Rucamanque, Region de la Araucania. Faeces were collected through three seasons of the year, identifying their diet composition. Results show a trend towards small mammals followed by birds, and in a lesser ratio, insects

HABITAT USE OF FOUR TERRESTRIAL CARNIVORES IN SOUTHERN CHILE

The process of landscape transformation has been more intense and extended in the central depression of central and southern Chile than in the nearby mountain ranges. The original forest cover has almost disappeared; only small fragments persist inserted into a matrix of agroecosystems. This situation may influence the distribution of carnivorous mammals, depending on their degree of habitat specialization and home range size. The goal of this study was to evaluate, through the study of feces dsitribution, the habitat selection of the carnivore assemblage in a fragmented environment in southern Chile. We document the selective use of exotic forest plantations of Pinus radiata with a scrub understory by Puma concolor, Galictis cuja, and Lycalopex griseus. Leopardus guigna, despite not showing a statistically significant selection of the native forest, presents a greater number of records in this type of habitat. Habitat selection by the predators studied shows a variable degree of use of altered and fragmented environments. Surrounding forest plantations present an understory of native vegetation, which fits the requirement of most of the carnivores. The levels of spatial overlapping and the adequacy to new environments are discussed

State of the art of the knowledge of Chilean raptor birds: Present situation and future projections

Increasing global interest for studying birds of prey has lead to the need to identify research priorities to better focus conservation efforts. In Chile, studies on raptors date back to 1891, and the number of publications has considerable increased in the last decades. To our knowledge, however, analysis on information gaps and research priorities is lacking. Based on the published information from 1970 and 2011, we assessed the current state of knowledge for Chilean raptors to identify the topics where information is absent or is insufficient and to determine what information is a research priority. We analyzed the information according to species, species groups (diurnal and nocturnal), research topics and geographical area where the studies were conducted. We found that the number of papers increased linearly with time, but the tendency was strong biased toward only two species (Tyto alba, Geranoaetus polyosoma). Most studies focused on diet and were with an interest more pronounced towards nocturnal than diurnal raptors. The remainder of topics was only moderately or poorly studies. The least studied raptors were migrant species (Buteo swainsoni, Pandion haliaetus, Circus buffoni), forest specialist (Strix rufipes. Accipiter bicolor, Buteo ventralis and B. albigula) and members of the genus Phalcoboenus, most of which have some conversation problem. The number of studies by geographical area was similar between diurnal and nocturnal raptors. Remarkably, a high proportion of studies concentrated in the Metropolitan Region of Chile. We conclude that research must be focused on (a) poorly studied and threatened species, (b) scarcely studied topics such as migration, population density, taxonomy, management, parasites and use and selection habitat, and (c) species inhabiting remote islands, fragmented or human-modified landscapes, and heavily populated areas

Waterbird assemblages of inland wetlands in Chile: A meta-analysis

Chile has a large number of wetlands that offer a wide variety of refuges and food to waterbird assemblages. This research hypothesises that these assemblages differ according to the structural characteristics of each type of inland wetland. The object is to identify the structure of these assemblages, evaluating their richness, alpha alpha diversity and some ecological characteristics, taxonomic structures and trophic guilds. We performed a meta-analysis by submitting pre-selected articles to multivariate reliability analysis. The selected articles were used to characterise the assemblages by alpha alpha diversity: species richness, Shannon-Wiener index, Pielou's Evenness Index, relative abundance and taxonomic distinctiveness Delta + and beta beta diversity: Bray-Curtis with analysis of similarity percentage. Diversity and evenness differed in the seven wetlands studied, among 12 to 45 species, Shannon-Wiener index H'= 0.08 to 0.94 bits and Pielou's Evenness Index J'= 0.06 to 0.71. Four wetlands were below and three above the expected value for taxonomic distinctiveness (Delta +) (73.2 units). Two clusters were identified using the beta diversity: one consisting of the High-Andean wetlands (Huasco and Negro Francisco); and the other of El Peral lagoon, the Cruces River wetlands complex and the Tranque San Rafael man-made wetland. The most remarkable dissimilarity was provided by three species (Cygnus melancoryphus, Phoenicoparrus jamesi and Phoenicoparrus andinus). Zoophagous species that eat invertebrates by the first choice are the dominant group, while in lagoon wetlands phytophages and omnivores are more evenly represented

Assessment of wetland visual landscape in the Cruces River, Ramsar site of Chile

Landscape is an environmental heritage, which includes cultural and natural values, a resource that represents the appearance of an area and reflects its nature and history. Thus, this heritage resource should be assessed and managed rationally, especially since there is an increasing demand for areas of high landscape value for ecotourism activities. Regarding the study of visual landscape, it was not considered as a measurable element until the mid-twentieth century and considerable progress has been made in assessing the quality, the fragility and capacity for use as a direct assessment of the landscape. Still pending is the indirect analysis which includes its basic visual features such as line, color, texture, spatial configuration and relief, and their components, both primary and secondary. Therefore, the objective of this study is to evaluate the visual landscape (direct analysis) of the Cruces River and surrounding area, its fragility and capacity for use, analyzing the relationship between the value of these landscapes with their visual characteristics and primary components (indirect analysis). The visual landscape quality was assessed using a mixed method with direct assessment: of representative subjectivity and subsequent indirect analysis of its components, using a standardized panel of assessors. We also determined the fragility of the landscape, which was integrated with the visual quality and spatialized in a GIS. Thus categories of landscape use in the study area were created. The landscape quality average value (+/- SD) was VP = 16.86 +/- 1.99. Recommended uses are in category 3 (high landscape quality and low fragility) that is tourism and recreation in 86.1 % of the study area. For indirect analysis, in each landscape, the basic visual features (line, color and texture) and its primary components were identified, analyzing their relationship with the visual quality. The landscape value is relate more strongly with the characteristics of line and texture such as grain and density and their assessment is dependent on its primary component. Landscapes with high VP relate to dense Salix and swamp vegetation and landscapes with forest vegetation

Diet, dietary selectivity and density of South American grey fox, Lycalopex griseus, in Central Chile

The South American grey fox Lycalopex griseus is a canid widely distributed in southern South America; however, some aspects of its biology are still poorly known. We studied the diet and density of L. griseus in the Lago Penuelas Biosphere Reserve, in Central Chile. The trophic niche breadth was B = 6.16 (B-sta = 0.47) and prey diversity was H = 2.46 (H-max' = 3.17, J' = 0.78). The highest proportions of prey consumed in the diet were Oryctolagus cuniculus (52.21%) and other mammals (32.78%). We compared these results with a latitudinal gradient of diet results for this species in Chile. L. griseus eats mostly mammals (>90% of total prey), consuming the rodent Phyllotis darwini and reptiles in the northern zone; Oryctolagus cuniculus, Octodon degus and Abrocoma bennetti in the central zone; Abrothrix spp. and lagomorphs in the southern zone; and Lepus capensis and Ovis aries in the austral zone. The estimated density of L. griseus in Lago Penuelas NR was 1.3 foxes/km(2)

Selective consumption of rodents by the Variable hawk Geranoaetus polyosoma (Accipitriformes: Accipitridae) in the Atacama Desert, northern Chile

Geranoaetus polyosoma (Quoy & Gaimard, 1824) is a diurnal raptor widely distributed in South America. Although the trophic ecology of this bird has been more studied in the southern extreme of its range, little information is available on its dietary response to prey supply in desert environments. In the present study, we report on the trophic ecology of G. polyosoma in a sub-urban desert zone in northern Chile, with the following objectives: (1) to quantitatively describe its diet and (2) to determine its dietary selectivity in response to prey supply in the study area. The diet of G. polyosoma consisted mainly of rodents (97.2%). A greater preference (p 19.5 g): two native rodent species, Phyllotis xanthopygus (Waterhouse, 1837) and Eligmodontia puerulus (Philippi, 1896); and two introduced rodent species: Rattus rattus (Linnaeus, 1769) and R. norvegkus (Berkenhout, 1769)

Raptor habitat management and its implication on the biological control of the Hantavirus

Rodents have a high impact on human activities, producing economical losses and diseases. One of these diseases is Hantavirus syndrome, whose reservoir is Oligoryzomys longicaudatus. Raptors are the natural biological controllers of rodents, being, therefore, our efficient and effective allies. Despite the existing legal dispositions for protection, 11 of the 33 species of raptors in Chile have conservation problems. We evaluated the effectiveness of nest boxes for Tyto alba, as a way to increase its population and propose a procedure for the biological control of O. longicaudatus. The study area was the National Reserve Lago Peuelas, Valparaiso, Chile. The variation of population density before and after the installation of the nest boxes was established both for T. alba and rodents. The results show that the nest boxes installed dramatically increased the population and the total density of T. alba, and a significant reduction of the abundance of small mammals was stated. We propose a methodological diagram for the biological control of the reservoir of the Hantavirus, which we have been implementing since 2001