Bruno Bruderer

Bio: Bruno Bruderer is an academic researcher from Swiss Ornithological Institute. The author has contributed to research in topics: Bird migration & Radar. The author has an hindex of 32, co-authored 58 publications receiving 2968 citations. Previous affiliations of Bruno Bruderer include University of Basel.

Flight characteristics of birds:: I. radar measurements of speeds

Abstract: This is the first part of a study on flight characteristics of birds and presents an annotated list of flight speeds of 139 western Palearctic species. All measurements were taken with the same tracking radar and corrected for wind influence according to radar-tracked wind-measuring balloons. Graphical presentation of the birds' air speeds emphasizes the wide variation of speeds within species and allows easy comparison between taxonomic groups, species, and types of flight. Unlike theoretical predictions, speeds increase only slightly with size. The larger species seem to be increasingly limited to speeds close to their speed of minimum power consumption Vmp',. Released birds, apparently reluctant to depart with migratory speed, fly at considerably lower speeds than migrating conspecifics. While large birds seem to be limited to speeds around Vmp', smaller birds seem to be capable of selecting between various speeds, approaching predicted Vmp, when tending to remain airborne at low cost, but flying at much higher speeds when tending to make best progress at low cost (around predicted speed of maximum range Vmr,). Predictions of air speeds by aerodynamic models proved to be too low for small birds because the models do not account for the gain in speed attained by the reduction in profile drag during bounding flight of small passerines. The models predict excessive speeds for large birds because the power output available for flight seems to decline much more with size than previously assumed.

The relevance of wind for optimal migration theory

Abstract: Tracking radar measurements of winds at the flight levels of bird migration during several migratory seasons in central Europe, southern Israel and the western Mediterranean are analysed with regard to optimal migratory behaviour in relation to wind. Birds migrating through central Europe and the Mediterranean area have to cope with windspeeds commonly ranging from 50 to 100% of their normal airspeed. Opposing winds prevail in central Europe, while at the western and eastern edge of the Mediterranean headand tailwinds occur in similar frequencies. Winds are highly variable in time and altitude. A bird migrating selectively during nights with favourable wind conditions speeds up its flight by 30% (on average) compared to an individual disregarding the wind situation. Selecting the most profitable flight altitude may result in an additional gain of 40% in flight speed. Therefore, taking into account the wind situation carefully, a bird can almost double its flight speed and save about half of the energy required for its migratory journey through central Europe and the Mediterranean. The time needed for refuelling decreases accordingly or the safety margins provided by fat reserves can be increased. For birds flying long distances in one step, the selection of favourable winds should be more important than adjusting departure to local fat accumulation rates.

The study of bird migration by radar. part 1 : the technical basis

Abstract: Since the 1960s radar has been an established research tool in bird migration studies. Radar informs us about the actual course of migration under various environmental conditions: it covers wide distances, is independent of light and reasonably independent of weather, provides data on migratory intensity, flight paths and with special equipment the wing-beat pattern of birds. It thus fills an important gap left by other methods such as visual and auditory observations, laboratory research, trapping, and ringing studies. For an appropriate use of the sophisticated tool, however, it is important to know its capabilities and limitations.

Wind and rain govern the intensity of nocturnal bird migration in central Europe: A log-linear regression analysis

Abstract: For the first time an almost complete sample of the seasonal course of nocturnal autumn migration was recorded by a conically scanning pencil-beam radar and was analysed with respect to weather, using a log-linear regression model. A variable aiming to estimate the number of birds ready to depart for migration due to preceding precipitation was included in the model. The density of nocturnal migration was strongly influenced by wind and by rain. It appears that birds distinguished between favourable and unfavourable wind conditions rather than to grade wind on a continuous scale from least to most favourable. The final model, including variables for actual wind, rain, previous precipitation, and the general seasonal trend explained 70% of the total deviance. Thus, the low correspondence of empirical data with predictions from models on stopover duration and optimal fuel loads with respect to fat deposition rates may be caused by the high impact of local weather conditions on the take off decision of the majority of nocturnal migrants passing through central Europe.

Songbird migration across the Sahara: the non-stop hypothesis rejected!

Abstract: Billions of songbirds breeding in the Western Palaearctic cross the largest desert of the world, the Sahara, twice a year. While crossing Europe, the vast majority use an intermittent flight strategy, i.e. fly at night and rest or feed during the day. However, it was long assumed that they overcome the Sahara in a 40 h non-stop flight. In this study, we observed bird migration with radar in the plain sand desert of the Western Sahara (Mauritania) during autumn and spring migration and revealed a clear prevalence of intermittent migration. Massive departures of songbirds just after sunset independent of site and season suggests strongly that songbirds spent the day in the plain desert. Thus, most songbirds cross the Sahara predominately by the intermittent flight strategy. Autumn migration took place mainly at low altitudes with high temperatures, its density decreased abruptly before sunrise, followed by very little daytime migration. Migration was highly restricted to night-time and matched perfectly the intermittent flight strategy. However, in spring, when migratory flights occurred at much higher altitudes than in autumn, in cool air, about 17% of the songbird migration occurred during the day. This suggests that flying in high temperatures and turbulent air, as is the case in autumn, may lead to an increase in water and/or energy loss and may prevent songbirds from prolonged flights into the day.

The physiology/life-history nexus

Abstract: The rate of reproduction, age at maturity and longevity vary widely among species. Most of this life-history variation falls on a slow-fast continuum, with low reproductive rate, slow development and long life span at one end and the opposite traits at the other end. The absence of alternative combinations of these variables implies constraint on the diversification of life histories, but the nature of this constraint remains elusive. Here, we argue that individual and adaptive responses to different environments are limited by physiological mechanisms. Although energy and materials allocations are important results of physiological tradeoffs, endocrine control mechanisms can produce incompatible physiological states that restrict life histories to a single dominant axis of variation. To approach the problem of life-history variation properly, studies should integrate behavior and physiology within the environmental and demographic contexts of selection.

The eBird enterprise: An integrated approach to development and application of citizen science

Abstract: Citizen-science projects engage volunteers to gather or process data to address scientific questions. But citizen-science projects vary in their ability to contribute usefully for science, conservation, or public policy. eBird has evolved from a basic citizen-science project into a collective enterprise, taking a novel approach to citizen science by developing cooperative partnerships among experts in a wide range of fields: population and distributions, conservation biologists, quantitative ecologists, statisticians, computer scientists, GIS and informatics specialists, application developers, and data administrators. The goal is to increase data quantity through participant recruitment and engagement, but also to quantify and control for data quality issues such as observer variability, imperfect detection of species, and both spatial and temporal bias in data collection. Advances at the interface among ecology, statistics, and computer science allow us to create new species distribution models that provide accurate estimates across broad spatial and temporal scales with extremely detailed resolution. eBird data are openly available and used by a broad spectrum of students, teachers, scientists, NGOs, government agencies, land managers, and policy makers. Feedback from this broad data use community helps identify development priorities. As a result, eBird has become a major source of biodiversity data, increasing our knowledge of the dynamics of species distributions, and having a direct impact on the conservation of birds and their habitats.

Avian Energetics and Nutritional Ecology

Abstract: Contributors. Preface. Units and Conversion Factors Contents. Avian Energetics, Ecology, and Evolution-- R E Ricklefs Nutrition and Metabolism-- M Murphy Digestive Plasticity in Avian Energetics and Feeding Ecology-- W H Karasov Energetic Features of Avian Thermoregulatory Responses-- W R Dawson and T.P. O'Connor Physiological and Ecological Aspects of Hypothermia-- R E Reinertsen Energetics and Nutrition of Molt-- M E Murphy Energetics of Flight-- U M Norberg Energetics of Avian Foraging-- B A Mauer Energetics of Migratory and Winter Fattening-- H Biebach Female Reproductive Energetics -- C Carey Energetics of Avian Incubation-- J Williams Embryonic energetics-- C M Vleck and D. Vleck Energetics of Post-natal Growth-- W Weathers Populational and Community Energetics-- J A Wiens and A H Farmer.

Technology on the Move: Recent and Forthcoming Innovations for Tracking Migratory Birds

Abstract: Basic questions about the life histories of migratory birds have confounded scientists for generations, yet we are nearing an era of historic discovery as new tracking technologies make it possible to determine the timing and routes of an increasing number of bird migrations. Tracking small flying animals as they travel over continental-scale distances is a difficult logistical and engineering challenge. Although no tracking system works well with all species, improvements to traditional technologies, such as satellite tracking, along with innovations related to global positioning systems, cellular networks, solar geolocation, radar, and information technology are improving our understanding of when and where birds go during their annual cycles and informing numerous scientific disciplines, including evolutionary biology, population ecology, and global change. The recent developments described in this article will help us answer many long-standing questions about animal behavior and life histories.

Integrating function and ecology in studies of adaptation: Investigations of locomotor capacity as a model system

Abstract: ▪ Abstract Understanding adaptation in morphological and physiological traits requires elucidation of how traits relate to whole-organism performance and how performance relates to fitness. A common assumption is that performance capacities are utilized by and important to organisms. For some systems, it is assumed that high levels of physical fitness, as indexed by measures of locomotor performance, lead to high fitness levels. Although biologists have appreciated this, little attention has been paid to quantifying how organisms use their performance capacities in nature. We argue that for the study of adaptation to proceed, greater integration of laboratory studies of performance and behavioral/ecological studies is needed, and we illustrate this approach by examining two questions. First, how does the environment affect locomotor function in nature? Second, what percentage of locomotor capacities do animals use in nature? A review of studies in several animal groups shows widespread effects of the envi...