Bird Tracks Research Articles

Only natural local odours allow homeward orientation in homing pigeons released at unfamiliar sites.

According to the olfactory navigation hypothesis, birds are able to exploit the spatial distribution of environmental odourants to determine the direction of displacement and navigate from non-familiar locations. The so-called "olfactory activation hypothesis" challenged the specific role of olfactory cues in navigation by suggesting that olfactory stimuli only activate a navigational system that is based on non-olfactory cues, predicting that even artificial odourants alone are sufficient to allow unimpaired navigation. In this experiment, we compared tracks of experimental birds exposed to different olfactory stimuli before being made anosmic at the release site prior to release. One group of pigeons was exposed to purified air enriched with artificial odourants, while a second group was exposed to environmental air. The birds stimulated with artificial nonsense odourants displayed several behavioural differences from both untreated controls and anosmic pigeons exposed to environmental air prior to release: nonsense odourants birds were unable to determine the home direction, they mostly flew within a space outside the homeward oriented quadrant, and they flew shorter distances on the day of release. Our data failed to support a mere activational role of olfactory stimuli in navigation, and are consistent with the olfactory navigation hypothesis.

Follow the rain? Environmental drivers ofTyrannusmigration across the New World

ABSTRACT Predictable seasonal changes in resources are thought to drive the timing of annual animal migrations; however, we currently understand little about which environmental cues or resources are tracked by different migratory bird species across the planet. Understanding which environmental cues or resources birds track in multiple migratory systems is a prerequisite to developing generalizable conservation plans for migratory birds in a changing global environment. Within the New World, climatic differences experienced by Nearctic–Neotropical migratory (NNM; i.e. breed in North America and spend the nonbreeding period in the Neotropics) and Neotropical austral migratory (NAM; i.e. breed and spend the nonbreeding period wholly within South America) bird species suggest that their migratory strategies may be shaped by unique selective pressures. We used data gathered from individuals fitted with light-level geolocators to build species distribution models (SDMs) to test which environmental factors dri...

Proximate mechanisms affecting seasonal differences in migration speed of avian species

Faster migration in spring than in autumn seems to be a common pattern in birds. This has been ultimately explained by seasonally different selection pressures. Variation in migration speed is proximately caused by adjusting travel speed (distance covered during flight) and/or stopover duration (times when birds rest and refuel). Yet, it remains unclear whether individual seasonal differences in migration speed match the common pattern and what the precise role of the proximate, behavioural mechanisms for adjusting migration speed is. By reviewing 64 studies of 401 tracks, I show that in waders, gulls, swifts, and songbirds speeds were significantly higher in spring, while the opposite was the case in waterfowl and owls. Thus, the ultimate mechanisms selecting for a faster migration in spring might not consistently act across bird groups. Breeding latitude, migration strategy, migration distance, flight style, body mass, and sex did not explain seasonal differences in speed. The ratio between spring and autumn total stopover duration of 257 bird tracks significantly negatively affected the seasonal migration speed ratio of the same individuals in a comparative analysis accounting for shared ancestry. Seasonal variation in stopover duration appears thus to be the main biological mechanism regulating seasonal differences in migration speed.

The hunter and the hunted ‒ first description of a jackal-like predator and associated bird and gazelle tracks from the Post-Messinian of the Sorbas Basin, SE Spain

The hunter and the hunted ‒ first description of a jackal-like predator and associated bird and gazelle tracks from the Post-Messinian of the Sorbas Basin, SE Spain

Rediscovery of the Tagragra Tracksite (Maastrichtian, Agadir, Morocco): Agadirichnus elegans Ambroggi and Lapparent 1954 is Pterosaurian Ichnotaxon

ABSTRACTDiscovered in 1954 by Ambroggi and Lapparent, the Tagragra tracksite (Maastrichtian, Agadir, Morocco) yielded tracks of theropod dinosaurs, birds and enigmatic forms tentatively attributed to Lacertilia under the name Agadirichnus elegans. The original specimens are today considered to be lost, and the status of A. elegans has been questioned, even though these footprints can retrospectively be referred to pterodactyloid pterosaur tracks. In order to discuss the status of these foot prints, the historical site has been actively sought and recently rediscovered by one of us (MdD). New material confirms the presence of pterodactyloid footprints, with two morphotypes, in two different facies, respectively associated with bird and theropod tracks. Morphotype I is tentatively conferred to Pteraichnus Stokes 1957, which extends the stratigraphical distribution of this ichnotaxon to the Maastrichtian. Morphotype II corresponds to the original ichnospecies A. elegans Ambroggi and Lapparent 1954, which is here reassessed as a valid ichnotaxon, with the designation of a neotype. Thus, A. elegans Ambroggi and Lapparent 1954 is historically the first pterosaurian ichnotaxon ever described.

ROLE OF ICHNOLOGY IN THE HISTORY OF PHOTOGRAPHY

ABSTRACT Vertebrate ichnology in North America has a long and distinguished history, starting with the remarkable discoveries by Edward Hitchcock of dinosaur footprints and trackways in the Connecticut River Valley. Hitchcock assembled a unique collection that is currently housed in the Beneski Museum of Natural History, Amherst College, and his work essentially constituted the beginnings of ichnology as a viable sub-discipline of paleontology. Although his original interpretation that these Late Triassic locomotion traces were bird tracks was incorrect, he indirectly linked birds and dinosaurs. Other talented amateurs including John Collins Warren, James Deane, Dexter Marsh and Roswell Field worked on these track sites and some were prolific authors. Three major books have significance, Dr. John Collins Warren published his book Remarks on Some Fossil Impressions in the Sandstone Rocks of Connecticut River in 1854 making it the second book ever published exclusively on ichnology and the second American publication (and first American scientific publication) to be illustrated with a photograph, a salt print, used as the frontispiece depicting what he interpreted as the fossilized tracks of prehistoric birds. James Deane published a book in 1861entitled Ichnographs from the Sandstone of Connecticut River containing photographs and etchings. Finally, Edward Hitchcock published The Supplement to the Ichnology of New England in 1865 that contained seven albumen prints by the professional photographer J. Lovell of Amherst. These volumes pioneered the use of photography in American scientific publications.

Lower Cretaceous avian tracks from Jiangsu Province, China: A first Chinese report for ichnogenus Goseongornipes (Ignotornidae)

The Ignotornidae had a global distribution during the Cretaceous (Aptian – Cenomanian), but reports have been limited to North America, and localities in South Korea. Until recently, despite the high diversity of Ignotornidae described from Asia, no ichnospecies of Ignotornidae have been described from China. Here we report the first occurrence of Ignotornidae from the Lower Cretaceous of Donghai County, Jiangsu Province, China. Morphological and multivariate statistical analyses demonstrate that these functionally tetradactyl, semi-palmate bird tracks are most similar to Goseongornipes ichnosp. The apparent limited paleogeographical distribution of Ignotornidae from the Lower Cretaceous is likely artificial, and more exploration and documentation of Lower Cretaceous strata will increase our understanding of the extent of the global distribution of Ignotornidae.

A NEW EXPERIMENTAL SETUP FOR STUDYING AVIAN NEOICHNOLOGY AND THE EFFECTS OF GRAIN SIZE AND MOISTURE CONTENT ON TRACKS: TRIALS USING THE DOMESTIC CHICKEN (GALLUS GALLUS)

Abstract: A new experimental setup using a collapsible wooden tray, monopod, and digital video camera is used to observe and collect modern bird tracks. This setup is unique because it simultaneously captures tracemaker behavior, trace morphology, and media consistency (i.e., grain size and moisture content), and can be used in the laboratory and in natural environments. Here we provide examples produced by domestic chickens (Gallus gallus). Using this setup we determined that bird track morphology varies in a predictable manner with respect to sediment grain size and the percent of water present. The finer the sediment grain size, the more detail is likely to be preserved. If the sediment is completely dry, no track details will be preserved––digit impressions will be broad and will not taper at the tips; digit impression length will be longer than the actual digit lengths. If the sediment is wet (8.8%–6.7%), digit impressions will taper to points, will not be as wide as in dry sediment, and will not pre...

Quantifying the strength of migratory connectivity

Abstract Technological advancements have spurred rapid growth in the study of migratory connectivity, the linkage of individuals and populations between seasons of the annual cycle. The strength of migratory connectivity is a measure of the co‐occurrence of populations throughout the annual cycle and can be represented by a correlation of the distances between individuals during one season and another (Mantel correlation, rM). However, measurement of seasonal distributions most often involves incomplete sampling and use of technologies that vary in accuracy and precision. For these reasons, we expanded rM to measure the strength of migratory connectivity (MC) with population‐specific transition probabilities that can be derived from many data types and uneven sampling. We explore the sensitivity of MC to possible real‐world variation in input parameters: transition probabilities, abundance among regions, spatial arrangement of regions, and sample sizes. We compare MC to rM, present a series of resampling approaches for propagating uncertainty in input values into estimation of MC and rM, and validate the method with bird tracking data. Migratory connectivity was negative when populations are further apart between seasons, positive when populations remain together between seasons, and zero when populations have no patterns in distribution between seasons. MC is most sensitive to transition probabilities and spatial arrangement of regions and performs better than rM when sampling effort is not proportional to true abundance, and when the strength of migratory connectivity varies across the range of the species. Our estimators for MC and rM performed well across several data types. We hope that these methods and the MigConnectivity r package will facilitate quantitative comparisons of migratory connectivity across studies, data types, and taxa to better understand the causes and consequences of the seasonal distributions of populations. Several study design recommendations emerge from our simulations: (1) incorporate abundance among regions when sampling is not proportional; (2) measure transition probabilities across as much of the range as logistically possible; (3) define study regions with either biological information about population delineation, or use discrete study locations as centroids of regions; and (4) estimate and report uncertainty from appropriate sources of sampling and process errors.

Seasonal and circadian biases in bird tracking with solar GPS-tags.

Global Positioning System (GPS) tags are nowadays widely used in wildlife tracking. This geolocation technique can suffer from fix loss biases due to poor satellite GPS geometry, that result in tracking data gaps leading to wrong research conclusions. In addition, new solar-powered GPS tags deployed on birds can suffer from a new “battery drain bias” currently ignored in movement ecology analyses. We use a GPS tracking dataset of bearded vultures (Gypaetus barbatus), tracked for several years with solar GPS tags, to evaluate the causes and triggers of fix and data retrieval loss biases. We compare two models of solar GPS tags using different data retrieval systems (Argos vs GSM-GPRS), and programmed with different duty cycles. Neither of the models was able to accomplish the duty cycle programed initially. Fix and data retrieval loss rates were always greater than expected, and showed non-random gaps in GPS locations. Number of fixes per month of tracking was a bad criterion to identify tags with smaller biases. Fix-loss rates were four times higher due to battery drain than due to poor GPS satellite geometry. Both tag models were biased due to the uneven solar energy available for the recharge of the tag throughout the annual cycle, resulting in greater fix-loss rates in winter compared to summer. In addition, we suggest that the bias found along the diurnal cycle is linked to a complex three-factor interaction of bird flight behavior, topography and fix interval. More fixes were lost when vultures were perching compared to flying, in rugged versus flat topography. But long fix-intervals caused greater loss of fixes in dynamic (flying) versus static situations (perching). To conclude, we emphasize the importance of evaluating fix-loss bias in current tracking projects, and deploying GPS tags that allow remote duty cycle updates so that the most appropriate fix and data retrieval intervals can be selected.

Match between soaring modes of black kites and the fine-scale distribution of updrafts

Understanding how soaring birds use updrafts at small spatial scales is important to identify ecological constraints of movement, and may help to prevent conflicts between wind-energy development and the conservation of wildlife. We combined high-frequency GPS animal tracking and fine-spatial-scale uplift modelling to establish a link between flight behaviour of soaring birds and the distribution of updrafts. We caught 21 black kites (Milvus migrans) and GPS-tracked them while flying over the Tarifa region, on the Spanish side of the Strait of Gibraltar. This region has a diverse topography and land cover, favouring a heterogeneous updraft spatial distribution. Bird tracks were segmented and classified into flight modes from motion parameters. Thermal and orographic uplift velocities were modelled from publically available remote-sensing and meteorological data. We found that birds perform circular soaring in areas of higher predicted thermal uplift and linear soaring in areas of higher predicted orographic uplift velocity. We show that updraft maps produced from publically available data can be used to predict where soaring birds will concentrate their flight paths and how they will behave in flight. We recommend the use of this methodological approach to improve environmental impact assessments of new wind-energy installations.

Vertebrate tracks from the Paso Córdoba fossiliferous site (Anacleto and Allen formations, Upper Cretaceous), Northern Patagonia, Argentina: Preservational, environmental and palaeobiological implications

The Paso Córdoba fossiliferous site (Río Negro, Northern Patagonia) is one of the first Mesozoic fossiliferous localities studied in Argentina. There, turtle, crocodile and dinosaur remains as well as dinosaur and bird tracks have been recorded. Recently, a new locality with vertebrate tracks, the Cañadón del Desvío, has been discovered in Paso Córdoba. Six track-bearing layers were located in outcrops belonging to the Anacleto (lower to middle Campanian, Neuquén Group) and Allen (middle Campanian-lower Maastrichtian, Malargüe Group) formations. The Cañadón del Desvío locality reveals that vertebrate trace fossils are distributed in two distinct environments, floodplains of a meandering fluvial to shallow lacustrine system and a wet interdune deposit that is associated to an aeolian setting. Also, in the logged section several soft sediment deformation structures were found. In regard of this, a sedimentary facies analysis is provided in order to assess the palaeoenvironmental implications of this new record. The analysed tracks are preserved in cross-sections, on bedding-planes and as natural casts. When it is possible, the tracking surface, true tracks, undertracks and overtracks/natural casts have been identified and the track preservation and the formation history of the tracksite are discussed. Only two tracks preserve enough anatomical details to relate them with their trackmakers, in this case hadrosaurid dinosaurs. The stratigraphical, facial and palaeoenvironmental data of this study support the idea of a transitional passage between the Anacleto and Allen Formation in Paso Córdoba. The presence of hadrosaurid dinosaur tracks suggests that the upper part of the log, where this kind of tracks were found, likely belong to Allen Formation due to this dinosaurs appear in the Southern Hemisphere in this epoch. The sum of osteological and ichnological remains improve the Paso Córdoba palaeofaunistic knowledge. The presence of six different levels in which the trackmakers walked reflects the abundance of vertebrates in the transition between Anacleto and Allen formations.

Using radar cross-section to enhance situational awareness tools for airport avian radars

Digital avian radars can track bird movements continuously in the vicinity of airports without interruption. The result is a wealth of bird-track data that can be used in mitigation efforts to reduce bird strikes on and near airfi elds. To make the sheer volume of bird track data generated by digital avian radars accessible to users, we developed tools to transform these data into analytical and visualization products to improve situational awareness for wildlife and airfi eld personnel. In addition to the parameters traditionally associated with radar tracking (latitude, longitude, altitude, speed, and heading), we have implemented a procedure to estimate the radar cross-section (RCS) of a target, which is related to its size or mass. This additional information can provide wildlife and airfi eld managers with the knowledge they need to prioritize their efforts to deal with the greatest hazards fi rst.

Scampering, trotting, walking tridactyl bipedal dinosaurs in southern Africa: ichnological account of a Lower Jurassic palaeosurface (upper Elliot Formation, Roma Valley) in Lesotho

In Gondwana, Early Jurassic dinosaur track sites are especially concentrated in Lesotho. Despite intensive investigations during the third quarter of the twentieth century, a limited number of vertebrate track sites of this country have been studied with rigorous ichnological and sedimentological methodology. Here, we present a previously mentioned, but undescribed track site in the upper Elliot Formation (Hettangian?) of Lesotho, located near Roma (at Lephoto dam). Two tridactyl ichnite morphologies, made by bipedal vertebrate trackmakers are recognised. The first can be identified as Grallator-like, an ichnotaxon common in the Lower Jurassic of both Laurasia and Gondwana that can be attributed to small and medium-size theropod dinosaurs. In contrast, the second ichnite type is reminiscent of Trisauropodiscus, which is a rare ichnotaxon that resembles tracks of small birds and is known with certainty in Lesotho from only a few places. We suggest that at our upper Elliot Formation study site, Trisauropodiscus was potentially made by a heterodontosaurid ornithischian dinosaur. Our work provides further evidence that the ichnological record of the Stormberg Group of southern Africa is in a unique position to shed light not only on Early Jurassic biostratigraphy and palaeoenvironments but also on the biodiversity and palaeobiology of early dinosaurs.

Resource tracking within and across continents in long-distance bird migrants.

Migratory birds track seasonal resources across and between continents. We propose a general strategy of tracking the broad seasonal abundance of resources throughout the annual cycle in the longest-distance migrating land birds as an alternative to tracking a certain climatic niche or shorter-term resource surplus occurring, for example, during spring foliation. Whether and how this is possible for complex annual spatiotemporal schedules is not known. New tracking technology enables unprecedented spatial and temporal mapping of long-distance movement of birds. We show that three Palearctic-African species track vegetation greenness throughout their annual cycle, adjusting the timing and direction of migratory movements with seasonal changes in resource availability over Europe and Africa. Common cuckoos maximize the vegetation greenness, whereas red-backed shrikes and thrush nightingales track seasonal surplus in greenness. Our results demonstrate that the longest-distance migrants move between consecutive staging areas even within the wintering region in Africa to match seasonal variation in regional climate. End-of-century climate projections indicate that optimizing greenness would be possible but that vegetation surplus might be more difficult to track in the future.

“A perspective close to our own”: footsteps travel and the Japanese reception of Isabella Bird’s Unbeaten Tracks in Japan, 1996–2016

ABSTRACTWhile it was the 1973 Takanashi translation of Unbeaten Tracks that first brought popular attention to Isabella Bird in Japan, the two decades since the mid-1990s have seen a steady flow of books which either rewrite Unbeaten Tracks or retrace Bird’s route through Tōhoku to Hokkaidō. This article analyses these footsteps travel texts in order to consider Bird’s appeal and the socio-cultural function of Bird and Unbeaten Tracks in post-Bubble Japan. I argue that the “connection” that these texts create between past and present is sometimes understood individually, as cross-identification between the historical Bird and the contemporary traveller/writer, but more commonly in terms of family or national genealogy, a promise of unbroken transmission from the past designed to assuage anxieties about the loss of national-cultural cohesion and distinction. In many cases, these texts allow nostalgia to be transformed into celebration of national continuity; in other cases, however, this project of recovery is forestalled by the very unfamiliarity of Bird’s perspective, which cannot help but reveal that, for modern Japanese readers, “the past is a foreign country”.

Isabella Bird, Victorian globalism, and Unbeaten Tracks in Japan (1880)

ABSTRACTIsabella Bird’s Unbeaten Tracks in Japan (1880, written 1878) is one of the rare Victorian travelogues about Asia that has not only won continued readership and critical prestige in the West, but has also been frequently valued by readers in the country it describes as an insightful perspective by an outsider. Our introduction to this special issue on Bird’s travel writing of Japan creates multiple frameworks for understanding this text. We position it within post-1850 representations of Japan and travelogues of the country by women writers, the overall development of Bird’s literary career, and recent theories of Victorian globalism. We argue that Unbeaten Tracks can be read as simultaneously radical and conservative, sympathetic and denunciatory, staunchly imperial and anticipatory of postcolonial critique, making it a rich object of study and an important touchstone in Victorian travel writing. If Bird’s writing occasionally seems to confirm (and to revel in) familiar stereotypes of Victorian travellers as condescending, repressed, and parochial, it can also be linked to more recent understandings of a global nineteenth century already possessing cosmopolitan awareness and utopian horizons.

Wind tunnel as a tool in bird migration research

Wind tunnels, in which birds fly against an artificially generated air flow, have since long been used to evaluate aerodynamic properties of steady bird flight. A new generation of wind tunnels has also allowed the many processes associated with migratory flights to be studied in captivity. We review how wind tunnel studies of aerodynamics and migratory performance together have helped advancing our understanding of bird migration. Current migration theory is based on the power‐speed relationship of flight as well as flight range equations, both of which can be evaluated using birds flying in wind tunnels. In addition, and depending on wind tunnel properties, performance during gliding and climbing flight, and effects of air pressure, humidity and turbulence on bird flight has been measured. Long‐distance migrant species have been flown repeatedly for up to 16 h non‐stop, allowing detailed studies of the energy expenditure, fuel composition, protein turnover, water balance, immunocompetence and stress associated with sustained migratory flights. In addition, wind tunnels allow the fuelling periods between migratory flights to be studied from new angles. We end our review by suggesting several important topics for future wind tunnel studies, ranging from on of the key questions remaining, the efficiency at which chemical power in converted to mechanical power, to new useful avenues, such as improving and calibrating the techniques used for tracking of individual birds in the wild.

A predictive model for risk assessment on imminent bird strikes on airport areas

Wildlife hazard assessment (WHA) is a compulsory procedure on every significant international airport. With the appearance and integration of avian radar systems, the estimation of future bird tracks is possible, therefore the probability and severity of a bird strike can be assessed several minutes before that occurrence happens. Taking that into account, some mitigation procedures and actions could be implemented on airports in order to reduce the risk of the hazard. This work proposes a methodology for real-time evaluation of the risk assessment based on avian radar and aircraft data. This risk evaluation can trigger actions or procedures, within enough time, to significantly reduce the risk of a bird strike during critical flight phases. The risk estimation model combines the track of a bird and an aircraft (based on speed, altitude and heading), the proximity of the future crossing paths, the bird speed and mass, and the angle of impact. Simulation scenarios have been established to confirm if the mitigation actions could be implemented considering time of reaction, aircraft capabilities, and avian radar coverage. The proposed Risk Assessment method and mitigation actions to reduce the probability of a bird strike on aircrafts are a systematic and scientific approach to enhance flight safety on airports. This approach could be the basis for future mitigation protocols using more sophisticated actions in accordance with present and future technology.

Complex In-Substrate Dinosaur (Sauropoda, Ornithopoda) Foot Pathways Revealed by Deep Natural Track Casts from the Lower Cretaceous Xiagou and Zhonggou Formations, Gansu Province, China

ABSTRACTSeveral new Early Cretaceous tracksites from the Lower Cretaceous Xiagou Formation of Gansu Province (China) with tracks of large sauropods and ornithopods are described. Previously reported bird tracks were missing due to human negligence. The studied specimens are preserved as impressions and shallow and deep natural track casts. These dinosaur tracks are first reported from the Jiuquan area in the Changma Basin, matching well with the skeletal record of diverse non-avian dinosaur-bird faunas of this region. Moreover, they add new data to the dinosaur ichnofaunas of the Lanzhou-Minhe Basin (Gansu Province) and indicate a wide distribution of dinosaur-bird assemblages in the Early Cretaceous. Regarding morphology, sauropod, and ornithopod tracks from the Lanzhou-Minhe Basin and the Jiuquan area are very similar to each other. Titanosauriform trackmakers are assumed for the sauropod tracks and possibly iguanodontids have left the large, tridactyl ornithopod tracks. Of particular interest are well-preserved, deep natural track casts of large ornithopods and sauropods preserving ridges and grooves as well as striation marks on the lateral sides of the casts that allow the reconstruction of complex pathways of the foot within the substrate. One particular sauropod pes–manus track cast even indicates lateral and vertical sliding within the sediment because of the presence of “double impressions of digits” on the bottom.