The Avian Migrant: The Biology of Bird Migration (NONE)

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Discriminatory ability was compared under different assumptions. These percentages are greater than those reported for these species using sexing methods based only on wing length. Our method was not affected by changes between years in the degree of dimorphism or mixture of populations from different geographical origins. In the Iberian Chiffchaff and the Willow Warbler, sexing was improved when our method was applied to immatures and adults separately. Sex ratio was estimated to be two females per male in the Common Chiffchaff and the Willow Warbler. In the latter species, females migrated one week later than males.

Sex ratio in the Iberian Chiffchaff was Our sexing method could be used for other species with known and apparent dimorphism or to any data set of birds with biometric measures. Inability of biometry to discriminate Iberian and Common Chiffchaffs during the autumn migration period. The Iberian Chiffchaff Phylloscopus ibericus has recently been accepted as a full species, but is still very difficult to distinguish from the Common Chiffchaff P.

Distinguishing these cryptospecies is essential for obtaining accurate population estimates for each, which is especially important in the case of the Iberian Chiffchaff due to its restricted distribution.


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We re-assessed the discriminant methods available in the literature and propose some alternative traits to distinguish both species. We used information from 24 morphological traits measured in c. Discriminatory methods available in the literature were unable to distinguish the two species efficiently. Despite some biometric differences, morphological measurements showed a high degree of overlap and so could not distinguish between Iberian and Common Chiffchaffs.

Those traits associated with migration, such as wing size and shape and fat deposits, were also able to discriminate the species, albeit weakly. This result fully concurs with the trans-Saharan migration of the Iberian Chiffchaff in contrast to the Common Chiffchaff, which chiefly winters in Mediterranean latitudes. In conclusion, biometric traits are useless for discriminating the two species and we do not recommend their use.

A comprehensive examination of colouration and plumage seems to be the only reliable way of guaranteeing the correct identification of these species in the hand. Key words: autumn migration, cryptic species, discriminant analysis, identification, morphology, Phylloscopus. Environmental effects on flying migrants revealed by radar. Migratory animals are affected by various factors during their journeys, and the study of animal movement by radars has been instrumental in revealing key influences of the environment on flying migrants.

Radars enable the simultaneous Radars enable the simultaneous tracking of many individuals of almost all sizes within the radar range during day and night, and under low visibility conditions. We review how atmospheric conditions, geographic features and human development affect the behavior of migrating insects and birds as recorded by radars.

We focus on flight initiation and termination, as well as in-flight behavior that includes changes in animal flight direction, speed and altitude. Several similarities and differences in the behavioral responses of different aerial migrants include an overlooked similarity in the use of thermal updrafts by very small e. We propose that many aerial migrants modulate their migratory flights in relation to the interaction between atmospheric conditions and geographic features. For example, aerial migrants that encounter crosswind during flight may terminate their flight or continue their migration and may also drift or compensate for lateral displacement depending on their position over land, near the coast or over sea.

We propose several promising directions for future research, including the development and application of algorithms for tracking insects, bats and large aggregations of animals in weather radars. Additionally, an important contribution will be the spatial expansion of aeroecological radar studies to Africa, most of Asia and South America where no such studies have been undertaken.

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Quantifying the role of migrants in ecosystems and specifically estimating the number of departing birds from stopover sites using low-elevation radar scans is important for quantifying migrant-habitat relationships. This information, together with estimates of population demographics and migrant abundance, can help resolve the long-term dynamics of migrant populations that face large-scale environmental changes. Altitudinal migration by birds: a review of the literature and a comprehensive list of species. Altitudinal migration is the seasonal altitudinal movement of birds from breeding areas to non-breeding or wintering areas at different elevations.

Although this type of migration is widely reported, questions remain concerning the number Although this type of migration is widely reported, questions remain concerning the number of species that perform altitudinal migration, possible variation among different taxa and geographic locations in the extent of altitudinal migration, and the foraging guilds of altitudinal migrants.


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We conducted an extensive bibliographic survey and compiled a list of altitudinal migrant birds worldwide. We characterized species in terms of their foraging guilds because the spatial distribution of food resources along altitudinal gradients is often evoked as a driver of bird altitudinal migration. We found a strong geographic bias in publications focusing on avian altitudinal migration toward the United States and Costa Rica, and a paucity of studies in megadiverse regions such as the Afrotropical and Indomalayan realms, and areas in the Neotropics other than Costa Rica.

We also found that most species of altitudinal migrants were invertivores rather than frugivores or nectarivores. This general pattern held true for all zoogeographic realms except the Neotropics, where nectarivores and frugivores predominated among altitudinal migrants. The prevalence of invertivore birds among altitudinal migrants is not unexpected because this is the most common foraging guild among birds worldwide. Overall, we found no prevalence of any specific foraging guild among altitudinal migrants across zoogeographic regions.

The results of studies to date suggest that altitudinal migration by birds may be driven by a number of factors, including access to increased food resources for breeding or molting, weather conditions, and mating and nesting opportunities. However, to better understand the mechanisms underlying altitudinal migration, broadening the geographic scope of studies is paramount, with additional study of altitudinal migration especially needed in the megadiverse tropical regions of sub-Saharan Africa, Southeast Asia, and South America.

Status of Greater Flamingos Phoenicopterus roseus in Kerala. Determining the wintering range of Broad-winged Hawk Buteo platypterus in South America using citizen-science database. Several species of raptors that breed in North America migrate to the southern hemisphere during the non-breeding period. The Broad-winged Hawk Buteo platypterus is one of them, and its wintering distribution reaches the north and The Broad-winged Hawk Buteo platypterus is one of them, and its wintering distribution reaches the north and central part of South America, although there are published records for the species in Argentina and southern Brazil.

We did an exhaustive search of records of the Broad-winged Hawk for South America, using bibliography, citizen-science initiatives, personal communications, and own records. We obtained georeferenced records for the period. Both the numbers of records per year and the geographical range of the species have apparently increased in recent years.

The wintering range of this species is estimated to cover While it is possible that the range has expanded km southwards recently, with the data available it is not possible to disentangle this possibility from changes in the distribution of bird observers. Jonas Kilpp. The present report puts forth a systematic checklist of bird species observed at Amboli Ghat in Maharashtra from to , along with information on their status. A family-wise analysis showed that the families Accipitridae and Muscicapidae 14 species each followed by Ardeidae dominated the avifauna of the region.

The study also revealed that the area consisted of 11 species of birds that are classified under Near Threatened category and two under Vulnerable category of IUCN. This study highlights the urgent need to conserve the biodiversity-rich area of Amboli Ghat with long-term plans.

The Asian region is home to a high diversity of waterbirds, including an increasing number of threatened species, many at risk of extinction. Conservation of these species and their habitats needs to be based on quality and current Conservation of these species and their habitats needs to be based on quality and current information on their distribution and trends. To address this need, the Asian Waterbird Census AWC has been collating and disseminating information since to inform governments, conventions and the public.

The IWC is considered one of the largest and longest-running internationally coordinated citizen science biodiversity monitoring programmes in the world. The AWC currently covers 25 countries and regions of Asia and Australasia and takes place annually during the second and third weeks of January with additional counts being provided from some countries between late November to February.

Animal Migration

The census is carried out by volunteers, and in some cases government staff, interested in collecting information on waterbirds and wetlands as a basis for contributing to their conservation. The AWC has also built and strengthened national networks of enthusiastic and dedicated volunteers and facilitated their training as an integral part of achieving its objectives.

Assessing the evidence for climate driven phenology change in high altitude wetlands of Ladakh. This suggests they respond to an external stimulus, something triggering that irresistible migratory urge known as zugunruhe — from the German zug , meaning movement, and unruhe , or restlessness. But what tells them to depart? The most important indicator that the seasons are changing is probably sunlight. It is far from the only thing they pay attention to, however: in studies where day length was artificially kept constant, several species of migratory birds still knew when to leave.

Changes in air pressure, predictive of incoming weather, seem to have an influence, as does food availability. In , Peter Marra at the Smithsonian Migratory Bird Center in Washington DC demonstrated that American redstarts delay their spring departures if dry conditions in their overwintering areas mean they struggle to find enough food to prepare for the journey. Take the Arctic tern, whose monster detour means it may travel 60, kilometres a year farther than the most direct trip. Such diversions are typically down to finding suitable rest stops, but wind has a big say too.

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Because birds fly at speeds comparable to typical wind speeds, head and side winds can pose a considerable challenge. Last year, for instance, a team led by Kyle Horton at the University of Oklahoma used weather radar to track flocks of songbirds that migrated by night across North America. They found that the birds drifted sideways on crosswinds but then adjusted their course near the Atlantic coast to get back on track.

Another recent tracking study, this time following frigate birds migrating across the Indian Ocean, revealed not only that they seek out cumulus clouds so they can ride on the strong updraughts beneath them, but also that they appear to sleep as they ascend. Bar-headed geese , which migrate over the Himalayas, have a similar appreciation for the optimal elevation.

They constantly change height , descending into valleys where the air is denser and more oxygen-rich whenever they can, then climbing when necessary, using updraughts where possible. This significantly reduces the energetic cost and physiological strains of the trip. In any case, the choice of route is critical: a study tracking cuckoos, for example, found that at least two-thirds of the birds following an eastern route through Italy or the Balkans were likely to survive, whereas animals choosing a shorter route across Spain or Portugal faced a much higher risk of dying on the trip.

The researchers suspect that drought conditions in Spain, increasingly common over the years they studied, are to blame. The senses that birds rely on to find their way largely remain mysterious. This is especially true for species that travel individually, which means young birds have to figure out where to go without a flock to follow. It is safe to say that birds probably use all their senses: visual landmarks as well as the sun and the stars provide them with information on their position, as do smells for some species, especially seabirds. But there must be something else, because birds still show a clear tendency to take off in the right direction even in total darkness.

The first relies on crystals of magnetite, a form of iron oxide, found in the upper beaks of several species, including European robins and garden warblers. But it has proven maddeningly difficult to demonstrate that magnetite plays a part in magnetoreception.

Seasonal Interactions - The Tonra Lab of Avian Ecology

Perhaps the most promising work comes from fish. In , Michael Winklhofer at the Ludwig Maximilian University of Munich, Germany, took cells containing magnetite clusters from the snouts of rainbow trout and placed them under a microscope around which an artificial magnetic field was rotated. Sure enough, the cells also rotated — and their sensitivity was much greater than expected. The alternative explanation involves light-sensitive proteins called cryptochromes, found in the eyes of all kinds of migratory animals.

The idea is that magnetic fields alter a quantum property called spin in the electrons within these molecules, flipping them back and forth between two different states. Studies have shown that these proteins are sensitive to magnetic fields. Again, though, the task is to see the process in action in a living being and show it is connected to its brain. One recent study suggested the two mechanisms could be part of the same system.

Although statistics on causes of death for migratory birds are hard to come by, there are plenty of ways to die. Storms, for starters. And yet one recent tracking study dramatically reveals how resilient some birds can be: a whimbrel caught in tropical storm Gert, off the coast of eastern Canada, was found to have endured extreme head winds for 27 hours.

By far the greatest threat comes from humans. Some of the countries in and around the Mediterranean are notorious for the annual slaughter of migratory birds. Some Caribbean islands have a similar reputation.



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