migratory birds use their visual system to perceive the reference compass direction of the geomagnetic field and that migratory birds “see” the reference compass direction provided by the geomagnetic field.
The magnetite-mediated mechanism seems to act as part of a magnetic map- or signpost sense, which could provide the animal with information about its geographic position, whereas the vision-mediated magnetic sense seems to be a pure compass sense that is based on radical-pair processes in the birds' eye(s)
(cryptochromes)
the Wulst is the telencephalic termination area of the thalamofugal pathway which conveys visual input from the retina onto the forebrain via the Gld [18], [19].
Cluster N processes some kind of night-time visual information processing which is a specialization of night-migratory birds [for detailed arguments], [see 13, 14]. Combined with these findings, the present tracing data for the first time suggest a putative magnetosensory compass pathway from the sensory organ (the eye) to its main integrative brain center (Cluster N) in night-migratory birds. This putative compass-magnetosensory pathway involves restricted subregions at all levels of the thalamofugal visual pathway: neuronal subpopulations in the retina, ventral parts of the thalamic Gld (lateral and ventral DLL, SpRt, LdOPT) and lateral parts of the visual wulst (Cluster N). Due to the fact that a known visual pathway connects the only brain structures that have been shown to be active during magnetic orientation, our findings strongly support the hypothesis that migratory birds perceive the magnetic field as a visual pattern and that they are thus likely to “see” the magnetic field.

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Bird Nerds: Using the Web to Net Our Feathered Friends: Scientific American

Combining standard field biology techniques with a Web-accessible robotic camera positioned at the Welder Wildlife Refuge in Sinton, Tex., scientists and amateur ornithologists are trying to determine whether the sighting of subtropical birds well north of their natural habitat is proof of climate change and a profound shift in wildlife migration patterns.

Tags: bird, migration, craigslist, climate_crisis on 2008-09-01 -All Annotations (0) -About

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Here To There Dept.: A Bird’s Life: The Talk of the Town: The New Yorker

After such a night, a warbler drops out of the predawn sky in a condition called “hyperphagia,’’ from the Greek for “eat’’ and “a lot.’’ It must rebuild its body fat to stay alive and to fuel the next stage of its journey. To know how the city affects birds, Seewagen and Slayton need to know whether they are able to get enough food to plump up to flying weight.

Tags: bird, migration, new_york, new_york_city, warbler on 2008-09-01 -All Annotations (0) -About

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PLoS Biology - Going, Going, Gone: Is Animal Migration Disappearing

Tags: bird, migration, ecology, conservation, open_science, biodiversity, world, government on 2008-08-15 -All Annotations (0) -About

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Birdwatchers in North America and Europe, for example, complain that fewer songbirds are returning each spring from their winter quarters in Latin America and Africa
the threats to migrants fall into four nonexclusive categories: habitat destruction, the creation of obstacles and barriers such as dams and fences, overexploitation, and climate change
Protecting the abundance of migrants is the key to protecting the ecological importance of migration. As the number of migrants declines, so too do many of the most important ecological properties and services associated with them.
But if migration is seen as a phenomenon of abundance, then its protection will require decision makers to adopt a much more proactive approach to conservation—in effect, to protect species while they are still abundant.
species with large breeding or wintering ranges and diffuse migratory routes may be less vulnerable to individual threats, yet more difficult to conserve.
The long-term conservation of the cerulean warbler (and, we suspect, many other migrants as well) will require a broad-based, mixed strategy: creation of numerous reserves in the breeding and wintering grounds (largely by government agencies); identification and protection of key stopover sites (by government agencies and private organizations); and the use of financial incentives to encourage landowners to protect smaller patches of habitat that may be important to the warblers during their migration.

woodcreeper » New arrivals overnight

Tags: bird, migration, zugunruhe, weather on 2008-04-21 -All Annotations (0) -About

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It's Time to Discuss Migration, but I've Got to Be Moving On

Tags: migration, bird, biology, behavior, zugunruhe on 2008-04-21 -All Annotations (0) -About

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Did Your Shopping List Kill a Songbird? - New York Times

Tags: agriculture, bird, farming, food, migration, organic, pesticide, pollution, south_america on 2008-04-01 -All Annotations (0) -About

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Migratory birds, modern-day canaries in the coal mine, reveal an environmental problem hidden to consumers. Testing by the United States Food and Drug Administration shows that fruits and vegetables imported from Latin America are three times as likely to violate Environmental Protection Agency standards for pesticide residues as the same foods grown in the United States. Some but not all pesticide residues can be removed by washing or peeling produce, but tests by the Centers for Disease Control show that most Americans carry traces of pesticides in their blood. American consumers can discourage this poisoning by avoiding foods that are bad for the environment, bad for farmers in Latin America and, in the worst cases, bad for their own families.
melons, green beans, tomatoes, bell peppers and strawberries, it can be difficult to find any that are organically grown. We should buy these foods only if they are not imported from Latin America.
traditional small coffee farmers grow their beans under a canopy of tropical trees, which provide shade and essential nitrogen, and fertilize their soil naturally with leaf litter.
A single application of a highly toxic pesticide to a field can kill seven to 25 songbirds per acre.
Since the 1980s, pesticide use has increased fivefold in Latin America as countries have expanded their production of nontraditional crops to fuel the demand for fresh produce during winter in North America and Europe. Rice farmers in the region use monocrotophos, methamidophos and carbofuran, all agricultural chemicals that are rated Class I toxins by the World Health Organization, are highly toxic to birds, and are either restricted or banned in the United States. In countries like Guatemala, Honduras and Ecuador, researchers have found that farmers spray their crops heavily and repeatedly with a chemical cocktail of dangerous pesticides.
Bananas are typically grown with one of the highest pesticide loads of any tropical crop. Although bananas present little risk of pesticide ingestion to the consumer, the environment where they are grown is heavily contaminated.

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Songs and Sojourns of the Season - New York Times

Tags: bird, migration on 2007-09-18 -All Annotations (0) -About

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