Category Archives: migration

Worse Year for Monarchs

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Monarch_butterflyDepending on where you live, you may have noticed it in autumn. There were very few monarch butterflies around. It wasn’t unexpected. Numbers were low last winter in Mexico, and the weather over the summer didn’t favor the hatching of new monarchs.

World Wildlife Fund, Mexico’s Environment Department and the Natural Protected Areas Commission just announced that the numbers of monarch butterflies overwintering among the Transvolcanic mountains of central Mexico are the lowest since they started keeping records back in 1993. They measure the butterflies in the number of hectares that they cover in the park. This winter they covered 0.67 hectares. At their recorded high, in the winter of ’95-’96 they covered over 20 hectares.

Why, oh, why, do you ask? At one time the forest where the monarchs roost over the winter was being cut down, but that problem seems to have been solved. Climate change is in the mix. But the big problem, according to MonarchWatch, at the University of Kansas, is that herbicide tolerant (HT) crops have removed milkweed from a part of the country vital to the monarchs’ migration: the Midwest.

Read the report from MonarchWatch, here. It includes all the details on the HT crops theory.
Read the Associated Press news story in SF Gate, here.

Photo: by Mark Musselman, courtesy US Fish and Wildlife Service

Bat Movement Study

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cumberland gap wns batBats move around a lot. Some bats migrate. Some bats move from summer or maternity roosts to winter hibernation caves. Finding out how bats move has suddenly become extremely important. White nose syndrome seems to be following the known patterns of bat movement. But just so little is known.

Erin Fraser used stable isotopes to study the migration patterns of tri-colored bats (aka eastern pipistrelles) for her doctoral work at Western University in London, Ontario, Canada. Bat Conservation International helped fund the work, so they have lots of details in their newsletter, here.

You can learn more about using stable isotopes in ecological research in this article in the online publication Yale Environment 360, here.

Photo: A tri-colored bat found at Cumberland Gap National Historical Park
shows visible signs of white-nose syndrome. Courtesy National Park Service

Geolocators in The Auk

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Auk 4 13 coverGeolocators are a relatively new tool that allows researchers to track the movements of small animals, such as birds.

Instead of sending and receiving a radio signal, geolocators record the angle of sunlight at given hours of the day. You must collect the geolocator unit to retrieve the data. Without the send and receive functions, the unit can be much smaller than other tracking devices. Geolocators have been used even on small songbirds. An algorithm lets you translate the sun angle at a given time into a latitude.

Clearly, it’s a technology with a lot of potential and a lot of limitations. If you are interested in how geolocators can inform your own research, check out the April issue of The Auk, which contains two special sections on geolocator research. The issue’s introductory article is a primer on geolocators, and it’s open access. Read it here.

Geolocators in The Auk

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Auk 4 13 coverGeolocators are a relatively new tool that allows researchers to track the movements of small animals, such as birds.

Instead of sending and receiving a radio signal, geolocators record the angle of sunlight at given hours of the day. You must collect the geolocator unit to retrieve the data. Without the send and receive functions, the unit can be much smaller than other tracking devices. Geolocators have been used even on small songbirds. An algorithm lets you translate the sun angle at a given time into a latitude.

Clearly, it’s a technology with a lot of potential and a lot of limitations. If you are interested in how geolocators can inform your own research, check out the April issue of The Auk, which contains two special sections on geolocator research. The issue’s introductory article is a primer on geolocators, and it’s open access. Read it here.

Thousands of Grebes Crash in Utah Desert

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eared grebe utahSome 5,000 eared grebes mistook pavement for water at the Dugway Proving Ground in Utah, the Salt Lake City Tribune reports. Hundreds of the birds died after their hard landing. Because the birds cannot take flight from dry land, Utah Division of Wildlife Resources personnel collected the living birds and transported them to nearby ponds.

Other birds were treated for their injuries or euthanized, the Tribune article says. The article also notes that the night was foggy, the pavement was wet and the grebes were on their spring migration to the Great Salt Lake.

The article also notes that 17 months ago migrating eared grebes crashed in a Wal-Mart parking lot, where about 1,500 of the grebes died.

Read the Salt Lake City Tribune article here.
Check out the slide show with the article, which includes beautiful grebe photos and state wildlife staffers at work.
Read a Utah DWR newsletter on loons and grebes.

Photo Copyright Nicky Davis. Eared grebe in happier times. Photo used courtesy of the Utah Department of Wildlife Resources.

Migrations At Risk

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The spectacular migrations of North America’s western half are under threat, says a new report from the Wildlife Conservation Society (WCS; the people who bring you the Bronx Zoo). These migrations include elk, caribou and calliope hummingbirds. The report doesn’t focus on specific threats to these long-distance migration as much as it points out which have the most potential to be saved by appealing to public interest.

The survey polled fish and wildlife biologists from 11 western states including Alaska, Washington, Oregon, Idaho, Montana, Nevada, Wyoming, Colorado, Utah, Arizona and New Mexico as well as drawing on the expertise of WCS’ own experts.

Read the report (a 45-page PDF here.)
Read a New York Times article on the report, here.

Photo: Caribou in the Arctic National Wildlife Refuge, courtesy US Fish and Wildlife Service

Water on the Wing

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It’s no surprise that birds lose fat during migration, but the loss of muscle mass, even when there is still fat to burn, has been a puzzle. A paper in the Sept. 9 issue of the journal Science shows that by metabolizing muscles and organs, the birds gain water.

In wind tunnel tests with Swainson’s thrushes, the researchers found that, even flying hard with no water to drink, the birds maintained their water balance in very dry conditions.

Read the paper in Science (fee or subscription required), here.

Or read the promotional blurb from the journal announcing the paper here.

NPR covered the story, as did the Los Angeles Times.

Photo: Swainson’s thrush, courtesy National Park Service

Climate change and bird feeders

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Even when bird feeders are readily available, some species of birds head for warmer climes, says a paper in the latest issue of the Journal of Animal Ecology. The scientists, who are affiliated with the Cornell Lab of Ornithology’s Project FeederWatch, studied 18 bird species that are common at bird feeders in the northeastern US and found that some species of birds did not stick around over the winter in spite of there being plenty to eat at bird feeders.

They also found that the birds that stayed north in winter were more likely to visit a bird feeder during a cold snap. Finally, the scientists found that for species that tolerate urban life, such as house sparrows, the abundant bird feeders in developed areas provide a winter refuge. Species that find urban life stressful, such as downy woodpeckers, are less likely to stay in developed areas during winter.

The scientists note that when predicting how climate change will influence a bird species, these other factors, such as tolerance to urbanization, need to be considered as well.

You can find the paper here, and a simple summary of the work on the Project FeederWatch blog.

Photo: I say it’s a nuthatch, although admittedly not the nuthatch species in this study. So don’t look too closely at the bird, just look at the bird feeder and the pretty green background, OK?

Climate change and bird feeders

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Even when bird feeders are readily available, some species of birds head for warmer climes, says a paper in the latest issue of the Journal of Animal Ecology. The scientists, who are affiliated with the Cornell Lab of Ornithology’s Project FeederWatch, studied 18 bird species that are common at bird feeders in the northeastern US and found that some species of birds did not stick around over the winter in spite of there being plenty to eat at bird feeders.

They also found that the birds that stayed north in winter were more likely to visit a bird feeder during a cold snap. Finally, the scientists found that for species that tolerate urban life, such as house sparrows, the abundant bird feeders in developed areas provide a winter refuge. Species that find urban life stressful, such as downy woodpeckers, are less likely to stay in developed areas during winter.

The scientists note that when predicting how climate change will influence a bird species, these other factors, such as tolerance to urbanization, need to be considered as well.

You can find the paper here, and a simple summary of the work on the Project FeederWatch blog.

Photo: I say it’s a nuthatch, although admittedly not the nuthatch species in this study. So don’t look too closely at the bird, just look at the bird feeder and the pretty green background, OK?

Stopover or staging area?

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A stopover site is any site where one bird or many stops to rest or feed during migration, says a paper in the current issue of the Journal of Avian Biology. The term “staging area” should be reserved for “sites with abundant, predictable food resources where birds prepare for an energetic challenge (usually a long flight over a barrier such as an ocean or a desert)” the author says.

Read more from the paper in the Journal of Avian Biology here.