Migration Hazards in the Mediterranean

Cyprus: A whitethroat, en route to winter grounds in Africa, is caught on a lime stick. © David Guttenfelder/National Geographic See more at the link.

Long-distance migrants pose complex problems for conservation. Such birds have far-flung breeding and wintering grounds and use multiple places to rest and refuel during migration. They may cross national, even continental, boundaries. A rapidly disappearing species may face threats at any or all of the places it visits. These threats may not all be of the same variety, and it may not be immediately clear which place poses the greatest hazard. In North America, we are familiar with the plight of the Red Knot, whose population is severely threatened because of two decades of overharvesting horseshoe crabs at migratory stopover points but which also might be affected by climate change on its breeding grounds. Loss of stopover habitat in eastern Asia may also explain the disappearance of most of the world's Spoon-billed Sandpiper population.

It seems that a similar situation has taken hold in the Mediterranean. Many birds breed in Europe and spend the rest of the year in Africa. While passing between those two areas, they must stop at multiple points around the Mediterranean. There danger lurks in the form of nearly unrestricted hunting, as Jonathan Franzen reports in the July issue of National Geographic:

Italian hunters and poachers are the most notorious; for much of the year, the woods and wetlands of rural Italy crackle with gunfire and songbird traps. The food-loving French continue to eat ortolan buntings illegally, and France’s singularly long list of huntable birds includes many struggling species of shorebirds. Songbird trapping is still widespread in parts of Spain; Maltese hunters, frustrated by a lack of native quarry, blast migrating raptors out of the sky; Cypriots harvest warblers on an industrial scale and consume them by the plateful, in defiance of the law.

In the European Union, however, there are at least theoretical constraints on the killing of migratory birds. Public opinion in the EU tends to favor conservation, and a variety of nature-protection groups are helping governments enforce the law. (In Sicily, formerly a hot spot for raptor killing, poaching has been all but eliminated, and some of the former poachers have even become bird-watchers.) Where the situation for migrants is not improving is in the non-EU Mediterranean. In fact, when I visited Albania and Egypt last year, I found that it’s becoming dramatically worse.

This is not simply subsistence hunting. The most sophisticated operations capture hundreds or thousands of birds to sell at market. Captured falcons may retail for tens of thousands of dollars. Some hunt birds as a form of recreation, but without the bag limits that restrain recreational hunting in North America. Bag totals have gone up thanks to technological improvements:

Even as quail are becoming very difficult to find in much of Europe, the take in Egypt is increasing, due to the burgeoning use of playback technology. The best system, Bird Sound, whose digital chip holds high-quality recordings of a hundred different bird sounds, is illegal to use for hunting purposes in the EU but is nevertheless sold in stores with no questions asked. In Alexandria, I spoke with a sport hunter, Wael Karawia, who claimed to have introduced Bird Sound to Egypt in 2009. Karawia said he now feels “very bad, very regretful” about it. Normally, perhaps three-quarters of incoming quail fly over the mist nets, but hunters using Bird Sound can attract the higher flying ones as well; already all the mist netters in north Sinai are doing it, some of them in spring as well as fall. Hunters on Egypt’s large lakes have also begun to use Bird Sound to capture entire flocks of ducks at night.

Both mist nets and bird sound recordings are useful for conservation. Bird banders use mist nets to capture, record, and release birds as a part of long-term population monitoring. Bird recordings help birders and ornithologists learn to identify bird sounds, and playback can be used for scientific surveys, particularly of nocturnal species. Like other tools, though, they can be used for good or ill, and in this article we see their darker side.

Hunting around the Mediterranean is not the only threat to these birds. On their European breeding grounds, they face habitat degradation and pressure from poachers and egg collectors. Climate change may disrupt food availability. As Franzen's report shows, the solutions for protecting long-distance migrants will not be simple or easy.

Read the full article.

On the Snowy Owl Invasion

Snowy Owls have migrated south in impressive numbers this winter. Unlike some irruptions, which affect one part of the continent but not others, this year's Snowy Owl irruption has been observed across North America. Even Hawaii recorded a Snowy Owl, a first state record (which was promptly shot by airport officials). The New York Times reports on the scale of the Snowy Owl irruption:

The irruption started in late fall and is expected to end by March or April. In few places are people as excited as in Kansas and Missouri, where snowy owls are exceedingly rare. Ninety have shown up in Kansas this winter and 40 in Missouri. Until this year, the highest number counted in Missouri had been eight.

“It’s a massive movement,” said Mark Robbins, the ornithology collection manager at the University of Kansas.

When five of the birds took up residency at Smithville Lake, near Kansas City, Mo., it created an “owl jam,” Mr. Robbins said. Thousands of people have driven there to see them, he said, and hundreds of owl seekers have shown up at Clinton Lake near Lawrence, Kan....

Geoff LeBaron, director of the Audubon Society’s Christmas bird count, said that it was hard to estimate how many snowy owls flew south in this irruption because the latest data has not been tallied, but that the overall number was probably a few thousand. Despite the surge, the society says, snowy owls are thought to have been in decline since 1945.

There is far more data on the scope of this migration than in years past, thanks to a citizen science project based at Cornell called eBird, which is run by the Cornell Lab of Ornithology and the Audubon Society. Bird-watchers around the country call in sightings, which are plotted on a map that shows precisely where the birds are wintering.

“A lot of people who have never seen one before have rushed out and seen multiples,” said Marshall Iliff, an ornithologist at Cornell and the project’s leader. “And photographers are having a field day.”

Additional hot spots include the mouth of the Columbia River in Washington State, with 10 to 13 birds; 20 at Lake Andes National Wildlife Refuge in South Dakota, and 30 in Boundary Bay, near Vancouver in British Columbia.

The owls are even showing up in urban and suburban areas, along highways, on signs and fence posts, and in other places where people can more easily spot them. It has been a good snowy owl year at Logan Airport in Boston, too. Because the airfield looks like tundra, snowy owls tend to flock there, and they must be trapped and removed.

“We’ve removed 21 so far this year, and the average is six,” said Norman Smith, who works for the Massachusetts Audubon Society and traps the birds. The most ever trapped was 43 in 1986, Mr. Smith said, “but the year’s not over.”

To be more precise, birders do not "call in sightings" to eBird but enter sightings through web-based checklist forms on the eBird website. For more on the causes behind this year's Snowy Owl irruption, see this post by David Sibley. He gives a more clear account of what probably happened than The New York Times does.

I have only seen the one Snowy Owl (pictured) that was present at Merrill Creek Reservoir so far this winter. So this winter has not been quite as memorable for me as the winter of 2009, when I saw four Snowy Owls over the course of the winter, or the winter of 2010, when I saw two Snowy Owls at Parker River NWR in Massachusetts during the Superbowl of Birding.

Whooping Cranes Headed South

Whooping Cranes / USFWS Photo

This year's flock of captive-bred Whooping Cranes will be headed south soon, under the guidance of Operation Migration's ultralight aircraft.

There are 10 cranes in the 2011 flock, five male and five female. This year, the birds were trained how to follow the ultralight planes at a new site, the White River Marsh State Wildlife Area, which is southeast of Necedah, Wis., where earlier flocks have been trained.

The endangered birds are part of an effort by the Whooping Crane Eastern Partnership, a consortium of government and private agencies from Canada and the United States that works to ensure the crane's survival.

Before the whoopers are born, the sound of ultralight aircraft is played near the eggs. After they are born, the birds are fed and cared for by people dressed in whooping crane costumes carrying whooping crane puppets. No one ever speaks near the birds to prevent them from bonding with humans.

The birds imprint on the ultralights and their costumed pilots, and are trained to follow the aircraft to learn how to migrate.

The program is designed to create a second migratory flock of whoopers in the event members of the only existing wild migrating flock, which flies from Canada to the Texas Gulf Coast, get sick or die off. The goal is to have 125 individual birds, including 25 breeding pairs, in the Eastern Migratory flock.

Once the birds finish their southern migration, they fly north on their own in the spring. The first year of the program, 2001, was also the migration that took the least amount of time, only 48 days. The longest migration was 97 days in 2007. The length of the trip depends on weather conditions. For the safety of the pilots and their precious charges, they only fly in favorable weather.

Half of the cranes will spend the winter at St. Mark's NWR, and the other half will winter at Chassahowitzka NWR. Currently there are 96 Whooping Cranes in the eastern migratory population and about 400 overall in the wild.

You can follow updates about the journey on the Operation Migration website.

Monarch Migration

There is a large butterfly bush with white flowers outside my window. On most days I see a few butterflies at it, and some days there are a lot, with multiple species visiting it. Yesterday, this bush was covered with Monarchs. I could see at least a dozen at a time, and I could tell that more were present because I cannot see the entire bush from one position, and Monarchs kept arriving and leaving. Normally there will only be one or two Monarchs among the butterflies at the bush, so I think there must have been a major migratory movement yesterday.

Monarchs are probably the most familiar insects to the general public, as they are often used in schools as examples of biological phenomena like metamorphosis and mimicry. They are also large, colorful, and (at times) plentiful, so they are easily noticed even by people whose eyes are not tuned to insect movements.

Unlike most butterflies, Monarchs are fully migratory. In the fall, the eastern population migrates to wintering grounds in central and southern Mexico, while the western population retreats to southern California. In spring, these routes are reversed. No individual Monarch completes the entire round trip. Rather, females from the wintering population lay eggs in February or March, and subsequent generations complete the northward journey.

As with birds, geography influences Monarch migration. The best places to see large numbers of Monarchs at once are at southward-pointing peninsulas, like Cape May Point in New Jersey. Sometimes the air will be so full of Monarchs (and dragonflies!) that it can be hard to pick out birds from other flying things. One of my most memorable experiences of Monarchs was at Point Lookout State Park in Maryland on a chilly October morning when thousands of Monarchs were gathered at the point of the peninsula as they waited to warm enough to continue their journey. Migration occurs across a broad front, however, so you may see increased numbers in other butterfly gardens as Monarchs migrate.

Winter Finch Forecast

Purple Finch / USFWS Photo

Even though the season just turned to autumn, Ron Pittaway has issued his annual forecast for the migration of winter finches and associated birds in eastern Canada and the northeastern United States. This is a useful service for birders since many finch species do not follow the same migration pattern each year. Instead they move in response to the availability of seed crops, which vary from year to year. If the seed crop in the boreal forest is really good, finches stay in the boreal forest. If the crop is sparse, they move to a location with a better crop, which could take them south, west, or east. Heavy southward movement of one or more finch species is known as an "irruption."

This year the seed crops are good, so mass southward migration is unlikely. These species seem the most likely to wander south:

PURPLE FINCH: Purple Finches will be uncommon in Ontario, but probably in higher numbers in Atlantic Canada, New York and New England where cone crops are excellent. A few may frequent feeders in southern Ontario. The Purple Finch has declined significantly in recent decades. Some suggest it declined due to competition with the House Finch. However, the drop in numbers began before House Finches were common in eastern North America and also occurred where House Finches were absent. A better explanation for the decrease is the absence of large spruce budworm outbreaks that probably sustained higher Purple Finch populations in the past....

PINE SISKIN: The nomadic siskin is a spruce seed specialist. There are currently large numbers of siskins in Yukon including a high proportion of hatch year birds. They will move because the spruce crop is average in Yukon and Alaska this year, possibly coming to the East. Siskins are expected to be widespread across Ontario this winter. Good numbers are likely to be drawn to the excellent spruce and hemlock crops in Atlantic Canada, New York and New England....

RED-BREASTED NUTHATCH: This nuthatch is a conifer seed specialist when it winters in the north and its movements are triggered by the same crops as some of the boreal finches. There has been very little southward movement indicating that this nuthatch will winter in areas with heavy cone crops such as the boreal forest, Quebec, Atlantic Canada, New York and New England States.

Read the full report for information on the other species. To read more about which birds are classed as winter finches and their habits, see this essay by Ron Pittaway (pdf).

Missing Life Birds

Yesterday I made an attempt to see the Painted Bunting that had been appearing at a feeder in Absecon, NJ. I waited in front of the feeder for about an hour and a half. In that time plenty of birds passed by the yard – resident House Sparrows, Northern Cardinals, and House Finches; a Red-bellied Woodpecker; singing Carolina Chickadees; an Osprey; and a flock of Double-crested Cormorants flying overhead. However, there was no sign of the bunting. From what I understand, the bird was last seen on Thursday. The bunting would have been a life bird, and it becomes one of several that I have missed this spring. After a glut of life birds at the Superbowl of Birding, my life list building has slowed considerably.

In the afternoon, I tried to find an Audubon's Yellow-rumped Warbler that had been spotted the previous morning at Lake Lily in Cape May Point. I walked all around the lake, checking every warbler and warbler-like flying object. There were plenty of Myrtles, but no sign of the Audubon's. For those unfamiliar with the terms, Myrtle is the subspecies of Yellow-rumped Warbler normally found in eastern North America, while Audubon's dwells in the west. These forms were previously considered separate species and may one day be split again.

Even though I missed the potential future armchair-lifer, the trip around the lake was not a waste. The Myrtles were nice to see and hear, especially in their bright spring plumage. I saw several year birds. These included Blue-gray Gnatcatcher, Great-crested Flycatcher, and Prairie Warbler. Even better, there was a very cooperative Yellow-throated Warbler in front of one of the houses bordering the lake. My only previous sighting of this species was a singing bird at the top of a tall pine tree in Virginia. The look was good enough to recognize it, but it was not very satisfying. This view was much better, as the warbler crept along a rooftop gutter like a nuthatch and then flitted through nearby trees and shrubs, usually no more than 10 feet off the ground.

I do not have a photograph of the Painted Bunting or Yellow-throated Warbler, so take a look at this Mute Swan instead.

Changes in Rainfall Affect Birds' Wintering Grounds

Migratory bird species that breed in the U.S. and Canada often winter in the Caribbean, Central America, and South America. A Smithsonian study of American Redstarts on their wintering grounds in Jamaica found that rainfall changes disrupted the birds' migration schedule in the spring.

Precipitation in Jamaica is highly seasonal, with consistent rainfall from September to November and a pronounced dry season from January to March. The scientists observed the redstarts in their non-breeding territories for five years during the dry season. They paid special attention to the annual variation in dry season rainfall. The correlation between the amount of insects in a bird's territory and the timing of its departure suggested to the team that annual variation in food availability was an important determining factor in the timing of spring migration. Had the redstarts relied on internal cues alone to schedule their spring departure, they would have all left their winter territories at the same time each year.

"Our results support the idea that environmental conditions on tropical non-breeding areas can influence the departure time for spring migration," said Colin Studds, a postdoctoral fellow at the Smithsonian Conservation Biology Institute's Migratory Bird Center and lead author of the study. "We found that the same birds changed their spring departure from one year to the next in relation to the amount of rainfall and food in March."

During the past 16 years, the dry season in Jamaica has become both increasingly severe and unpredictable, leading to an 11 percent drop in total rainfall during the three-month annual drought. Making the future even more dire, climate models predict not only increased warming on temperate breeding areas but also continued drying in the Caribbean.

The result has obvious implications for climate change, since warmer average temperatures are likely to reduce rainfall in many areas. A major question is how birds will cope with the disrupted migration schedule. In many cases, birds time their migrations to arrive on their breeding grounds just as certain food sources are becoming available, whether those are insects or seeds or some other source.

Migrating Shorebirds May Use Food from Stopover Sites for Egg-laying

Since migration and egg production both require a significant amount of energy, it was uncertain whether long distance migrants used all of the food they consumed at stopover sites for migrating (and used food from the breeding grounds for egg production) or whether they used some for migrating and some for egg production. The question now appears to have an answer, at least for Pectoral Sandpipers. Sandpipers that arrive early at the breeding grounds use energy stored from stopover sites, and birds that arrive later eat to produce eggs.

By means of an isotope ratio mass spectrometer, the scientists studied different isotopes in the diet and the tissue of the birds to determine the origin of the accumulated resources. Using the distribution of stable carbon and hydrogen isotopes they could reveal when those elements had been incorporated through the diet. First, it was found that the values of the stable carbon isotope C13 in blood plasma of females, but also in feathers and claws, were different from those of their chicks. Moreover, the chick values showed an isotopic signature that was clearly different from the local diet.

From this observation the researchers concluded that the resources for egg formation could not originate from nutrients of the breeding area. Interestingly, isotopic values of female red blood cells matched those of the offspring, suggesting that resources were acquired somewhere along the migratory route. The wintering site as origin could be excluded, because in this case the red blood cell values should correspond to those of claws and feathers (assuming that birds moult in the wintering site). "The stable isotope analysis allowed us to confirm the hypothesis that body stores of migrating sandpipers are acquired at stopover sites along their migratory routes. This finding emphasizes the importance of these stopover sites for the well-being of the population", explains Bart Kempenaers, director at the Max Planck Institute for Ornithology in Seewiesen.

The data analysis revealed another surprising result. As the breeding season progressed, the isotopic values of females and chicks became more similar to those of the diet. This means, females that started egg laying later in the season mainly used dietary items from the breeding site, such as crane fly larvae and oligochaetes, as resources for egg production. "It suggests that pectoral sandpipers adopt different strategies for resource allocation according to their arrival time and the start of breeding", argues Elizabeth Yohannes, first author of the study.

But the question remains why some birds arrive earlier than others. Again, this could be answered with the help of stable isotopes. When the researchers analysed the hydrogen isotopic composition from feathers of female pectoral sandpipers, they found that these values corresponded closely to those of precipitation in northeastern South America. Presumably, birds overwinter in different areas (where they also moult their feathers), and those that start off from northern South America migrate shorter distances and therefore, arrive at the breeding ground in Alaska earlier than their conspecifics that start further south. However, details on the routes and timing of migration, and whether the different breeding strategies have an impact on the reproductive success of pectoral sandpipers are still unknown.

Winter Finch Forecast for 2010-2011

Purple Finch / USFWS Photo

Ron Pittaway, a respected Canadian ornithologist, recently released his winter finch forecast for the upcoming winter. It has already bounced around a few birding listserves; that link points to the version on eBird. The forecast will eventually be posted on the Ontario Field Ornithologists website, where you can see an archive of forecasts from past years. Pittaway's forecasts are written primarily for birders in Ontario, but they are useful for birders in the northeastern and mid-Atlantic U.S. as well.

Most migratory songbird species, such as wood warblers and thrushes, migrate south each winter because their primary food sources (invertebrates) are not available during northern winters. Other species, such as cardinals and chickadees, tend to stay where they are since their food sources are usually not disrupted. A small group of boreal species, mostly finches, migrates south in some years but not in others. These migrations, known as irruptions, are triggered by year-to-year changes in the seed crops of conifers, birches, aspens, and mountain-ashes in the boreal forest.

Which bird species will irrupt in a given year can be predicted on the basis of which seed crops are abundant and which are scarce. Here are a few species that may migrate south this winter:

Purple Finch: This finch winters in the north when the majority of deciduous and coniferous seed crops are abundant, which is not the case this year. Most Purple Finches will migrate south of Ontario this fall. A few may frequent feeders in southern Ontario. Purple Finch numbers have declined significantly in recent decades due in part to a decrease of spruce budworm outbreaks since the 1980s (Leckie and Cadman in Atlas of Breeding Birds of Ontario 2007).

Common Redpoll: Redpolls should irrupt into southern Canada and the northern United States this winter. The Common Redpoll's breeding range in Ontario is mainly in the Hudson Bay Lowlands from the Manitoba border southeast to southern James Bay (Leckie and Pittaway in Atlas of Breeding Birds of Ontario 2007). Redpolls in winter are a birch seed specialist and movements are linked in part to the size of the birch crop. The white birch crop is poor across much of northern Canada. Another indicator of an upcoming irruption was a good redpoll breeding season in 2010 with double and possibly triple broods reported in Quebec. High breeding success also was reported in Yukon. Samuel Denault of McGill University has shown that redpoll movements at Tadoussac, Quebec, are more related to reproductive success than to tree seed crops in the boreal forest. Redpolls will be attracted to the good birch seed crops on native white birch and European white birch in southern Ontario and to weedy fields. They should be frequent this winter at feeders offering nyger and black oil sunflower seeds. Watch for the larger, darker and browner "Greater" Common Redpolls (rostrata subspecies) in the flocks. It is reliably identified by its larger size and proportionally longer thicker bill and longer tail in direct comparison with "Southern" Common Redpolls (nominate flammea subspecies).

Hoary Redpoll: The breeding population in northern Ontario is the most southerly in the world (Leckie and Pittaway in Atlas of Breeding Birds of Ontario 2007). Careful checking of redpoll flocks should produce a few Hoary Redpolls. There are two subspecies. Most Hoaries seen in southern Canada and northern United States are "Southern" Hoary Redpolls (exilipes subspecies). During the last large redpoll irruption in 2007/2008, several "Hornemann's" Hoary Redpolls (nominate hornemanni subspecies) were found and supported by photographs. Hornemann's Redpoll was previously regarded as a great rarity south of the Arctic, but it may be more frequent than formerly believed. Hornemann's is most reliably identified by its much larger size in direct comparison with flammea Common Redpolls or exilipes Hoary Redpoll. Note that white birds loom larger than life among darker birds and size illusions are possible.

Red-breasted Nuthatch: This nuthatch is a conifer seed specialist when it winters in the north, thus its movements are triggered by the same crops as the boreal winter finches. The southward movement, which began in the summer, signaled the generally poor cone crops on spruces, balsam fir and white pine in the mixed coniferous/deciduous forest region across Ontario and in Atlantic Canada, New York and New England States. Red-breasted Nuthatches will be very scarce this winter in central Ontario such as Algonquin Park. White spruce crops are excellent in the northern half of the boreal forest, but it is uncertain how many Red-breasted Nuthatches will winter that far north.

Most other species are unlikely to come south because they have abundant food sources somewhere in the boreal forest. See the full forecast for comments on the rest of the irruptive species. The species comments are informative, even for birds that will not come south. Past forecasts usually included some notes on boreal raptors as well, but those seem to be left out this year.

How Far Can a Bird Fly Nonstop During Migration?

Bar-tailed Godwits / Image: Phil Battley

Recent studies using satellite telemetry or geolocators have shown that some bird species are capable of very long nonstop flight during migration, far longer than previously thought. Some of the longest belong to Bar-tailed Godwits, which have been tracked performing nonstop flights of over 11,000 km (or about 7,000 miles). Ruddy Turnstones perform similarly impressive flights. A new study in PLoS Biology tries to measure whether there are any limits to nonstop flights.

How long a bird is able to fly depends on a few factors. First, it needs to be able to use fuel efficiently. Bar-tailed Godwits do this very well, burning only 0.42% of their body mass per hour of flight. Ruddy Turnstones, Greater Knots, and Blackpoll Warblers have slightly lower efficiency. Flight speed is also important. Bar-tailed Godwits and Blackpoll Warblers have similar fuel efficiency, but a Bar-tailed Godwit can fly twice as far without stopping because it flies more quickly (see graph below). A faster bird will not only fly farther on the same fuel supply but also will be less likely to be blown off course by turbulence.

Potential flight range for the bar-tailed godwit (blue curve) and the blackpoll warbler (red curve).

Other factors that may influence long-distance flight include body shape and energy consumption. A long-distance migrant must be able to carry sufficient fuel supplies for the flight but do so in a very streamlined body. One way that godwits achieve this is by eliminating unnecessary organ mass and burning muscle mass in the latter stages of a migration flight. Other shorebirds share this trait.

A few other species like Sharp-tailed Sandpiper might attempt similar flights, but the Earth imposes its own limit on how far a bird might need to migrate. There are relatively few combinations of wintering grounds and breeding grounds that would require such a long nonstop flight. Some Pectoral Sandpipers breed in Central Asia and winter in South America, but they break up their migration into two stages. Arctic Terns have a longer trip (24,000 km!) but can feed along the way. It seems that the Bar-tailed Godwit's 11,000 km is about as far as a bird is likely to fly without stopping to feed.

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Hedenström, A. (2010). Extreme Endurance Migration: What Is the Limit to Non-Stop Flight? PLoS Biology, 8 (5) DOI: 10.1371/journal.pbio.1000362

Bird Migration in New York City

As a follow-up to my post on birding in Central Park, here is a neat article on bird migration moving through New York City.

The urban jungle is a natural attraction for birds who travel thousands of miles over water down two migratory flyways along the coast. The trip is arduous, and lush greenery in the parks and marshes lures them in, offering a rich bounty of insects, buds and seeds to feed on....

In Central Park, the varied habitats of the north end and the Ramble offer the top places to spot birds, among them hummingbirds and orioles feeding on trees, and thrushes that "sing ethereal songs from dawn to dusk," Willow said.

Brooklyn's Prospect Park has one of the city's largest populations of spring migratory birds. Also, the Jamaica Bay Wildlife Refuge is a prime birding spot for thousands of shorebirds, waders, waterfowl and dozens of migratory songbirds that feast on the eggs of the horseshoe crab during its mating season.

Still, migration can be risky. The trip is not only exhausting, but the birds travel over unfamiliar territory, and have to endure natural and manmade threats along the way.

Backyard cats, power lines and windows pose the greatest threats - and many birds die en route.

The ever-expanding skyline also makes the journey difficult.

I also have one addendum to yesterday's post. The trip on Saturday put my eBird list for Manhattan over 100 for the first time, and my Manhattan list is higher than my Queens list for the first time in a while. These are lists that I probably would not keep if I maintained my lists by hand, but eBird keeps county lists for me by default.

A Possible Way for Wild Birds to Spread Influenza

Northern Pintail fitted with a transmitter / USGS

One of the great questions during the outbreak of the H5N1 influenza virus a few years ago was how the virus spread so quickly. The virus outbreak was most severe in the domestic poultry industry, but it was also detected among waterfowl and spread to humans, many of whom died. New research from the USGS suggests a possible route the virus could have spread via wild birds.

In the study, scientists from the USGS Alaska Science Center and the University of Tokyo attached satellite transmitters to 92 northern pintail ducks several months before the H5N1 virus was discovered in dead and dying whooper swans at wetlands in Japan.

They found that 12 percent of marked pintails used the same wetlands as infected swans and that pintails were present at those sites on dates the virus was discovered in swans. During the first week after they become infected with H5N1, ducks such as pintails can shed the virus orally or in their feces, potentially contributing to the virus’ spread.

Researchers found that some of the marked pintails migrated 700 miles within four days of leaving the outbreak sites; marked pintails ultimately migrated more than 2,000 miles to nesting areas in eastern Russia.  The study’s discovery that northern pintails made long-distance migrations during the period when an infected duck would likely shed the virus offers insight on how H5N1 could be spread by wild birds across large areas.

The research, published in the journal Ibis, does not prove the marked pintails were actually infected with the H5N1 virus or that they definitively contributed to its spread.  However, it does demonstrate that pintails satisfied two requirements necessary for migratory birds to spread the virus: they used outbreak sites at times when the virus was present and some birds migrated long distances within a week of using the sites.

Jerry Hupp, Ph.D., a U. S. Geological Survey scientist and one of the lead authors of the study, noted that the H5N1 virus has been found in wild birds, including northern pintails, which show no visible signs of illness. Also, laboratory studies have shown that pintails and some other wild birds remain healthy when infected with H5N1.

While the study does not prove that wild birds spread H5N1, it does show that they are at least a possible vector. Because waterfowl migrate between Asia and North America and birds have carried less pathogenic viruses from Asia to Alaska in the past, infected Northern Pintails might spread H5N1 into North America. However, this highly pathogenic strain still has not been detected in North America despite its rapid spread in Eurasia and Africa several years ago. Whether this will happen in the future remains to be seen. 

Northern Pintails wintering in Japan / USGS

Tracking the Impressive Migration of Ruddy Turnstones

Using geolocators, Australian scientists have tracked the complete migration cycle of Ruddy Turnstones, one of my favorite shorebird species. The birds in question spend their winters in southeast Australia and breed in the Aleutian Islands.

"We have been amazed at the feats of Bar-tailed Godwit tracked by satellite from Australia and New Zealand to their breeding grounds in the high Arctic and back", said Dr Clive Minton from the Australasian Wader Studies Group. "Unfortunately the size of the satellite transmitters, and the batteries required to power them, precluded their use on smaller shorebirds like Ruddy Turnstone".

The researchers therefore decided to use new 1 gram light-sensor geolocators - supplied by British Antarctic Survey in Cambridge, England - and fitted them to eight Ruddy Turnstone spending their non-breeding season in south-east Australia in April 2009. Four geolocators were eventually retrieved from birds between 20 October 2009 and 8 January 2010.

"All four birds flew 7,600 km non-stop to Taiwan in just over six days, with three apparently travelling together", said Dr Clive Minton. They then flew on to northern Siberia, following separate paths and stopping over at different sites. "By early August, two had moved to Korea and south-eastern Siberia, respectively, but another bird returned to Australia via the Central Pacific!"

The Pacific bird spent 26 July -15 October on the Aleutian Islands before flying 6,200 km across the Pacific in four days to Kiribati, and then it made another four-day, 5,000-km flight to eastern Australia. "Five days later it was back in south-east Australia having completed a 27,000-km round trip", added Ken Gosbell - Chairman of the Australasian Wader Studies Group.

The turnstones were estimated to fly at about 50-55 km per hour (or about 30-35 mph). During their southbound flights, they averaged about 65 km per hour (or 40 mph), which suggests they may have had a tailwind at times. Because the pilot project was so successful, the research team is tagging an additional 60 turnstones with geolocators and extend the project to 30 Greater Sand Plovers and 4 Sharp-tailed Sandpipers. Shorebird migrations have long been known to be among the most impressive performed by any bird species. Thanks to contemporary technology we are getting a better picture of just how impressive shorebird flights can be!

Songbirds, Berries, and Anti-oxidants

Researchers believe that migratory songbirds at Block Island choose to eat arrow-wood berries specifically for their anti-oxidant content. The berries might relieve some of the physical stress that songbirds endure during long-distance migration flights. Arrow-wood berries contain higher levels of anti-oxidants than many of the other berries present on the island at the same time.

"When I started studying birds during their migratory stopover on Block Island, I was impressed that most of the migratory birds ate berry fruits even though they usually eat insects or seeds at other times of the year," said McWilliams, who came to URI in 1999. "I began studying the relationship between the nutritional qualities of fruits and how those nutrients might fuel migration." ...

The research indicates that birds prefer to eat certain fruits that have more antioxidants and key nutrients. In return, the seeds in the berries are dispersed by the birds. "It's the way plants ensure their survival. Birds eat the berries, digest them and defecate the seeds over wide areas," McWilliams said.

"Meanwhile, the birds are attracted to the berries because of their rich color, which we believe is a plant's response to the stress of constant exposure to the sun and other stresses. Berry color could be a plant's way of fighting oxidative stress. It's a partnership that benefits plant and bird."

The Seeram-McWilliams partnership will continue. "We've only measured a few of these anti-oxidants," Seeram said. "Our next step is to determine how birds can detect these compounds."

"Whenever we exercise, we undergo oxidative stress, and the same is true for birds," McWilliams said. "We're flying birds in wind tunnels to produce oxidative stress, and then we are going to see if anti-oxidants found in these berries alleviate that stress," McWilliams said.

The research may benefit human health as well as bird conservation. If further research shows the direct link between bird health and diet, then the findings will play a critical role in habitat protection for migratory birds, McWilliams said.

This is interesting, if true. I wonder how much of the preference could be explained simply by availability, size, or taste. I also wonder whether this would really mean much for humans. Anti-oxidants already receive quite a lot of publicity for their ability to treat or prevent various ailments. I am not sure that adding one more would change food consumption habits.

Color-marked Piping Plovers

 Color-marked Piping Plover / Photo by Ann Maddock

Within the next few weeks, Piping Plovers will start arriving in the Mid-Atlantic states, either to stay and breed or to rest briefly en route to breeding grounds farther north. (Last year, I saw my first of the year on March 14 in New York.) This year, some of the plovers may be marked with colored leg bands as part of a migration study. A Piping Plover with a black flag near the top of its left leg, like the one above, is likely to be part of a population that winters in the Bahamas.

How may a sighting be reported? Simple. Report all sightings to CHERI GRATTO-TREVOR, Prairie and Northern Wildlife Research Centre, Environment Canada, 115 Perimeter Road, Saskatoon, SK S7N 0X4 Canada, EM: cheri.gratto-trevor@ec.gc.ca , noting the color and location of each band on the bird, and location and behaviour of the bird (on nest, brooding, foraging at migratory stop-over, etc.), as well as presumed sex of the bird, if possible.

What do color bands of The Bahamas plovers look like? They look like the three Bahamas plovers pictured above. All have a black flag on the upper left leg. Each have a single white band on one of the lower legs, right or left. Each have two color bands (neither of which is a white band) on the lower leg opposite the leg with the single white band. Colors used were: red, orange, yellow, white, light green, dark green, dark blue, and black. No metal bands were placed on any of The Bahamas birds; nor were color bands placed on the upper right legs of the birds.

So far only the only previously banded Piping Plover to be resighted belonged to the Great Lakes population. That bird, an adult female, was banded in 2005 on her breeding grounds in Michigan. She has returned to Michigan to nest each year since then but was not recorded elsewhere until she was seen in the Bahamas.

Of the 57 color-marked Piping Plovers that are part of the current study, 50 were observed again within 24 hours of being banded. Many were seen during subsequent weeks, but they will be leaving the Bahamas very soon. These birds could be part of the Great Lakes population, or they could migrate and breed elsewhere. If you notice any Piping Plovers with color bands this year, make sure to record the colors and positions of all the bands and report the sighting.

The Piping Plover is federally listed as endangered in the Great Lakes region and threatened in the Northern Great Plains and Atlantic Coast. While their status has been improving thanks to the recovery program, the species is still vulnerable. More information about where each of the populations migrates and breeds will assist recovery efforts.

More details on the project and how to report sightings, along with additional photos of banded plovers, are available at the Coastal Virginia Wildlife Observatory blog.

Iron in the Beaks of Birds

Birders know well that birds migrate – the cycle of bird movements keeps birding interesting throughout the year. Many landbird migration routes are well-documented, and even some over-water routes are starting to be determined. What is less understood is how the birds know where they are going. Recent research has focused on how birds might sense, or even see, the Earth's magnetic field for orientation. At least one recent study proposed that some birds use an olfactory sense for guidance. Visual cues, such as the stars for nocturnal migrants or waterways for diurnal migrants, have also been proposed.

One new study finds iron-containing cells in the upper beaks of birds. Three years ago, the same research team reported that the upper beaks of homing pigeons contain iron minerals arranged in structures that could allow a pigeon to sense a magnetic field. This study found similar structures in the beaks of three other bird species: Garden Warbler (Sylvia borin), European Robin (Erithacus rubecula), and domestic chickens (Gallus gallus).

 

Prussian blue stained dendrites in the inner lining of the upper beak of (A) homing pigeon, (B) garden warbler, (C) European robin, and (D) domestic chicken. (E) General semi-schematic drawing of an iron containing dendrite. (F) Axon bundle with several iron containing dendrites.

In all four species, the iron-rich dendritic cells are located near the top of the upper beak and not in the lower beak or in any other tissue. The iron particles are arranged in narrow rod-like clusters, which appear to lie parallel to one another. The clusters are connected to the ophthalmic nerve, so they form part of a bird's sensory system. The iron minerals contained in the dendritic cells appear to be maghemite (Fe(III)2O3) rather than magnetite (Fe (II)Fe(III)2O4), but the sample was too small to determine that conclusively. Given that such similar clusters are present in several bird species that are not closely related, including a nonmigratory bird, they may be present in many more (or even all) bird species, and an important part of avian direction-finding abilities.

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Falkenberg, G., Fleissner, G., Schuchardt, K., Kuehbacher, M., Thalau, P., Mouritsen, H., Heyers, D., Wellenreuther, G., & Fleissner, G. (2010). Avian Magnetoreception: Elaborate Iron Mineral Containing Dendrites in the Upper Beak Seem to Be a Common Feature of Birds PLoS ONE, 5 (2) DOI: 10.1371/journal.pone.0009231

Mapping the Extraordinary Journeys of Arctic Terns

Arctic Tern / Photo by Ólafur Larsen

I have posted before about some of the incredible migration flights undertaken by birds, such as the nonstop flights of Bar-tailed Godwits across the Pacific or the circumoceanic wanderings of Sooty Shearwaters. Red Knots travel each year from Patagonia to the Arctic and back, as do some other shorebird species. Another bird species that undertakes impressive migration flights is the Arctic Tern (Sterna paradisaea). Every year, Arctic Terns make a 43,000-mile round trip between their wintering grounds in Antarctica and their breeding grounds in the Arctic.

The terns' routes were finally mapped through a banding study that outfitted each of the banded terns with tiny geolocators to track the birds' geographical locations along the way.

The first surprise is that the terns do not make straight for the Antarctic when they leave the Arctic, but make a lengthy stop-over in the middle of the North Atlantic, about 1,000km (620 miles) north of the Azores.

Here, they feed on zooplankton and fish to fuel themselves for the long journey ahead.

Terns take one of two routes on the way south:

The birds then head south along the coast of western Europe and western Africa before making a choice, either to continue hugging Africa or sweep across the Atlantic from the Cape Verde Islands to continue the journey along the Brazilian coast.

About half the birds that were tracked decided to take the South American path. It is not clear why, but the researchers believe wind might make either route seem favourable to the terns.

After spending their northern winter months in Antarctic waters, the terns then fly back towards the Arctic.

But rather than retracing their southward flight paths, the birds follow a gigantic "S" pattern up the middle of the Atlantic Ocean.

Interpolated geolocation tracks of 11 Arctic terns tracked from breeding colonies in Greenland (n = 10 birds) and Iceland (n = 1 bird). Green = autumn (postbreeding) migration (August–November), red = winter range (December–March), and yellow = spring (return) migration (April–May). Dotted lines link locations during the equinoxes. Credit: Greenland Institute of Natural Resources.

The spring route carries the terns northward along the west coast of Africa and then along the east coast of North America. (See the maps included in the BBC article.) This may mean traveling a longer distance than a more direct route would be, but the article's authors explain the different migration routes in fall and spring based on prevailing winds. It may be more energy efficient for the birds to move clockwise in the North Atlantic a counter-clockwise in the South Atlantic since they can benefit from a tailwind both ways. It is worth noting that ocean currents follow a similar pattern and could potentially influence the ease of finding food along the way.

Whatever the reason for their routes, these terns give us an additional reason to marvel at the natural world and its avian inhabitants.

Update: I added the map of the terns' routes from the project website, which has additional images and information: http://www.arctictern.info/

Understanding Migratory Bird Declines

The RSPB and BTO are trying to figure out why some formerly common migratory bird species have lost much of their populations.

Some of the greatest declines of birds in the UK are among migratory songbirds such as Common Cuckoo Cuculus canorus, European Turtle-dove Streptopelia turtur, Common Nightingale Luscinia megarhynchos and Spotted Flycatcher Muscicapa striata. These species breeding in Europe and migrate to sub-Saharan Africa.

Recent figures suggest that more than 40 per cent of all migratory species passing between Europe and Africa have declined in the last three decades. Alarmingly, one in 10 of these are classified by BirdLife as Globally Threatened or Near Threatened on the IUCN Red List.

The project will involve researchers monitoring birds along a corridor stretching from Ghana’s Atlantic coast to northern Burkina Faso, spanning a range of habitats from coastal rainforest to the edge of the Sahara desert.

With migratory birds there is always a question of where a bird species is being harmed the most. A declining species could be having difficulties on its breeding range, along its migration route, or in its winter habitat (or perhaps all of the above). With some species the issues are fairly clear, but with others it takes a lot of field research to determine the precise causes. Good luck to the RSPB and BTO in solving these birds' declines.

Click through the link for a great photo of a Spotted Flycatcher.

Winter Finch Forecast for 2009-2010

Common Redpoll / Sizerin flammé / Photo by Eric Bégin

Ron Pittaway has released via email his annual forecast for irruptions of winter finches and other boreal species. (An irruption is a mass movement of birds in response to food shortages or other temporary conditions. Read more about irruptive birds at Seabrooke's blog.) The upshot is that he expects very few finches (or other birds) to come south this year. Instead, many finches will either stay north or head west. The reason is that key food crops (the seeds of spruces, birches, mountain-ashes, and other trees) are excellent this year across Canada.

There are a few possible highlights, though. Note that the forecasts are written from the perspective of someone living in Ontario.

Purple Finch: Most Purple Finches should migrate south out of the province this fall because many seed crops are poor in the north. This finch has declined significantly in recent decades.

Common and Hoary Redpolls: Redpolls are a birch seed specialist in winter. Since the birch crop is poor in northeastern Ontario and Quebec, a few Common Redpolls should move south into southern Ontario and farther east and south. However, most redpolls may be drawn to good birch crops in northwestern Ontario and westward in the boreal forest into Saskatchewan.

Northern Goshawk: A good flight is very possible this fall or next. Goshawks in the boreal forest in winter prey on hares, grouse and red squirrels. Snowshoe Hares have been abundant in parts of northern Ontario the past few years and they should crash soon. Also, Ruffed Grouse likely had a poor breeding season due to a cool, wet spring and summer, which lowered chick survival.

You can find Pittaway's full forecast at the Ontario Field Ornithologists website.

Highlights from past forecasts are available on this blog: 2008-09, 2007-08, 2006-07, 2005-06

Photo Study of a Dead Cuckoo

Yesterday, I saw a Black-billed Cuckoo. While not a rare species, it can be a difficult bird to find, even during migration. Unfortunately it was deceased. This cuckoo was lying in the bushes outside my cousin's house.

The cause of death is unclear. There were no visible wounds, which rules out a predator, like a raptor or a cat. However, its neck is broken, and there is some sort of shiny fluid around the bird's face (visible more clearly in the photo below). It may have crashed into one of my cousin's front windows and died from impact. A second possibility, since there was heavy migration the previous night, is that the bird died from exhaustion and broke its neck upon hitting the ground.

This was an immature Black-billed Cuckoo, which is apparent from the buffy shading on its neck. The long tail feathers also do not have as bold of a black and white pattern as would be expected on an adult. Yellow-billed Cuckoos, by the way, have much larger white spots on their tails, making the tail pattern an easy way to identify a perched cuckoo if you cannot see its bill.

While Black-billed Cuckoos have much less rufous on their wings than Yellow-billed Cuckoos, they still retain some. Their rufous is hard to see in the field, as it blends in with the dominant brown, but in the hand it shows much better.

In contrast to the dark upper wing, the underside is creamy white.

I was sorry to encounter such an awesome bird in such unfortunate circumstances. However, it was interesting to see some of its features up close, in a way that is rarely possible outside of a banding blind or a museum collection.

For larger images and a few more photos, see the cuckoo set on my Flickr account.