We all love the birds who visit our backyard feeders, but although we think of them as "our" birds, many of them spend most of the year elsewhere, sometimes very far away.  Roughly 75 percent of North America's nesting species migrate, and fully 50 percent spend the winter south of the U.S. border.

Biologists think that many North American species, including flycatchers, hummingbirds, orioles and wood warblers, descended from adventurous individuals that ventured north from the New World tropics to take advantage of abundant food and less competition during the summer nesting season.  After nesting, most of these species return to the Neotropics for the bulk of their year.

Eastern Kingbirds winter primarily in Amazonia.  Also in South America enjoying the winter are Chimney Swifts and Purple Martins.  These birds provide examples of "complete migration", which is just one version of three types of bird migration.

American Crows are examples of "partial migrants".  Many of those individuals move southward during the cold months, but a few remain on part or all of the breeding range.  American Crows entirely vacate most regions north of the Canadian border, while some crows south of Canada move farther south.  Still others stay put.  So, you might think "your" birds are still with you and you may be right, but you may be seeing replacements from somewhere else while "yours" have flown the coop!  Other partial migrants from the back yard include Blue Jays, Chipping Sparrows and Red-tailed Hawks.

Baltimore Orioles belong to the third class of migrant sometimes known as "half-hardies".  Most individual Orioles are complete migrants, though they travel shorter distances than the likes of Eastern Kingbirds, generally wintering in Mexico or Middle America.  A few Orioles succeed in overwintering in southern states, especially in milder winters.  We have a large local flock that winters here, in fact.  All of this illustrates an important point:  Many species have very broad wintering ranges.

Birders in northern climes can take comfort in the fact that some of "their" birds are now hosted by peers in southern states.  Consider White-throated Sparrows:  a Michigan birder's white-throats might now be in Texas.  White-throats and many other species are so consistent in their winter ranges that they return to the same back yards every winter throughout their lives.

Relatively few birds live in the same place year round, but it happens that many in this group are our most familiar birds.  Whatever chickadee happens to live in your part of the world - Black-capped in the Northeast, Carolina in the Southeast, Mountain in the West, Chestnut-backed in the far west or Boreal in the North - those same chickadees live there during the summer and winter.  There are some exceptions, but Chickadees stay put for the most part.  We can similarly claim titmice, Northern Cardinals and Downy Woodpeckers as our own all year long.  Where are they now?  Just check the back yard and see!

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This issue deals with pesticides:

The United States applies 660 million pounds of agricultural pesticides yearly.  Central America, smaller by far, imports 100 million pounds.  Although the US uses more than ever, at least they've changed the kind of chemicals used dramatically due to environmental concerns.   This cannot be said for Central America where many of our migratory birds spend their winters.

DDT, deildrin and heptachlor and other similar chemicals known as organochlorines used in the 50's and 60's are fat soluble which means they are stored in the fatty tissues of animals and are hard to metabolize, therefore, these poisons accumulate in the food chain.  Plants and small animals at the bottom of the food chain may contain barely detectable traces of DDT, but a top predator who eats hundreds of tainted prey will build up DDT concentrations that are ten thousand times higher or more.

DDT and other similar chemicals have been banned or restricted by most countries, but they are not gone.  In their day they were valued for the length of time they stayed in the soil and on the leaves of crops and forests.  An estimated 1.4 billion pounds of DDT were applied in the US before it was banned and decades later the chemical and its breakdown product DDE linger in the environment.  One study of apple orchards that were heavily sprayed with DDT in the early 1970's found that the soil was still contaminated twenty years later and robins nesting in the orchard carried high levels of DDE in their bodies.  All major pesticides of this sort are still found worldwide in water, plants, animals, and people. 

In 1999-2000, the US Center for Disease Control tested the "body burden" of pesticides in more than nine thousand people of all ages across the United States.  The study found that almost everyone has DDE in their blood stream; you probably do, so do I and even our children do!

In many ways, birds are in greater danger today than in the 1950's because modern pesticides are more lethal.  The older pesticides were replaced in the 1970's and 1980's by "safer" pesticides like organophosphates and carbamates.  These pesticides are safer because they break down within a few days and are not stored in the body, and so do not accumulate in the food chain.  But many, like monocrotophos, are vastly more toxic to birds (and people) than were the older pesticides.

Modern insecticides are designed to kill their target swiftly and then break down before "non-target" animals come into contact with the poison.  This is easier said than done.  Birds can be exposed to these insecticides via direct contact with sprayed plants, by eating insects and fruits in areas that have been recently sprayed or by eating pesticides that are applied to the ground in the form of granules.  Birds can also breathe in the insecticide, or get it on their skin and feathers during aerial spraying and drift from spraying.  Contact with these pesticides during and soon after application can kill large numbers of birds.  If not used carefully, these pesticides can also cause serious illness and death in the farmers who mix and apply the pesticides.  We have traded persistence for toxicity. 

The numbers of "kills" resulting from specific agricultural spraying can be staggering.  One incident in a vineyard in California in the fall of 1993 killed at least 1 blackbird, 12 finches, 11 western bluebirds, 133 yellow-rumped warblers, 34 mourning doves, 22 northern flickers and 1 sharp-shinned hawk.  In 2009, an even bigger kill happened after carbofuran was illegally applied on a farm in Illinois; thousands of blackbirds, cowbirds, grackles and horned larks were found dead.

Modern pesticides affect birds at concentrations so low it defies belief.  Despite this they are used widely in North America and other countries.  There are regulations in place for toxicity tests on birds to be completed before a chemical can be registered for use.  The irony is that in the US this is determined on a cost-benefit basis.  Harmful pesticides are often used widely because the economic benefits from increased food production are thought to outweigh the harm.  Ethyl parathion was known to readily kill birds soon after it was registered in the US, yet it took some 47 years before the product was withdrawn.  Granular carbofuran is a notorious bird killer, yet its use was virtually eliminated in the US only after a 20 year struggle by environmental groups and scientists. 

The pesticide list for most crops is surprisingly long, with many types of pesticides, fungicides and herbicides used routinely to grow a single crop, many of them acutely toxic to birds.

As bad as this sounds, some of the worst problems for birds lie on their wintering grounds.  In Latin American countries, regulations controlling pesticide use are much looser, and many chemicals that are restricted in use or not even registered in the US are widely used.  These pesticides are popular because they are so much cheaper than alternative less toxic pesticides.  Most government agencies are underfunded and understaffed, and have trouble enforcing the regulations that do exist.  Pesticides that are banned for use in one country are often used freely next door and food from neighboring countries is imported and consumed with little or no testing for pesticide residues.  The sheer quantity of dangerous   pesticides use in Latin America is downright scary and may be to blame for the decline of many of our migratory songbirds.

In fertile, bountiful places like Almolonga, Guatemala, families subsist on farming as little as a half acre.  The family does all the labor, including spraying, sometimes daily, of heavy doses of pesticides in amounts way more than the manufacturers recommend with heavy human and environmental toll.  Pesticide containers are routinely washed out in irrigation canals then dumped at the edges of fields.  Farmers mix and apply highly toxic pesticides without even wearing gloves, falsely believing that many years of exposure makes them immune to any ill effects.  The US Food and Drug Administration rejects shipments from Guatemala because pesticide residues exceed limits.  Other countries nearby, however, do not have strict laws and provide a steady demand for the poisoned food of Almolonga.

This chemical culture is typical of most parts of Latin America.  It is an ecological nightmare.  Latin American countries have vastly expanded the production and export of cash crops and have moved into non-traditional crops such as broccoli and cantaloupes.  These non-traditional crops had not been grown in tropical regions before and farmers quickly encountered pest problems.  Solution?  Dramatically increased pesticide use!

Pesticide use is heavy because farmers spray pesticides according to a regular schedule, rather than as needed.  The export crops are so valuable that most growers feel they cannot risk a pest outbreak and would rather spray pesticides as a pre-emptive strike.  Most advice on what pesticides to spray, and how often to spray them comes from the pesticide vendors who clearly have an interest in seeing wide and frequent use.  To minimize the labor costs, farmers typically combine many different pesticides into one deadly cocktail and make a single pass through a field. 

The export market demands high quality produce.  Pesticides are used not only to increase production but also to meet the standards of picky consumers in North America and Europe.  By some estimates, 10-20 percent of pesticide use is for cosmetic purposes only.  Farmers get a better price for unblemished crops.

Up to one hundred pounds of pesticides can be applied in Latin America per acre.  By comparison, similar fruits and vegetables grown in the US receive about eleven pounds or less per acre.  Unknowing Latin American farmers are mixing several different pesticides that actually contain the same active ingredient resulting in an application well over ten times the recommended amount!

Latin America is seeing an epidemic of human poisonings and terrible health consequences for farmers and their families.  Now, what about the birds?

Certain birds have become undesirables through no fault of their own.  When a bird's habitat is destroyed through deforestation and his food source is taken, he will eat whatever becomes available and that just might be the crop that has taken over.  Some farmers admit to deliberately poisoning birds with pesticides.  They put the poison in watering holes used by birds and spray feeding areas early in the morning just before the birds arrive.  They have sprayed with a crop duster over the birds as they sleep.  Farmers describe wading knee-deep in dead birds at the roost.  This is what has happened to the population of dickcissels and bobolinks.

Grassland birds across North America are a group experiencing the most severe and consistent decline in numbers due to Latin America's large-scale deforestation and loss of natural grasslands, forcing more and more birds to live near people.  Loss of forest has not just taken away the wintering place for forest birds, it has pushed birds into areas where they are more likely to encounter people and the chemicals.  Worm-eating warblers, Kentucky warblers and wood thrush seek shelter inside the forest so are probably not running into pesticides in their daily lives.  The birds at risk include the grassland birds and dozens of forest species, among them the American redstart, hooded warbler, black and white warbler and summer tanager, which are routinely found near agricultural fields.

Because modern pesticides break down so quickly pesticide poisoning is hard to prove because you have to be there soon after it happens.  The investigation of whether modern pesticides are causing declines in migratory songbirds is not so easy because the murder weapon is rarely found, and neither is the body of the victim, therefore researchers turn to North American studies, even though those numbers can be sketchy.  The National Wildlife Health Center of US Geological Survey has tracked incidents of large scale bird kills in the US since 1980.  Most bird mortality goes unnoticed.  The small bodies of songbirds may lie in the middle of a farmer's field to slowly rot in the sun or be carried away by scavengers.

Carbofuran, used on corn fields in the US in the late 70's is estimated to have killed 8 million birds each year.  Today carbofuran is not registered for use in the US and is banned in Canada.  In Latin America, it is still used heavily.  Birds in the places where it is used must be dropping like stones.

But, while some birds drop like stones, birds suffering from a pesticide poisoning are easy pickings for predators or they die from collisions with buildings and other objects and if they live near roadsides could be hit by cars.  A poisoned bird may be unable to catch food and suffer dramatic weight loss and then death.

The ghosts of pesticides past also haunt our songbird populations today.  Migratory birds are widely contaminated with an old enemy, the DDT and related chemicals that almost drove eagles and hawks to extinction in the 60's.  Although DDT was banned in the US long ago, it and other persistent pesticides take a very long time to degrade and are still around us, in our air, water and food and inside our bodies. 

What can we do?  We can remember the lessons we have learned from shade coffee and choose to buy crops that use fewer and safer pesticides or buy organically grown foods.  Making wise choices about the food we consume promotes a safer environment for the birds and other wildlife, as well as for the people who live where the food was grown.  Buying "bird-friendly" produce helps to create a market for crops grown with safer and fewer pesticides, which in turn provides a financial incentive to farmers to reduce their dependency on pesticides. 

Since the 1980's many new pesticides that have been introduced to the market have a negligible toxic effect on birds.  From 1990 to 2003, the general trend in the US was an overall reduction in the percentage of a given crop that is potentially lethal to birds.  This steady improvement in the chemical environment for birds has come not because we are using fewer pesticides but because in the US a new generation of pesticides is replacing the deadly organophosphate and carbamate pesticides. 

This bird-friendly approach to crops can be used to identify which foods present the greatest risk to birds, at least in North America.  At the level of a farmer's field, Brussels sprouts are grown with repeated insecticide applications and were ranked the highest risk to birds living near these fields.  Other crops that are not bird friendly on a per acre level include celery, cranberries, cabbage, potatoes, sweet potatoes, sweet peppers and hot peppers.  Blueberries should be on the list too because they are one of the few crops that pose an increasing danger to birds over the past fifteen years.  The risk to birds depends on how much acreage is used to grow particular crops.  Brussels sprouts are the worst crop but since they are a minor crop they do not account for high bird mortality compared with more widespread crops.  Corn ranks as the number one enemy for birds because it occupies such a large amount of land.  Safer pesticides are used on corn today than in the past, but even if only one bird were killed per acre of corn this would still add up to more than five million dead birds each year.  The top five crops with greatest potential for nationwide bird mortality are corn, cotton, alfalfa, wheat and potatoes.

We can also help our migratory birds by using our consumer power to encourage bird friendly agriculture in Latin America.  Here it is less clear which crops to target, since few are grown with light pesticide use.  Therefore, perhaps only organically grown crops are safe from there.  At the grocery, look carefully at where the food was grown.  Buy organic for domestic crops that are harmful to birds, like celery, potatoes and blueberries.  Buy only organic bananas because bananas receive among the highest pesticide loads of any tropical fruit.  This consumer-driven strategy is a broader version of bird friendly coffee:  it is good for consumers, good for farming families and communities and, of course, good for birds and other wildlife.

Linda