First in a Series Derived From:

"SILENCE OF THE SONGBIRDS" By Bridget Stutchbury

The list is long of North American migratory songbirds that are disappearing at frightening rates.  Among these are wood thrush, Kentucky warblers, bobolinks and Eastern kingbirds.   The world under the wings of our migratory birds is not the same landscape their ancestors flew over.  Logged forests, drained marshes, plowed prairies and natural habitats have been replaced with millions of square miles of fields of corn, rice, wheat etc to feed an exploding human population.  We may have already lost almost one half of the songbirds that filled the skies forty years ago.  When birds begin disappearing - are we next?

Wild birds are powerful indicators of the health of our outdoor environment.  You may remember during the 60's-70's when the eagle population was dwindling because of DDT and other such poisons which disrupted reproductive hormones making it hard for them to put calcium into their eggs, resulting in fewer eggs hatching.  DDT was used from the 40's to the 70's.  When it was banned in 1972, birds of prey began producing young again and the population grew rapidly, thus providing undeniable evidence of the toxin's affect!

There are many threats besides pesticides that are causing the disappearance of our migratory birds: 

-destruction of tropical wintering habitat

-cowbirds and other predators

-light pollution

-poor northern breeding habitat

-coffee growing

-obstructions such as buildings, communication towers, wind farms

Dramatic declines are being seen around the world, not just in North America.  In this series which will continue in successive newsletters I (Linda) will write extensively on each of these threats which should be of great concern to us whether we are bird watchers or not.

The Center of Conservation Biology at Stanford published a formal analysis of the state of the world's birds and ended with an ominous warning for all of us.  They analyzed the current status of all bird species living today, almost ten thousand in all, as well as the hundred or so that have gone extinct in recent times.  The International Union for Conservation of Nature and Natural Resources currently lists 1.3% of the world's birds as recently extinct and 12% as threatened with extinction in the near future.  The Stanford group used different scenarios for the effect of climate change and habitat loss on birds to forecast what is likely to happen by the end of this century.  If forest loss continues at its present pace, it is quite realistic to think that within a few human generations we will lose one quarterof the world's bird species.

Let us begin with an explanation of what a migratory bird is.  Birds migrate because of the bonanza of insect food that comes with spring in the northern reaches and so they spend a few hectic months there mating, building nests and feeding young.  The long dangerous trip from the tropics is worthwhile because the rich food supply means they can raise many offspring in a single nest.  At summer's end they return en masse to resume their tropical lifestyle.  Neotropical migrant is the technical name given to these birds that move seasonally between the New World Tropics and the temperate zone in North America.  Some of these are:  Eastern kingbird, Least flycatcher, Barn swallow, Baltimore oriole, Rose-breasted grosbeak, Painted bunting, Indigo bunting, Wilson's warbler, Mourning warbler, Common yellow throat, Prairie warbler, Prothonotary warbler, Wood thrush, Bell's vireo, etc.

There are two migration seasons:  March to May (going north) and August to October(returning to the tropics).  A very popular destination for neotropical migrators is the boreal (meaning "north" or "tundra area")forest of Canada.  The boreal forest is one of the largest intact ecosystems left in the world, even bigger than the Amazon rainforest.   The boreal forest of North America is a migratory bird nursery.  It stretches across the entire northern half of the continent from Newfoundland to Alaska.  It is home to one quarter of the world's remaining forest.  It is home to billions of neotropical migrants.  The boreal forest is a combination of many types of forest:  bogs, peatlands, lakes, etc.  Foresting and burns leave huge areas of regenerating scrubby forest.  It is under siege by lumbering, mining, oil and gas development.  It is logged at several acres a minute to fuel demand for paper products in the US which buys 80% of Canada's lumber exports.  There are groups at work to create sustainable forests to learn from mistakes of the past.  The goal is to continue to extract resources but leave 17 million acres intact. 

All of the neotropical migratory birds are experiencing population declines.  Since they all eat different things and live in different places, it is hard to come up with a single problem that explains why so many are in trouble.  The dangers that threaten these birds are as varied and complex as their own lives and the world we have created for ourselves.  These declining species are the "canaries in the mine", warning that we have gone too far already. 

Songbirds provide important functions in our ecosystem, ranging from insect control to seed and fruit dispersal.  For example, insects are our biggest competitor for food and eat up to 20% of our crops before and after harvest.  This loss would be much higher without birds providing insect control.  We cannot live without the birds!  They, however, can live perfectly well without us. 

Birds are also our sanitation workers.  For example, in the 1990's, three kinds of vulture populations in India and Pakistan dropped by 95% in just 10 years.  The cause was a drug commonly used in human medicine that was given to cattle, causing kidney failure in the vultures that ate the carcasses of the treated cattle.  Without the vultures, the uneaten carcasses sat rotting for weeks causing an increase in diseases such as anthrax and foot and mouth disease.  Other scavengers then consumed the rotting carcasses, such as foxes and feral dogs, resulting in an increase in their population and that caused a spread of rabies to the human population.  It is plain to see how such a chain of events can lead to extreme human suffering.

Birds are such an important part of our world and are irreplaceable.  Plants depend on them to pollinate flowers and to carry their seeds and fruits away from the parent plant.  Plants also count on birds to keep leaf and seed eating insects under control.  We can't afford to lose our birds.  They are part of the complex web of life that sustains the life of our planet.

How else do we know birds are on a downhill slide?  Plenty of older bird enthusiasts and scientists have been paying attention since the 1950's.  They remember the good old days of spring migration when they could see dozens of migrants in tree after tree rather than just a handful at a time.  But scientists must have proof and numbers to analyze, therefore, in the early sixties the US Forest and Wildlife Service designed a nationwide bird monitoring program, the "Breeding Bird Survey" (BBS).  At the peak of breeding season, volunteers on predetermined routes make fifty stops, each 3 minutes long, ½ mile apart along a 14.5 mile route to count birds.  The problem is what used to be a rural route is no longer!  The volunteer must count all birds seen and HEARD (they must know bird calls, too).  Each year volunteers survey 2,000 routes, drive 50,000 miles of roads and make 100,000 different census stops to count the migrants who have spread across the continent.  A good birder can count birds with her eyes closed just by listening!  The strength of the BBS lies in its massive geographic scale and not it its precision in counting the birds at each stop.  Only a small subsample of birds that actually live in a given place are counted.   BBS is not precise and never was meant to be.  It does a good job as a continental health test for breeding birds because it gives a rough estimate of the overall abundance of a bird species averaged over hundreds of BBS routes, in other words the "big picture".  The results from the first twenty years of the BBS sent a shockwave and made headlines around the world and rattled scientists because neotropical migratory songbird populations were in a tailspin.  Songbird species that live in North America all year round fared better suggesting that neotropical migrants are running into problems during migration or on their tropical grounds.  The result was many new studies and groups, such as the Smithsonian Migratory Bird Center were formed, but as yet there are still no signs that the declines have been halted.

Counting also takes place in tropical wintering grounds where numbers are found to be declining.  Exceptionally low numbers of wintering migrants have been caught in recent test years.  It is hard to make accurate counts.  Under such long distances, it is impossible to keep track of how many birds are in a given area.  We can only glimpse the true numbers through radar and breeding surveys and banding.