Hawkwatching

At this time of year, all across the northern hemisphere, people are starting to go out to particular places that combine specific geographic characteristics.  They are places that generally have reliable winds out of the north, they are elevated up above the surrounding landscape and so give a good vantage of the area, and they are situated where the land is constrained in some way (by coastlines or mountain ranges), and they are at mid-latitudes such that there is a large amount of potential breeding areas to the north and is not south of the wintering areas.  The places that meet these requirements and have these characteristics are places where migratory birds of prey tend to concentrate.  If you look at a map of the world, you can predict where the good hawkwatch sites are.  Anywhere that is shaped like a funnel with the wide end to the north and the narrow tip to the south will likely be the site of a fall hawk migration.  There is a hawkwatch on the Rock of Gibraltar at the tip of the Iberian peninsula funneling birds out of western Europe and constrained by the Mediterranean Sea and the Atlantic Ocean.  There is a hawkwatch in Ilat, Israel funneling birds out of eastern Europe and western Asia and constrained by the Mediterranean and the Black and Caspian Seas.  There is a hawkwatch on the Thailand/Malaysian peninsula funneling birds out of eastern Asia and constrained by the Gulf of Thailand and the South China Sea to the east and the Bay of Bengal and the Andaman Sea to the wet.  There are a series of hawkwatches along the funnel of central America funneling birds out of North America and constrained by the Pacific Ocean and the Gulf of Mexico.  The largest of these hawkwatches is also the largest hawkwatch in the world at Vera Cruz, Mexico.  The birds are drawn by the tailwinds that help to push them south and guided by the coastlines and ridges in the attempt to avoid large bodies of water or open land that lack the aerodynamic aid of thermals and updrafts.

And the people are going out to high points in such areas to count the raptors as they pass by.  Hawkwatchers all around the world are starting their yearly endeavors to monitor the populations of migrating birds of prey.  Some of these counts are done only one or two days a week while others have people out every day of the season.  A large majority of them use volunteers, to at least some extent, and this is an excellent way for anyone to become a citizen scientist and add to the understanding of birds of prey.

By conducting these counts every year, the size of raptor populations can be tracked.  If drops are seen, the causes of these drops can be investigated.  One of the most famous example of this process was when Rachel Carson noted a drop in the numbers of the young Bald Eagles and Peregrine Falcons during migration.  The investigation of the extremely high rates of nest failures in these species, led to the finding that the nests were failing because the eggs being laid in them had very thin shells and so cracked when an adult bird attempted to incubate them.   When egg shell fragments were tested, they were found to contain very high levels of the pesticide DDT and its derivative DDE.  All this led to two major events.  One was that Carson wrote the book “Silent Spring” which grabbed the attention of the nation and was one of the large steps in getting DDT banned.  The second was that researchers began taking eggs out of nests and incubating them in captivity.  With the help and knowledge of falconers, they were able to raise the chicks that hatched from these eggs and release them into the wild where they have succeeded in thriving and breeding and so bringing the populations of a number of species back from the edge of extinction to large and stable populations.  And none of this would have happened if people had not been going out into hill tops and mountain ridge-lines to count the birds as they pass by each year.

So go out and join a hawkwatch near you, or start your own!  There are many organizations that either run hawkwatches or can help you start one.  The data from all these sites is compiled so that trends across large area, or even continents, can be monitored.  But it only works if there are people out counting.