Remember, when we were kids and people said that the birds "flew south" for the winter?Well, believe it or not, that was about all we knew for a lot of species. Birds disappeared flying south in the Fall and came back, flying north, in the Spring. Where these birds went, exactly, and what they did when they got there, were a bit of a mystery.
All of that changed with the devopment of very small micro-transmitters capable of uploading information to satellites.
Three of the very first transmitters capable of being carried by a bird were attached to Swainson's hawks back in 1994. Within a few days, two of the transmitters conked out, but the transmitter on the third bird retained power and showed the hawk traveled from southern Canada down the American Midwest into Mexico, Guatemala, Costa Rica, and past Ecuador into the Pampass region of Venezuela.
Scientists quickly scurried off to see if they could locate the animal.
What they found in Argentina was both amazing and disturbing.
The amazing part was the Swainson's hawks (which are solitary hunters in North America) assembled into large communal flocks of as many as 7,000 birds on their winter hunting grounds.
The scary part was that in Argentina Swainson's hawks lived on swarms of locust-like grasshoppers, which were being systematically poisoned by organo-phosphate pesticides.
The bug spray, in turn, was killing off the Swainson's hawks in droves.
As they drove into the area where the hawk's signal had last been heard from, the scientists were alarmed to find thousands of dead hawks already dead under their roosts.
To make a long story short, that year 25 percent of all the Swainson's hawks in the world were killed by pesticides in Argentina -- a phenomenon that would never have been known had it not been for wildlife tracking telemetry.
The good news is that by switching to different type of pesticides, Argentina's farmers were able to sharply reduce grasshopper infestations while doing little serious harm to wildlife --a "win-win" for all sides.
The two tracking transmitters at the top of this post are made by an outfit that specializes in micro-tramsitters for bats, birds and other wildlife . The very smallest of birds can
now carry tracking trasmitters glued or harnessed onto their backs or tail feathers, with batteries providing power for 30 days or more.The tiny collar, pictured at right, holds the even tinier dot-like transmitter next to it.
The transmitter pictured at the very top of this post is even smaller than the one at right, and is arrayed for a tail mount on a very small bird. This is a complete rig with battery, transmitter and aerial, believe it or not.
Either one of the two micro-transmitters shown have an above-ground trackable range of 1-2 kilometres. .
4 For more information on wildlife and terrier transmitters on this blog, click here.
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3 comments:
Luckily, the birds in your story actually went to South America.
My homepage is the peregrine falcons nesting at the Rachel Carson Building in Harrisburg, which houses our Department of Environmental Protection here:
http://www.dep.state.pa.us/dep/falcon/
Anyway, about 3 years ago, DEP came up with big bucks to put transmitters on two baby falcons to see where they would migrate to. There was great excitment as we were all going to get to follow these birds all the way to South America -- the website was amended with a Western Hemisphere map for tracking, etc.
Turned out the male went to New York City and the female went to the Jersey Shore -- although after a few months there, she finally emigrated to Cape Hatteras (sp?), NC.
Big disappointment throughout PA DEP and we've never gotten the funding to track the falcons since. Just totally rots when the wildlife won't cooperate on putting on a show! ;-)
Dorene
That's a great story, actually, and rather than a poor result is a good one as it too tells a lot.
In fact very few bird migrate as far as South America -- most go no father than Mexico and the Caribbean, while another body goes as far as central America, a few more species as far as northern South America, and only two or three dozen bird species go much farther.
A lot of birds of all kinds are like your falcons -- they are turning into "short stoppers."
The real reason birds migrate is not to avoid cold so much as to keep up with food sources. When insects disappear and the cold buries seed, the small birds run, and with them a lot of the hawks and falcons and even the vultures (which prefer warmer air for flying purposes). Redtails of course, hang around, and so do some of the owls.
In any case, with cities providing ready rats, and bird feeders putting out millions of pounds of food, massive soy and corn fields to glean, nicely mowed city ponds and golf courses, etc. some of the birds are not going the distance any more.
In the case of some birds, historical migration patterns may also not have been taught. The Canada Geese, for example, short stop because so many were raised in captive flocks 30 generations ago, while many peregrine ancestors can trace their origins to being "hacked back" to nature during their recovery process.
Starlings were brought over from Europe and are still looking around to find Africa in order to migrate to it, etc.
Swallows come a long way, red knots, and purple martins too if you are looking for long distance fliers. Some of the ocean birds are amazing, of course -- shearwaters and albatrosses and the like.
Patrick
Alaska Bird Makes Longest Nonstop Flight Ever Measured
http://news.nationalgeographic.com/news/2007/09/070913-longest-flight.html
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