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Archive for March, 2012

Lead-free Zone

Stanley, The Falkland Islands
2 March 2012
By Keith L. Bildstein. Ph. D.

Three major human threats continue face raptors in our modern world.  They are (1) direct human persecution, which, in my lifetime, has faded into a largely local problem in most, but not all, landscapes, (2) land-use change, which remains problematic in many places including the species-rich New and Old World tropics, and (3) environmental contaminants, which continues to threaten raptors across many ecosystems globally. 

Yellow Z8 and Yellow K2 sharing the remains of a Gentoo Penguin that appeared to have be killed and partly consumed by a Sea Lion. Our examination of lead in the blood of these and other Johnny Rooks on Saunders Island in February 2012 suggests that all three species remain lead free.

The later poses a particular threat to scavenging birds of prey, whose food habits, which include feasting on dead and dying animals and human garbage, expose it to all sorts of problematic materials, including veterinary drugs and antibiotics that “contaminate” the carcasses of domestic livestock, and heavy metals that “contaminate” our dumping grounds. 

In both North and South America lead from lead shot used in hunting continues to turn up in the bodies of both California and Andean condors. And in California Condors, at least, the levels are so high that they pose the greatest threat to successful reintroduction of the species in the American West. In an effort to determine the scope of lead contamination in more widespread scavenging birds of prey, together with colleagues at West Virginia University, we are now examining lead levels in the blood of Turkey Vultures and Black Vultures. Although our initial sample sizes remain small, suffice to say that some of the vultures we have tested have high leaves of lead in their blood.

Which brings me to our work with scavenging birds on the Falkland Islands… 

During the past three weeks we collected and tested the blood of 28 Striated Caracaras, or Johnny Rooks as they are called here, that we captured on Saunders Island.  The test kit we used was designed to test for lead in children. This month’s results (we plan to test additional birds in July and August) suggest that the Falklands remains a “Lead-free Zone.”  None of the caracara blood sampled reached the test-detectable level of 3.3 micrograms/deciliter.  (Ten micrograms/deciliter or higher in human blood suggests a clinically significant level of contamination.) That scavengers on the Falklands appear to be clean of Lead suggests that the food bases they depend upon are clean as well. 

This then is good news, not only for the Johnny Rooks, but also for the penguins upon which they depend. Our long-term goal includes testing the Island’s Turkey Vultures as well.  Having a clean species-baseline to work with should help us better study the impacts of lead in contaminated populations of Turkey Vultures in the eastern United States.

More later.

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Saunders Island, The Falkland Islands
29 February 2012
By Keith L. Bildstein, Ph.D.

Walking around 20-square-mile Saunders Island is fun, but only up to a point. Studying Johnny Rooks on the island requires being all over the map and walking is not best way to cover the entire 20-square-mile territory. Land Rovers are one way to go, but they are expensive to rent and are all-but-possible to drive off-track.

With that in mind I ordered a quad several months ago. My new ATV is due to arrive from England in April and should be ready to go when I return to Saunders in July-August for next “winter’s” field season (recall that the seasons are reversed in the Southern Hemisphere). That said I continue to be befuddled by the walking behavior of the Striated Caracaras I am studying.

Like many other raptors, Johnny Rooks are relatively lightly “wing loaded” by bird standards. Simply put they have relatively large wing areas for their body mass and, as such, are capable of engaging in soaring as well as in flapping flight. Even so Johnny Rooks are exceptionally terrestrial in their movements overall. Several early researchers claimed that adults nesting on the perimeters of large seabird colonies could simply hop off of their low, tussock grass nests, walk into the colony, snag a dead or dying penguin chick, and walk back to their nest with it in their beak to feed their young.

Blue C5 running toward a trap in July 2011. Johnny Rooks are unusually terrestial for a raptor

Relatively sluggish in flight, with ponderous and rowing wing-beat somewhat like that of American Crows, Johnny Rooks are equally as likely to walk the 200 to 300 meters to our trapping site as they are to fly toward it. And unlike Turkey Vultures that regularly approach our trap and always fly over a wire fence five meters from it when they have landed on the other side, Johnny Rooks consistently crawl through the fence like cats when moving from one side to the other.

Striated Caracaras are island birds after all and island birds have been known to become flightless over time, more so than are continental species. Recall the Moas of New Zealand and the flightless rails of the South Pacific, for example. But, even so, it does seem odd to watch a bird walk, rather than fly, half a kilometer uphill to reach the trap set outside our cabin for the opportunity of being banded and bled.

This February, the birds seemed to be especially inclined to walk. Most are in both wing and tail molt, with numerous primaries, secondaries, and tail feathers missing from their bodies, and the lack of a proper airfoil may have accentuated their terrestrial travel. Overall their willingness to walk rather than fly such distances makes them appear to be working even harder to interact with us. It also makes them far easier to handle, as it tends to blunt their talons, making them far less dangerous to manipulate in the hand.

More later.

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Saunders Island, The Falkland Islands
24 February 2012
By Keith L. Bildstein, Ph.D.

Studying the behavior of wild animals is not always easy.  It took Jane Goodall six months in the field to come eye-to-eye with the chimpanzees she studied in the Gombe Forest Reserve.  And other secretive vertebrates can be equally difficult to contact and observe.  Indeed, many marine species necessitate acquiring costly scuba gear before one can even think about approaching them. 

At times raptors, too, can be difficult to study, especially when they live in dense forests or routinely travel across long distances. Striated Caracaras or Johnny Rooks, as they are called on the Falkland Islands, are not like that.  The most southerly distributed raptor in the world actually likes to interact with people.  The Johnny Rooks that I have been studying on the Falkland Islands since December 2010 are both approachable and, amazingly enough, sometimes even “approaching,” making their study relatively easy.  That is, so long as you are willing to travel to the distant islands of the South Atlantic they inhabit in the first place.

ImageThe first Johnny Rook I ever saw was a juvenile that appeared as a distant speck on the horizon and flapped its way toward me while I waited impatiently in a Land Rover behind 500 hundred sheep that were crossing the road in front of me near the West Falklands settlement of Hill Cove.  Half a minute later the bird had closed to within two yards of our still stationary Rover.  The bird hovered for several seconds above the hood of the car, peered at me through the windshield, abruptly turned about, and flew off.  Apparently he (or she) had seen enough.  That remarkable encounter, which happened nearly four years ago while I was surveying the island’s Turkey Vultures, convinced me that the species was literally “begging” to be studied, and that I needed to start working on them as soon as possible. 

Flash forward to 7:15 this morning when, in the midst of a walking survey of Johnny Rooks on Saunders Island less than 20 miles from the site of my first encounter with the species, another juvenile caracara ran up to me on the beach, leapt atop a small rock, coughed up a regurgitation pellet, retreated several meters, and turned around to stare at me for several seconds before sauntering off, presumably in search of its breakfast.  The bird in question, “Yellow A8” had been banded five days earlier with an alpha-numeric ring that identified him (or her) as one of more than 130 individually marked Johnny Rooks that currently form the core of our long-term study effort.  The regurgitation pellet, which I picked up, placed in a baggie, and pocketed, is now part of our caracara diet study.  Working with Striated Caracaras is clearly different than working with most other “wild” animals. 

My 2 km. walkabout this morning produced sightings of 23 rooks, 17 of which were banded, and could be identified as individuals.  Each of the ringed birds had been weighed and measured at the time of banding, and a tiny amount of their blood had also been collected, allowing my colleagues and me (eventually) to determine the bird’s clinical health and sex.  A growing number of rooks have been caught, weighed, and bled in both summer and winter… allowing us to assess the nutritional stresses that the birds go through during the harsh Falklands’ winter.  The regurgitation pellet Yellow A8 provided, together with dozens of others collected this month, will help us compare the diets of caracaras in summer (February in the Falklands is equivalent to August in Pennsylvania) with those of caracaras in the winter when the population migrates all of six miles from the relative nutritional largess of several multi-thousand pair penguin colonies I am currently working to a far more nutritionally limited farming settlement six miles off, where the bulk of the Saunders Island population of more than 100 Johnny Rooks spends the winter.

Think about it… in summer these birds live off a “marine subsidy” of dead and dying penguin chicks and adults.  In winter they high-tail to a farm settlement to live off a “human subsidy” of scraps provided the family that owns Saunders Island.  Initial findings indicate that the birds lose about 14% of their body mass each winter as they struggle to make it through the “lean” season.  How individual differences in behavior affect their chances of survival remains uncertain.  One thing that is certain, however, is that the birds themselves are helping accelerate our study by their allowing me and my colleagues to get close to them as they go about their daily business.  Now if only “Blue H4,” “Green K1,” “Yellow Y2” and more than 100 the other ringed birds would cooperate like “Yellow Y8,” we would really be able to speed things along.

More later.    

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