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Archive for February, 2010

Contrasts and Chickens

The Delmarva Peninsula, is a study in contrasts; its currently developed and developing northern three-quarters reflecting Delaware and Maryland’s proximity to Philadelphia and Washington, D. C.; and its relatively yet-to-be-developed southern quarter reflecting its Virginia Tidewater origins.  Traveling the Delmarva from north to south, which is what Lauriane Streit and I did last Saturday, is almost like driving back in time from an “up-to-date beachside resort” replete with outlet strip malls, to antebellum mansions and the “old cotton fields back home.”  Sandwiched between the two is the highest density of chicken farms I have ever seen.  Both Tyson and Perdue have mega processing plants on the Delmarva, and even at temperatures hovering in the low thirties, truck loads of chickens were being hauled to their destiny. 

Vultures have long been associated with chicken farms, and “modern” or not, every chicken farm we passed—except for a few that were closed and shuttered—had flocks of vultures attending them.  Saturday’s  route from Milford, Delaware, to the toll booth at Chesapeake Bay Bridge Tunnel near Cape Charles, Virginia, produced a total of 268 scavengers, including 245 Turkey Vultures and 23 Black Vultures, by far the highest I have recorded in winter on any survey route in the United States.  How many were overwintering in the peninsula, and how many were year-round residents, waits to be seen.  I should have the answer in July when we conduct our summertime counts in the area.  Whatever the percentage, the Delmarva looks to be one of the biggest, if not the biggest  East Coast winter resorts for vultures our surveys have detected.

Having thought about what we saw for a week, I remain more than a little confused.  You may recall that last month’s surveys in West Virginia, northeastern Tennessee, northwestern North Carolina, and western Virginia, produced counts that clearly indicated more Black than Turkey vultures in the region.  That said last week’s counts in New Jersey, Delaware, Maryland, Pennsylvania, and Virginia, indicate that Turkey Vultures outnumber Black Vultures there by about ten to one.  The differences, although apparent, remain enigmatic.  I will be conducting the surveys in both areas next year.  I hope by then to be able to explain the differences. 

No new North American surveys are planned until June.  That said Corinne Kendall arrived in Kenya earlier this week and should be updating us on her East African work, so please stay tuned.

Keith

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10 de febrero del 2010

Vimos a Roger (uno de nuestros buitres moteados) por última vez hace dos semanas. En ese momento, estaba haciendo viajes de ida y vuelta entre el parque nacional Amboseli y el área de conservación Shompole. Recientemente, Roger ha estado en Maji Moto y Narok, y sorpresivamente se ha quedado justo al norte de la reserva nacional Masai Mara sin entrar al parque durante esta semana.

Sus movimientos tan esparcidos sugieren que en su búsqueda de comida, al contrario de muchas aves que se quedan en un área pequeña, se ha movido constantemente. Roger también ha tomado ventaja de la gran capacidad de planeo por la cual se conoce a los buitres. Alcanzó una velocidad de 88 km/h esta semana, probablemente tomando una buena termal en el aire.

Es difícil imaginarse el viajar a esa velocidad fuera de un vehículo sin que nada que proteja la cara del viento, pero Roger lo logró varias veces.

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Dias de Gloria

12 de febrero del 2010

Hoy al fin tuve la oportunidad de volver a Nueva Jersey para un poco de trabajo de campo con zopilotes. Lauriane Streit, una estudiante francesa de postgrado extremadamente entusiasta va a pasar los próximos seis meses en Hawk Mountain Sanctuary analizando algunos datos de zopilotes para su tesis de maestría, y es justo que participe en un par de censos antes de iniciar.

Rescaté a Lauriane de la nieve que cubría Washington, DC, temprano en la mañana del martes, y nuestro primer conteo inició en Frederick, Maryland y terminó en Centralia, Pensilvania, al norte del santuario. El plan era salir hacia Nueva Jersey al siguiente día, pero una nevada de 55 centímetros interrumpió el trabajo de campo hasta esta mañana, cuando al fin pudimos salir hacia el Garden State. Nuestro conteo inició justo al este de Phillipsburg, Nueva Jersey y comenzamos a ver aves a menos de tres kilómetros del inicio. Para cuando llegamos a Washington, Nueva Jersey, habíamos visto siete, y al finalizar el día en Cape May, habíamos visto un total de 81 zopilotes cabecirrojos y 5 zopilotes negros. Aunque pensé que veríamos la mayoría de las aves en la Ruta 9 en la costa de Nueva Jersey, vimos la mayoría en la parte nor-central y en Pine Barrens.

La mujer que vino corriendo desde su tienda de perros calientes en la carretera estatal 31 cerca a Glen Gardner, Nueva Jersey, tipificó nuestras experiencias con los lugareños. Nos habíamos detenido a contar unos zopilotes cabecirrojos que perchaban en unas ramas en el camino, y ella nos dijo que estaban ahi siempre, durante todo el día, todos los días por más de un año. A ella no le gustan en particular, pero dijo “hacen lo que tienen que hacer” y los deja en paz. Son unos 30 dijo. Nosotros contamos 31.

Todo el suelo estaba cubierto de nieve, y no hay nada como ver un zopilote cabecirrojo planeando sin esfuerzo encima del blanco en un día soleado; y la luz que refleja la nieve ilumina el borde de sus alas en una manera que solo puedo describir como eterea.

Lauriane estaba impresionada, tanto con los números de zopilotes que vimos como con su primer águila calva… un adulto planeando justo al norte de Absecon, Nueva Jersey.

Con nuestro trabajo terminado, tomamos el Ferry de las 4:30 de Cape May a Lewes, Delaware, y conseguimos unas tortas de cangrejo decentes en la playa Rehoboth para cenar. Mañana el plan es “hacer” la Península Delmarva.

Más… luego.

Keith

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Glory Days

12 February 2010

Today, I finally got the chance to go back to New Jersey for some vulture field work.  Lauriane Streit, an extremely enthusiastic graduate student from France, is about to spend six months at Hawk Mountain Sanctuary analyzing some of our vulture data for her Master’s Thesis, and it seemed only fair to have her participate in a couple of vulture surveys before doing so. 

I had rescued Lauriane from snow-covered Washington, DC, early Tuesday morning, and our first count started in Frederick, Maryland and finished in Centralia, Pennsylvania north of the Sanctuary.   The plan was to take off for New Jersey the next day, but a 22-inch snowfall interrupted field work until this morning, when the two of us finally set off for the Garden State.  Our count started just east of Phillipsburg, New Jersey, and we started seeing birds less than two miles down the road.  By the time we reached Washington, New Jersey, we had seen seven, and by day’s end in Cape May, we had seen totals of 81 Turkey Vultures and 5 Black Vultures.  Although I thought that we would see most of the birds on Route 9 along the Jersey Shore, we actually saw the greatest numbers in north-central Jersey and the New Jersey Pine Barrens.

The woman who came running out of her hot dog shop on State Highway 31 near Glen Gardner, New Jersey, typified our experiences with the locals.  We had stopped to count some Turkey Vultures roosting in several snags along the road, and she told us they were there 24-7, round the clock, every day, for more than a year.  She didn’t necessarily like them, but “they had to do what they had to do,” so she left them alone.  About 30, she said.  We counted 31.

The ground was snow covered throughout, and there is nothing quite like seeing a Turkey Vulture soaring effortlessly above the white stuff on a sunny day; the trailing edge of its wings lit by reflected sunlight in a way that can only be described as ethereal. 

Lauriane was impressed, both with the numbers of vultures we saw, and with her first look at Bald Eagle… a soaring adult just north of Absecon, New Jersey.

Our work done, we caught the 4:30 Cape May Ferry for Lewes, Delaware, and managed to find some decent crab cakes at Rehoboth Beach for dinner.  Tomorrow the plan is to “do” the Delmarva Peninsula. 

More later.

Keith

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February 10, 2010

We last watched Roger, one of our Ruppell’s Vultures, two weeks ago. At that time, he was darting back and forth between Amboseli National Park and Shompole Conservancy. More recently, Roger has been handing around Maji Moto and Narok, and surprisingly he has continued to stay just north of Masai Mara National Reserve, not entering the park a single time this past week.

His scattered distant movement suggests that his search for food has been trying, and unlike many of the birds which seem to stick to one small area, he has been on the move constantly. Roger has also been taking advantage of the incredibly efficient soaring flight that vultures are known for. He reached top speed of 88 km/hr (55 mph) this week, probably catching a nice thermal in the air.

It is difficult to imagine travelling that speed outside a vehicle with nothing to block your face from the wind, but Roger managed it several times.

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Biología de sillón

3 de febrero del 2010

Créanlo o no, yo no paso tanto tiempo en el campo. De hecho, mucho de mi tiempo lo gasto en el Centro Acopian hablando con compañeros de trabajo, escribiendo a colegas, analizando datos, y escribiendo artículos y reportes. Mi tiempo para la lectura profesional es en las noches, en un sillón en el Hill House, no muy lejos del Centro de Visitantes del Santuario.

Mucho de lo que leo son las publicaciones recientes sobre aves rapaces. Sin embargo, de vez en cuando algo que se escribió hace décadas llega a mi lista. Y es exactamente lo que pasó la semana pasada, cuando, encima de todos, estaba una monografía de 150 páginas publicada en 1946 en American Midland Naturalist. A simple vista, la monografía de Harvey Irvin Fisher titulada “Adaptation and comparative anatomy of the locomotor apparatus of New World vultures” no parecía merecer pasar de la primer página. Pero el mundo está lleno de sorpresas, y terminé de leer la monografía esa misma noche.

Un consumado trabajador de museo, Fisher disectó cuidadosamente los músculos y huesos de los zopilotes del nuevo mundo esperando proveer un registro permanente de la mecánica comparativa del cóndor de california, el cual, inclusive en ese tiempo se creía en peligro. No fué el trabajo de Fisher sobre la anotomía del condor lo que me intrigó; lo que si hizo sus comparaciones entre los músculos y huesos entre zopilotes cabecirrojos y zopilotes negros.

No es sorpresa que Fisher encontrara que el húmero, o el hueso de la parte anterior del brazo, de ambas especies está repleto de cavidades huecas, lo que lo hace escepcionalmente neumático y liviano; precisamente lo que uno espera para una especie que pasa su mayor parte en el aire planeando. Pero el también descubrió que el húmero del zopilote cabecirrojo era mucho más liviano que el del zopilote negro, haciéndolo aparentemente más débil, y explicando, en parte, el aleteo menos fuerte del cabecirrojo. Además, Fisher encontró grandes diferencias en los metacarpos, o huesos de la mano, en las dos especies, en donde los del zopilote cabecirrojo son mucho más largos que los del zopilote negro, haciéndolo más diestro en el vuelo.

Fisher también descubrió diferencias considerables en la musculatura de vuelo en las dos especies. Los músculos de vuelo de los zopilotes cabecirrojos, por ejemplo, ocupan impresionantemente un 52% de su masa corporal, donde los del zopilote negro ocupan sólo un 33%. Aún así, los zopilotes negros tienen en proporción, más masa muscular cerca de su cuerpo, lo que les permite utilizar sus fuertes húmeros para aletear más fuerte que los cabecirrojos. Los cabecirrojos, en comparación, tienen más masa muscular distal, lo que les permite un mejor control de las superficies en los extremos de sus alas. Ello, junto con tendones metacarpales largos, ayudará al zopilote cabecirrojo a mantener sus alas extendidas, sin aletear, por períodos mas largos.

Aunque estas y otras diferencias estructurales que Fisher reporta no son sorprendentes – todos sabemos que los zopilotes cabecirrojos aletean menos y más debilmente que los zopilotes negros – su detallada investigación provee una sólida base anatómica para las diferencias en el comportamiento de vuelo de las dos especies, y sugiere que la selección natural ha estado actuando por algún tiempo en estas dos especies, que aunque son similares en apariencia, por dentro no lo son tanto.

“Adaptation and comparative anatomy of the locomotor apparatus of New World vultures” es un ejemplo perfecto de como estudios de las aves “por dentro” pueden ayudarnos a los que estudiamos aves “por fuera”. Es también un ejemplo perfecto de como la “biología de sillón” puede ayudar a los biólogos de hoy día a aprender algo nuevo sobre las aves que estudian, inclusive cuando no las estén observando.

Vuelvo al campo la semana que viene. Esperen más para entonces.

Keith L. Bildstein

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February 8, 2010

The GSM-GPS transmitters have now been on the vultures for over six months. With over 8,000 data points, we can learn a lot from the movement of these 14 birds. Today I calculated the home range size or the size of the area that a single bird has used based on every location point that we have. The home range sizes are astounding.

A single bird, an African White-backed Vulture to be exact, can have a range size of up to 97,000 km2 (37,500 mi2). That is almost the size of Pennsylvania, about 1/6 the size of Kenya, and nearly twice the size of one of the largest protected parks in Africa (Selous Game Reserve in Tanzania). In just six months, a single bird can thus span far beyond the entire Serengeti-Mara ecosystem, using many of the other protected areas scattered around southern Kenya and northern Tanzania. If just one individual needs such a large area to survive, it is easy to imagine why the conservation of these species is so complicated. No park will ever be large enough to protect the entire range of even a single individual for most vulture species. Instead we must hope that the birds can travel safely over cities, towns, villages, farms, and livestock pastures.

Sadly, with people poisoning carcasses, we know that safe passage isn’t guaranteed. With such huge range sizes we know something else. The vultures have a lot to tell us about ecosystem health. Their survival and population numbers give us information not just about a single park, but about the entire system of protected areas in East Africa. Vultures could be the key to monitoring these preserves and the areas around them, providing us with vital information about the other wildlife species they depend on for food and about the use of poisons, chemicals, and pollution across these large land areas on which they rely. By studying them, we are learning not just about the vultures but about the larger East African savanna.

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February 1, 2010
A view of the Lake

If I had been flying with Laila this week, I could have seen the largest lake in Africa for the first time. As a fledgling Lappet-faced Vulture, it was Laila’s first visit there too. Laila spent most of her time in Serengeti National Park this week, but then took an unexpected adventure, heading west to Lake Victoria. The third-largest lake in the world and largest in Africa, it must have been an impressive sight. Laila flew within 10 miles of the lake’s border perhaps finding a nice carcass not too far from the water.

Although she stayed on the Tanzania side, Lake Victoria is actually split between three countries with the largest portions in Uganda and Tanzania and a tiny sliver in Kenya. The lake is known for its exceptional fishing and once housed nearly 500 different species of fish, but I have always known it for its hippos. What Laila saw in it I don’t know, but it must have been quite a week for her with lots of new sites.  

February 4, 2010
Back in the Masai Mara National Reserve (MMNR)

This week, Quagmire, an adult African White-backed Vulture, decided to leave the wildebeest. Initially this 10 pound bird was in Serengeti, moving to the southern tip where many of the migratory wildebeest are likely to be hanging out these days. But then he turned north returning to Masai Mara National Reserve (MMNR).

Back in the MMNR, Quagmire spent his days wandering along the huge Mara River before moving even farther north. Surprisingly he stopped not too far from Narok, the closest large town to the Masai Mara National Reserve. In this heavily grazed and urban area, I can’t imagine him finding much food, but he spent quite a few days there. Perhaps I will see him upon my return at the end of the month, soaring over the road, as I drive back to my home at Ilkiliani Lodge on the border of the park.

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Arm-chair biology

3 February 2010

Believe it or not, I don’t get to spend all of my time in the field. In fact, I spend a great deal of time at the Acopian Center talking with co-workers, emailing colleagues, analyzing data, and writing papers and reports. Professional “reading time” occurs in the evening in an arm-chair at Hill House, not far from the Sanctuary’s Visitor Center.

Most of my reading involves pouring over recent publications on raptors. Once in a while, however, something that was written decades ago finds its way onto my list. And that is exactly what happened last week when a 150-page monograph published in the American Midland Naturalist in 1946 reached the top of my pile. At first blush, Harvey Irvin Fisher’s “Adaptation and comparative anatomy of the locomotor apparatus of New World vultures” didn’t appear to be a “page-turner.” But the world is full of surprises, and I ripped through Fisher’s monograph in a single evening.

A consummate museum worker, Fisher had painstakingly dissected the muscles and bones of New World vultures in hopes of providing a permanent record of the comparative flight mechanics of the California Condor, which even then was thought to be endangered. It wasn’t Fisher’s work on the flight anatomy of the condor that intrigued me, however; but rather his comparisons of the muscles and bones of Turkey Vultures and Black Vultures.

Not surprisingly, Fisher found the humerus, or upper-arm bone, of both species to be riddled with airspaces, making it exceptionally pneumatic and lightweight; precisely what one would expect for birds that spend most of their time aloft in soaring flight. But he also discovered that the humerus of the Turkey Vulture was substantially lighter than that of the Black Vulture, presumably making it weaker, and explaining in part, the former’s less forceful flapping flight. Further out on the wing, Fisher found substantial differences in the metacarpals, or hand bones, of the two species, with those of Turkey Vultures being much longer than those of Black Vultures, making them more dexterous in flight.

Fisher also discovered considerable differences in the flight musculature of the two species. The flight muscles of Turkey Vultures, for example, make up an impressive 52% of their total body mass, whereas those of Black Vultures make up only 33%. Even so Black Vultures have proportionately greater muscle mass close to their bodies, allowing them to use their stronger upper-arm bones to flap more forcefully than Turkey Vultures. The latter, by comparison, have greater muscle mass distally, allowing them to better control the surfaces of their outer wings. This, together with larger metacarpal tendons, presumably, helps Turkey Vultures keep their wings outstretched–and not flapping–for longer periods of time.

Although these and other structural differences Fisher reports are not surprising–we all know that Turkey Vultures flap less frequently and less forcefully than do Black Vultures–his detailed research provides a solid anatomical foundation for differences in the flight behavior of the two species, and suggests that natural selection has been acting for some time on these two outwardly similar, but in fact structurally very different avian scavengers.

“Adaptation and comparative anatomy of the locomotor apparatus of New World vultures” is a perfect example of how studies of a bird from the “skin-side-in” can help those of us studying birds from the “skin-side-out.” It also is a perfect example of how arm-chair biology can help modern biologists learn something new about the birds they are studying, even when they are not watching them.

I get to go back into the field next week.  So expect more then.

Keith L. Bildstein

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