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Toxicology in Red-Shouldered Hawks

Julia Nelson | Wednesday, July 19th 2017

Research done by Dr. Dave Scott, veterinarian at Carolina Raptor Center

Carolina Raptor Center sees up to around 1,000 injured raptors a year. Many of the birds that come in have tremors and neurological issues. Birds with these symptoms often don’t often live past 24 hours. These symptoms can be caused by either trauma, infection, or toxins. Trauma and infection are relatively easy and inexpensive to diagnose. Trauma, often caused by cars or window strikes, will involve broken bones and other physical injuries. A simple blood test will show if the bird is infected by West Nile Virus, the Avian Influenza, or another infection that causes the clinical signs of neurological issues. A bird poisoned by a toxin, though, needs a post-mortem diagnosis that costs about $200.

 A young owl displaying torticollis, a neurologic sign  

Recently, CRC’s budget is allowing for the testing of toxins in raptor necropsies. The results are surprising, and sad. Toxins cause a greater number of deaths than previously thought. In the last 18th months, toxins have been found as a source of death in 33% of Red-Shouldered Hawks that were brought in with the neurological signs of tremors and seizures.��

The necropsies done on these raptors have startling results. One case study at CRC shows that a single raptor’s liver contained 17.1 ppm of Heptachlor (this is 4x the lethal dose) and 705 ppm of Dieldrin (this 150x the lethal dose!) Heptachlor and Dieldrin are organochlorine pesticides. Heptachlor is labeled as being “one of the most potent carcinogen ever tested on animal models.” Heptachlor was banned in the US in 1988 and Dieldrin in 1987. These chemicals bio-accumulate and do not break down in nature. That’s why these toxins are still being found today. Bioaccumulation occurs when a toxic substance is absorbed at a rate greater than that as which the substance is lost. This increases the risk of chronic poisoning because the substance has a longer biological half-life. This mean even small levels of the substance in the environment can be deadly. 

Red-Shouldered Hawks seem to be most susceptible to these toxins because of their diets. These Hawks feed on grubs or insects found on residential lawns that use pesticides/herbicides. Other species that are being found harmed by these toxins include the Barred Owl and Red-Tailed Hawk. These birds are a living testament to the fact that chemicals banned several decades ago can still harm living things in current times. Today, we as humans are tasked with making daily decisions that have the potential to impact more than just ourselves in the years to come.

What can you do to help prevent the death of raptors by toxins? 

STOP using pesticides, insecticides, and herbicides whenever possible. 

If you find old lawn care substances or chemicals in a shed, do not use it and dispose of it properly. Click here to learn how to safely manage household hazardous waste as defined by the EPA, and Click here for Disposal sites in Mecklenburg County

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It’s been a rewarding weekend at Carolina Raptor Center - in the past 3 days, we have released 20 birds.  Red-tailed hawks, red-shouldered hawks, barred owls, and a turkey vulture all flying free.  This is the best part of what we do.

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Silent Night

Looking at the structure of Owl feathers to explain their soundless flight

Julia Nelson | Saturday July 1st, 2017

If you’ve ever taken a biology class you were probably told that a certain biological structure allows for a certain function. This can be found on every biological scale, from bear’s using their claws to roll over logs in search of bugs, to the structure of proteins that are shaped so specific substances are catalyzed. Owl’s have very unique feathers which allow for a specialized predation style.

Owls hunt in total darkness and rely on stealth to catch prey. Nocturnal animals have an acute sense of hearing, so owls must be silent to capture prey. These animals have evolved to be soundless fliers.

Willow, a resident Barn Owl at Carolina Raptor Center. Photo by William Krumpelman

Aerodynamic noise is caused by air molecules hitting a surface. The faster a flying mass is moving, the louder it will be. Compared to other birds of prey, owls are relatively slow-moving. This is one of the factors for reduced noise. The rest of the majority of an owl’s silent flight can be attributed to three special aspects of their feathers; a leading edge comb, trailing edge fringe, and soft downy feathers.

In flight, air will first hit the front of the bird’s wings. The leading edge of an owl’s wing feathers is comb-like. The barbs in the comb are designed to lessen the local pressure gradient of air around the leading edge to reduce noise.

Basically, the air is cut up into smaller micro-turbulences by the leading edge comb which has less of a noise impact than one turbulence interacting with a non-barbed feather. Adding to the noise reduction is the angle of the barbs towards the wing tip. This angle decreases the surface area where air will strike against the feather. (Air will impact in the small crevice between each comb as opposed to the whole feather surface if there were no combs.)

Pictured above are the comb-like serrations on an owl feather’s leading edge

Next, air will flow to the trailing edge of the feather after interacting with the leading edge. Most noise when flying is caused by air turbulence on the trailing edge. The porous, jagged edge mixes the air streams which prevents air vortexes and stops any fluttering that would produce sound.

Pictured above is the soft trailing edge of an owl’s feather

Lastly, Owls are blanketed in soft downy feathers. This canopy of fluff muffles noise. This also provides padding and removes friction between feathers during flight which reduces noise.

Pictured above is the soft downy covering that blankets an owl’s wings and body

You can try an experiment at home. Grab a piece of paper and flap it up and down mimicking a wingbeat. Take note the sound. Next try the same thing with a piece of soft fabric or a shirt sleeve. The soft fabric muffles most noise. Now imagine if that fabric were aerodynamic, downy, and even softer and you can imagine how an owl flies silently. Feathers of some other birds such as pigeons and falcons are stiff, plasticky, and rounded and can be likened to the flapping of paper. Those feathers are built for other utilities such as speed or agility, not silence.  

How does an owl’s soundless flight compare to other birds? Click to find out

Owl feather’s are being intensively studied for human use in engineering. One of the factors limiting the wide-spread use of wind turbines is the bothersome noise produced. Biomimicry studies are being done to apply the structure of an owl feathers to a wind turbine to stifle the sound.

If you ever find yourself lucky enough to witness an owl in flight in close proximity, listen to what you hear...rather, listen to what you don’t hear. You can visit Carolina Raptor Center on the weekend for a flight show for a chance to see these silent fliers in action right over your head.

Sources and further reading:

https://www.acoustics.asn.au/conference_proceedings/INTERNOISE2014/papers/p26.pdf

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3162239/

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Stopping the Stoop of Peregrine Populations

The struggle of reintroducing a raptor species to North Carolina

Julia Nelson | Thursday June 29, 2017 

Despite being the world’s most widespread raptor and being taken off the federal Endangered Species list in 1991, The Peregrine Falcon is currently state-listed as an endangered species in North Carolina.

Decline in population can be mostly attributed to the pesticide DDT which causes soft-shelled eggs that are frail and break during incubation. DDT was responsible for wiping out the entire population of Peregrine Falcons in the eastern United States.

The last breeding pair of Peregrine Falcons in NC was documented in 1957 before the raptors went extinct state-wide. DDT was banned by the EPA in 1972. From 1984-1991 The Wildlife Commission took aggressive steps towards restoration and began hacking efforts in an attempt to reintroduce the state-wide extinct population. (Hacking is the release of captive raised falcons into the wild. You can read more about this process here.) 80 young falcons were released into the wild. 1986 saw the first nesting pair of Peregrine Falcons. That number has slowly risen to about a dozen pairs into the turn of the century and to current time.

The main problem with bolstering the population is nesting success. Peregrine Falcon pairs stay bonded for life and will mate and nest in the same location annually. They nest primarily on cliffs, but will also use trees, bridges, and buildings. Peregrines are very territorial, so a nesting site will only benefit up to one pair if nesting is successful. If the location is disturbed, most often by human behavior, the pair will simply not nest for that entire year. An ideal location may be unused for the year if the nesting pair is unsuccessful and other pairs will not use that site. The finicky nature of the Peregrine’s nesting habits makes population restoration difficult and slow moving.

Reintroduction was pushed in areas with suitable nesting locations such as Grandfather Mountain, Mt. Mitchell, White Rock Cliff, Chimney Rock, and Linville Gorge. These birds have proved to be very adaptive to the urban landscape. They have been known to nest in tall skyscrapers which mimic natural cliff faces. One nesting pair in NC has chosen the Wells Fargo building as a nesting site and has returned intermittently to fledge young.

The population of Peregrine Falcons has stabilized to around 11-15 nesting pairs. Continued conservation efforts include the monitoring of nesting sites and examinations of adult birds. Although the population of Peregrine Falcons in North Carolina is still considered endangered, the birds have come a long way since state-extinction 60 years ago. With continued conservation efforts, their numbers will hopefully continue to rise.

How can you help Peregrine Falcon populations in NC?

 • Avoid or limit the use of herbicides and pesticides to prevent contamination of prey animals for these raptors 

• When rock climbing or hiking, do not attempt to access closed rock faces or trails

 • Visit the The Peregrine Fund’s website to learn more about the history and current efforts of raptor conservation

 • Visit the Carolina Raptor Center to learn about raptors and see our resident Peregrine Falcon (Aragorn pictured below)

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Where We Came From

A historical glance at Carolina Raptor Center

Julia Nelson | Friday June 23, 2017 

I have just completed my first year at the University of North Carolina at Charlotte. And in that year I had a single class in McEniry. I would’ve never imagined that under the many pairs of feet in my Earth Science lecture hall the basement of this old biology building held a deep, feathered history. Many decades ago, there was a sign to the basement stairs that read: “Caution, open door slowly.” The basement halls of this building were used as flight training for birds regaining flight strength. Makeshift avian surgery rooms were set up alongside offices and classrooms. An imprinted Vulture named Campbell (named after the soup he was fed by his finder) ambled the halls hoping for an elevator ride. This was the fledgling organization that would be known as Carolina Raptor Center.

Carolina Raptor Center first took flight in 1975 when an injured Broad-winged Hawk was taken to UNCC biology professor and ornithologist Dr. Richard Brown. Dr. Brown attended a raptor rehabilitation workshop with a few students in 1981 and afterwards discussed plans for a center in UNCC. In a local pizza parlor, the plan for the early center was composed and ideas and goals were jotted down on a napkin. That year CRC was officially cofounded by Dr. Brown and student Deb Sue Griffin and incorporated as a nonprofit.

The makeshift clinic began to grow in the basement, expanding from 23 birds in 1980 to 200 in 1983. Any description of the early days of the Raptor Center would be inaccurate without emphasizing its uniqueness. Office supplies sat next to a cutting board full of medicine-laced chicken hearts, a coffee pot rested beside I.V bags, a refrigerator full of chicken ribs and medicine stood next to cluttered filing cabinets. The center was run mostly by volunteers and didn’t have a full-time vet.

In 1984, CRC moved to the Latta Plantation Nature Preserve. At this time, the center consisted of a couple trailers and outdoor chain link fences. There was no established well at the site and water had to be carried in buckets from the lake. A visitor center was built a few years later. CRC becomes more than raptor rehabilitation, it is a hub for education and research. 

CRC has grown exponentially rising from a basement-level clinic to a center of regional, national, and international importance. The RaptorVet Externship Program attracts vet students from all over the globe. CRC’s veterinarian Dr. Dave Scott has installed his RaptorMed electronic medical record in centers in California, Beijing, Taiwan, and Qatar. CRC became the site for many ‘firsts’ in the raptor world. In 2006 Len and Lola were the first Bald Eagles in North Carolina to be hatched in captivity and released into the wild. 

Flashforward to 2017. Much time has passed and with it has come monumental change. Based on admitted avian patients, Carolina Raptor Center holds the title of the largest raptor medical center in the US. CRC now plans further expansion to a different location with a new Quest Center and exhibition trails breaking ground in the fall. Throughout change and growth, it is important to reflect upon the roots of the organization and realize that the mission remains at the heart of all efforts; past, present, and future. A mission of environmental stewardship and the conservation of birds of prey with the goal of connecting humans with nature.