Red hawk down

ID tags, lab work help­ing clear up mys­tery of rap­tor found dead near Hot Springs

Northwest Arkansas Democrat-Gazette - - STYLE - JERRY BUT­LER

A male red-tailed hawk with a metal band on its an­kle and large cir­cu­lar tags with the num­ber 146 at­tached to each wing was found life­less Jan. 12 at the John and Donna Simp­son Pre­serve off Amity Road south of Hot Springs.

By us­ing data re­leased by the re­searchers who banded the bird, in­for­ma­tion about such hawks from the Cor­nell Lab of Or­nithol­ogy, an X-ray of the hawk and in­for­ma­tion about the necropsy by the Arkansas Live­stock and Poul­try Com­mis­sion’s lab­o­ra­tory, it’s pos­si­ble to piece to­gether a sort of obituary for the well-trav­eled bird.

Hawk No. 146 hatched in spring 2011 to monog­a­mous par­ents who lived, more than likely, in a forested area of north­ern Illi­nois. Its first home, a nest its par­ents built of twigs, was lined with bark — and per­haps with corn husks since these hawks lived in the heart of the Corn Belt. That large nest was likely 40 feet high in a tree or even higher if they used some man-made struc­ture.

The egg from which Hawk 146 hatched was pale brown or pur­ple and about two-thirds the size of most gro­cery-store chicken eggs. It was in­cu­bated pri­mar­ily by the mother and broke from its shell 28 to 35 days af­ter she laid the egg. It may have had as many as four sib­lings, but it is doubt­ful all of them sur­vived into adult­hood.

Their fa­ther fed the nestling hawks (called eyasses) mostly mice, rab­bits and other small mam­mals.

Forty-five days af­ter hatch­ing, in early or mid-sum­mer 2011, Hawk 146 took flight and be­gan life on its own.

In Oc­to­ber 2011, fully grown but not yet sex­u­ally ma­ture, Hawk 146 was cap­tured at O’Hare In­ter­na­tional Air­port in Chicago by a team of U.S. De­part­ment of Agri­cul­ture An­i­mal and Plant Health In­spec­tion Ser­vice (APHIS) wildlife ser­vices re­searchers, who were study­ing ways to pre­vent col­li­sions be­tween rap­tors and air­planes.

Cap­tur­ing, tag­ging and re­lo­cat­ing the hawks is an al­ter­na­tive to shoot­ing them, which is done at many air­ports (see, for in­stance, bit.ly/2kRTeeR).

Among the ques­tions the re­searchers wanted to an­swer were:

If a bird is trapped and re­moved from a busy air­port, is it likely to re­turn?

At what dis­tance should a bird be re­lo­cated to re­duce the like­li­hood of its re­turn? 25 miles? 50 miles? 100 miles?

Which birds can be re­lo­cated most suc­cess­fully? Young ones or older ones, males or fe­males?

Is it bet­ter to re­lo­cate them in breed­ing sea­son or some other time?

Shortly af­ter Hawk 146’s cap­ture, re­searchers put a me­tal­lic an­kle bracelet on its right leg and ny­lon tags on the up­per side of each wing, with the num­ber 146 writ­ten in in­deli­ble marker. The red-tail was taken to a park in White­side County, Illi­nois, ad­ja­cent to the Mis­sis­sippi River (114 miles west of O’Hare) and re­leased.

At that point, the thread of the bird’s his­tory snags. Had its de­vel­op­ment fol­lowed the life cy­cle of most red-tailed hawks, it could have found a mate, fa­thered four clutches of eggs and raised young be­tween 2013 and 2016. But at some point in this pe­riod it in­gested, as prey, some crea­ture with lead in its body, likely a rab­bit or squir­rel.

IN­VES­TI­GA­TION

Dr. John Simp­son, a Hot Springs pri­mary care physi­cian, found the dead rap­tor on a large wooded plot that is owned by the Arkansas Na­ture Con­ser­vancy at Trap Moun­tain south of Amity Road. He do­nated much of the 880 acres to the con­ser­vancy, and he reg­u­larly checks the prop­erty. He is try­ing to re­store it to its na­tive state by re­mov­ing in­va­sive plants.

On one of these main­te­nance trips, he found the dead hawk ly­ing in pine straw be­side a nar­row log­ging road.

“I saw the white tag and thought it was lit­ter, so I stopped to pick it up,” he said. “It may have been there when I passed ear­lier but I did not see it, or it may have fallen dead at that place while I was far­ther east on the road.”

The red-tail had no ap­par­ent in­juries. It was not stiff, and it did not have the stench of death.

“Since I was go­ing to the Gar­land County Audubon So­ci­ety meet­ing that night, I put the bird in a black plas­tic garbage bag and took it along to see if any­one there could tell me any­thing about the large vinyl wing tags,” he said.

Be­sides the iden­ti­fy­ing num­ber, a bracelet just above the clenched talon had the phone num­ber of the bird-band­ing reg­istry where Simp­son could re­port his dis­cov­ery. From the Bird Band­ing Lab at the Patux­ent Wildlife Re­search Cen­ter in Mary­land, Simp­son learned that the hawk had been banded and fit­ted with the wing tags in 2011.

When he showed the car­cass at the Audubon meet­ing and later when pho­tos were posted on ARBird-L, a Univer­sity of Arkansas-spon­sored list­serv, other bird­ers ex­pressed con­cern that the wing tags — pata­gial tags — had con­trib­uted to the bird’s demise. Ex­pert opin­ion, how­ever, is that was not the case.

Karen Rowe, bird con­ser­va­tion co­or­di­na­tor with the Arkansas Game and Fish Com­mis­sion, con­tacted the band­ing re­searchers and shared with the list­serv what she learned from Travis Guer­rant, as­sis­tant state di­rec­tor of USDA APHIS Wildlife Ser­vices in Spring­field, Ill.

“Given that the hawk was over 5 years old when it died,” Rowe wrote, “it is highly un­likely that the pata­gial tags on the hawk’s wings had a neg­a­tive im­pact on the hawk’s sur­vival. Mr. Guer­rant said that they banded over 600 red-tailed hawks and had no is­sues caused by the pata­gial tags.”

(A man­u­script de­scrib­ing Guer­rant’s re­search team’s meth­ods and find­ings has been ac­cepted to ap­pear in a fu­ture is­sue of the Jour­nal of Wildlife Man­age­ment.)

Riv­et­ing vinyl-coated ny­lon cloth tags (with the flex­i­bil­ity and feel of a shower cur­tain) to wings in a man­ner ap­proved by the U.S. Ge­o­log­i­cal Sur­vey is a com­mon prac­tice in avian re­search, par­tic­u­larly among larger birds. The method­ol­ogy has been used by re­searchers in Arkansas on swans and vul­tures. Robert Hawkins, past pres­i­dent of Wildlife Ma­te­ri­als Inc., con­firmed that the pata­gial tags are much cheaper than ra­dio trans­mit­ters and as­so­ci­ated track­ing equip­ment. Given that the re­searchers around O’Hare cap­tured more than 600 birds, it rep­re­sents a sig­nif­i­cant sav­ings in re­search dol­lars.

A cur­sory re­view of wildlife re­search jour­nals found no ar­ti­cles that em­pir­i­cally demon­strated that pata­gial tags lim­ited bird flight or sur­vival, but there are many re­search re­ports that demon­strate birds wear­ing pata­gial tags have sur­vived in the wild for decades.

“The bird, at 5 years old, had al­ready out­lived many of its co­horts,” Rowe told this re­porter. In fact, it had al­ready beaten the odds against red­tailed hawk sur­vival when it was banded in 2011. Mor­tal­ity rates for first-year rap­tors are high — “around 80 per­cent,” Rowe said.

She added that the Game and Fish Com­mis­sion re­ceives many re­ports of dead hawks, “and we can­not in­ves­ti­gate them all be­cause mor­tal­ity is a nor­mal and nec­es­sary part of the nat­u­ral sys­tem. We do in­ves­ti­gate hawk deaths due to il­le­gal ac­tiv­i­ties such as shoot­ing or pos­si­ble poi­son­ings.”

The most com­mon causes of death, she said, turn out to be col­li­sions with pow­er­lines or ve­hi­cles, lead poi­son­ing, il­le­gal shoot­ing, or in­fec­tion with the fun­gal dis­ease as­pergillo­sis or other avian dis­eases.

NECROPSY RE­SULTS

The Arkansas Live­stock and Poul­try Com­mis­sion’s lab­o­ra­tory did a necropsy on

the hawk. A few test re­sults were still pend­ing at press time, but the lab al­lowed the Game and Fish Com­mis­sion to re­lease its pre­lim­i­nary find­ing.

“While some peo­ple wanted to im­pli­cate the pata­gial tags as caus­ing the bird’s death, the pre­lim­i­nary necropsy re­port’s heavy met­als tests in­di­cate that the hawk died of lead poi­son­ing,” Rowe said. “Liver lead lev­els higher than 6 parts per mil­lion (ppm) are con­sid­ered lethal. The hawk’s liver lead level was 142.1 ppm.

“Birds of prey get lead poi­son­ing by in­gest­ing an­i­mals or fish (or parts of an­i­mals and fish) that con­tain lead fish­ing tackle such as sinkers, or lead am­mu­ni­tion such as lead shot or lead bul­let frag­ments.”

Rowe told the Arkansas Demo­crat-Gazette on Feb. 17 that she wouldn’t be sur­prised if the out­stand­ing test re­sults show that a bac­te­rial or vi­ral in­fec­tion played a sec­ondary role in the hawk’s death.

“It is very com­mon to see rap­tors with lead poi­son­ing also con­tract res­pi­ra­tory in­fec­tions be­cause the lead has com­pro­mised their im­mune sys­tems,” she said.

SICK EA­GLE

Lead poi­son­ing also can lead to col­li­sions.

“Ear­lier this month, one of our re­ha­bil­i­ta­tors took in a bald ea­gle that had se­ri­ous in­juries from a ve­hi­cle col­li­sion,” Rowe told the Demo­crat-Gazette. The Game and Fish Com­mis­sion pays for lead test­ing and lead poi­son­ing treat­ment for all the ea­gles taken in by Arkansas re­hab­bers, so the re­ha­bil­i­ta­tor’s vet­eri­nar­ian sent the ea­gle’s blood sam­ple to the Live­stock and Poul­try Com­mis­sion lab.

The num­bers used in blood tests are dif­fer­ent from those used in liver tests. In bird blood, less than 0.1 ppm is con­sid­ered “back­ground noise” — nor­mal. Be­tween 0.1 and 0.2 ppm in­di­cates ex­po­sure to lead but not poi­son­ing (i.e. lethal by it­self). Above 0.2 ppm is lead poi­son­ing, a lethal ex­po­sure.

“The ea­gle that was hit by the ve­hi­cle had a blood lead level of 0.41,” Rowe said. It died in a few days.

She be­lieves the ea­gle was scav­eng­ing along the road be­cause it was too im­paired to hunt.

She added that “the re­mains of wild nongame birds

should be left where they fall. It is against both state and fed­eral law for un­li­censed peo­ple to pos­sess these birds or their feath­ers” un­der the Mi­gra­tory Bird Treaty Act and AGFC Code of Reg­u­la­tion 14:01. She ex­plained that “dead birds are an im­por­tant part of the ecosys­tem, just as the live ones are.”

Car­rion, in the form of dead birds, is part of the diet of vul­tures, opos­sums, many

in­sects and ea­gles.

If a coy­ote, fox or do­mes­tic dog had eaten this par­tic­u­lar red-tailed hawk, it too would have been at risk for lead poi­son­ing.

Arkansas Demo­crat-Gazette/NIKKI DAWES

Arkansas Demo­crat-Gazette/NIKKI DAWES

Spe­cial to the Demo­crat-Gazette/ JOHN SIMP­SON

Hawk 146’s pata­gial tag mounts and a metal ID bracelet are seen in Dr. John Simp­son’s X-ray. Simp­son found the red­tailed hawk on Na­ture Con­ser­vancy land south of Hot Springs.

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