Interesting...
http://www.chron.com/disp/story.mpl/...s/3726810.html
http://www.chron.com/disp/story.mpl/...s/3726810.html
quote:
Studies suggest lead poisoning is killing millions of doves
By SHANNON TOMPKINS
RESOURCES
DOVES AND LEAD SHOT POISONING
• With a North American population estimated at 475 million in the 1980s, mourning doves are the continent's most common game bird and one of its five most common birds of any species.
• Mourning doves are the most popular game bird in the country, attracting an estimated 1.9 million hunters each season. Texas fields the most dove hunters, an estimated 300,000 each season.
• About 75 percent of the shotgun shells purchased each year are bought for dove hunting. Those shotshells are loaded with lead pellets.
• Waterfowl hunters , who have had to use non-toxic shot since 1991, purchase about 10 percent of the shotgun shells sold in the U.S.
• Research indicates 1-6 percent of doves taken by hunters have ingested lead shot in their gizzards.
• Studies have found 6-11 percent of doves taken by hunters have elevated lead levels indicating past exposure to ingested lead shot.
• Lead poisoning caused by doves ingesting spent lead pellets as grit for their gizzards could be responsible for the death of 8-16 million doves each year.
• Recent research in Missouri suggests doves ingesting as few as one or two lead pellets have about a 50/50 chance of dying from the toxic effects within three weeks.
• Some states have imposed bans on use of lead shot for hunting doves and other upland game birds on state-controlled tracts. Use of lead shot is prohibited for all wingshooting on federal refuges, waterfowl production areas and other tracts controlled by the U.S. Fish and Wildlife Service.
• Lead shot is prohibited for use when hunting doves on four of the 53 Texas Parks and Wildlife Department wildlife management areas that allow dove hunting.
Mounting evidence that ingestion of lead pellets poses an as-yet-unquantified detrimental effect on dove populations has wildlife managers across the country beginning to look seriously at the issue.
Already, the federal government and some states have banned lead shot for all wingshooting, including hunting for doves and other upland birds, on some government-controlled areas such as federal refuges, state wildlife management areas and government-leased hunting tracts.
No sweeping rule mandating a switch to non-toxic shot for dove hunting has been proposed by either federal or state wildlife agencies. And any such rule at the federal level could take years to impose.
But the subject is gaining scrutiny.
Recently, the International Association of Fish and Wildlife Agencies alerted its members to new research on the issue of lead poisoning of doves and raised the question of whether non-toxic shot should be required for hunting doves.
At a Monday meeting in Austin of the Texas Parks and Wildlife Department's Game Bird Advisory Board, Jay Roberson of TPWD's wildlife division offered the citizen advisory group an overview of the issue and some of the research triggering the topic's increasing significance among wildlife managers.
Any move to require non-toxic shot for dove hunting would have a huge impact on wingshooters across the nation and, in particular, Texas.
Doves are the most popular and populous game bird in the nation. An estimated 1.2-1.6 million wingshooters hunt doves in the United States, with 300,000 or so in Texas, the most of any state.
A switch from using shotshells loaded with lead pellets, traditional shot material for doves and other upland game birds, to those packed with non-toxic pellets would precipitate a near total upheaval of ammunition manufacturing and cost hunters a lot more money.
Dove hunters are shotshell manufacturers' biggest customers. Dove hunters purchase almost 75 percent of the shotshells sold in the US, according to Tom Roster, leading researcher and instructor for the Cooperative North American Shotgunning Education Program.
Almost all of those "dove" loads are filled with lead shot.
Currently, a 25-shell box of No. 7 1/2 lead shot "dove loads" costs $3-$5.
A 25-shell box of similar shotshells loaded with small (No. 7) "steel" shot costs $8-$12. Shotshells loaded with No. 7 1/2 shot in one of the more exotic and ballistically superior non-toxic materials such as Hevi-Shot cost as much as $2-$2.50 per shell.
Wildlife scientists have known for decades that birds ingesting spent lead shot suffer from the metal's toxic effects.
Birds ingest the small lead pellets, which look much like the small pieces of sand and gravel they swallow to use in digestion. This hard "grit" is used in a bird's muscular gizzard to crush and break down seeds and other forage.
The lead pellets are ground down, and lead is absorbed into the bird's bloodstream, where its toxicity can kill a bird quickly through acute toxicosis or, at lower levels, decrease a bird's immune system, making it susceptible to secondary illnesses and delayed mortality.
Studies involving waterfowl indicated an estimated 4 percent of the continent's ducks and geese died each year from the effects of lead pellets they ingested as grit.
Federal regulations beginning a phase-out of lead shot for waterfowl hunting were imposed in the 1970s. A nationwide ban on using lead shot when hunting ducks and geese took effect in 1991.
While considerable continent-wide research documented the chronic and persistent problem of lead poisoning in waterfowl, comparably little has focused on the effects of lead shot ingested by doves.
But that scattered research has shown doves do ingest spent lead shot and suffer its toxic effects.
A 1982-83 study involving about 3,000 hunter-harvested mourning and white-winged doves taken on wildlife management areas in South Texas indicated about 2 percent of those doves had lead shot in their gizzards.
Studies in other states suggest overall lead shot ingestion rates by doves are as low as 0.2 percent to as high as 6.4 percent. But in some specific areas, as many as 20 percent of doves were found to have ingested lead shot.
Some doves were found to have ingested as many as two dozen lead pellets.
Plenty of spent lead shot is out there for the birds to find. Most dove hunting occurs over and around feeding fields or, in Texas and other Southwestern states, water holes — just the places where doves pick up grit. And the same fields and water holes tend to be hunted year after year.
How much lead is being spewed onto their fields?
A lot.
Telling numbers
If each of Texas' 300,000 dove hunters were to fire only 16 shots a season (far below the real average), that's about a pound of lead per dove hunter, or 150 tons of lead each year. Actual amount of lead fired dove hunting is several times that amount.
Recent studies conducted by the Missouri Department of Conservation, one of the nation's most-respected state wildlife agencies, indicate a dove ingesting spent lead shot is almost certain of suffering its toxic effects.
To test the acute toxicity of lead on doves, the Missouri study used 180 mourning
doves divided into seven
groups during three separate trials.
One group was fed no lead pellets. The others were fed a one-time dose of 2, 4, 8, 12, 18 or 24 lead No. 7 1/2 pellets from commercially available shotshells. The birds were monitored for 21 days.
By the end of the 21-day period, 104 of the treated doves had died, with 53 surviving.
All 22 doves that had not ingested lead shot survived the study.
The more lead pellets the doves ingested, the more likely and the quicker they were to die, the study showed. But even doves that ingested only two pellets were quickly impacted — almost half died by the end of the 21-day study. And only 22 percent of the doves that ingested 5-8 pellets were alive after three weeks.
Research in other states has indicated elevated lead levels in the blood of 2-11 percent of doves, pointing to those birds having at least some exposure to lead pellets.
Research to continue
Some researchers believe data indicate lead-caused mortality could be as widespread in doves as it was in waterfowl before the lead shot ban. If so, that would mean lead poisoning annually claims about 16 million doves.
The annual legal dove harvest in the U.S. is estimated to be 19-21 million birds.
Texas wildlife managers are looking at the lead/dove issue and hoping to increase their research in that area.
"One of the things we're looking for is research that will give us some real-world insight into the scope and depth of the problem — if it is a problem," Vernon Bevill, director of TPWD's small game and habitat assessment programs, told the Game Bird Advisory Board. "We don't need to get to a decision on this until we have a lot more information."
But, he added, "It's certainly an issue that deserves our interest."
shannon.tompkins@chron.com