Did pesticide kill the birds?

Posted: Thursday, July 05, 2001

Late in May I found three dead red-breasted sapsuckers during a two- week span within close vicinity to my home at the end of Mendenhall Peninsula.

Finding the third dead red-breasted sapsucker made me curious to go beyond examining its beautiful feathers and tomato-red head and investigate possible causes of death. This investigation yielded some very interesting information I would like to make available to everyone.

It appears that the use of pesticides to kill spruce needle aphids may harm or kill sap-eating birds.

I've long admired these bright red flashes of color zipping from tree to tree and perching high in the canopy loudly drumming their messages through the forest.

The first dead sapsucker I found was lying in the road, still warm, an apparent road kill. The second bird I found was old and cold on the forest floor. The third bird dropped into my hand from my puppy's proud and happy mouth. This last bird was so old and long-dead that I immediately buried it among the roots of a spruce tree. The other two were bright and fresh (with a bit of dog spit) and after admiring their wings and feathers I tossed them in the freezer to show to my kids later.

I am not really an avid birder. I do not have a life-list or make travel and vacation plans around bird migrations, but I do own binoculars and a bird book and have been known to get excited about watching birds. So, as a self-admitted dork in the world of serious birding, I began reading about these birds and their habits in the hope of gaining some clues about how they might have died.

It was a surprise for me to discover that sapsuckers really do suck sap! I always thought that they drilled holes into trees to find insects - beetles and stuff, and that the insects attracted to the oozing sap were side-benefits from all this drilling - the chips and pretzels of bird diets. But, I was amazed to discover that these birds actually do drink sap, along with eating the insects attracted to the sap.

Apparently these birds return repeatedly to the same trees and maintain many little sap wells to sip from. Other species of birds, such as nuthatches, hummingbirds, and warblers also take advantage of these perennial wells and stop by for quick sips of sap before being chased off by the defending red-headed, sap-sucking, well-drillers. Even red squirrels enjoy the tasty sweet sap and will stop by for a few drops from time to time.

It was about the time of this amazing sap-sucking discovery that a friend asked me if I knew whether the ACE Caps being used locally to fight invasions of spruce needle aphids had the potential to harm any bird or wildlife species. Well, I'm a fishery biologist, so I just didn't know. But I felt as if finding these three dead birds compelled me to investigate.

The active ingredient in ACE Caps is acephate, which belongs to a class of pesticides known as organophosphates.

Organophosphates kill insects by disrupting their brains and nervous systems. Specifically, they inhibit function of a key enzyme in the nervous system, cholinesterase. Death is generally attributed to respiratory failure, but sub-lethal doses or several small doses over the course of a few meals can alter animal behavior and increase death rates from accidents or predation.

Cholinesterase, however, is not unique to insects. It plays a pivotal role in the regulation of nervous function in all animals, whether you are an aphid, a bird or a person. This class of pesticides is most toxic to invertebrates such as insects, but is also highly toxic to fish, moderately toxic to birds, and has a lowered toxicity to mammals.

Hmmm, I thought, maybe acephate is killing the sapsuckers?

I read all I could find about acephate, ACE Caps and the effects of this class of pesticides on birds. And I sent the two frozen birds to Dr. Grace McLaughlin, a Wildlife Disease Specialist at the National Wildlife Health Center in Madison, WI, for necropsy and brain-tissue analysis.

The Raptor Center had seen three live sapsuckers which were behaving oddly. The birds were not flying but were eating okay and seemed to be doing well and then after a couple of days they died.

I found that none of the several articles on spruce needle aphid control mentioned any possibility that the heavy use of acephate had the potential for harming or killing birds or other wildlife.

The necropsy report on the two frozen birds identified their causes of death as trauma, one probably hit by a car, the other the victim of predation. The test performed to look for the effects of organophosphate pesticides - brain cholinesterase activity, was normal. Based on these findings, there is no indication that acephate played a role in the deaths of these birds.

I have one more bird in the freezer from the Raptor Center which I plan to submit for analysis. I would be interested in receiving any others which are found dead or acting oddly.

Did I find a smoking gun? I don't know.

What I do know is this: Acephate is being applied to large spruce trees to kill spruce needle aphids. The pesticide in ACE Caps is active in the tree sap for about 14 to 18 weeks. The amount of acephate in the sap is not known. Acephate has never been applied in this manner before and it has the potential for killing sap-eating birds.

Interestingly, I found that within the tree acephate reacts with water to form methamidophos - a much more toxic and persistent pesticide that is highly toxic to birds.

My intent in sharing this information is to make known the potential effects of this pesticide on sap-eating birds.

I am not advocating that people stop using ACE Caps, but I do believe in informed consent and in choosing a treatment based on a thorough examination of a product's benefits and negative effects.

If my own spruce trees were infested with spruce needle aphids and I was faced with potentially losing them, I would carefully consider treatment. But I would feel much better about making my choice if I had all the facts in front of me.

As Rachel Carson said, "It is the public that is being asked to assume the risks that the insect controllers calculate. The public must decide whether it wishes to continue on the present road, and it can do so only when in full possession of the facts."

Sue Walker is a Fishery Biologist for the U.S. Fish and Wildlife Service in Juneau, and an occasional casual observer of birds. If you do find any dead or ailing birds, please call the U.S. Fish and Wildlife Service's Contaminants Biologist, Deborah Rudis, at 586-7648. Juneau Audubon Society will resume monthly meetings on September 13.



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