Pesticide Poisonings in Raptors an indicator of toxic contaminants in the Fraser River Delta

What is Happening?

From 1991 to 1997, Environment Canada's Canadian Wildlife Service (CWS) recovered 754 dead or debilitated raptors from across British Columbia. Due to their large body size, public profile, scavenging habits and their high numbers in the Fraser River delta, Bald Eagles (Haliaeetus leucocephalus) were more likely to be found and reported to authorities. Consequently, more Bald Eagles (a total of 458) were collected in BC than any other raptor species.

Between 1991 and 1997, the number of Bald Eagle pesticide poisonings in the Fraser River delta fluctuated  as the effort to recover eagles varied from year to year. However, the percentage of eagles that were found to have been poisoned by pesticides decreased steadily over this period. This reflects an overall trend of decreasing pesticide poisonings for many raptor species, including Bald Eagles, Red-tailed Hawks, Great Horned Owls,  Rough-legged Hawks and Northern Harriers.

Source: L. Wilson, Environment Canada, Canadian Wildlife Service, Delta, B.C. 1999. Note: all the above pesticide poisonings are attributed to organophosate and carbamate insecticides. These chemicals, often referred as anti-chlolinesterase pesticides, are acutely toxic quick acting compounds which affect the nervous system.

Of all Bald Eagles recovered in the province during this period, 12% were poisoned by anti-cholinesterase pesticides. The majority of these poisoning incidents occurred in the intensive agricultural area of the Fraser River delta, where a large number of raptors winter. At the time the incidents occurred, most of the chemicals involved in these poisonings were registered for use in BC as granular formulations (pesticides infused into fine particles of clay, sand or other substances for gradual released to surrounding soil).

The Fraser River delta provides habitat for millions of migratory birds throughout the winter. This includes the highest concentrations of wintering waterfowl, shorebirds and raptors in Canada (Butler and Campbell 1987). Farmland is critical habitat for these species. Agriculture is also an important economic sector in BC, particularly in the Fraser River delta. In order to remain competitive, it is essential for farmers to use all tools currently available to them. Some of these tools, such as pesticides, can have adverse impacts on wildlife populations. Between 1960 and 1994, more than 100 avian mortality incidents involving at least 3700 birds (songbirds, waterfowl and raptors) were attributed to agricultural pesticides in the Fraser River delta and southeastern Vancouver Island (Wilson et al. 1995).

Source: L. Wilson, Environment Canada, Canadian Wildlife Service, Delta, B.C. 1999. "Other trauma" refers to eagles that had died from traumatic injuries including gunshot, drownings and vehicle collisions. Other "natural" causes include eagles which died from infection, disease, starvation, parental abandonment, physical exhaustion or from falling out of their nests. The causes are categorized as per Wilson et al., 1995.

Overall, the primary causes of mortality to Bald Eagles in BC from 1991 to 1997 were electrocution and other types of trauma (such as gun shot, collisions with vehicles and drownings). In the Fraser River delta, electrocution and pesticide poisoning were the dominant causes.

Why is it Happening?

Poisoned wintering ducks in an agricultural field (February, 1994), Fraser River Delta, BC

Photo courtesy of J. Elliott, Environment Canada, Canadian Wildlife Service, Delta, BC

The most common types of pesticides applied on agricultural crops today in BC are anti-cholinesterase insecticides, which disrupt the nervous system. Unlike previously used pesticides, such as DDT (dichlorodiphenyltrichloroethane), these chemicals usually break down quickly in the environment. However, while present they can be extremely toxic, and a serious threat to "non-target" species present in the area.

Some wildlife poisonings were due to intentional misuse but the majority of incidences occurred with recommended agricultural practices. Wintering waterfowl foraging for seed and grit in agricultural fields were poisoned when they ingested insecticide granules still containing pesticides. Raptors were then poisoned when they scavenged on the dead or injured waterfowl.

Frequent flooding from rain water and high acidity of agricultural soil in the Fraser River delta can slow the degradation rates of granular formulations of these chemicals. Research by CWS and Agriculture and Agri-Food Canada (AAFC) has shown significant concentrations of the active ingredient in granular formulations of some anticholinesterase insecticides can persist for up to 9 months in local soils (Wilson et al. 1996).

Reduction in the number of raptor poisonings is due in large part to the influence of these research studies. They resulted in the removal of specific pesticides from the local market, and efforts by AAFC to promote alternative pest management strategies. For instance, up to 1994, the insecticide phorate was the preferred method to control wireworm, a common pest in potato fields in the Fraser River delta. Significant numbers of phorate poisoned raptors resulted in the manufacturer voluntarily withdrawing it from the local market. The next year, potato growers used a different insecticide, fonofos, to control wireworm. That winter, no poisoning incidences were attributed to phorate, however, nine fonofos related poisonings occurred. Following these events, AAFC advised local potato growers of the hazards to "non-target" wildlife when using granular formulations of phorate and fonofos. Consequently, some farmers elected to not use any granular fonofos while others modified their use by treating only the perimeter of fields with suspected wireworm infestation. Fewer fonofos-related incidences were reported the next winter.

Bald Eagle pesticide poisoning incidents correspond with a large increase in Bald Eagle numbers wintering in the delta. For example, in 1989-90 the number of wintering eagles in the Fraser River delta almost doubled over the previous year (Wilson et al. 1999).

When more eagles are present, there is a better chance of dead waterfowl being found and scavenged. Eagle poisoning incidents peak during winter months when eagle numbers in the Fraser River delta are highest. Studies during the winter found that when duck carcasses were placed in fields, 78% were located by avian scavengers within 24 hours (Peterson et al., 1999).

While toxicological studies suggest agricultural practices are an important route by which eagles may be poisoned by pesticides, there is the potential that some eagles are poisoned at the Vancouver Municipal Landfill, located in the midst of the Fraser River delta in Burns Bog. At times, more than 100 eagles have been observed at the landfill but no poisoning incidents have been directly linked with feeding there (J. Elliott, CWS, unpublished data, August, 1999).

Why is it Significant?

Poisonings by anti-cholinesterase pesticides do not seem to have a large effect on the overall status of Bald Eagle populations in southwestern BC. Bald Eagle populations continue to increase (see Bald Eagle indicator), and the reproductive success of the local Fraser River delta population is higher than other populations along the BC coast. However, because poisonings happen during the winter months when numerous migrant eagles are present, some of the poisoned eagles are likely wintering birds and therefore the impact on their breeding area populations is unknown.

The Fraser River delta is of international significance for wintering raptors as well as for other migratory birds. Birds wintering in this area are placed under multiple stresses. Shrinking wildlife habitat and exposure to toxic contaminants are consequences of the ever increasing human population and economic growth in the Georgia Basin. Therefore efforts to minimize impacts and increase the chances of survival for these species through the raptor pesticide monitoring program are important.

During the winter of 1995-96, an estimated 20,000 Swainson's Hawks died in Argentina after feeding on contaminated grasshoppers. This represented approximately 5% of the global Swainson's Hawk population, demonstrating the importance of regulating and monitoring pesticide usage (Henny et al. 1998). The pesticide responsible for this incident was banned in Argentina in 1999.

Eagles are highly visible top predators whose injuries and deaths are more likely to be noticed by the public. Even so, it is doubtful that the majority of poisoned eagles are found and reported to the Canadian Wildlife Service. Lower-profile species, which are important in the local food chain, may also have been poisoned and gone unnoticed. Impacts on these species may not be realized until it may be too late to prevent irreversible damage to the local food web. Utilizing the Bald Eagle as a sentinel species for pesticide contamination has likely benefited many of these lower-profile species.

What is Being Done?

Granular formulations of five of the seven pesticides implicated in raptor poisonings (carbofuran, fensulfothion, fenthion, parathion and phorate) have been removed from the local BC market. Wildlife poisonings were chiefly responsible for at least three of the withdrawals. The sixth pesticide, fonofos, is scheduled to be removed in 1999 after existing stocks have been used. The seventh pesticide, terbufos, is the least persistent of those implicated and remains in use. Other granular products available in the local market include diazinon, disulfoton, chlorpyrifos and ethion (all anticholinesterase pesticides), none of which have been linked to date with raptor poisonings. All of the changes in pesticide usage have been brought about through a consultative process and the ongoing cooperation among the various stakeholders including the Delta farming community, Agriculture and Agri-Food Canada (AAFC), Environment Canada and the Pesticide Management Regulatory Agency (PMRA).

A program to collect and properly dispose of obsolete and unwanted pesticides from farmers and nursery owners in the Lower Fraser Valley took place in February, 2000. Over 33,000 kg of pest control products were collected at temporary collection depots. The BC Agricultural Council coordinated the project which was funded by the Crop Protection Institute of Canada representing pesticide manufacturers, the BC Investment Agriculture Foundation through Agriculture and Agri-Food Canada, and Environment Canada’s Georgia Basin Ecosystem Initiative. The BC Ministries of Agriculture, Fisheries and Food and Environment, Lands and Parks also provided assistance.

Raptor poisoning incidences are still monitored by CWS since pesticides pose an ongoing risk to avian species. CWS has also created a network which includes several government agencies (AAFC and the federal Pest Management Regulatory Agency) that immediately responds to any suspected pesticide poisoning incident regardless of species. The objective of this network is to investigate and contain the incident to thereby limit the impact of a poisoning event on the wildlife food chain. Local wildlife rehabilitators can now recognize anticholinesterase poisoned wildlife and can treat them more successfully so fewer mortalities result. AAFC is working with CWS and non-governmental organizations to find alternatives to pesticides.

CWS is also addressing other factors affecting raptor health. For example, hunting of waterfowl using lead shot has been banned, primarily due to the lead-poisoning of Bald Eagles after scavenging on waterfowl carrying lead shot. CWS is also monitoring raptors which may have been poisoned by rodenticides when ingesting poisoned rodents.

For more information contact: John.Elliott@ec.gc.ca or Laurie.Wilson@ec.gc.ca

Check the following sites for additional information on this indicator:

• Hinterland's Who's Who
• Canadian Bird Trends Database for Bald Eagle
• What you can do for wildlife
• CWS - Pesticides and wild birds
• Georgia Basin Ecosystem Initiative (GBEI) - Bird Under Stress

  Other Federal Department  web sites:

• Agriculture and Agri-Foods Canada survey report on -"Manure, Fertilizer and Pesticide Management in Canada"
• Health Canada's Pest Management Regulatory Agency

  The following sites are external to Environment Canada. As the organizations that maintain these sites may not be subject to the Official Languages Act, information found on these sites may be presented only in the language in which it was written.

• BC government  Integrated Pest Management
• BC government - Protecting Birds from Pesticides
• BC government - Alternative Contol Methods for Birds
• For alternatives to chemical pesticides and herbicides and other environmentally sound food production issues consult "Organic Gardening"
• For pesticides in air consult USGS's site on "Pesticides in the atmosphere"
• Pesticide Action Network
• For general information consult Information on Pesticides
• World Wildlife Fund (WWF) Canada site on "Reducing your risk from pesticides"
• Environmental education classroom project on pesticides "Deadly Links"

For references used in this indicator click here.