Are other species in addition to Swainson's Hawks involved in the
pesticide-induced die-off in Argentina? I am thinking in particular of other
North American grassland species wintering in Argentina, e.g. golden plover,
upland sandpiper, and bobolink. What about other South American species,
including the scavengers e.g. carcara and vultures that are quickly consuming
the dead Swainson's Hawk carcasses.

I was absolutely stunned when this post appeared on BirdChat yesterday, and
surprised that it has yet to generate any discussion if not just plain
outrage (some on Tweeters, none in BirdChat). Is there any precident where
such a large number of individuals of any one species has ever been
similarily impacted?

>
>INFORMATION SHEET ON
>
>SWAINSON'S HAWK DEATHS
>
>Date: 12 February 1996
>
>ISSUE: Mass deaths of Swainson's Hawks are occurring in Argentina due to
>insecticide spraying
>
>CURRENT STATUS:
>
>3909 dead Swainson's Hawks have been counted in Argentina as a result of
> insecticide spraying which is expected to continue until the end of
>February. This count is only the actual carcasses encountered. Likely the
>total kill is well over 20,000 hawks. The insecticide, Monocrotophos and
>other pesticides are being sprayed to control grasshoppers in alfalfa fields
>and other crops. The US universities are working with a local Argentinean
>agency called INTA and plan to propose alternate pesticides. Environment
>Canada is funding the continuation of field work by the Argentinean agency
>INTA.
>
>
>BACKGROUND -
>
>INTA is an Argentinean scientific research agency comprised of government
>and university staff with strong, positive connections to the developing
>agricultural industry in Argentina. INTA staff have been working with the
>US cooperators to document the situation, collect samples and develop
>alternative control methods.
>
>Two Swainson's Hawks that had satellite transmitters attached in Alberta are
>at the same location as the dead hawks in Argentina. Of 12 leg bands that
>have been recovered from the dead Swainson's Hawks, 9 originated in Alberta
>and Saskatchewan, and 1 each from Colorado, Idaho, and California. Most
>of the dead hawks are white colour phase indicating that they are from
>Canada and adjacent US (northern Great Plains). Thus we can conclude that
>a high proportion of this mortality are hawks that breed in Canada. Thus
>this mortality is of concern to Canada.
>
>Last year 2 Swainson's Hawks were tagged with satellite transmitters in
>California and they travelled to the Argentinean pampas. Brian Woodbridge,
>US Forest Service, travelled to this region and found 700 dead Swainson's
>Hawks in this agricultural area. Deaths were suspected to be due to
>pesticide spraying. One of the 700 dead hawks was banded in Saskatchewan.
>
>In 1995, 8 Swainson's Hawks were tagged with satellite transmitters in 1996
>across western US and Canada (2 in Alberta) and are now on their traditional
>winter range in Argentina. Marc Bechard, Univerisity of Idaho, travelled
>there January 13-18 to examine the winter habitat and he did not record any
>spraying. Subsequently, a local farmer called after the hawks started
>dying. Then Brian Woodbridge went to Argentina and documented the
>mortalities. In his survey area of 50km by 50km, near the town of General
>Pico, he talked with landowners but did not get complete coverage in his
>counts of dead hawks. In addition the area affected by sprays is larger
that
>his study area. Thus he believes his count of 3909 hawks may represent
>20,000 dead hawks in this region of Argentina. Most (90%) of the dead hawks
>were adults (ie. the breeding population). The winter range of the
>sub-adults is unknown.
>
>The study area is at the junction of the three states of Cordoba, Buenos
>Aires, and La Pampa. This is only a small portion of the winter range of
>Swainson's Hawks and a small portion of the cultivated agricultural land in
>the grasslands of Argentina. The geographic extent of the problem is
>unknown.
>
>Cultivated agriculture is relatively new in this region of Argentina.
> Previously, the region was dominated by cattle ranches. Recent irrigation
>developments have encouraged the development of cultivation.
>
>The Canadian population is estimated at 20,000 - 50,000 pairs (Kirk et al.
>1995). Both Stuart Houston and Joe Schmutz, who monitor populations of
>Swainson's Hawks in Saskatchewan and Alberta, respectively, report declining
>populations and productivity in the Canadian prairies. The total population
>is estimated at 350,000 to 400,000 Swainson's Hawks
>
>The pesticides are being sprayed from planes and air blasters towed by
>tractors. The hawks are following the tractors to catch disturbed
>grasshoppers. The hawks are receiving direct sprays as well as secondary
>dosage from the grasshoppers. Many species of grasshoppers are involved
>with different life cycles which requires multiple pesticide applications
>which are continuing in February. We do not know when the pesticide
>applications will end, but it is estimated to continue for 3 weeks.
>
>Dead hawks are quickly scavenged by caracara and vultures. Many carcasses
>comprise of head, skin, feathers and gastrointestinal tract, including the
>crop containing grasshoppers. Samples for toxicology assessment are
>collected from these scavenged carcasses. Results from the first set of
>samples are expected in late February.
>
>In November, when the Swainson's Hawks arrive in Argentina, sunflower crops
>are sprayed with insecticides to kill grasshoppers. Hawks may also be
>killed at this time. Alternative products and methods are needed to control
>grasshoppers but not kill Swainson's Hawks.
>
>Geoff Holroyd
>Canadian Wildlife Service
>403-951-8689
>email: holroydg at edm.ab.doe.ca
>
>
>

Richard Rowlett <pagodroma at aol.com>
Bellevue, WA, USA