Bird strikes are a significant aircraft hazard
(Murton and Wright 1968, Blokpoel 1976). Because birds fly below the
cruising altitudes of most commercial airplanes, the maximum strike
likelihood occurs during take-off and early climb, and approach and
landing at or near airports (Burger 1983). The most serious collisions
have involved large (>1 kg), flocking species, and jet-powered planes
(Staples and New 1968).
Although the Canada goose (Branta canadensis)
may have nested in the area in presettlement times, recent nesting on the
Minneapolis-St. Paul International Airport was first recorded in 1975
when a 2-year-old female, banded at the Hyland Park Reserve in
Bloomington, hatched young on Mother Lake (J. A. Cooper, Univ. Minn.,
unpubl. data). By 1981, an estimated 100-150 geese were using sites on
or near the airport (U.S. Fish and Wildlife Service 1981). The birds
reached peak numbers in late summer and fall, fed and roosted on or near
the airport grounds, and made frequent low altitude flights through the
aircraft landing and take-off paths (operations airspace). The Twin
Cities Metropolitan Airports Commission (MAC) deemed, "the presence of
geese near active runways as undesirable due to possible bird strike
accidents," and requested advice from the U. S. Fish and Wildlife Service
(USFWS) on methods to reduce the number of geese on or near the airport
(U.S. Fish and Wildlife Service 1981).
Because a bird-proof aircraft capable of flight
has not been developed (Blokpoel 1976:89) and bird-avoidance maneuvers
are limited during take-off and landing, hazard reduction must focus on
bird management. Hazard bird reduction techniques suggested for the
Minneapolis-St. Paul International Airport included habitat modification
to make the airport less attractive to geese, visual or acoustical
harassment, and translocating or killing of the birds.
Habitat modification was deemed unfeasible. The
geese prefer the short, mowed-grass on the runway borders, adjacent golf
course greens and fairways, and nearby city parks over the longer
vegetation present in unmowed areas (U.S. Fish and Wildlife Service 1981).
The short grass reduces the airport fire hazard and is essential to parks
and golf course management (U.S. Fish and Wildlife Service 1981).
Harassment, when employed at the airport, was ineffective because "when
chased by airport vehicles they [the geese] merely fly to the other side
of the runway or to the nearby golf course" (U.S. Fish and Wildlife
Service 1981). Harassment also had the disadvantage of additional goose
flights, thus increasing the potential for a strike. Intensive,
long-term goose shooting on the airport property was discussed as an
alternative if an effective, but less drastic procedure was not found.
The most promising but untested procedure remaining was bird capture and
shipment of the birds to distant sites, i.e, translocation.
The biologic and cost effectiveness of a
translocation program depends on whether the geese use a site selectively
or randomly, and the number of breeding groups associated with the
specific area. Recent research suggested that selective use would likely
be the case. Koerner (1973) reported that Canada geese in southwestern
Lake Erie were observed in the same locations annually. Zicus (1981a)
suggested that Canada geese maintain distinct social groups and that
these units were established on brood-rearing marshes. Zicus further
speculated that the individual groups had predictable flight patterns and
repeatedly used specific feeding and roosting areas throughout summer and
fall. Schultz (1983) (see Schultz et al. 1988) found that geese from
specific brood-rearing sites not only remained together, but that the
birds did not readily abandon the summer and fall flight patterns or
feeding sites when hunted. Thus, from these studies, it was surmised
that: 1) a limited set of locally breeding geese were likely to be using
the airport and nearby areas, and 2) these birds, if removed, would not
be replaced quickly by others.
This 4-year (1984-1987) study was designed to
test the hypothesis that if the geese using the airport could be
identified and reduced, there would be a corresponding reduction in the
number of geese and goose flights at the airport. By default, the study
also was a test of the existence of non-random summer-fall movement and
site use behavior described by Zicus (1981a) and Schultz et al. (1988).
The primary goal of the present study, however, was to reduce goose
numbers and flights through the airport operations airspace as much as
possible. Late summer and fall (August-November) were targeted for study
because this was the time of maximum goose numbers and flights (U.S. Fish
and Wildlife Service 1981).