This study consisted of five steps: 1) the identification of brood-rearing locations for Canada geese that potentially could be using the airport, adjacent parks, golf courses, and wetlands, 2) the marking of geese at these sites, 3) the pre-removal measurement of marked goose occurrence and goose populations in the ASA, and the intensity of flights through the operations airspace as a baseline for evaluating the removal effectiveness, 4) reduction of goose groups found to be using the airport by capture and translocation, and 5) estimation of program effectiveness by monitoring of post-removal airport goose use, populations, and operations airspace flight levels.
Field Work
Potential Canada goose brood-rearing areas were surveyed within a 10-km radius of the airport in the spring (May-June) of 1984 by University of Minnesota and USFWS personnel (Table 1). Goose groups, consisting of flightless families and non-breeding (not associated with a family group) individuals, were drive-trapped and banded during mid-June and early July 1984. Captured geese were sexed, aged, and legbanded with USFWS aluminum legbands. Adult birds were neckbanded with markers similar to those described by Sherwood (1968), but with routed-symbols and sealed with a pop-rivet. In 1984, a subsample of adult geese was fitted with radio transmitters (Dwyer 1972) to determine daily flight time budgets. Geese on Gun Club Lake, Snelling Lake, and Mother Lake were not trapped and banded because these birds were assumed to be human safety hazards due to their close proximity to the
Table 1. Study area locations by city, distance to the Minneapolis-St. Paul International Airport, size, wetland type class, and use by geese, 1984-1987.
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Distancea Size Wetland
Location City (km) (ha) typeb Usec
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Apple Lake Richfield 1.7 2.9 V A,F,R
Bass Ponds,(Minnesota Bloomington 2.4 1.6 V B
River Valley NWR) 8.5 V B
1.2 V B
Blackdog Lake Burnsville 6.8 261.9 V B,F,R
Dodge Nature Center West St. Paul 9.2 1.6 V B,F,R
Gun Club Lake Mendota Heights 1.1 210.1 V B,R
Hwy. 110 and Delaware Mendota Heights 7.1 44.0 V B
Lake Cornelia Edina 7.1 19.4 V B,F,R
Wetland Complex 1.2 V B,F,R
1.8 V B,F,R
2.0 V B,F,R
2.4 V B,F,R
Lake Hiawatha Minneapolis 2.6 21.9 V A,F
Lake Nokomis Minneapolis 1.2 80.6 V A,B,F
Miller's Playlot Bloomington 6.8 6.9 V B,F
Mother Lake Minneapolis 0.0 125.5 V A,B
Normandale Lake Bloomington 8.8 44.9 V B,F
N.W. Chiro. Clinic Bloomington 5.4 2.8 V F
Pauley's Pond Bloomington 6.6 2.8 V B,F
Penn Lake Bloomington 4.9 19.0 V B,F
Pickeral Lake St. Paul 6.2 10.0 V B
Rich Acres G.C. Richfield 0.0 <1.0 IV A,F
Richfield Lake Richfield 3.7 62.8 IV B,R
Schaefer Road Edina 11.1 2.5 V B,R
Snelling Lake Minneapolis 0.5 44.5 V A,B
Wood Lake Richfield 3.7 66.8 IV B,R
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aDistance from middle of water area to nearest airport boundary.
bSee Cowardin et al. 1979.
cUse codes are: A=airport study area, B=Banding site, F=feeding
and resting site, R=removal site.
airport. Additional banding was done at Blackdog Lake in 1985, Normandale Lake
in 1986 and 1987, and at Miller's Playlot in 1987 to maintain marked-goose
numbers. In 1985, banding was done at a wetland on Schaefer Road in Edina
(11 km from the airport) to determine if birds from this area of concentrated
breeding were using the airport area. Similarly, birds from a newly established
brood-rearing group on Pickerel Lake in St. Paul (6 km for the airport) were
banded to ascertain if they used the ASA.
Goose use of the ASA was ascertained from 1 August
until the geese left the area in late November or December, 1984 and 1985.
Because only one flight was observed in August, 1984 and 1985, observations and
counts were delayed until 1 September in 1986 and 1987. Population counts and
neckband readings were conducted 4-5 times per week within the ASA and weekly at
the other feeding and resting locations. Neckband codes, location, time, number
of geese present, and pertinent comments were recorded in the field using a
portable lap computer. The highest daily population count per week at each site
was used in the analysis.
Brood-rearing groups were arbitrarily assigned "hazard"
or "non-hazard" status based on repeated ASA neckband sightings. ASA use
indices were calculated by dividing the total number of neckband sightings per
banding site by the number of marked geese in that group on 1 August each year.
Due to removal, too few neckbanded geese remained from control locations in 1986
and 1987 for meaningful estimates and the 1984-1985 hazard classifications were
used. Groups with an observation rate of one or more per neckband were assigned
to the "hazard" category. The exception to this was the Bass Pond geese.
Although no marked geese from this small (<20) group were seen in the airport
area in 1984, a Bass Pond-banded male, associated with the Wood Lake birds in
1985 and 1986, was frequently found at the airport. As a result, the Bass Pond
geese were not classified as hazards in spite of an observation index of 9 and
6.5 in 1985 and 1986, respectively. Hazard status groups were drive-trapped
during the molt (June-July 1985-1987), and the adults translocated to Oklahoma
and the immatures to Minnesota locations (Cooper 1987).
Because all groups of geese encountered in the ASA
contained markers, the influx of migrant geese was detected by the occurrence of
flocks without markers.
Radio-marked geese were monitored from dawn to dark 1
day/week during August and September 1984 to determine daily flight activity.
Groups of geese containing radio-marked individuals were constantly observed
from the time they flew into the ASA in the morning until they left at night.
If a group divided, the one with the most radio transmitters was followed. When
possible, all radio-marked birds were located. However, interference from the
airport air traffic control tower and other radio transmissions prevented
consistent radio relocation and required frequent visual confirmation.
Goose flights through the airport operations airspace
were monitored at the peak goose flight times, five times/week from the air
traffic control tower. The tower, located near the western border of the
airport, stands 55 m high. Based on radio tracking, peak flight activity
occurred 30 minutes before and after sunrise and 30 minutes before and after
sunset. Observations were made at these times except when fog, rain, or snow
obscured portions of the operations airspace. The airspace monitored consisted
of that over the airport and within 4 km of the runway ends and below 100 m.
Although somewhat arbitrary, this space constituted the zone of highest hazard
for the ascent and descent paths of aircraft (T.B. Haberkorn, MAC, pers.
commun.). The number of goose flights per session, time, estimated altitude,
direction, and birds per flight, and weather conditions (temperature, wind
speed, and cloud cover) recorded for an observation period. Direction was
estimated as one of the eight ordinal directions and altitude classified at or
below 100 m or above 100 m based on known heights of nearby towers and
buildings. Weather data were provided by the air traffic controllers. Tower
observations started 1 August 1984-1985 and 1 September 1986-1987, and ended
30 November each year.
Because dense cattail (Typha spp.) at Wood Lake and
Mother Lake reduced 1986 drive-trapping efficiency, an alternative method of
goose removal was developed. Nests were located by searching on foot and from a
canoe during April, 1986 and 1987. A mini-rocket system was used to trap
incubating females. The trap consisted of two remotely fired rockets and a 5 by
14 m gill net. When placed within 2 m of an active nest, the rocket propelled
the net over the incubating bird. Once captured the females were translocated.
The efficiency of shooting small numbers of geese
during the last 2 weeks of July and the first 2 weeks of August was evaluated in
1987. Birds were collected opportunistically on the airport with a shotgun.
Data Analysis
Paired t-tests were used to test for differences in the highest weekly 1984 ASA goose population, number of flights, and geese per flight with those following removals in 1985, 1986, and 1987. This test also was done for the number of geese in an unmanipulated area (Miller's Playlot, Normandale Lake, and Northwestern Clinic ponds in Bloomington) to ascertain the effects of natural fluctuation on the ASA geese. Cross-classified categorical data analysis was used to evaluate the effects of weather on airspace goose flight intensity.