Three hundred-seventeen flightless geese at 11 sites were located and captured in June 1984. One hundred twenty-seven adults were neckbanded and 190 immatures legbanded. Fifty-one geese were caught at two sites in June 1985; 19 adults were neckbanded and 34 goslings legbanded. In 1987, in addition to data presented in Table 2, 126 adults were drive-trapped and legbanded and 199 young legbanded at two Bloomington locations. Six adults were fitted with radio transmitters in 1984 (Table 2).
Table 2. Number of breeding adult Canada geese neckbanded in the vicinity of the Minneapolis-St. Paul International Airport, 1984-1987.
_______________________________________________________ Year Location 1984 1985 1986 1987 _______________________________________________________ Bass Ponds 3 0 0 0 Blackdog Lake 2 10 0 0 Dodge Nature Center 3 0 0 0 Hwy. 110 and Delaware 3 0 0 0 Lake Cornelia 21 0 0 0 Lake Nokomis 2 0 0 0 Miller's Playlot 24 0 0 29 Normandale Lake 23(2)a 0 25 64 Penn Lake 7 0 0 0 Pickerel Lake 0 0 0 3 Richfield Lake 1 0 0 0 Schaefer Road 0 9 0 0 Wood Lake 38(4) 0 0 0 Total 127(6) 19 25 93 _______________________________________________________ aNumber of radio-marked individuals in parenthesis.
Neckbanded geese from seven of the 11 banding sites were observed in the ASA in 1984, six of 11 in 1985 and six of 10 in 1986, and two of 9 in 1987 (Table 3). The use rates declined over the study due to removal, but followed a similar pattern. Most marked geese seen in the airport study were captured at the Wood Lake Nature Interpretive Center. These geese comprised 90, 70, 53, and 56% of the observations in 1984-1987, respectively. Certain banded geese, e.g., Wood Lake Nature Interpretive Center and Lake Nokomis birds, were observed in the ASA repeatedly, whereas other groups such as Normandale and Miller's Playlot geese were infrequently found in the ASA. These results support the subpopulation concept strongly. However, there were exceptions. Geese banded at Penn Lake were not seen in the ASA in 1984 but were observed an average of 9 times/neckband in 1985, and were translocated in 1986 and 1987. The Schaefer Road birds, not observed at the airport in 1985, were seen an average of 3.3 times/neckband in 1986 when they used Lake Hiawatha exclusively while in the ASA. This group was caught in 1987 and translocated.
Table 3. Banding location, number of neckbanded Canada geese, reobservation of neckbanded individuals, and observation per neckband in the airport study area, 1984-1987.
___________________________________________________________________________________________________________________ Neckbanded Number of Observation/ geesea observations neckband Banding ___________________________ ___________________________ ___________________________ location '84 '85 '86 '87 '84 '85 '86 '87 '84 '85 '86 '87 ___________________________________________________________________________________________________________________ Bass Ponds 3 2 2 1 0 18 13 0 0.0 9.0 6.5 0.0 Blackdog Lake 1 11 8 3 0 15 3 0 0.0 1.4 0.4 0.0 Dodge Nature Center 3 3 1 1 2 0 0 0 0.7 0.0 0.0 0.0 Hwy. 110 and Delaware 3 2 0 0 0 0 0 0 0.0 0.0 Lake Cornelia 18 4 2 1 33 0 0 0 1.8 0.0 0.0 0.0 Lake Nokomis 2 2 1 0 118 98 35 0 59.0 49.0 35.0 Miller's Playlot 22 17 8 29 2 9 0 0 0.1 0.5 0.0 0.0 Normandale Lake 23 19 30 64 11 0 7 19 0.5 0.0 0.2 0.3 Penn Lake 7 2 1 0 1 18 0 0 0.1 9.0 0.0 Pickeral Lake 0 0 0 3 0 0 0 0 0.0 Richfield Lake 1 0 0 0 0 0 0 0 0.0 Schaefer Road 0 7 6 1 0 0 20 0 0.0 3.3 0.0 Wood Lake 37 14 7 4 1529 368 87 24 41.3 26.3 12.4 6.0 ___________________________________________________________________________________________________________________ Combined areas 120 83 66 107 1708 526 165 43 14.2 6.3 2.5 0.4 ___________________________________________________________________________________________________________________ aNeckbanded geese known to be alive on 1 August.
Thirty-six of the 37 neckbanded geese from the Wood Lake brood-rearing area were seen in the ASA from 1 August until the birds left the area on 20 December 1984. However, not all birds were encountered with the same intensity. In 1984, 10 geese were observed 0-25% of the sampling period, eight geese 26-50%, 10 geese 51-75%, and nine geese 75% or more. Eleven of the 14 Wood Lake neckbanded birds, known to be alive on 1 August 1985, were observed in the ASA in 1985. Three geese were observed 0-25% of the sampling period, three geese 26-50%, five geese 51-75%, and no geese were observed more than 75%. Four out of the five geese observed most frequently in 1984 also were observed most frequently in 1985. Thus, some birds used the airport more than others and the intensity of use was similar between years. To further evaluate repeated use, observations/sampling day for Wood Lake birds were computed for 1984 and 1985 and regressed. The fit was highly significant (P < 0.01, Fig. 2).
Based on 1984 repeated observations in the ASA, brood-rearing groups with a use rate greater than one and geese breeding or molting within the ASA were deemed "hazards" and slated for removal. One hundred ninety-two geese from six sites were captured and translocated in June, 1985, 61 from four sites in 1986, and 141 from seven locations in 1987 (Table 4). Based on 1985-1987 pre-trapping counts, 93, 82, and 86% of the flightless geese present at hazard group sites were removed in the respective years. Adult and immature geese were banded and shipped by truck; the adults to Oklahoma and immatures to Minnesota wetlands at distances ranging from 50 to 300 km from the ASA. Recapture of translocated geese indicated that 10% of the 1985 translocated adults returned while no immatures were encountered 1986 or 1987. All adults caught in 1986 and 1987 were pinioned (rendered permanently flightless) and moved to a captive rearing facility at the Red Lake Indian Reservation in northern Minnesota.
Table 4. Canada geese removed in June, 1985-1987 by location, age, and percent of pre-removal population, Minneapolis-St. Paul International Airport study area.
___________________________________________________________________________________________________________ 1985 1986 1987 Location Ad. Im. Total % Ad. Im. Total % Ad. Im. Total % ___________________________________________________________________________________________________________ Apple Lake 2 4 6 100 0 0 0 0 0 0 Gun Club Lake 5 10 15 94 0 0 0 4 15 19 66 Lake Cornelia 23 6 29 94 4 8 12 80 4 7 11 100 Lake Nokomis 2 6 8 100 0 0 0 0 0 0 Mothers Lake 0 0 0 b b b b 6 11 17 100 Penn Lake a a a a 17 19 36 97 1 5 6 86 Richfield Lake 2 4 6 100 3 10 13 93 2 8 10 83 Schaefer Road a a a a a a a a 10 29 39 80 Wood Lake 35 80 115 92 b b b b 6 33 39 74 Combined areas 69 110 192 93 24 37 71 82 33 108 141 86 ___________________________________________________________________________________________________________ aNot trapped. bBreeding females rocket netted at nest and birds and eggs removed.
Nest trapping of breeding females at Mother Lake and
Wood Lake proved moderately effective (9 of 16 females captured). Drawbacks of
the technique centered on the net and rocket positioning. With modifications,
the technique should be highly effective, permitting capture and removal of
incubating geese from wetlands where dense cattail hampers drive-trapping.
The shooting of flying or sitting birds on the airport
property from 1 July to 15 August 1987 proved inefficient. A month of labor was
expended and seven birds were shot from a population of 23. Once exposed to
shooting, the geese shifted to nearby public use parks and golf courses and were
rarely found where they could be safely collected.
The pattern of change in the ASA population was similar
each year, but with an increasing decline in the number of birds seen in the
August, September, and October (Fig. 3). Goose numbers were lowest from August
until the third week of September. They then increased slightly, probably
because of the returning molt-migration birds (see Zicus 1981b). Migrant geese
were first seen in the area in late October. From this time until the second
week in November, the populations fluctuated but steadily increased, peaking in
late November or early December. Snow and freezing weather stimulated departure
and all birds left the ASA by early December.
Fig. 3. Weekly maximum Minneapolis-St. Paul International Airport study area Canada goose population counts, August to December, 1984 and 1985; and September to December, 1986 and 1987.
Weekly airport area populations declined significantly (P < 0.001) in August 1985, in September 1985-1987, and October 1986-1987. The rate of decline increased by year (Fig. 4) and averaged 75% for these months from 1984 to 1987. Population levels after 1 November, when migrant geese were present, were not significantly different (P > 0.05) between 1985, 1986, or 1987, but overall levels for the entire study period were significantly lower than 1984 in all years (P < 0.05). The biweekly 1984 and weekly 1985 through 1987 Bloomington population counts were more variable compared to the ASA numbers, but did not differ significantly (P > 0.05) between years (Fig. 4). Thus, while the airport population declined in all months but November, there was no concurrent decline in the uncontrolled Bloomington concentration.
The number of goose flights and the number of geese observed from the control tower decreased significantly (P < 0.001, Fig. 5). There were 87 flights in 1984, and 42, 39, and 15 in 1985, 1986, and 1987, respectively. After 3 years of removal, flights were 83% below 1984 levels. The decrease in numbers of geese observed in the airspace between 1984 and 1987 was even lower at 85% (1,476 vs. 222). The greatest number of flights occurred in October until 1987, when proportionately more flights were in September.
Fig. 5. Canada goose flights and total number of geese observed through Minneapolis-St. Paul International Airport operations airspace by month, 1984-1987.
Tower observation data suggested that there was a relationship between flight intensity and weather. Goodness-of-fit tests conducted between temperature and wind speed, and flights observed (Fig. 6) were significant (P < 0.005, G2=13.37, df=3; and P < 0.005, G2=15.17, df=3, respectively). The effects of cloud cover could not be determined because flights could not be seen during heavy fog or rain. A three-way classification of temperature, wind, and flights indicated the best fit included all three factors and that the wind speed and temperature interaction was significant (P < 0.005, G2=4.24, df=9). Four categories of temperature, cloud cover, and wind speed description were used in the analysis. The greatest proportion of flights was associated with low temperatures (-12.2 to -1.7 C), and high winds (34+ km/hr).
Fig. 6. Classification of Minneapolis-St. Paul International Airport Canada goose flights by air temperature and wind speed categories, 1984 and 1985 combined.