06-11-2003 Council Agenda - Laserfiche WebLink

Home Browse Search

Results Page 2 of 8 With 39,343 ha of Type 3, 4, and 5 wetlands in Twin Cites, we estimated that the area could support 118,000 breeding pairs, or a summer population of 472,000 geese (236,000 adults plus 236,000 young), assuming a conservative production of 2 goslings per nesting attempt (Sayler, 1977). If the birds were to nest colonially, as they do on islands (Ewaschuk and Boag 1972), then, the maximum population would be higher. Moreover, because Canada geese do not breed until 2 or 3 years of age (Cooper 1978) and these non - breeding birds make a molt migration to northern areas in summer (Zicus 1981, Fashingbauer 1993), the fall population when the molt migrants return are typically twice that of summer. Thus, if the summer population were to approach one -half million geese, the fall population would likely be >1 million. Geese were found on 107 of 254 (42 %) wetlands randomly surveyed wetlands in 1994. The amount of open shoreline, estimated to the nearest 25 %, ranged from none (36 %), 1 -25 (30 %), 26 -50 (11 %), 51 -75 (19 %), and 76 -100 (4%). Wetlands with geese had a significantly higher (P <.05) amount of shoreline mowed or pastured than those without geese (Figure 2). To assess the relationship between the a length of shoreline habitat and geese using the wetland, we computed shoreline length as circumference of a circle with an area equal to that of the wetland. Shoreline grass - pasture length was then calculated multiplying circumference by the percent of shoreline in mowed or pastured grass. This yielded a minimum shoreline estimate for the respective wetlands inasmuch as few of the water areas were round. We found a strong relationship between the amount of grass shoreline and the number of geese at site (Figure 3). During the 1994 survey 2,313 geese were counted on the 254 wetlands sampled. The expanded population estimate was 25,000 birds; less than 25% of the level predicted by the exponential model (Figure 1). Geese were found most frequently on type 5 wetlands (47 %), lakes (42 %), and least often on type 4 marshes (28 %); group sizes averaged 25 birds on type 4, 28 in type 5, and 34 on lakes, and were not significantly different (P >.05). Goose densities per km2 of wetland and lake were significantly higher (P <.05) in the cities and towns closed to hunting (61/km2) than those open to goose shooting 22 /km2). Goose Complaint Levels Goose complaints were received for 391 locations during the 1982 -96 period and 176 of these sites visited at the time of the complaint. Summer brood - rearing period problems were most common (94 %). The 23 fall complaints came from primarily from golf courses (11), athletic fields (3), and airports (3). Most complaints came from residential sites (52 %), followed by parks (17 %), golf courses (16 %), swimming beaches (10 %), and corporate grounds (6 %). The geese causing a complaint was highly variable, ranging from 4 to 456 and averaged 70 birds, SD =62. Among complaint classes, commercial sites had the lowest tolerance threshold (59) and beach areas the highest (87); ANOVA showed no Aber of Wetlands 1001 60 - 60- 40 - f • Geese ® No Geese -36- http://www.fw.umn.edu/ research /goose /html /urban /manage6.html 4/7/00