. Bulletin. Natural history; Natural history. 462 Illinois Natural History Survey Bulletin Vol. 27, Art. b drop in mallard production. In 1957, ponds were down in number in both provinces, and mallard production de- clined. In the following year, 1958, water areas continued down in number in Mani- toba but increased in Saskatchewan; mal- lard production showed a further decline. In 1959, water conditions in Manitoba remained about the same as the year be- fore, but the number of ponds in Saskatch- ewan declined sharply. For the fourth consecutive year mallard production de- mile in May) follow
. Bulletin. Natural history; Natural history. 462 Illinois Natural History Survey Bulletin Vol. 27, Art. b drop in mallard production. In 1957, ponds were down in number in both provinces, and mallard production de- clined. In the following year, 1958, water areas continued down in number in Mani- toba but increased in Saskatchewan; mal- lard production showed a further decline. In 1959, water conditions in Manitoba remained about the same as the year be- fore, but the number of ponds in Saskatch- ewan declined sharply. For the fourth consecutive year mallard production de- mile in May) followed similar trends in most years of the period 1948-1959, fig. 22. Mallard production and water abun- dance followed divergent trends in 1950, 1953, and 1958. In 1954, mallard pro- duction showed no decisive trend, while water abundance rose markedly. In Manitoba, mallard production tended to parallel water abundance in the years 1956-1959 but not in the 3 years previous. In 1945, 1950, and 1953, when water conditions on the breeding grounds were. JUVENILES 1952 1953 1954 1955 1956 1957 1958 1959 Fig. 23.—Relationship between the density of the adult mallard population on the Canadian breeding grounds in spring and the production of young, 1952-1959, as indicated by the number of ponds per mallard in southern Manitoba and southern Saskatchewan in May and by the num- ber of juveniles per adult checked in hunters' bags in the Mississippi Flyway the autumn fol- lowing. Data for the breeding grounds in 1952 represent Saskatchewan only. Points on the graph representing number of juveniles per adult for 1952-1955 are based principally on data from Illinois, table 58; points for 1956-1959 are based on data from Missouri, table 59, as ex- plained in the legend for fig. 22. Data for the breeding grounds are from the U. S. Fish and Wildlife Service and the Canadian Wildlife Service. clined; the number of juveniles per adult in the Mississippi Flyway, as represented by data from Missouri
Size: 2178px × 1148px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., booka, bookcentury1900, bookdecade1910, booksubjectnaturalhistory
