. Bulletin. Natural history; Natural history. 400 Illinois Natural History Survey Bulletin Vol. 28, Art. 3 and 1909 in all zones censused than in 1957 and 1958, fig. 19. The pattern is one that can be observed over and over for the open-field habitats; that is, in these habitats the earlier avifauna of com- mon species was more varied than the re- cent. Related to this change is the fact that only three species (horned lark, red- winged blackbird, and barn swallow) comprised more of the cornfield popula- tion in 1957-1958 than in 1907-1909, while at least nine species were less prom- inent in
. Bulletin. Natural history; Natural history. 400 Illinois Natural History Survey Bulletin Vol. 28, Art. 3 and 1909 in all zones censused than in 1957 and 1958, fig. 19. The pattern is one that can be observed over and over for the open-field habitats; that is, in these habitats the earlier avifauna of com- mon species was more varied than the re- cent. Related to this change is the fact that only three species (horned lark, red- winged blackbird, and barn swallow) comprised more of the cornfield popula- tion in 1957-1958 than in 1907-1909, while at least nine species were less prom- inent in the recent than the earlier corn- field avifauna, fig. 12. 70 60 SO In northern and central Illinois, by 1957 the horned lark had become the pre- dominant cornfield species, a change re- flected in the density figures, table 5. The change in the southern zone was less pronounced. The nesting avifauna for cornfields probably is composed principally of three species: the horned lark, vesper sparrow, and killdeer. Because so much of the summer avi- fauna of cornfields does not breed in this habitat, the list of species in table 5 must reflect marginal or edge habitat to some 40 30 q20 ID O 0 CORNFIELDS NORTHERN ZONE- CENTRAL ZONE- SOUTHERN ZONE. 1907 09 57 58 07 09 57 58 07 09 57 58 07 09 57 58 07 09 57 58 07 REDWINGED BARN CRACKLE BLACKBIRD HORNED LARK BARN SWALLOW MOURNING DOVE 09 57 58 CROW 10 \ \ 07 09 57 58 07 09 57 58 07 09 57 58 07 09 57 58 07 09 57 58 07 09 5758 FLICKER ROBIN RED-HEADED KINGBIRD MOCKINGBIRD BLUEBIRD WOODPECKER Fig. 12.—Relative abundance of common species of birds censused in cornfields of the northern, central, and southern zones of Illinois in the summers of 1907, 1909, 1957, and 1958. Only those species are included that showed changes in relative abundance (per cent of all birds counted in cornfields) between 1909 and Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - co
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Keywords: ., booka, bookcentury1900, bookdecade1910, booksubjectnaturalhistory
