. Animal Ecology. Animal ecology. ^8 YEAR Territorial 66, Trelease Woods, Illinois" I I I I I I I I I I I I I FIG. 17-2 Yearly variations in populations of the house wren. The data for northern Ohio are for total males and females on a 15-acre estate, most of the males being banded and captured at their nest-boxes. The data for Trelease Woods, in central Illinois, are for territorial males censused on a 55-acre tract by the spot-map method, tvlean temperatures are for the winter- ing range only, based on monthly weather data for Tampa and Jacksonville, Florida; Savannah, Georgia; Montgome
. Animal Ecology. Animal ecology. ^8 YEAR Territorial 66, Trelease Woods, Illinois" I I I I I I I I I I I I I FIG. 17-2 Yearly variations in populations of the house wren. The data for northern Ohio are for total males and females on a 15-acre estate, most of the males being banded and captured at their nest-boxes. The data for Trelease Woods, in central Illinois, are for territorial males censused on a 55-acre tract by the spot-map method, tvlean temperatures are for the winter- ing range only, based on monthly weather data for Tampa and Jacksonville, Florida; Savannah, Georgia; Montgomery and Mobile, Alabama (Kendeigh and Baldwin 1937, Kendeigh 1944). in this curve occur in 1918, 1926, 1940, and 1958. Information from observers indicated that low popu- lations were widespread in eastern North America both in this species and in many other song and game birds during these years. There is considerable evi- dence that these conspicuous variations in abundance, as well as some less pronounced, were the result of severely low winter temperatures. It is of interest that, in England, severe winters causing high mor- tality among such song birds as thrushes, blackbirds, and tits were recorded in 1111, 1115, 1124, 1335, 1407, 1462, 1609, 1708, 1716, 1879, 1917 (Elton 1927). To birds that feed on the ground, the depth of snow is as critical a factor as low temperature in determining the number that survive. Among mammals, fluctuations in the population of the common hare in Denmark have been correlated with the varying effects of summer rainfall, spring temperatures, and the number of days of frost during the winter (Andersen 1957). Catastrophes may occur with practically any type of animal life. The severe winter of 1917-18, for instance, produced a marked reduction in the num- bers of many species of marine invertebrates in the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and
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Keywords: ., bookcentury1900, bookcollectionbiodive, booksubjectanimalecology
