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• 51. [Article] Food selection and juvenile survival in Nuttall's cottontails in central Oregon

  A population of Nuttall's cottontails (Sylvilagus nuttallii) in Deschutes County, Oregon, decreased fromm 166 individuals in August 1978 to 76 individuals in August 1979. Survival rates of four annual ...

  Citation × Citation Citation Abstract Copy Title: Food selection and juvenile survival in Nuttall's cottontails in central Oregon Author: Hundertmark, Kris Joseph A population of Nuttall's cottontails (Sylvilagus nuttallii) in Deschutes County, Oregon, decreased fromm 166 individuals in August 1978 to 76 individuals in August 1979. Survival rates of four annual litter groups in 1978 were 0.74, 0.35, 0.72, and 0.93; survival rates for the same litter groups, respectively, in 1979 were 0.12, 0.28, 0.07, and 0.18. Population density and juvenile survival decreased between the 2 years possibly because of alterations in forage quality and quantity caused by precipitation. Numbers of cottontails on the study area on 30 August were related significantly (P<0.O1) to initial breeding density and to precipitation falling during the breeding season (February - July). Survival in juvenile cottontails from birth to 30 August was related significantly to precipitation in the first (P<O.05), third (P<O.01), and fourth (p<0.O1) annual litter groups. Vegetative abundance at the end of the growing season (September) decreased by approximately 30% between the 2 years; the decline corresponded with a 45% decrease in crop-year (September - June) precipitation. Succulence of grasses, forbs, and shrubs was greatest in spring, declined in summer, and increased slightly in late summer. Forbs consistently were the most succulent group, except in September when shrubs were most succulent. Grasses exhibited the greatest variation in succulence in response to precipitation; shrubs exhibited the least. A moisture availability index (MAI) indicated that, despite approximately equal estimates of succulence between the 2 years, moisture was more available to cottontails in 1978 because of greater abundance of vegetation. Cottontails seemingly selected forage groups in relation to their relative succulence, within limits. Shrubs were avoided, and succulent juniper (Juniperus occidentalis) foliage was eaten only in dry periods, possibly because of low tolerance in cottontails to plant secondary compounds, particularly terpenoids. Juveniles selected forbs in significantly (P<0.05) greater proportions than adults, possibly to aquire additional moisture for growth; diets of younger (<600 g) and older (>600 g) juveniles did not differ. Breeding females selected forbs in significantly (P<0.05) greater proportions than males, possibly because of moisture demands associated with reproduction and lactation. Other nutrients, especially protein, that are associated with moisture content of plants, possibly were as important as moisture in determining food habits and population fluctuations in Nuttall's cottontails in central Oregon. The relationship between juvenile survival and precipitation possibly was caused by genotypic variation in efficiency in cottontails to utilize moisture and nutrients. Title: Food selection and juvenile survival in Nuttall's cottontails in central Oregon Author: Hundertmark, Kris Joseph A population of Nuttall's cottontails (Sylvilagus nuttallii) in Deschutes County, Oregon, decreased fromm 166 individuals in August 1978 to 76 individuals in August 1979. Survival rates of four annual litter groups in 1978 were 0.74, 0.35, 0.72, and 0.93; survival rates for the same litter groups, respectively, in 1979 were 0.12, 0.28, 0.07, and 0.18. Population density and juvenile survival decreased between the 2 years possibly because of alterations in forage quality and quantity caused by precipitation. Numbers of cottontails on the study area on 30 August were related significantly (P<0.O1) to initial breeding density and to precipitation falling during the breeding season (February - July). Survival in juvenile cottontails from birth to 30 August was related significantly to precipitation in the first (P<O.05), third (P<O.01), and fourth (p<0.O1) annual litter groups. Vegetative abundance at the end of the growing season (September) decreased by approximately 30% between the 2 years; the decline corresponded with a 45% decrease in crop-year (September - June) precipitation. Succulence of grasses, forbs, and shrubs was greatest in spring, declined in summer, and increased slightly in late summer. Forbs consistently were the most succulent group, except in September when shrubs were most succulent. Grasses exhibited the greatest variation in succulence in response to precipitation; shrubs exhibited the least. A moisture availability index (MAI) indicated that, despite approximately equal estimates of succulence between the 2 years, moisture was more available to cottontails in 1978 because of greater abundance of vegetation. Cottontails seemingly selected forage groups in relation to their relative succulence, within limits. Shrubs were avoided, and succulent juniper (Juniperus occidentalis) foliage was eaten only in dry periods, possibly because of low tolerance in cottontails to plant secondary compounds, particularly terpenoids. Juveniles selected forbs in significantly (P<0.05) greater proportions than adults, possibly to aquire additional moisture for growth; diets of younger (<600 g) and older (>600 g) juveniles did not differ. Breeding females selected forbs in significantly (P<0.05) greater proportions than males, possibly because of moisture demands associated with reproduction and lactation. Other nutrients, especially protein, that are associated with moisture content of plants, possibly were as important as moisture in determining food habits and population fluctuations in Nuttall's cottontails in central Oregon. The relationship between juvenile survival and precipitation possibly was caused by genotypic variation in efficiency in cottontails to utilize moisture and nutrients. Close

• 52. [Article] Bird and rodent nesting in excavated cavities in Pinon-juniper woodland, southeastern Colorado

  I studied bird and rodent nesting in woodpecker-excavated cavities in pifion-juniper (Pinus edulis-Juniperus monosperma) (P-J) woodland in southeastern Colorado during the spring and summer of 1987 and ...

  Citation × Citation Citation Abstract Copy Title: Bird and rodent nesting in excavated cavities in Pinon-juniper woodland, southeastern Colorado Author: Youkey, Donald E. I studied bird and rodent nesting in woodpecker-excavated cavities in pifion-juniper (Pinus edulis-Juniperus monosperma) (P-J) woodland in southeastern Colorado during the spring and summer of 1987 and 1988. Two related investigations were conducted: one described characteristics of habitat used by birds and rodents nesting in woodpecker-excavated cavities and the other evaluated whether or not birds and rodents were competing for the nest-cavity resource. Seven species of birds and 4 species of rodents were included in the study: American kestrel (Falco sparverius), western screech-owl (Otus kennicottii), northern flicker (Colaptus auratus), ash-throated flycatcher (Mviarchus cinerascens), plain titmouse (Parus inornatus), Bewick's wren (Thrvothorus bewickii), mountain bluebird (Sialia currucoides), white-footed mouse (Peromvscus leucopus), deer mouse (P. maniculatus), pition mouse (P. truei), and woodrat (Neotoma spp.). 1987 was a preliminary year. In 1988, 248 nests were located in 433 cavities monitored, and cavity density averaged 1.5/ha. Western screech-owls nested earlier than all other species (P < 0.001), plain titmice nested earlier than ash-throated flycatchers (P = 0.033), and other species of birds and rodents nested at the same time (P < 0.05). Seven of 19 characteristics associated with nests differed (P < 0.05) among species: 4 of 5 at the cavity-level, 2 of 5 at the cavity-tree level, and 1 of 9 at the cavity-site level. Generally, larger species (kestrels, screech-owls, and flickers) nested in larger cavities and smaller species (white-footed, deer, and pitlon mice, and Bewick's wren) nested in smaller cavities. Characteristics of cavities used for nesting by secondary cavity-nesting species also differed from characteristics of all cavities monitored most frequently on characteristics associated with cavity size. Differences were demonstrated using univariate analysis (Kruskal-Wallis ANOVA) because with the considerable overlap among species, multivariate analysis (discriminant function analysis [DFA]) could not discriminate among species. Management implications include the need to evaluate impacts to the P-J woodland cavity-nesting community before converting the woodland to rangeland, evaluate impacts of logging in higher elevation forests where many of the cavity-excavating woodpeckers breed, and evaluate the influence of the nest-parasitic brown-headed cowbird (Molothrus ater) and the highly competitive European starling (Sturnus vulqaris). In 1988, 95 cavities were manipulated to yield 47 rodent exclusions and 48 bird exclusions. Proportions of these manipulated cavities used for nesting by birds and rodents were compared to the proportions of 83 control cavities used for nesting by the appropriate group of species. Cavities were revisited at 10-day intervals 4 May - 6 August 1988 and evidence of use recorded. The proportions of cavities used as nests by rodents was significantly greater in manipulated cavities than in control cavities (P = 0.0083). Thus, interspecific competition was experimentally demonstrated between birds and rodents for nest-sites in woodpecker-excavated cavities. Title: Bird and rodent nesting in excavated cavities in Pinon-juniper woodland, southeastern Colorado Author: Youkey, Donald E. I studied bird and rodent nesting in woodpecker-excavated cavities in pifion-juniper (Pinus edulis-Juniperus monosperma) (P-J) woodland in southeastern Colorado during the spring and summer of 1987 and 1988. Two related investigations were conducted: one described characteristics of habitat used by birds and rodents nesting in woodpecker-excavated cavities and the other evaluated whether or not birds and rodents were competing for the nest-cavity resource. Seven species of birds and 4 species of rodents were included in the study: American kestrel (Falco sparverius), western screech-owl (Otus kennicottii), northern flicker (Colaptus auratus), ash-throated flycatcher (Mviarchus cinerascens), plain titmouse (Parus inornatus), Bewick's wren (Thrvothorus bewickii), mountain bluebird (Sialia currucoides), white-footed mouse (Peromvscus leucopus), deer mouse (P. maniculatus), pition mouse (P. truei), and woodrat (Neotoma spp.). 1987 was a preliminary year. In 1988, 248 nests were located in 433 cavities monitored, and cavity density averaged 1.5/ha. Western screech-owls nested earlier than all other species (P < 0.001), plain titmice nested earlier than ash-throated flycatchers (P = 0.033), and other species of birds and rodents nested at the same time (P < 0.05). Seven of 19 characteristics associated with nests differed (P < 0.05) among species: 4 of 5 at the cavity-level, 2 of 5 at the cavity-tree level, and 1 of 9 at the cavity-site level. Generally, larger species (kestrels, screech-owls, and flickers) nested in larger cavities and smaller species (white-footed, deer, and pitlon mice, and Bewick's wren) nested in smaller cavities. Characteristics of cavities used for nesting by secondary cavity-nesting species also differed from characteristics of all cavities monitored most frequently on characteristics associated with cavity size. Differences were demonstrated using univariate analysis (Kruskal-Wallis ANOVA) because with the considerable overlap among species, multivariate analysis (discriminant function analysis [DFA]) could not discriminate among species. Management implications include the need to evaluate impacts to the P-J woodland cavity-nesting community before converting the woodland to rangeland, evaluate impacts of logging in higher elevation forests where many of the cavity-excavating woodpeckers breed, and evaluate the influence of the nest-parasitic brown-headed cowbird (Molothrus ater) and the highly competitive European starling (Sturnus vulqaris). In 1988, 95 cavities were manipulated to yield 47 rodent exclusions and 48 bird exclusions. Proportions of these manipulated cavities used for nesting by birds and rodents were compared to the proportions of 83 control cavities used for nesting by the appropriate group of species. Cavities were revisited at 10-day intervals 4 May - 6 August 1988 and evidence of use recorded. The proportions of cavities used as nests by rodents was significantly greater in manipulated cavities than in control cavities (P = 0.0083). Thus, interspecific competition was experimentally demonstrated between birds and rodents for nest-sites in woodpecker-excavated cavities. Close

• 53. [Article] Ecological effects of spring and fall prescribed burning on basin big sagebrush : Idaho fescue--bluebunch wheatgrass communities

  The vegetation response of spring and fall prescribed fires in basin big sagebrush (Artemisia tridentata subsp. tridentata Nutt.)/Idaho fescue (Festuca idahoensis Elmer)--bluebunch wheatgrass (Agropyron ...

  Citation × Citation Citation Abstract Copy Title: Ecological effects of spring and fall prescribed burning on basin big sagebrush : Idaho fescue--bluebunch wheatgrass communities Author: Sapsis, David B. The vegetation response of spring and fall prescribed fires in basin big sagebrush (Artemisia tridentata subsp. tridentata Nutt.)/Idaho fescue (Festuca idahoensis Elmer)--bluebunch wheatgrass (Agropyron spicatum Pursh. (Scribn. & Smith)) communities was measured at the John Day Fossil Beds National Monument in eastern Oregon. Objectives of the study were to quantify fuel loads, environmental conditions, fire behavior and vegetation response corresponding to these two fire treatments. Pretreatment fuel loads in the experimental units ranged from 5 to 12 Mg/ha, with the fall treatment units averaging 10.5 Mg/ha, and the spring units averaging 6.2 Mg/ha. Both treatments contained large amounts (> 3 Mg/ha) of herbaceous fuels. Moisture content of grass and herb fuels were significantly greater in the spring burned units. This is believed to be largely responsible for the less severe fire behavior observed in the spring burn treatment. Flame lengths averaged 4.2 m in fall burns, compared to a mean of 1.7 m in the spring plots. Similarly, rate of spread was significantly greater in the fall units, averaging 1.6 m/s, compared to 0.2 m/s in the spring treatment. Fireline Intensity was seven times greater, and total energy release was twice was great in the fall burns. Neither burn treatment resulted in significant mortality of bluebunch wheatgrass, but fall burning did cause significant mortality of Idaho fescue, where 20% of the population was killed. Fall burning stimulated tillering of bluebunch wheatgrass, as the average basal area increased both one and two years following burning. Average basal area per plant of Idaho fescue was reduced by 23% the first year following fall burning; however plants recovered to 90% of their preburn size by the second post-fire year. Spring burning resulted in no significant change in basal area of either species. Fall burning significantly reduced the number of flowering culms on bluebunch wheatgrass plants the first post-fire year (from 36 to 12 per plant); however, by the second post-fire year, number of flowering culms was significantly greater than either pre-burn or control levels (59/plant). Similarly, fall burning of Idaho fescue averaged 60% more flowering culms per plant as adjacent controls (11 compared to 7/plant). Spring burning reduced flowering of both species the first year following burning. Both burn treatments reduced the frequency of annual grasses, while causing no change in frequency of perennial grasses. Annual forbs increased in abundance following both burn treatments. Fire resulted in replacement of exotic annual grasses with annual forb species. Dominant perennial forbs responded variably in both burn treatments, as well as control plots. Frequency of sagebrush increased significantly in both spring and control experimental units in 1989 (one year after spring burning), while fall burns (two years posttreatment) demonstrated no such increase. Apparently, factors relating to the greater fire severity (e.g. consumption, total energy) in the fall burns reduced the rate and degree of reinvasion by sagebrush in the fall burn plots. Densities of annual grasses and woody species were significantly reduced by both burn treatments. Cheatgrass (Bromus tectorum L.) density before burning averaged 446 and 552/m2 in fall and spring units, respectively, as compared to 10 and 85/m2, respectively, the first post-fire year. Big sagebrush was completely eliminated by the fall fire, while spring burning resulted in an 84% decrease in density. Density of western juniper (Juniperus occidentalls Hook.) was reduced 100% by both burn treatments. Species diversity, as measured by the Shannon-Weaver Index (H'), was reduced by fall burning from 2.69 before treatment to 2.53 the first year following burning , but increased to 2.81 second post-fire year. Control plots behaved similarly, although changes were not as great. Changes were most evident in terms of rare species, many of which were not present prior to burning. Spring burning resulted in an no change in species diversity the first year after burning, although, species richness increased from 34 to 41. Both burn treatments appeared effective at changing stand structure to that of a dominance by native perrenial grasses and forbs. The reduced competition from woody plants has, and presumably will continue to favor surviving herbaceous plants. Overall fire effects appear to fit into land management policy of the National Park Service in regard to maintaining wildlands in a pristine state. Specifically, both spring and fall burning reduced fuel hazard, and increased the relative abundance of native species, indicating that prescribed burning may be an effective land management tool for the National Park Service and others managing similar rangelands. Title: Ecological effects of spring and fall prescribed burning on basin big sagebrush : Idaho fescue--bluebunch wheatgrass communities Author: Sapsis, David B. The vegetation response of spring and fall prescribed fires in basin big sagebrush (Artemisia tridentata subsp. tridentata Nutt.)/Idaho fescue (Festuca idahoensis Elmer)--bluebunch wheatgrass (Agropyron spicatum Pursh. (Scribn. & Smith)) communities was measured at the John Day Fossil Beds National Monument in eastern Oregon. Objectives of the study were to quantify fuel loads, environmental conditions, fire behavior and vegetation response corresponding to these two fire treatments. Pretreatment fuel loads in the experimental units ranged from 5 to 12 Mg/ha, with the fall treatment units averaging 10.5 Mg/ha, and the spring units averaging 6.2 Mg/ha. Both treatments contained large amounts (> 3 Mg/ha) of herbaceous fuels. Moisture content of grass and herb fuels were significantly greater in the spring burned units. This is believed to be largely responsible for the less severe fire behavior observed in the spring burn treatment. Flame lengths averaged 4.2 m in fall burns, compared to a mean of 1.7 m in the spring plots. Similarly, rate of spread was significantly greater in the fall units, averaging 1.6 m/s, compared to 0.2 m/s in the spring treatment. Fireline Intensity was seven times greater, and total energy release was twice was great in the fall burns. Neither burn treatment resulted in significant mortality of bluebunch wheatgrass, but fall burning did cause significant mortality of Idaho fescue, where 20% of the population was killed. Fall burning stimulated tillering of bluebunch wheatgrass, as the average basal area increased both one and two years following burning. Average basal area per plant of Idaho fescue was reduced by 23% the first year following fall burning; however plants recovered to 90% of their preburn size by the second post-fire year. Spring burning resulted in no significant change in basal area of either species. Fall burning significantly reduced the number of flowering culms on bluebunch wheatgrass plants the first post-fire year (from 36 to 12 per plant); however, by the second post-fire year, number of flowering culms was significantly greater than either pre-burn or control levels (59/plant). Similarly, fall burning of Idaho fescue averaged 60% more flowering culms per plant as adjacent controls (11 compared to 7/plant). Spring burning reduced flowering of both species the first year following burning. Both burn treatments reduced the frequency of annual grasses, while causing no change in frequency of perennial grasses. Annual forbs increased in abundance following both burn treatments. Fire resulted in replacement of exotic annual grasses with annual forb species. Dominant perennial forbs responded variably in both burn treatments, as well as control plots. Frequency of sagebrush increased significantly in both spring and control experimental units in 1989 (one year after spring burning), while fall burns (two years posttreatment) demonstrated no such increase. Apparently, factors relating to the greater fire severity (e.g. consumption, total energy) in the fall burns reduced the rate and degree of reinvasion by sagebrush in the fall burn plots. Densities of annual grasses and woody species were significantly reduced by both burn treatments. Cheatgrass (Bromus tectorum L.) density before burning averaged 446 and 552/m2 in fall and spring units, respectively, as compared to 10 and 85/m2, respectively, the first post-fire year. Big sagebrush was completely eliminated by the fall fire, while spring burning resulted in an 84% decrease in density. Density of western juniper (Juniperus occidentalls Hook.) was reduced 100% by both burn treatments. Species diversity, as measured by the Shannon-Weaver Index (H'), was reduced by fall burning from 2.69 before treatment to 2.53 the first year following burning , but increased to 2.81 second post-fire year. Control plots behaved similarly, although changes were not as great. Changes were most evident in terms of rare species, many of which were not present prior to burning. Spring burning resulted in an no change in species diversity the first year after burning, although, species richness increased from 34 to 41. Both burn treatments appeared effective at changing stand structure to that of a dominance by native perrenial grasses and forbs. The reduced competition from woody plants has, and presumably will continue to favor surviving herbaceous plants. Overall fire effects appear to fit into land management policy of the National Park Service in regard to maintaining wildlands in a pristine state. Specifically, both spring and fall burning reduced fuel hazard, and increased the relative abundance of native species, indicating that prescribed burning may be an effective land management tool for the National Park Service and others managing similar rangelands. Close