Ecosystem HealthVolume 7, Issue 2 p. 77-78 Can Ecosystem Health be Ecocentric? Glenn C. Sutter Curator of Ornithology and Human Ecology, Glenn C. Sutter Curator of Ornithology and Human Ecology Life Sciences DivisionRoyal Saskatchewan Museum2340 Albert StreetRegina, SaskatchewanS4P 3V7CanadaE-mail [email protected]Search for more papers by this author Glenn C. Sutter Curator of Ornithology and Human Ecology, Glenn C. Sutter Curator of Ornithology and Human Ecology Life Sciences DivisionRoyal Saskatchewan Museum2340 Albert StreetRegina, SaskatchewanS4P 3V7CanadaE-mail [email protected]Search for more papers by this author First published: 20 December 2001 https://doi.org/10.1046/j.1526-0992.2001.007002077.xCitations: 2Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article.Citing Literature Volume7, Issue2June 2001Pages 77-78 RelatedInformation

Many North American grassland songbirds are experiencing significant population declines, partly because of land-use practices associated with agricultural activity. The aim of this study was to compare the habitat correlates of songbirds breeding in native mixed-grass prairie with patterns found in introduced vegetation dominated by crested wheat grass (Agropyron pectiniforme). We assessed plant species composition, habitat structure, and bird species diversity over 2 years to document species- and community-level trends in southwestern Saskatchewan, Canada. In addition to having higher plant species richness and diversity, native vegetation consisted of significantly more grass and sedge cover, less bare ground, deeper litter, and higher density within 10 cm of the ground than introduced vegetation. Bird species richness and diversity and the abundance of Baird's Sparrows (Ammodramus bairdii) and Savannah Sparrows (Passerculus sandwichensis) increased significantly along a multivariate gradient from open to more sheltered habitat, regardless of vegetation type. Sprague's Pipits (Anthus spragueii) showed a curvilinear increase along the same gradient, occurring in high numbers where habitats offered an intermediate level of cover. Our findings suggest that species richness and diversity within songbird communities and the abundance of some species may be reduced where conversion to crested wheat grass results in more open habitat.

Nest-site selection and nest-entrance orientation patterns in Sprague's Pipit (Anthus spragueii), an endemic grassland passerine that builds a domed nest on the ground were measured at nest sites and randomly selected non-nest sites, and nest-entrance orientations were compared to random, circular distributions and dawn azimuths. Pipits showed a preference for sites in dense, grassy, and relatively tall vegetation with low forb density and little bare ground, presumably because such sites offer protection against predation and heat stress. There was no significant directionality in terms of nest-entrance orientation, implying that potential thermal benefits of an east-facing nest play a limited role during nest-site selection.

Many bird species will attempt to raise more than one clutch in a given breeding season. For grassland songbirds, the interval between nesting attempts is usually measured indirectly because individual birds are difficult to track once a nest has failed or their chicks have fledged. Here we report observations of renesting by Sprague's Pipits (Anthus spragueii) carrying radio transmitters. As part of a larger study of pipit nesting ecology, we monitored activity patterns of radio-tagged adult females in 1994 and 1995. Three birds started replacement nests 10-15 days after losing a clutch, and one started a second nest 21 days after successfully fledging chicks. Such long intervals between nesting attempts support the impression that the frequency of renesting in pipits is relatively low.

Endemic grassland songbirds, including the Baird's sparrow (Ammodramus bairdii), are adapted to breed in North American native prairie, an extremely rare habitat that is often grazed by cattle and continues to be threatened by cultivation. We determined the degree to which Baird's sparrow numbers in mixed-grass prairie are associated with plant species composition and grazing pressure. Bird numbers in grazed native prairie correlated positively with grass/sedge cover and negatively with bare ground cover. Mean numbers of singing males were generally highest on ungrazed native prairie and similar in grazed introduced and grazed native vegetation, suggesting that birds are more affected by grazing pressure than by plant species composition. What attracts this species to introduced vegetation remains unclear.

1. Developmental changes in metabolic rate and thermoregulatory ability were documented in the American coot (Fulica americana).2. Prenatal metabolic rate rose exponentially with age, reaching a plateau of 0.083 W by 3-4 days prehatch.3. Neonates could elevate resting metabolic rate by 40% in cold air. This capacity increased to 140% by 1-5 days posthatch.4. By 8-15 days of age, hatchlings were homeothermic at air and water temperatures of 25-35-degrees-C.5. In air, the lower critical temperature declined with age, reaching a minimum value of 19-21-degrees-C at the fledgling stage.6. Achievement of homeothermy in this species appeared to depend on the attainment of adequate insulation, thermal inertia and thermogenic ability.

The precision and metabolic costs of temperature regulation in air and water were studied in hand-reared fledgling American coots (Fulica americana). In birds acclimated to both 23 and 8 °C, cloacal temperature was independent of air temperature over an air temperature range of −10 to 33 °C. Minimum resting metabolic rate and thermal conductance averaged 1.2–1.6 times higher in water than in air, and neither variable was significantly affected by cold acclimation. Despite differences in minimal thermal conductance, the lower critical temperature was similar in air and water (19–21 °C). Trunk skin temperature averaged 3.4–4.3 °C below cloacal temperature in both media, and did not differ between dorsal and ventral aspects of the bird. Peripheral cooling was most pronounced in submerged appendages. Coots displayed a high resistance to immersion hypothermia; cloacal temperature remained stable at 40–41 °C during 4 h exposure to 5 °C water. Exposure to a −10 °C atmosphere of helium–oxygen (helox) similarly failed to induce even mild hypothermia in all but one of the birds tested. The unusual tolerance of F. americana to helox and immersion in cold water could not be attributed to an enhanced thermogenic ability. Maximum resting metabolic rate of birds exposed to cold was only 3.0–3.5 times the thermoneutral rate. Aquatic homeothermy in this species may instead reflect superior insulation and exceptional buoyancy provided by a dense, water-repellent plumage.