Stephanie L. Jones

ANNUAL RETURN RATES OF BREEDING GRASSLAND SONGBIRDS

Abstract We used reobservation of color-banded birds to index annual breeding site fidelity of four species of songbirds that nest in the northern mixed-grass prairie of northcentral Montana (1996–2005). Territorial males of Spragues Pipits (Anthus spragueii), and Savannah (Passerculus sandwichensis), Grasshopper (Ammodramus savannarum), and Bairds (A. bairdii) sparrows were located on five permanent study sites (1998– 2004) and lured into mist-nets using tape broadcasts of conspecific songs and calls. The proportion reobserved was 5.3% (n = 247) across all banded adult males. Grasshopper Sparrows had the highest proportion of returns (8.9%), followed by Savannah Sparrows (5.4%), Bairds Sparrows (5.1%), and Spragues Pipits (2.1%). Three nestling Savannah Sparrows were reobserved in subsequent years (n = 193), while no nestlings of the other species were reobserved (n = 401). Our return rates were low for all adults in comparison with typical reports of return rates for songbird species of woodland and shrubland habitats. Migratory nomadism may explain this phenomenon, where grassland migrants are opportunistic in site selection, rather than faithfully returning to potentially uninhabitable former breeding sites.

GRASSLAND SONGBIRD NEST SITE SELECTION PATTERNS IN NORTHCENTRAL MONTANA

Abstract We explored nest site habitat selection patterns for six grassland passerine species in northcentral Montana: Spragues Pipit (Anthus spragueii), Savannah Sparrow (Passerculus sandwichensis), Grasshopper Sparrow (Ammodramus savannarum), Bairds Sparrow (A. bairdii), Chestnut-collared Longspur (Calcarius ornatus), and Western Meadowlark (Sturnella neglecta). We quantified habitat characteristics at sites chosen for nesting and compared them to randomly selected sites, both spatially and temporally. Using discriminant analysis, two species groups were discernable based on a combination of habitat characteristics, which were distinct from random sites. Nest sites had greater foliage height and density than random sites. This pattern generally was shown most strongly by Western Meadowlarks, Bairds, and Savannah sparrows. Three bird species selected nest patches (5-m radius plots centered on nests) having little or no clubmoss (Selaginella densa) cover, which was one of the most powerful discriminating variables in this analysis. The conservation implications of increasing clubmoss cover in relationship to nest site selection in northern Great Plains grasslands are discussed.

Reproductive biology of a grassland songbird community in Northcentral Montana.

Abstract Successful conservation of grassland bird populations requires basic information on their breeding biology; in particular, information from undisturbed native prairie over an extended period of time. We present data collected at Bowdoin National Wildlife Refuge in northcentral Montana on the reproductive biology of six grassland bird species that breed in mixed-grass prairie: Spragues Pipit (Anthus spragueii), Savannah (Passerculus sandwichensis), Grasshopper (Ammodramus savannarum), and Bairds (A. bairdii) sparrows, Chestnut-collared Longspur (Calcarius ornatus), and Western Meadowlark (Sturnella neglecta). Basic measures of reproductive biology are presented, including estimates of nest density, phenology, fecundity, parasitism rates, and nest success, and how these and other characteristics varied across years. Nests (n  =  1,494) of the six focal species accounted for 98% of all passerine nests found during 1997–2007; Chestnut-collared Longspurs (51%) were the dominant breeding species. Total nest density across years ranged from 20 to 41 nests per 40 ha (CV  =  26%) on unburned sites. Mean clutch initiation date and clutch size varied little across years; however, clutch size tended to decrease over the course of a season, regardless of bird species. Daily nest survival rates did not differ markedly among bird species, but did vary substantially among years, suggesting that year-dependent factors were affecting nest success among all species similarly.

A field test of the area search method for measuring breeding bird populations

Abstract This paper evaluates the effectiveness of the area search method to measure breeding landbird populations at the plot level. During June 1999, 10 plots in grassland and shelterbelt habitats of north-central South Dakota were surveyed three times using the area search method. The results were then compared with those simultaneously obtained by the spot mapping census method, which served as the standard for comparison. Area searches detected an average of 96.0% of the landbird species present on the grassland plots, and 84.2% of the species on the shelterbelt plots. Species accumulation curves were identical between techniques, suggesting that an increase in number of visits to each plot would likely increase the number of species detected during area search surveys. Estimates of territory density from spot mapping were available for five passerine species. Across all species, area searches underestimated territory densities by an average of 50% when visit data were summarized by taking the average. When data were summarized using the maximum value among visits to each plot, area searches underestimated territory density by an average of 26%. Precision of density estimates using area search was similar between summarization methods, and was generally lower in comparison to spot mapping. Across all species, area search and spot mapping density estimates were strongly associated, suggesting that area search has potential as an index to abundance. However, correlation coefficients in abundance varied considerably within individual species. Since area search surveys typically underestimated both species richness and density of territories, further experimentation with increased survey duration is warranted.

Breeding Abundance and Distribution of Long-billed Curlews (Numenius americanus) in North America

Abstract A population survey for Long-billed Curlews (Numenius americanus) was completed in the western United States and Canada in 2004 and 2005. This survey was conducted during the early breeding season, using a stratified random sample from habitat strata. The survey design was a 32-km road transect with 40 five-min point counts at 800-m intervals. Detection probabilities were estimated using the removal method in which observations in one-min intervals were removed from further consideration. Model selection based on Akaike’s Information Criterion resulted in a model where detection probability varied among observers, but was constant throughout the point count for each observer. Estimated detection probabilities for the point count duration were greater than 0.68 for all observers. Counts were adjusted for detection probability and then used to estimate the mean density within surveyed point count plots. Overall, the range-wide estimate of total population size was 161,181 individuals. The estimates were 183,231 individuals for 2004 and 139,131 for 2005, with corresponding 90% confidence intervals of 113,324 to 422,046 and 97,611 to 198,252, respectively. In addition to estimates for both the United States and Canada, population densities were estimated for geographic sub-regions: Bird Conservation Regions, Shorebird Planning Regions, administrative regions, and for each Canadian province. Issues and assumptions inherent in the study design and their implications are discussed.

Great Blue Heron deaths caused by predation on Pacific lamprey

Etude de la mort accidentelle de predateurs causee par leurs proies. Description de deux cas relatifs a Ardea herodias et a Entosphenus tridentata

Multiscale Habitat Selection by Long-Billed Curlews (Numenius americanus) Breeding in the United States

Abstract. Long-billed Curlew (Numenius americanus) populations have declined during the past 150 years in part due to destruction and fragmentation of grasslands used during the breeding season. Here, multiscale habitat characteristics best predicting number of Long-billed Curlews, detected during range-wide surveys conducted throughout the United States in 2004 and 2005, were determined. Long-billed Curlews were most often observed in habitats classified primarily as grassland habitat and secondarily as shortgrass or pasture/rangeland, all with low vegetation heights (i.e. 4–15 cm). Numbers of Long-billed Curlews were positively associated with wetland habitats on a local scale and hay/pasture areas on a landscape scale, but negatively associated with shrub/scrub on local and landscape scales and evergreen forests on a landscape scale. The study confirmed the importance of grassland, cropland, pasture and wetland habitats for breeding Long-billed Curlews across its geographic range in the United States. These results reinforce the need to conserve, manage, or create contiguous tracts of grasslands containing emergent wetlands for Long-billed Curlews throughout the breeding season and their range in the United States.

REPRODUCTIVE BIOLOGY OF CANYON WRENS IN THE FRONT RANGE OF COLORADO

Abstract Canyon Wrens (Catherpes mexicanus) occur throughout the semiarid regions of the western United States in habitats dominated by canyons and steep rock formations. Their inaccessible habitat has made them one of the least studied among North American birds. We studied a population of Canyon Wrens in the Front Range of Colorado, documenting many aspects of their breeding biology. We report on territory density and size, nest site characteristics, nesting phenology, nesting success, and nestling development.

The Effect of Habitat Edges on Nest Survival of Sprague's Pipits

Abstract We explored the relationship between Spragues Pipit (Anthus spragueii) nest (n  =  125) survival and the distance from their nests to grassland edge and other linear features on Bowdoin National Wildlife Refuge in north-central Montana from 1997 to 2007. Specifically, we studied the effect of distance to roads (secondary paved road and tertiary improved and unimproved dirt roads), an agriculture field, an active railroad right-of-way, and lacustrine shoreline on nest daily survival rate (DSR). The overall DSR was 0.95 ± 0.0057 (SE) with a 95% confidence interval of 0.94–0.96. We considered how models with distance thresholds (within 50, 100, 200, or 300 m) affected DSR while controlling for important covariates. None of the distance models improved the model over the minimum AICc model containing only non-distance covariates. There was no support for distance to any of the edges, including roads, having an effect on DSR relative to the minimum AICc model that contained three non-distance covariates.