Variation in Surrogate Breeding Habitat Quality Between Continuously Grazed Rangelands and Late-Cut Hayfields for a Threatened Grassland Birds

Pintaric, Alice Lea; Reid, Ron; Nol, Erica

doi:10.1016/j.rama.2019.01.001

Cited by 3 publications

(11 citation statements)

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“…This is likely because the continuous variable stocking rate provides a better overall representation of grazing pressure or lack thereof (i.e., hayfields, ungrazed pastures, restored fields, fallow fields, and pastures grazed before 21 May or after 23 June had a stocking rate of 0 cattle-days/ha). Additionally, in some grazed pastures with low stocking rates, Bobolinks still reproduced successfully (MacDonald and Nol 2017, Campomizzi et al 2019, Pintaric et al 2019). Although we categorized fields based on their use, there are probably within-field variables that help to explain nest survival when cattle are not present, e.g., vegetation density (Warren and Anderson 2005) and vegetation height (Pintaric et al 2019) around each nest.…”

Section: Discussionmentioning

confidence: 94%

“…This ease of movement coupled with the increased ability of a predator to observe parental activity and nest locations in shorter vegetation may enable greater instances of nest predation to occur in grazed pastures compared to ungrazed areas (Sutter and Richison 2005). Studies investigating the direct effects of cattle grazing on nest survival have found that the percent of nests trampled increases as cattle density increases and that the potential for nest trampling increases exponentially with the length of time cattle remain in a field (Jensen et al 1990, Perlut and Strong 2011, MacDonald and Nol 2017, Campomizzi et al 2019, Pintaric et al 2019. In contrast, Bleho et al (2014) found that rates of trampling of grassland bird nests by cattle were low in Canada, although the majority of their data were from grasslands in Alberta, Saskatchewan, and Manitoba, with a small sample of duck nests in the Great Lakes-St. Lawrence Lowlands in Québec where nest destruction by cattle was highest.…”

Section: Discussionmentioning

confidence: 99%

“…Additional variables that have been found to influence nest survival include field use, field area, and distance to forest edge. Studies comparing grassland bird nest survival across field uses have shown that nests are more successful in late-cut hayfields in which harvest is delayed until after nesting, compared to cattle pastures (Perlut et al 2006, MacDonald and Nol 2017, Pintaric et al 2019, ungrazed areas compared to grazed pastures (Temple et al 1999), and restored fields compared to row crops (Patterson and Best 1996). Field use, i.e., pasture and hayfield, was not found to affect the relationship between distance to edge and daily nest survival for Bobolinks (Renfrew et al 2005, Perkins et al 2013.…”

Section: Introductionmentioning

confidence: 98%

“…These gaps are important to address given that daily survival rate, i.e., the probability a nest survives one day (Mayfield 1961, Dinsmore et al 2002, is a useful metric, albeit imperfect (Jones et al 2005), for informing conservation efforts by identifying areas that are most conducive to successful reproduction. We specifically addressed how daily survival rates of Bobolink nests vary across land-cover types and uses at different spatial scales by collating Bobolink nest monitoring data from previous projects that had various objectives (MacDonald and Nol 2017, Campomizzi et al 2019, Pintaric et al 2019 and collecting additional nest data to assess which variables had the greatest influence on daily survival rates.…”

Section: Introductionmentioning

confidence: 99%

“…We also predicted that landscapes with more grassland cover and less forest cover would positively affect daily survival rate of Bobolink nests because landscape composition strongly influences predator assemblages and thus nest predation. Additionally, we predicted that the daily survival rate of Bobolink nests would vary among regions and across the breeding season because of potential differences in predator and prey abundance and vegetation height caused by variation in annual precipitation and differences in land use and management (George et al 1992, Grant et al 2005, Pintaric et al 2019.…”

Section: Introductionmentioning

confidence: 99%

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Factors affecting Bobolink nest survival across grassland types

Fromberger¹,

Campomizzi²,

Lebrun‐Southcott³

et al. 2020

ACE

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Bird Ecology and Conservation Ontario ABSTRACT. Grassland birds, including Bobolinks (Dolichonyx oryzivorus), have experienced steep population declines across their breeding range in North America. Because of these declines, Bobolinks were listed as threatened by the Ontario and Canadian governments. We assessed nest survival across land-cover types and uses to identify pertinent factors important for conservation of this species-at-risk. We analyzed nest survival for 463 Bobolink nests monitored over 6 years from 3 regions across southern and eastern Ontario, Canada. We used RMark to analyze daily survival rate of nests by assessing 53 models that incorporated temporal, local, and landscape variables. Daily survival rate of Bobolink nests was strongly associated with cattle (Bos taurus) stocking rate (cattle-days/ ha) and date. Daily survival rate decreased across the nesting season from 0.98 (CI 95% = 0.97-0.99) to 0.92 (CI 95% = 0.87-0.95). Stocking rate was the only important local variable and was negatively associated with daily survival rate, which decreased from 0.96 (CI 95% = 0.96-0.97) to 0.69 (CI 95% = 0.51-0.82) as stocking rate increased from 0 to 243 cattle-days/ha. Landscape variables, including region, percent forest, cropland, and grassland within 2, 5, and 10 km, were not in competitive models. Our results suggest that all field uses we studied have potential for conservation actions because daily survival rate of nests did not vary significantly across late-cut hayfields, fallow fields, restored grasslands, or pastures; however, stocking rate is important in pastures. In grazed pastures where Bobolink conservation is a priority, we recommend keeping stocking rates low (≤ 40 cattle-days/ha) when most Bobolink nests are active, e.g., 21 May (earliest date of incubation) through 30 June (one week after median date of fledging for first nesting attempts) in our study area. pendant la période d'activité de la plupart des nids de goglus des prés, c'est-à-dire du 21 mai (la date d'incubation la plus précoce) au 30 juin (une semaine après la date médiane d'envol des oisillons pour la première tentative de nidification) dans notre zone d'étude.

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Factors affecting Bobolink nest survival across grassland types

Fromberger¹,

Campomizzi²,

Lebrun‐Southcott³

et al. 2020

ACE

Self Cite

View full text Add to dashboard Cite

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Fully accounting for nest age reduces bias when quantifying nest survival

Weiser

2021

Ornithological Applications

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Accurately measuring nest survival is challenging because nests must be discovered to be monitored, but nests are typically not found on the first day of the nesting interval. Studies of nest survival therefore often monitor a sample that overrepresents older nests. To account for this sampling bias, a daily survival rate (DSR) is estimated and then used to calculate nest survival to the end of the interval. However, estimates of DSR (and thus nest survival) can still be biased if DSR changes with nest age and nests are not found at age 0. Including nest age as a covariate of DSR and carefully considering the method of estimating nest survival can prevent such biases, but many published studies have not fully accounted for changes in DSR with nest age. I used a simulation study to quantify biases in estimates of nest survival resulting from changes in DSR with nest age under a variety of scenarios. I tested four methods of estimating nest survival from the simulated datasets and evaluated the bias and variance of each estimate. Nest survival estimates were often strongly biased when DSR varied with age but DSR was assumed to be constant, as well as when the model included age as a covariate but calculated nest survival from DSR at the mean monitored nest age (the method typically used in previous studies). In contrast, biases were usually avoided when nest survival was calculated as the product of age-specific estimates of DSR across the full nesting interval. However, the unbiased estimates often showed large variance, especially when few nests were found at young ages. Future field studies can maximize the accuracy and precision of nest survival estimates by aiming to find nests at young ages, including age as a covariate in the DSR model, and calculating nest survival as the product of age-specific estimates of DSR when DSR changes with nest age.

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Evaluating the ability of occurrence models to predict nest locations and associated vegetation

Fogarty

Fleishman

Zillig

2021

Ibis

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Occurrence models are frequently used to infer characteristics of habitat and inform management plans for large areas, but the extent to which these models predict reproduction, or the environmental characteristics associated with reproduction, is uncertain. We examined whether occurrence models based on point‐count data, and vegetation attributes within 50 m of presences, predicted the locations where birds were nesting in the Great Basin, USA. This work has practical relevance given that occurrence data require less time and effort to collect than direct measures of reproduction. We hypothesized that occurrence models would better characterize where two nest stratum generalists, Brewer's Sparrow Spizella breweri and Green‐tailed Towhee Pipilo chlorurus, nest than where a nest stratum specialist, American Dusky Flycatcher Empidonax oberholseri, nests. First, we compared which environmental covariates were associated with occurrence, via a model fitted to point‐count data, and nest locations, via a model fitted to data from confirmed nests. Second, we used data on the vegetation within 50 m of known nests to evaluate whether predictions from our occurrence model accurately classified the presence of nests. Third, we examined whether vegetation within 5 m of a known nest differed from vegetation at randomly chosen locations of equal size within 20–80 m of the nest. Occurrence models classified nest locations with relatively high accuracy for Brewer's Sparrow and American Dusky Flycatcher, and with moderate accuracy for Green‐tailed Towhee. Vegetation within 5 m of nests differed from that of random locations within 20–80 m, suggesting that even the nest stratum generalists based nest selection on fine‐grained attributes. Models that rely on point‐count data to examine species–habitat relationships assume that occupancy indicates breeding activity. Our results suggest that for some species, this is a valid assumption, although it is probably conditional on a well‐fitted occurrence model.

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Variation in Surrogate Breeding Habitat Quality Between Continuously Grazed Rangelands and Late-Cut Hayfields for a Threatened Grassland Birds

Cited by 3 publications

References 53 publications

Factors affecting Bobolink nest survival across grassland types

Factors affecting Bobolink nest survival across grassland types

Fully accounting for nest age reduces bias when quantifying nest survival

Evaluating the ability of occurrence models to predict nest locations and associated vegetation

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