A Multicriteria Decision Analysis For Identifying Priority Conservation Areas For Grassland Birds

Biodiversity conservation frequently competes with the needs of society for agricultural production and development. However, properly designed and efficiently implemented conservation programs can be used to integrate wildlife and human needs. We tested the efficacy of multicriteria decision analysis as a tool to select priority areas for conservation in human-dominated landscapes using grassland birds in the northeastern US as a test case. We created detailed GIS layers including landscape- (forest, grassland, development, and roads within a 3000-m buffer around each grassland patch) and patch-level (size, management, and conservation status) criteria important in grassland bird habitat selection and conservation. We developed a set of 36 scenarios in which we varied the relative weights associated with different patch attributes. A sensitivity analysis showed that the habitat quality score for each patch was less sensitive to changes in weights at the landscape level, and more sensitive to changes at the patch level. Integrating the GIS dataset into a multicriteria decision analysis framework, we produced maps in which grassland patches were ranked based on habitat quality and used these maps to identify priority conservation areas. Grassland blocks of \u3e100 ha were mainly concentrated in 2 regions and were identified as priority sites that had the highest quality values for grassland bird conservation. This approach resulted in maps that managers can use to focus conservation efforts. The integration of GIS with multicriteria decision analysis can serve as a model for researchers to help set priorities for land conservation for other species and in other regions

Management Schemes, Not Philopatry Or Breeding Experience, Affect Nest Success Of Two Songbirds In Vermont Hayfields

Songbirds can benefit from natal philopatry through prior knowledge about site‐specific resources and local adaptation to environmental conditions. Likewise, breeding experience may also play a role in reproductive success. However, for birds that breed in managed habitats, management activities may overwhelm any potential benefits of philopatry or breeding experience. We examined the effect of site fidelity on reproductive success in 1,823 bobolink and Savannah sparrow nests in agricultural grasslands in Vermont, USA. From 2003–2019 we monitored the nests of 51 female Savannah sparrows and 72 female bobolinks that returned to breed on or near fields in which they hatched between 2002 and 2018). Using program MARK, we found that daily nest survival (DNS) differed between species and grassland treatment types and was not affected by philopatry. Bobolinks had greater DNS than Savannah sparrows, and DNS was generally greater on late‐hayed fields than either early‐hayed fields or rotationally‐grazed pastures. Our results show that despite the potential for increased fitness through site fidelity or breeding experience, agricultural management has an equal or greater influence on female reproductive success

Mixed Consequences Of Divorce On Reproductive Success Of Songbirds Nesting In Agricultural Hayfields

Agricultural management, particularly haying, can cause synchronous nest failure of ground-nesting songbirds. As a consequence, these birds may subsequently renest and choose a new social mate (divorce). This study (1) quantified within-year and between-year divorce rates of grassland songbirds, and (2) determined if divorce rates differed after haying or predation-caused nest failure, and if so, whether divorce influenced reproductive success. From 2002 to 2017, we monitored 121 Bobolink (Dolichonyx oryzivorus) pairs and 436 Savannah Sparrow (Passerculus sandwichensis) pairs in an agricultural region of Vermont, USA. Within-year and between-year divorce rates were 0–84.9% for Bobolinks and 17–69.1% for Savannah Sparrows. Between years, Bobolinks, but not Savannah Sparrows, were more likely to divorce after nest failure, but haying did not influence divorce rates. Within years, Savannah Sparrows were more likely to divorce after nest failure, but as with Bobolinks, divorce rates in Savannah Sparrows were not different between nests that failed due to haying or predation. Across all Savannah Sparrow renests, divorce had no influence on the number of young fledged per female. However, between years, female Bobolinks that divorced fledged more young in their first attempt while those that did not divorce fledged more young in their second attempt. This study showed that pairing decisions were not differentially affected by cause of nest failure. Further, we identified no reproductive benefit to divorce. Our results indicate no adaptive benefit and potentially a significant reproductive cost to divorce, and that these effects vary between species

Aggressive Response Of Adult Bobolinks To Neck Ligatures On Nestlings

We monitored provisioning behavior at 18 Bobolink (Dolichonyx oryzivorus) nests during 240.5 min of videotape data from June to July 2006, and observed 64 nest visits by adults while nestlings were fitted with neck ligatures. Adults pecked or pulled at the ligatures, often aggressively, at 72% of nests (n = 18) and 52% of visits (n = 64). These behavioral responses by adults indicate the neck ligature technique is more invasive than previously believed. We documented no mortality as a result of ligature placement, but researchers should minimize the time that ligatures are in place to reduce stress to both parents and nestlings

Minor Fitness Benefits For Edge Avoidance In Nesting Grassland Birds In The Northeastern United States

Grassland birds are often affected negatively by habitat fragmentation. Outcomes include greater nest predation and brood parasitism, decreased colonization rates of small, isolated patches, and greater nest density in remnant core habitats. These effects have been well documented in the Midwest, but little is known about fragmentation and edge effects on grassland birds in the fragmented agricultural fields within the forested landscapes of the northeastern United States. From 2002 to 2010, we assessed how edges and edge types affected nest-site location and daily nest survival (DNS) of Savannah Sparrows (Passerculus sandwichensis) and Bobolinks (Dolichonyx oryzivorus) breeding in 11 fields (range: 13.2–38.3 ha; mean = 21.1 ha) within a large agricultural region of Vermont. Mean (± SD) distance to edge was 80.3 ± 39.6 m for Savannah Sparrows (n = 995) and 94.5 ± 56.5 m for Bobolinks (n = 652). Both species nested significantly less than expected within 50 m of the edge. For Savannah Sparrows nesting within 50 m of the edge, DNS increased with increased distance from the edge. Birds initiating nests later in the season nested closer to edges, but renests were farther from edges than first nests. Distance to edge had no detectable consequence for Bobolink nest success. Both species used portions of fields near hedgerows less than expected but used wetland, forest, agricultural, road, and developed edges in proportion to availability. For both species, DNS did not vary among edge types. Although edges were used less than expected, nesting near edges had only minor consequences for nest success

Agriculture Is Adapting To Phenological Shifts Caused By Climate Change, But Grassland Songbirds Are Not

Migratory birds time their migration based on cues that signal resource availability for reproduction. However, with climate change, the timing of seasonal events may shift, potentially inhibiting the ability of some species to use them as accurate cues for migration. We studied the relationship between phenological shifts and reproduction by long- and short-distance migratory songbirds—Bobolinks (Dolichonyx oryzivorus) and Savannah Sparrows (Passerculus sandwichensis). Our study population breeds in hayfields and pastures in Vermont, USA, where farmers are also changing management activities in response to climate change. From 2002 to 2019, we monitored nest initiation dates to quantify correlations with environmental factors and the timing of nest initiation. We collected historical and projected precipitation and temperature data for the breeding grounds, and their respective wintering and stopover sites, the North Atlantic Oscillation (NAO) and the El Niño Southern Oscillation (ENSO). We predicted that winter conditions experienced by the short-distance migrant, the Savannah Sparrow, but not the long-distance migrant, the Bobolink, would explain the timing and success of nesting, however that this timing would be misaligned with changes in agricultural practices by hay farmers. Nest initiation dates did not show significant directional change for either species, but did vary among years. Interannual variation in Savannah Sparrow nest initiation dates was best explained by the interaction between precipitation on the breeding grounds and average wintering site (Wilmington, North Carolina). For Bobolinks, interannual variation in nest initiation dates was best explained by the interaction between breeding ground precipitation and average temperature in their fall stopover site (Barquisimieto, Venezuela). However, first haying dates in Vermont advanced by ~10 days over 18 years. These results suggest that the conflict between the timing of hay harvests and grassland songbird reproduction will increase, further threatening population processes for these species, as early harvests notably decrease annual productivity

The Potential Of Uncut Patches To Increase The Nesting Success Of Grassland Songbirds In Intensively Managed Hayfields: A Preliminary Study From The Champlain Valley Of Vermont

Changes in land use and intensification of agricultural practices are associated with declines of grassland songbird populations in North America. Hay harvests in the northeastern United States are occurring earlier and more frequently today than 30 years ago, resulting in substantially decreased nesting success of grassland songbirds on early-hayed fields. Few studies have examined whether uncut patches within fields cut during the breeding season can increase the nesting success of grassland songbirds. Twenty-nine artificial nests were placed in 17 uncut patches (mean = 0.337 ha, median = 0.103 ha) on four early-hayed fields in Shelburne, VT. Only one of the 29 artificial nests was depredated. Despite the small sample size, these data suggest that minimal nest cover may allow some reproductive success during hay harvest. Investigating the effect of patch size variation, patch placement, and vegetation structure within uncut patches would prove useful for potential management strategies. While most farmers will be unable to find and cut around grassland songbird nests, larger uncut patches (i.e., ≥1 ha) encompassing areas with high avian nesting densities may be a useful management strategy for grassland birds in intensively managed hayfields of the Champlain Valley of Vermont and New York or similar dairy-dominated agricultural landscapes

Diverse Demographic Factors Influence Apparent Juvenile Survival In A Migratory Songbird

To better understand the dynamics of avian populations and their role in population trends, we require an in-depth understanding of the factors influencing the survival of adults and juveniles. How-ever, assessing survival in juveniles is often challenging, especially in small, migratory species where individuals typically disperse from the study area and are not available for recapture in subsequent years. Bobolinks (Dolichonyx oryzivorus) are a long-distance migrant that exhibits natal philopatry in at least one population, allowing for more comprehensive juvenile survival analyses than in many other long-distance avian migrants. Using a 17-yr dataset from two sites representing a Vermont population of Bobolinks, we used Program MARK to assess factors influencing apparent juvenile survival, including factors related to nesting timing, nest attempt number, the philopatric behaviors of relatives, body mass, brood size, and agricultural management scheme. Our top models indicated that nest attempt number and whether or not a nest mate also survived and returned to breed locally were important factors explaining variation in apparent survival in juvenile Bobolinks. Specifically, juveniles from first nest attempts that fledged earlier in the season, with siblings that did not survive and return to breed locally, showed higher apparent survival. Factors such as site and the philopatric behavior of females associated with nests also appeared in top-ranking models, while factors such as body mass and brood size did not. These results indicate the importance of providing high-quality breeding habitat to birds early in the season when juvenile survival is greatest and indicate that individuals may be utilizing inbreeding avoidance strategies. These results provide new insight into the ecological and agricultural management factors influencing survival in migratory species that use managed habitats and underscore the importance of integrating juvenile survival data into current management schemes to better support this and other declining species

Natal and Breeding Dispersal of Bobolinks (Dolichonyx Oryzivorus) And Savannah Sparrows (Passerculus Sandwichensis) In An Agricultural Landscape

Dispersal is a key process in the metapopulation dynamics and genetic structure of spatially segregated populations. However, our knowledge of avian dispersal, particularly in migratory passerines, remains limited. We studied dispersal of Bobolinks (Dolichonyx oryzivorus) and Savannah Sparrows (Passerculus sandwichensis) to determine whether agricultural management practices affected dispersal patterns and habitat selection. From 2002 to 2006, we banded adults and nestlings on six focal hay fields and two pastures in the Champlain Valley of Vermont and New York and searched for banded birds within 1.5 km of Vermont field sites during two years. Natal dispersal distances were greater than breeding dispersal in both species, and breeding dispersal distances of Bobolinks were greater than those of Savannah Sparrows. Site fidelity was high in both species, with \u3e80% of detected adults and ~30% of detected natal dispersers returning to the same field in subsequent years. During natal dispersal, movement was random with respect to habitat quality. Adult Bobolinks dispersed to fields with annual reproductive rates greater than or equal to those of their original field; by contrast, adult Savannah Sparrows were more likely to move to or remain in low-quality habitats. During breeding dispersal, strong site fidelity took precedence over the effect of the previous year’s nest success on the probability of dispersal, particularly for Savannah Sparrows. Site fidelity has implications for management of agricultural fields because consistency of cropping patterns and cutting dates are important for maintaining populations of these species

Male Savannah Sparrows Provide Less Parental Care With Increasing Paternity Loss

Male parental care can significantly affect fledging success and, therefore, is a strong target of both natural and sexual selection. However, for songbird species that exhibit extra-pair paternity, males may reduce parental care based on how much paternity they have lost in a brood. We studied Passerculus sandwichensis (Savannah Sparrow) male parental care relative to the proportion of extra-pair young in the nest, to see if males adjusted care in response to increasing loss of paternity. Males brought less food (mass) with increasing rates of extra-pair paternity, although male provisioning did not influence fledging success. These results contrast with a previously published study of an island population of this species, where males provided more parental care with increased loss of paternity. We hypothesize that high rates of annual survival in this mainland population, where males have a greater potential for reproduction in future years, may explain this difference in behavior