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Bobolink - Dolichonyx oryzivorus
Species of Concern Native Species Global Rank :
G5
State Rank :
S3B
(see State Rank Reason below)
Agency Status USFWS :
MBTA; BCC10; BCC11; BCC17
USFS :
BLM :
FWP SWAP :
SGCN3
PIF :
3
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Copyright by: The Macaulay Library at the Cornell Lab of Ornithology, Ithaca, NY, all rights reserved.
State Rank Reason (see State Rank above)
Species has undergone recent large population declines in Montana and a patchwork of declines and increases have been documented in surrounding states and provinces.
Details on Status Ranking and Review
Bobolink (Dolichonyx oryzivorus ) Conservation Status Review
Population Size
Score U - Unknown
Comment Unknown.
Range Extent
Score G - 200,000-2,500,000 km squared (about 80,000-1,000,000 square miles)
Comment 380,531 square kilometers based on Natural Heritage Program range maps that appear on the Montana Field Guide
Area of Occupancy
Score U - Unknown
Comment Unknown.
Long-term Trend
Score E - Relatively Stable (±25% change)
Comment Species requires higher cover wetter grasslands with taller grasses. Some wetlands have been lost, but irrigation has increased since European arrival so overall trend is probably stable within +/-25% since European arrival.
Short-term Trend
Score C - Rapidly Declining. Decline of 30-50% in population, range, area occupied, and/or number or condition of occurrences
Comment Breeding Bird Survey (BBS) data for Montana is of highest credibility and shows a -6.4% decline per year or 48% decline per decade. Patchwork of declines and increases for surrounding states and provinces. There are stable trends for percentages of point counts and abundances on North Valley County Point Counts between 2001 and 2008.
Threats
Score F - Widespread, low-severity threat. Threat is of low severity but affects (or would affect) most or a significant portion of the population or area.
Comment Habitat loss, drought in relation to climate change, and mowing are probably the greatest threats to the species.
Severity Low - Low but nontrivial reduction of species population or reversible degradation or reduction of habitat in area affected, with recovery expected in 10-50 years.
Comment Species seems capable of responding quickly when water is returned to allow denser taller grasses.
Scope High - > 60% of total population or area affected
Comment >60% of population is impacted by drought and/or mowing/grazing.
Immediacy Moderate - Threat is likely to be operational within 2-5 years.
Comment Ongoing and accelerating
Intrinsic Vulnerability
Score C - Not Intrinsically Vulnerable. Species matures quickly, reproduces frequently, and/or has high fecundity such that populations recover quickly (< 5 years or 2 generations) from decreases in abundance; or species has high dispersal capability such that extirpated populations soon become reestablished through natural recolonization (unaided by humans).
Comment Not Intrinsically Vulnerable. Species matures quickly, reproduces frequently, and/or has a high fecundity such that populations recover quickly (< 5 years or 2 generations) from decreases in abundance. Species has good dispersal capabilities such that extirpated populations generally become reestablished through natural recolonization.
Environmental Specificity
Score B - Narrow. Specialist. Specific habitat(s) or other abiotic and/or biotic factors (see above) are used or required by the Element, but these key requirements are common and within the generalized range of the species within the area of interest.
Comment Narrow Specialist. Need deep cover grasslands which are very limited in Montana so in Montana their specificity is narrow.
Raw Conservation Status Score
Score
3.5 + 0.0 (geographic distribution) + 0.0 (environmental specificity) - 0.5 (short-term trend) + 0.0 (threats) = 3.0
General Description
The Bobolink is approximately 18 centimeters long with a stout, relatively short, pointed bill and sharply pointed tail feathers. The breeding male is black below, with a buff to whitish hind-neck, white scapulars, and white rump; early in spring the male has pale feather edgings. The breeding female is buffy with dark streaks on the back, rump, sides, and head. The juvenile resembles the breeding female but lacks streaks below. Fall adults and immatures resemble breeding female but are darker above and richer buff below. (Renfrew et al. 2015)
For a comprehensive review of the conservation status, habitat use, and ecology of this and other Montana bird species, please see
Marks et al. 2016, Birds of Montana. Diagnostic Characteristics
Breeding males are unique among North American passerines in being entirely black underneath and lighter above (Renfrew et al. 2015).
Species Range
Montana Range
Range Descriptions Western Hemisphere Range
eBird Occurrence Map
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Observations in Montana Natural Heritage Program Database
Number of Observations: 4475
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
Relative Density
Recency
SUMMER (Feb 16 - Dec 14)
Direct Evidence of Breeding
Indirect Evidence of Breeding
No Evidence of Breeding
WINTER (Dec 15 - Feb 15)
Regularly Observed
Not Regularly Observed
(Observations spanning multiple months or years are excluded from time charts)
Migration
In the Bozeman area, normal migration periods are May 20 to June 5 and August 15 to September 1.
Habitat
Nests built in tall grass and mixed-grass prairies. Prefers "old" hay fields with high grass-to-legume ratios.
Ecological Systems Associated with this Species
Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system,
even if point observations were associated with that system.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at:
mtnhp.org/requests ) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.
Literature Cited
Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
Maxell, B.A. 2000. Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
Food Habits
During the breeding season, diet consists of weed seeds and a large variety of larvae and insects. During the winter, diet consists of wild and domesticated rice, oats, other small grains, corn, tassels, weed seeds, and occasional insects.
Ecology
Strongly territorial during the early breeding season, but social and highly gregarious the rest of the year (Renfrew et al. 2015).
Reproductive Characteristics
Single brooded species with five to six eggs per brood. Incubation period 10 to 13 days. Young able to fly after 10 to 14 days.
Management
Bobolinks have declined in abundance by nearly 60% since 1970 (Renfrew et al. 2019). This is due largely to changes in land use, particularly loss of meadows and hay fields (Renfrew et al. 2015). Over the next two decades, it is predicted that populations of bobolinks will decline by 30%. This species depends on grasslands throughout its annual range, so conservation and management requires a geographically and biologically coordinated effort. Renfrew et al. (2019) identifies the strategies that merge biological, social, economic, and conservation needs and span a wide range of actions in greater detail in
A Full Life Cycle Conservation Plan for Bobolink (Dolichonyx oryzivorus) .
Stewardship Responsibility
References
Literature Cited AboveLegend: Dolichonyx oryzivorus ). The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/176
Additional ReferencesLegend: Do you know of a citation we're missing? Effects of recreation on Rocky Mountain wildlife: a review for Montana . [Montana]: Montana Chapter of the Wildlife Society.Dolichonyx oryzivorus ). Species Account Number 176. The Birds of North America Online (A. Poole, Ed.). Ithaca, NY: Cornell Laboratory of Ornithology; Retrieved 3/25/2008 from The Birds of North America Online database
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