A strangely-patterned sparrow-sized (6-8 inches) bird, the male Bobolink in summer plumage is most easily identified by its black head and breast, buff-brown nape, light-gray rump patch, and large white wing bars. In its winter plumage, the male Bobolink looses much of striking coloration, becoming mottled brown above and tan below with a brown-striped head. Female Bobolinks resemble winter males. The Bobolink breeds across a large part of southern Canada and the northern United States. This species is a long-distance migrant, wintering in southern South America. Migrating Bobolinks pass southward along the coast of the southeastern U.S.before continuing south to South America via Jamaica. In summer, Bobolinks breed in grasslands, prairie, and, more recently, agricultural fields. During the winter, this species utilizes habitats similar to those inhabited during the summer in the pampas region of South America. Bobolinks primarily eat seeds, grains, and insects. Most North American birdwatchers never visit the Bobolink’s winter range in South America. However, this species is relatively easy to observe during the summer months as it forages for food on the ground below tall grasses or on the grass stalks themselves. Bobolinks are most active during the day.
- Martin, Stephen G. and Thomas A. Gavin. 1995. Bobolink (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
- Peterson, Roger Tory. Birds of Eastern and Central North America. Boston: Houghton Mifflin, 1980. Print.
- eBird Range Map - Bobolink. eBird. Cornell Lab of Ornithology, N.d. Web. 20 July 2012. http://ebird.org/ebird/map/boboli.
- Dolichonyx oryzivorus. Xeno-canto. Xeno-canto Foundation, n.d. Web. 20 July 2012. http://xeno-canto.org/browse.php?query=Dolichonyx+oryzivorus.
- Bobolink (Dolichonyx oryzivorus). The Internet Bird Collection. Lynx Edicions, n.d. Web. 20 July 2012. http://ibc.lynxeds.com/species/bobolink-dolichonyx-oryzivorus.
- Clements, J. F., T. S. Schulenberg, M. J. Iliff, B.L. Sullivan, C. L. Wood, and D. Roberson. 2012. The eBird/Clements checklist of birds of the world: Version 6.7. Downloaded from http://www.birds.cornell.edu/clementschecklist/downloadable-clements-checklist
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Breeding
Regularity: Regularly occurring
Type of Residency: Breeding
Global Range: (200,000 to >2,500,000 square km (about 80,000 to >1,000,000 square miles)) Breeding range extends from southern British Columbia across southern Canada to Nova Scotia and Newfoundland, south to central Washington, eastern Oregon, northern Utah, Kansas, Illinois, Ohio, southern Pennsylvania, and central New Jersey, locally to north-central Kentucky, western North Carolina, and western Maryland (AOU 1998). During the northern winter, the range is in central and southern South America, mainly from Peru, eastern Bolivia, and central Brazil to northern Argentina (Stiles and Skutch 1989, Martin and Gavin 1995, AOU 1998); mostly in the pampas of southwestern Brazil, Paraguay, and Argentina (Ridgely and Tudor 1989, Martin and Gavin 1995).
Length: 18 cm
Weight: 47 grams
Catalog Number: USNM 61728
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Birds
Sex/Stage: Male; Adult
Preparation: Skin: Whole
Collector(s): C. Merriam
Year Collected: 1872
Locality: Ogden, Weber, Utah, United States, North America
- Type: Ridgway. November 1873. Bull. Essex Inst. 5 (11): 192.
Habitat and Ecology
Comments: Breeding habitat includes tall grass areas, flooded meadows, prairie, deep cultivated grains, and hayfields (AOU 1998). In New York, old hayfields, at least 8 years since planting and including a minimum of alfalfa, were important nesting habitat (Bollinger and Gavin 1992). Nests are on the ground in small hollows in areas of concealing herbaceous vegetation. Individuals tend to return to breed in the same area in successive years, especially if that site has had good bobolink productivity (Bollinger and Gavin 1989).
This species generally selects habitat with moderate to tall vegetation, moderate to dense vegetation, and moderately deep litter (Tester and Marshall 1961, Bent 1958, Harrison 1974, Bollinger 1995), lacking oody vegetation (Sample 1989, Bollinger and Gavin 1992). It is found in native and tame grasslands, haylands, lightly to moderately grazed pastures, no-till cropland, small-grain fields, oldfields, wet meadows, and planted cover (e.g., Conservation Reserve Program [CRP] fields, Permanent Cover Program [PCP] fields, and Dense Nesting Cover [DNC]) (Bent 1958; Speirs and Orenstein 1967; Birkenholz 1973; Harrison 1974; Skinner 1974, 1975; Stewart 1975; Joyner 1978; Johnsgard 1979, 1980; Faanes 1981; Kantrud 1981; Kantrud and Kologiski 1982; Renken 1983; Huber and Steuter 1984; Basore et al. 1986; Renken and Dinsmore 1987; Bollinger 1988, 1991, 1995; Sample 1989; Bollinger et al. 1990; Messmer 1990; Herkert 1991a, 1994a,1997; Bollinger and Gavin 1992; Bock et al. 1993; Johnson and Schwartz 1993; Dhol et al. 1994; Hartley 1994; Jones 1994; King and Savidge 1995; Madden 1996; Patterson and Best 1996; Prescott and Murphy 1996; Best et al. 1997; Dale et al. 1997; Delisle and Savidge 1997; McMaster and Davis 1998; Schneider 1998). Commonly it occurs in areas with high percent grass cover and moderate percent forb cover (Wiens 1969, Skinner 1974, Renken 1983, Renken and Dinsmore 1987, Sample 1989, Herkert 1994a, Madden 1996). Bollinger (1988, 1995) noted preference for haylands with high grass-to-forb ratios and avoidance of haylands with high legume-to-grass ratios; however, a forb component was beneficial for nesting cover.
Within mixed-grass pastures in North Dakota, abundance was positively associated with percent grass cover, litter depth, density of low-growing shrubs (western snowberry, Symphoricarpos occidentalis; silverberry, Elaeagnus commutata), vegetation density, and plant communities dominated by Kentucky bluegrass (Poa pratensis) and native grasses (Stipa, Bouteloua, Koeleria, and Schizachyrium) (Schneider 1998). Abundance was negatively associated with percent clubmoss (Selaginella densa) cover, bare ground, and plant communities dominated solely by native grass. Strongest vegetational predictors of the presence of bobolinks were decreasing bare ground, increasing litter, and increasing vegetation density. Madden (1996) found that the best predictors of occurrence in North Dakota mixed-grass prairie were increasing amounts of forb and grass cover, decreasing amounts of shrub cover, and decreasing frequency of native grasses.
In Illinois tallgrass prairie fragments, the best predictors of occurrence were mean number of live forb contacts, mean vegetation height, and mean grass height (Herkert 1994a). In another Illinois study, occurred only in patches of Kentucky bluegrass and were absent from tallgrass prairie (Birkenholz 1973).
In Nebraska, abundance in CRP planted to cool-season grasses was significantly and positively correlated with percent litter cover and negatively correlated with vertical density of vegetation (measured using a Robel pole) (Delisle and Savidge 1997). In tame CRP grasslands in Iowa, abundance was positively correlated with litter cover and grass canopy cover and negatively correlated with forb cover and the horizontal patchiness of vegetation (Patterson and Best 1996). Abundance in Wisconsin was highest in cool-season grasses, followed by wet pastures, bluegrass (Poa)/quackgrass (Agropyron repens) communities, and alfalfa (Medicago sativa/grass hayfields (Sample 1989). In New York tame hayfields, increased in abundance as the hayfields aged (Bollinger 1988, 1995). Older hayfields (more than 3 years old) were characterized by sparse, patchy, grass-dominated vegetation and high litter cover.
In Nebraska, boblinks nested in wet prairie, alfalfa, upland native prairie, domestic hayland, and wheat (Faanes and Lingle 1995). In Iowa they nested under or near native bluestem (Andropogon or Schizachyrium not specified) or Kentucky bluegrass (Kendeigh 1941). In Wisconsin boblinks nested at the bases of large forbs (Martin 1971). In Montana, nested in a wet-meadow pasture (Silloway 1904). In Ontario, they nested in a weedy meadow near a wetland; nests were built in the litter layer, had a canopy of dead grasses, and were surrounded by living vegetation 33-41 centimeters tall (Boyer and Devitt 1961, Joyner 1978). Boblinks have been found nesting in CRP fields in Iowa and Michigan (Best et al. 1997).
Boblinks occasionally nest in cropland. In Iowa, they nested at low densities in untilled fields of corn that were idle in the fall and spring and contained year-round crop residue, rather than in tilled fields or strip cover (Basore et al. 1986). In Wisconsin, a few were found in small-grain fields, but none were found in rowcrops (Sample 1989). Graber and Graber (1963) reported fairly heavy use of small grain fields in Illinois. The species was absent from cropland in Saskatchewan and Manitoba (Hartley 1994, Jones 1994).
During the nonbreeding season, boblinks also occur in rice fields, marshes, and open woody areas (AOU 1983).
In Argentina, bobolinks primarily use natural wet grassland habitats associated with main rivers and huge marshes (Di Giacomo et al. 2005).
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.
Bobolinks arrive in northern nesting areas late April-early May; males arrive a few days to a week before females (Terres 1980). Bobolinks are uncommon migrants in fall in Puerto Rico and the Virgin Islands, rare in spring (Raffaele 1983). Migration occurs mostly via the West Indies; small numbers reach Middle America (Ridgely and Gwynne 1989). Bobolinks are rare fall migrants in Costa Rica, mid-September to October, and are basically absent in spring (Stiles and Skutch 1989). They are transient in Colombia, mainly early September-late November and early March to mid-May (Hilty and Brown 1986).
Comments: Diet includes insects, seeds, grain (Terres 1980); mainly seeds (Stiles and Skutch 1989).
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 81 to >300
Comments: This species is represented by a large number of occurrences (subpopulations).
Comments: Total adult population size is unknown but certainly exceeds 1,000,000. Rich et al. (2004) estimated population size at 11,000,000. Concentrations of ~140,000 bobolinks have been observed in Bolivia (Renfrew and Saavedra 2007).
Bobolinks often are in large flocks during northward migration.
Life History and Behavior
Lifespan, longevity, and ageing
Clutch size is four to seven (usually five to six). Incubation, by female, lasts 11-13 days. Young are tended by both parents, leave nest at 10-14 days (still unable to fly). In some areas, individual females very rarely may produce a second clutch (unsuccessful) after the first brood fledges (Gavin 1984).
Molecular Biology and Genetics
Barcode data: Dolichonyx oryzivorus
There are 8 barcode sequences available from BOLD and GenBank. Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species. See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Dolichonyx oryzivorus
Public Records: 8
Specimens with Barcodes: 9
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: N4B - Apparently Secure
Rounded National Status Rank: N5B - Secure
IUCN Red List Assessment
Red List Category
Red List Criteria
- 2008Least Concern
- 2004Least Concern
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Reasons: Large nesting range in North America; many subpopulations; nesting range expanded with historical anthropogenic habitat changes; large population size, but has declined over the past several decades, likely due to incompatible agricultural practices in the nesting range and probably also in the winter range.
Global Short Term Trend: Relatively stable (=10% change)
Comments: Breeding Bird Survey (BBS) data for 1980-2007 indicate a significant decline averaging 3.0% per year; this rate of decline amounts to a 26% decline over 10 years. Three generations probably is roughly 15 years; a 3% annual decline over 15 years amounts to a 37% decline over an estimated three generations. However, BBS counts have been highly variable over the past 15 years, and the trend for that period appears to be a very small decline. Abundance declined much more steeply in the 1980s.
Global Long Term Trend: Unknown
Comments: Long-term trend (past 200 years) in unknown. Much habitat appears to have been lost in some areas due to intensive agriculture, but on the other hand the species likely increased its range with historical deforestation and agricultural development in eastern North America and with development and expansion of irrigated agriculture in the west (Martin and Gavin 1995).
Winter range in Argentina has decreased by at least 25% (Di Giacomo et al. 2005).
Breeding Bird Survey (BBS) data for 1966-2007 indicate a significant decline averaging 1.8 percent per year; this amounts to a 53% decline for the time period. BBS abundance (average number of birds per route) reclined from around 6 in the late 1960s and early 1970s to 3-4 in 2000-2007.
BBS data for 1966-2003 indicates widepsread declines throughout most of the range, with increasing trends that are much more geographaically restricted and mostly in the north-central United States.
Degree of Threat: High
Comments: Primary threat in the breeding range is habitat loss (Herkert 1997). Declines in some areas have been attributed to decrease in hayfield area, earlier and more frequent hay-cropping, and shift from timothy and clover to alfalfa; earlier, agricultural practices that converted wooded land to open land resulted in an increase in range (Bollinger et al. 1990, Bollinger and Gavin 1992).
Hay-cropping destroyed 16-23% of the yearly production of fledglings in upstate New York, with up to 29-45% in an area with intensive dairy farming (Bollinger et al. 1990; Bollinger, pers. comm.).
Bobolinks generally are considered to be an uncommon (Friedmann 1963, Martin and Gavin 1995) or rare (Martin 1967) host of the brown-headed cowbird.
Scope and severity of threats in the winter range are not well documented (Martin and Gavin 1995), but habitat loss is a significant concern in Argentina (Di Giacomo et al. 2005). Bobolink populations in winter in Bolivia face conservation threats because of the degree to which they concentrate in rice production regions, their status as a pest, and the pesticides currently used on rice (Renfrew and Saavedra 2007).
Restoration Potential: Plant late maturing hay species rather than legumes, ideally with no-till seeding (Jones and Vickery 1997).
Preserve Selection and Design Considerations: Minimum grassland size two to four hectares (Jones and Vickery 1997). Territories include both foraging and nesting areas (Martin 1967). Average territory size ranged from 0.45 to 0.69 hectares in a mixed hayland on a floodplain in Wisconsin (Martin 1967, 1971), 0.49 hectares at six tame hayfields in New York (Bollinger 1988), 1.4 hectares in a tame hayfield in Michigan (Raim 1975), and 2.6 hectares in a dry, sparsely vegetated pasture in Wisconsin (Wiens 1969). Appear to be area sensitive, preferring large grassland areas over small (Herkert et al. 1993). Herkert (1991b) reported that the minimum area on which Bobolinks were found was 10-30 hectares in Illinois tallgrass prairie fragments. The minimum patch size requirement in wet meadows in Nebraska was more than 40 hectares (Helzer 1996). Abundance in tallgrass prairie fragments was positively related to area (Herkert 1994b). Abundance also was positively correlated with fragment size in New York and Maine (Bollinger and Gavin 1992, Vickery et al. 1994).
In Minnesota tallgrass prairie, nest depredation and Brown-headed Cowbird (Molothrus ater) brood parasitism decreased farther from woody edges, and nest depredation rates were lower on large (130-486 hectares) than on small (16-32 hectares) grasslands (Johnson and Temple 1990). Nest productivity in Minnestoa was highest for nests in habitats far (more than 45 meters) from a forest edge (Johnson and Temple 1986). In Nebraska, abundance was lower near woody edges (less than 100 meters) than far (more than 100 meters) from woody edges (Helzer 1996).
Management Requirements: Prairie management to maximize nest productivity should provide large (more then 130 hectares), regularly burned prairies with no nearby wooded edges (Johnson and Temple 1990). Bollinger and Gavin (1992) recommended that, in an agricultural landscape, habitat patches be larger than 10-15 hectares. Timing of hay-cropping has large effects on reproductive success; Bollinger et al. (1990) recommended that conservation lands be hayed every 2-3 years, with cutting not to begin before mid-July. Hay should be removed to prevent thatch build-up. Will tolerate light, but not heavy, grazing, with grass heights of 8-12 inches. Burns should be conducted every 2-5 years, but do not burn all of one unit in one year (Jones and Vickery 1997).
BURNING: If habitat is not maintained, use declines significantly, possibly due to the accumulation of litter and encroachment of woody vegetation (Johnson 1997). Respond positively to properly timed burning or mowing treatments (Herkert 1991a, 1994b; Bollinger and Gavin 1992; Madden 1996; Johnson 1997). In Wisconsin, a field that was burned in April each year was occupied in early June; the year it was not burned, the field was occupied by mid-May (Martin 1971). Absent in Minnesota tallgrass prairie 1 year postburn but established territories 2 years postburn (Tester and Marshall 1961). Nest productivity in Minnesota was highest 1 year postburn, and the probability of encountering Bobolinks was highest on areas 1 year postburn (Johnson and Temple 1986). In Illinois tallgrass prairie fragments, preferred recently burned or mowed (burned or mowed 1-4 months prior to the breeding season) sites over areas burned more then 1 year previous or to unmowed areas (Herkert 1991a, 1994b). In North Dakota, abundance peaked 1-3 years postburn (Madden 1996, Johnson 1997), but declined 5 years postburn (Johnson 1997). Abundance in Maine declined in the burn year, but peaked 1-2 years postburn (Vickery 1993).
HAYLAND: In Nebraska, occurred more frequently in tallgrass hayland than tallgrass pasture (Helzer 1996). In North Dakota, Kantrud (1981) found the highest densities in hayland mowed the previous year, with lightly grazed areas containing the second highest densities. In Michigan and Wisconsin, were common in hayfields before mowing, but deserted these fields after the fields were mowed (Harrison 1974, Sample 1989). In Missouri, however, found in hayfields before and after mowing (Skinner 1974). In Illinois, a decline in abundance was significantly correlated to declines in the number of hectares of alfalfa, oats, and pasture in the northern one-third of the state from 1952 to 1992 (Herkert 1997). In Saskatchewan, were more abundant in emergency-mowed (mowed during drought years) tame hayfields than in native grassland, tame grassland, or annually mowed tame haylands (Dale 1992). Dale et al. (1997) found that abundance in Saskatchewan was higher in annually or periodically (idle for 4-8 years) mowed tame hayland than in idle native grassland.
GRAZING: In the Great Plains, measures of abundance indicated positive responses to moderate grazing in tallgrass, but negative responses to heavy grazing in shortgrass (Bock et al. 1993). In southeastern North Dakota, occurred in grazed areas that had few shrubs and moderate to deep litter (Messmer 1990). Higher densities were found in areas under a short-duration grazing treatment (involved a system of pastures rotated through a grazing schedule of about 1 week grazed and 1 month ungrazed) than in idle areas. In South Dakota, preferred lightly grazed (grazed by American bison [Bison bison]) areas over spring-burned areas (Huber and Steuter 1984). In southeastern South Dakota, preferred lightly grazed areas on typic ustoll soils (Kantrud and Kologiski 1982). In Missouri, were most abundant in lightly to moderately grazed tallgrass prairie and were not present in idle prairie (Skinner 1974, 1975). In Alberta, were found in tame pastures but not in native pastures (Prescott and Murphy 1996).
CONSERVATION RESERVE PROGRAM (CRP): Nested or were found in CRP fields in Illinois, Iowa, Michigan, Minnesota, Montana, Nebraska, North Dakota, and South Dakota (Johnson and Schwartz 1993, Patterson and Best 1996, Best et al. 1997, Delisle and Savidge 1997, Davison 1998). In North Dakota, higher densities were found in Dense Nesting Cover (DNC) planted to alfalfa and wheatgrass (Agropyron spp.) than in idle mixed-grass prairie (Renken 1983, Renken and Dinsmore 1987). In CRP fields in Nebraska, abundance was significantly higher in cool-season grasses than in warm-season grasses, possibly because of shorter vegetation in cool-season grasses (Delisle and Savidge 1997). King and Savidge (1995) found Bobolinks in tallgrass prairie and CRP planted to cool-season grasses but did not find them in CRP planted to warm-season grasses. In Manitoba and Saskatchewan, were found in native and tame DNC and in idle native grassland (Dhol et al. 1994, Hartley 1994); wheat fields were avoided (Hartley 1994). Also were found in Permanent Cover Program (PCP) lands in Canada (McMaster and Davis 1998). PCP is a Canadian program that pays farmers to seed highly erodible land to perennial grassland cover; it differs from CRP in the United States in that haying and grazing are allowed annually in PCP. In Canadian aspen parkland, occurred significantly more frequently in PCP than in cropland (McMaster and Davis 1998). However, their frequency of occurrence did not differ between hay and pasture sites within the parkland PCP sites. In North Dakota, were present in areas seeded to native grasses 1 year after seeding occurred (Higgins et al. 1984). In Wisconsin, occurred in a restored native tallgrass prairie site 3 years following seeding (Volkert 1992).
Global Protection: Very many (>40) occurrences appropriately protected and managed
Comments: Many occurrences are in protected areas, but some of these are not managed in a way that benefits bobolinks.
Relevance to Humans and Ecosystems
Stewardship Overview: Keys to management are providing large areas of suitable habitat (native and tame grasslands of moderate height and density, with adequate litter), controlling succession, and protecting nesting habitat from disturbance during the breeding season. Regardless of geographic location, avoid disturbing (e.g., haying, burning, moderately or heavily grazing) nesting habitat during the breeding season, approximately early May to mid-July (Bollinger 1991). Treatments can be done in early spring (several weeks prior to the arrival of adults on the breeding grounds) or in the fall after the breeding season (Martin and Gavin 1995).
GREAT PLAINS: Create large patches of habitat and minimize woody edges whenever possible to increase densities (Johnson and Temple 1990, Helzer 1996). In Nebraska, minimum patch size requirement for wet meadows was greater than 40 hectares, and abundance was lower near woody edges (less than 100 meters) than far (greater then 100 meters) from woody edges (Helzer 1996). Burn habitat once every 2-4 years to prevent encroachment of woody vegetation and remove deep litter (Johnson and Temple 1990, Madden 1996, Johnson 1997). Conduct controlled burns on Conservation Reserve Program (CRP) fields every 3-5 years to reduce dense vegetation (King and Savidge 1995). In Nebraska, Bobolink abundance was negatively correlated with vertical density of vegetation (Delisle and Savidge 1997). Burn large areas on a rotational basis, burning portions of the total area each year (Johnson 1997). Burn small areas periodically. Ensure that adjacent areas are burned in different years to create a variety of successional stages. Provide hayland areas, and mow as late as possible. In Nebraska, occurred more frequently in native hayland than pastures (Helzer 1996). Kantrud (1981) found densities to be highest in hayland mowed the previous year, with lightly grazed areas containing the second highest density. Dale et al. (1997) found that abundance in Saskatchewan was higher in annually or periodically mowed tame hayland than in native grassland. Delay mowing until after 15 July, by which time at least 70 percent of nestlings will have fledged in years of normal breeding phenology (Dale et al. 1997). To maintain dense cover in idle haylands, mow some fields in alternate years while leaving others idle for at least 3 years. Divide large fields in half, with each half being mowed in alternate years, thus ensuring productivity of hay and of birds. Lightly graze areas where Bobolinks have exhibited positive responses to this treatment; heavy or moderate grazing may have negative impact on populations (Kantrud 1981).
EAST AND MIDWEST: Delay treatments until late July or August to protect fledglings and late-nesting females (Bollinger 1991). Create large habitat patches (greater then 10-30 hectares) and minimize woody edges whenever possible (Bollinger and Gavin 1992). Use a rotating treatment schedule on several nearby prairie fragments to make a variety of successional stages available (Herkert 1994b). Adjacent patches of alternative habitat provide refuge for fledglings to escape from mowed areas and for late-nesting females (Bollinger et al. 1990). Create or maintain patches of relatively sparse, grass-dominated vegetation resembling old (more then 8 years since planted) hayfields (Bollinger and Gavin 1992). Scattered forbs (e.g., clover [Trifolium SPP.]) should be encouraged for nest-site cover. Bollinger (1988, 1995) found that a minimal forb component for nesting cover was beneficial, but Bobolinks preferred haylands with high grass-to-forb ratios and avoided haylands with high legume-to-grass ratios. Burn large areas (greater then 80 hectares) using a rotational system. Subunits of more than 30 hectares in area, or about 20-30 percent of the total area, should be treated in a year (Herkert 1994b). Johnson and Temple (1990) found lower rates of nest depredation of nests in recently burned (less then 3 years ago) areas in Minnesota. In small, isolated prairie fragments, burn more 50-60 percent of the total area at a time (Herkert 1994b). Mow or burn patches every 2-3 years to prevent excessive encroachment of woody vegetation (Bollinger and Gavin 1992, Herkert 1994a). In most years, delaying mowing until the end of June may allow young Bobolinks time to fledge (Harrison 1974). Graze at moderate levels to provide diverse grass heights and densities in areas where the average height of vegetation is 20-30 centimeters (Skinner 1974, 1975). Graze using a rotational system of two or more grazing units (Skinner 1974). This will increase the variation in grass heights and densities within and between units. To maintain plant vigor, do not graze warm-season grasses in tallgrass prairie to a height of less than 25 centimeters during the growing season (Skinner 1975).
Adults are 16–18 cm (6.3–7.1 in) long with short finch-like bills. They weigh about 1 oz (28 g). Adult males are mostly black with creamy napes and white scapulars, lower backs, and rumps. Adult females are mostly light brown, although their coloring includes black streaks on the back and flanks, and dark stripes on the head; their wings and tails are darker. The collective name for a group of Bobolinks is a chain.
Distribution and movements
They often migrate in flocks, feeding on cultivated grains and rice, which leads to them being considered a pest by farmers in some areas. Although Bobolinks migrate long distances, they have rarely been sighted in Europe—like many vagrants from the Americas, the overwhelming majority of records are from the British Isles.
Each fall, Bobolinks gather in large numbers in South American rice fields to feed on grain. This has earned them the name "Ricebird" in these parts. In Jamaica, however, they are called "Butterbirds" and are collected as food, having fattened up before passing through on migration.
Their breeding habitats are open grassy fields, especially hay fields, across North America. In high-quality habitats, males are often polygynous. Females lay 5 to 6 eggs in a cup-shaped nest, which is always situated on the ground and is usually well-hidden in dense vegetation. Both parents feed the young.
Males sing bright, bubbly songs in flight; these songs gave this species its common name.
Status and conservation
The numbers of these birds are declining due to loss of habitat. In Vermont, a 75% decline was noted between 1966 to 2007. Originally, they were found in tall grass prairie and other open areas with dense grass. Although hay fields are suitable nesting habitat, fields which are harvested early, or at multiple times, in a season may not allow sufficient time for young birds to fledge. This species increased in numbers when horses were the primary mode of transportation, requiring larger supplies of hay.
Emily Dickinson penned many poems about the bird (The text follows R.W. Franklin's edition; the numbering is 1620 in Franklin's edition, while it is listed as 1591 in Thomas H. Johnson's.)
- Evelina, won't ya ever take a shine to that moon?
- Evelina, ain't ya bothered by the Bobolink's tune?
Sophia Jewett ends her poem An Exile's Garden (1910) with a reference to a Bobolink.
- BirdLife International (2012). "Dolichonyx oryzivorus". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
- Page, Candace (25 June 2010). "1,100 miles in a day". Burlington, Vermont: Burlington Free Press. pp. 1A.
- "Collective nouns, groups of animals, terms for animal and other groups including birds". Hintsandthings.co.uk. 1980-04-28. Retrieved 2013-05-26.
- Who Put the Rainbow in the " Wizard of Oz? ": Yip Harburg, Lyricist - Harold Meyerson, Ernest Harburg - Google Books. Books.google.com. Retrieved 2013-05-26.
- The poems of Sophie Jewett - Sophie Jewett - Google Boeken. Books.google.com. Retrieved 2013-05-26.