Bobolinks are found in grassy fields and wetlands, earning them the nickname, “reedbirds”. They nest in hay fields, primarily in the eastern and Midwestern portion of the United States. Their winter region includes the grassy fields of Brazil, Uruguay, Paraguay, and northern Argentina. During migration, they stop along the way in rice fields, which has also earned them another nickname, “rice-birds”. Nesting survival rate is greater in areas near old fields and pastures. These birds select areas with tall grasses, away from woodlands, and often nest in the same areas each year. (Bollinger and Gavin, 2004; Bollinger, et al., 1990; Dechant, et al., 2001; Gavin, 1991; Lawyer, 1918)
- Habitat Regions
- Terrestrial Biomes
- savanna or grassland
- Aquatic Biomes
- lakes and ponds
- Other Habitat Features
Bobolinks exhibit sexual dimorphism during the breeding season. Because male breeding plumage is black, they blend into their tall grass habitat. In breeding plumage, males display an extensive white patch down their backs with a buttery rear crown and shiny black bill. When they are not in breeding plumage, males look very similar to females. Females and immature males have pale bills. All sexes and age-classes have short, cone-shaped bills. Female and immature male bobolinks are yellowish brown with black stripes falling behind the eyes and continuing down their back. There is a stripe above their eyes and in the center of their crown. Their wings are brown with stripes and their tails are short, pointy, and brown. (Chapman, 1890; Sibley, 2003)
- Sexual Dimorphism
- sexes colored or patterned differently
- male more colorful
- Average mass
- 43 g
- 1.52 oz
- Average length
- 17.78 cm
- 7.00 in
- Average wingspan
- 29.21 cm
- 11.50 in
Polygyny has been observed in many grassland bird species, including bobolinks. Males may be able to mate with up to 4 females. Polygyny often occurs when food sources are available in the surrounding area and there is ample vegetation for protection. The first mated females are called “primary females”, while the second mated females are “secondary females”. Male bobolinks perform flight displays as advertisements, which correlate with their health and the number of offspring produced. Males that continue their displays the longest are usually preferred by females. Bobolinks may also engage in extra-pair fertilizations. In such cases, members of the same brood are sired by different males. Extra-pair fertilizations are most frequently committed by younger males and older females. (Bollinger and Gavin, 1991; Gill, 2007; Mather and Robertson, 1992; Semenchuck, 1992; Wittenberger, 1980)
- Mating System
Bobolinks return to breeding grounds in late April to early June, depending on their range. These birds often return to the same breeding sites each year, although they may select a new breeding area if their previous area is no longer optimal. Females build shallow cup nests made of grasses and other plant materials, generally on the ground in grassland areas. These birds typically have only one brood per year, with 3 to 7 splotchy, gray or cinnamon colored eggs. The eggs are incubated by the female for about 10 to 13 days. Nestlings fledge in about 10 to 14 days, but are not able to fly for several additional days, in that time; nestlings hide in the tall grass. (Dechant, et al., 2001; Engels, 1962; Gavin, 1991; Petersen and Meservey, 2003; Semenchuck, 1992)
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- Breeding interval
- Bobolinks breed once a year.
- Breeding season
- Their reproductive season occurs from March to August.
- Range eggs per season
- 3 to 7
- Average time to hatching
- 12 days
- Average fledging age
- 1 weeks
- Average age at sexual or reproductive maturity (female)
- 1 years
- Average age at sexual or reproductive maturity (male)
- 1 years
Due to weather conditions and food availability, time spent with nestlings is divided between male and female bobolinks. When food is scarce, males tend to brood less and feed nestlings more, while females maintain feeding rates and brood nestlings more when food is scarce and weather is unfavorable. However, females brood nestlings less and feed them more when weather conditions are favorable, to compensate for the food scarcity. Nestlings coincide with the hatching of primary nestling food sources, such as caterpillar hatching. Bobolinks feed their young for 10 to 13 days. They have a mean clutch size of 5 eggs; there is no significant difference in the clutch sizes of primary and secondary females. The average number of fledglings from a primary nest is 3.4, while the average number of fledglings from a secondary nest is 2.3. (Wittenberger, 1978; Wittenberger, 1982)
- Range lifespan
- 2 to 9 years
- Range lifespan
- Average lifespan
- 5 years
- Average lifespan
As male bobolinks enter their breeding grounds, they quickly establish territories by song. Much of their behavior is linked to song. When attracting a mate, a male sings and shows off with aerial displays, to prove he has the best genes to ensure the next generation's survival. During nesting season, females often hide. If they are startled when they are near their nest, they often run through the grass, presumably to lead a predator away from their nestlings. Likewise, females do not land directly in their nests, but instead land several meters away and walk to their nest. Although these birds are territorial during nesting and breeding season, they are generally very gregarious and may be found in large flocks. During migration, bobolinks flock to roosting sites within one hour of dusk, particularly in areas near rice fields. Flocks include hundreds to thousands of individuals, which all depart about an hour from dawn. (Avery and Oring, 1977; Mather and Robertson, 1992; Petersen and Meservey, 2003; Renfrew and Saavedra, 2007; Semenchuck, 1992)
- Range territory size
- 4500 to 25,000 m^2
Their territory size varies from habitat to habitat. In a mixed hayland, their territory can be from 0.45 to 0.69 ha, but it can increase to 2.5 ha in dry, sparsely vegetated pastures. (Dechant, et al., 2001)
Communication and Perception
Bobolinks produce songs that sound like a bubbly laugh that warbles with short notes on a wide pitch range. Their call is a soft "chuk" and their flight call is a musical "bink" or "bwink". Song variations are based on male-male and male-female interactions. Evidence suggests aggression or sexual motivation affects song switching and song frequency. Each male sings the same two stereotyped song types, known as alpha and beta songs; the alpha is about 7 seconds, while the beta is 4.5 seconds. Each song ends with a series of warbled notes. While the alpha begins with alpha introductory notes leading into a series of interior notes, the beta song begins with its own beta introductory notes. Males flutter in fields, singing their song and exhibiting flight pattern displays. Bobolinks are also extraordinary due to their long distance migrations. This is partially achieved by their ability to navigate magnetic fields, due in part to magnetite (iron oxide) present in their skulls. (Ammer and Capp, 1999; Avery and Oring, 1977; Capp and William, 1991; Capp, 1992; Gavin, 1991; Gill, 2007; Mather and Robertson, 1992; Sibley, 2003)
Feeding young depends on food availability and weather conditions. Male bobolinks spend most of their time at the primary females' (first mated) nests, as opposed to the secondary female's nests. The food delivered to nestlings consists of Lepidoptera, sawfly, and arctiid larvae, as well as mayflies. In May, male bobolinks gorge themselves on dandelion seeds and occasionally eat cutworms. By June, males begin eating cinquefoil seeds, yarrow, Canadian thistle, false lupine, dock, and mallow; habitat permitting. While migrating, bobolinks make extended pit stops to feed in rice fields. Bobolinks are diurnal foragers and have night-time roosts on their migration routes. Bobolinks are ground predators, foraging for insects and seeds. (Lawyer, 1918; Renfrew and Saavedra, 2007; Wittenberger, 1978; Wittenberger, 1980; Wittenberger, 1982)
- Animal Foods
- Plant Foods
- seeds, grains, and nuts
The rate at which nests are predated upon varies across their range. Predation rates are low in Oregon and high in Wisconsin. Likewise, nests located near the forest's edge, tend to have a high mortality rate. Nests are protected primarily by vegetation, consisting of tall grasses and shrubs. Along with other grassland birds, bobolinks' primary predators are other birds, snakes, and mammals. (Vickery, et al., 1992; Wittenberger, 1978; Wittenberger, 1980)
- Anti-predator Adaptations
Bobolinks influence insect populations within grassland ecosystems. They are also affected by the brood parasitism of brown-headed cowbirds. Bobolinks exhibit aggressive behavior towards female brown-headed cowbirds to prevent the brood parasitism. (Capinera, 2010; Robertson and Norman, 1976)
- Ecosystem Impact
- disperses seeds
- brown-headed cowbirds (Molothrus ater)
Economic Importance for Humans: Positive
Bobolinks are beneficial to farmers because they primarily consume insects while they care for their young. From May to August, when they are found in North America, their stomach contents are composed of 70 to 90% pest insects and 5% useful insects. Outside of the breeding season, bobolinks consume plant material. (Capinera, 2010; Dechant, et al., 2001)
- Positive Impacts
- controls pest population
Economic Importance for Humans: Negative
Bobolinks may consume rice from agricultural fields and may generally act as agricultural pests. (Lawyer, 1918)
- Negative Impacts
- crop pest
Currently, bobolinks have a conservation status of 'least concern' according to the IUCN Red List of Threatened Species. This has changed over the past 100 years, as these birds were previously hunted in very large numbers due to their propensity for stealing crops; fortunately, this form of large scale hunting of bobolinks is generally no longer occurring. However, several threats exist for the species such as habitat destruction and climate change. Before European settlement, North America’s grasslands were vast (around 162 x 106 ha). The grasslands made up three regions: tallgrass prairie, shortgrass prairie, and mixed-grass prairie; which all but disappeared since European settlement, having been replaced with farms and croplands. The grasslands developed from natural fires and fires set by Native Americans. Bobolinks respond to the fires by inhabiting a site 2 years after a fire, prior to woodland growth. Habitat loss, fire prevention and development have impacted all grassland birds, leaving pockets of protected areas throughout North America. Climate change has also impacted bobolinks; global warming can cause major shifts in North American bird species, causing southern birds to replace bobolinks in parts of southern Minnesota. Grassland conservation benefits bobolinks and other fellow inhabitants. To protect the nesting grounds of grassland birds, a strategy of mowing half of large grasslands and leaving the other half idle has been proposed. This strategy encourages ecosystem diversity, depending on where the birds prefer to nest. (Azpiroz, et al., 2012; Brawn, et al., 2001; Gill, 2007; Horn and Koford, 2000; Petersen and Meservey, 2003)
Amber Simon (author), Northern Michigan University, Alec Lindsay (editor), Northern Michigan University, Leila Siciliano Martina (editor), Animal Diversity Web Staff.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
uses sound to communicate
living in landscapes dominated by human agriculture.
- bilateral symmetry
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
- active during the day, 2. lasting for one day.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
- female parental care
parental care is carried out by females
an animal that mainly eats seeds
An animal that eats mainly plants or parts of plants.
An animal that eats mainly insects or spiders.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
(as perception channel keyword). This animal has a special ability to detect the Earth's magnetic fields.
- male parental care
parental care is carried out by males
marshes are wetland areas often dominated by grasses and reeds.
makes seasonal movements between breeding and wintering grounds
having the capacity to move from one place to another.
- native range
the area in which the animal is naturally found, the region in which it is endemic.
an animal that mainly eats all kinds of things, including plants and animals
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
having more than one female as a mate at one time
- seasonal breeding
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
- tropical savanna and grassland
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
- temperate grassland
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
uses sight to communicate
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