Bobolink
| Scientific Name | Dolichonyx oryzivorus |
| Survival Strategy | Long-distance Migrant/ Neotropical migrant |
| Arrival in Upper Midwest | Late April to late May |
| Departure | Late July to early September |
| Destination | Brazil, Paraguay, and Argentina |
| Conservation Status | Least Concern |
Spring
Male Bobolinks return to the grasslands of the Upper Midwest in early May, with the females arriving a week later. The female builds a nest on the ground, concealed in tall grasses. She will typically lay five eggs in mid-May and incubate her young for 12 days. The young are born naked, blind, and helpless (altricial), and both parents work to feed their hatchlings protein-rich invertebrates. Although still flightless, the young will leave the nest by the tenth or eleventh day.
Summer
Sixteen days after hatching, the fledgling bobolinks can fly well enough to evade most predators. The adults will continue to feed their young for about a month after the birds leave the nest. When parents have completed their family obligations for the season, bobolinks gather in large flocks, molt, and add body fat before migrating. The migration to the bobolink’s winter range begins from late July to early September.
Fall
Bobolinks are neotropical migrants and will travel by night more than 5000 miles to the pampas region of southwestern Brazil, Paraguay, and Argentina.
Winter
Bobolinks spend the winter in massive flocks in the native grasslands of the Pampas and cultivated fields, predominately rice.
Behavior
Defending Territory
The male bobolink vigorously defends his territory, which averages about one acre, from neighboring males. Defensive behaviors include high-speed aerial chases and face-to-face (feet-to-feet) aerial fights, similar to young roosters battling for dominance in a farmyard. Parallel walks are performed by two males walking across from each other along their shared territorial border while showing signs of hostility. The aggressive behavior often includes bill-flipping, nodding, and song-spread displays (like an angry red-winged blackbird). Parallel walks can continue for up to three hours. Once the eggs hatch and the male begins feeding his young, the territorial behavior ends.
Physiology
Internal Compass
The bobolink’s ability to detect Earth’s magnetic field (magnetoreception) is an essential tool for finding its way during migration. Although the research is still ongoing, it seems that cryptochromes, light-sensitive proteins found in birds’ eyes, might be the magnetoreceptor that allows some animals to sense the direction of the magnetic field. Additionally, magnetite crystals in the tissues around the olfactory bulb enable the bird to detect the strength of the magnetic field.
Star Maps
Bobolinks also use the location of stars for navigation. Unlike magnetoreceptors, the star compass is not an innate ability; it must be learned. Hatch-year birds develop their star map by observing stars rotating in the night sky and detecting the center of rotation. In one study, hand-raised birds that had never seen the night sky could not navigate. Another study found that it takes at least 14 nights of “star watching” for migratory birds to form a star compass.
Research on animal navigation is moving forward on many fronts. As our knowledge increases, some hypotheses will need to be refined or abandoned, while others will become stepping stones to new theories.
Diet
The bobolinks diet consists of insects and the seeds of native and cultivated plants such as rice. The bobolink’s species name, “oryzivorus,” means “rice-eating.”
Lifespan and Mortality
Bobolinks often live for 4 to 6 years.
Predators
Adult bobolinks are preyed on by cooper’s hawks, northern harriers, and merlins.
Bobolink eggs and nestlings are eaten by garter snakes, sandhill cranes, crows, skunks, thirteen-lined ground squirrels, cats, and dogs.
Weather
Cold temperatures, rainy weather, and the flooding of nest sites are significant causes of nestling mortality.
Human Activity
When bobolinks feed in rice fields in their winter range, they are often exposed to organophosphate pesticides and shot as pests. Mowing of hayfields during the breeding season destroys bobolink nests.
Climate Vulnerability
The range of the bobolink will likely decrease in area and shift northward due to a warming climate.
Never Stop Learning
Fact Check: Credit for the bobolink’s common name is often attributed to the poem “The Bobolink,” written by William Cullen Bryant in 1864. However, in 1827 John James Audubon referred to “boblinks [sic]” in Birds of America (Plate 54. Rice Bird).
Ultra-Marathon: The bobolink migrates to southern South America every year, a 20,000 km (12,500 mi) round trip. In the course of a lifetime, this small songbird may travel about 4 or 5 times the circumference of the Earth.
References
| Renfrew, R.B., K.A. Peters, J.R. Herkert, K.R. VanBeek, and T. Will. 2019. A full life cycle conservation plan for Bobolink (Dolichonyx oryzivorus). U.S. Fish & Wildlife Service. https://partnersinflight.org/wp-content/uploads/2019/07/A-Full-Life-Cycle-Conservation-Plan-for-Bobolink.pdf |
| Bobolink – American Bird Conservancy https://abcbirds.org/bird/bobolink/ |
| Renfrew, R., A. M. Strong, N. G. Perlut, S. G. Martin, and T. A. Gavin (2020). Bobolink (Dolichonyx oryzivorus), version 1.0. In Birds of the World (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.boboli.01 |
| Wisconsin All-Bird Conservation Plan: Bobolink http://www.wisconsinbirds.org/plan/species/bobo.htm |
| How Climate Change Will Reshape the Range of the Bobolink https://www.audubon.org/field-guide/bird/bobolink |
| Watch: How do birds use Earth’s magnetic field? https://wildlife.org/watch-how-do-birds-use-earths-magnetic-field/#:~:text=A%20protein%20inside%20songbirds’%20eyes,in%20how%20the%20animals%20navigate.&text=They%20showed%20that%20in%20birds,don’t%20migrate%20like%20chickens. |
| Wiltschko R, Wiltschko W. 2019 Magnetoreception in birds. J. R. Soc.Interface 16: 20190295. http://dx.doi.org/10.1098/rsif.2019.0295 |
| Plate 54. Rice Bird, John James Audubon’s Birds of America https://www.audubon.org/birds-of-america/rice-bird |
| Anna Zolotareva, Gleb Utvenko, Nadezhda Romanova, Alexander Pakhomov, Nikita Chernetsov; Ontogeny of the star compass in birds: pied flycatchers (Ficedula hypoleuca) can establish the star compass in spring. J Exp Biol 1 February 2021; 224 (3): jeb237875. doi: https://doi.org/10.1242/jeb.237875 |