| impacts of tree rows on grassland birds and potential nest predators: a removal experiment. | globally, grasslands and the wildlife that inhabit them are widely imperiled. encroachment by shrubs and trees has widely impacted grasslands in the past 150 years. in north america, most grassland birds avoid nesting near woody vegetation. because woody vegetation fragments grasslands and potential nest predator diversity and abundance is often greater along wooded edge and grassland transitions, we measured the impacts of removing rows of trees and shrubs that intersected grasslands on potenti ... | 2013 | 23565144 |
| spatiotemporal variation in mechanisms driving regional-scale population dynamics of a threatened grassland bird. | to achieve national population targets for migratory birds, landscape-level conservation approaches are increasingly encouraged. however, knowledge of the mechanisms that drive spatiotemporal patterns in population dynamics are needed to inform scale-variant policy development. using hierarchical bayesian models and variable selection, we determined by which mechanism(s), and to what extent, changes in quantity and quality of surrogate grassland habitats contributed to regional variation in popu ... | 2017 | 28649328 |
| bobolink polygyny in a homogeneous habitat: a test of the asynchronous settlement model. | | 1992 | 19426033 |
| haemosporidian parasite community in migrating bobolinks on the galapagos islands. | bobolinks (dolichonyx oryzivorus) migrate from their breeding grounds in north america to their wintering grounds in south america during the fall each year. a small number of bobolinks stop temporarily in galapagos, and potentially carry parasites. on the north american breeding grounds, bobolinks carry a least two of the four plasmodium lineages recently detected in resident galapagos birds. we hypothesized that bobolinks carried these parasites to galapagos, where they were bitten by mosquito ... | 2018 | 29988782 |
| doing more with less: removing trees in a prairie system improves value of grasslands for obligate bird species. | grassland birds endemic to the northern great plains have declined faster and more severely than any other avian guild on the continent. remaining prairie fragments that sustain breeding populations are continually converted to a disturbed state, or degraded by fragmentation. planted tree rows (shelterbelts) in prairie landscapes are a prominent feature and have been implicated in propagating negative edge effects on breeding birds, perhaps through harboring a diverse suite of nest predators. we ... | 2017 | 28460323 |
| the inheritance of song in passerine birds. remarks and observations on the song of hand-reared bobolinks and redwinged blackbirds (dolichonyx oryzivorus and agelaius phoeligniceus). | | 1904 | 17839724 |
| magnetic responses of the trigeminal nerve system of the bobolink (dolichonyx oryzivorus). | extracellular recordings using glass microelectrodes were made from the ophthalmic and supraorbital nerves of a transequatorial migratory bird, the bobolink. the rate of electrical activity was modified in 15% of the spontaneously active units by earth-strength alterations of the horizontal or vertical component of the ambient magnetic field using box coils. responses to magnetic stimulation included augmentation or inhibition of spontaneous activity, or an on-off or off response. responses to m ... | 1987 | 3683981 |
| responses to small magnetic variations by the trigeminal system of the bobolink. | electrophysiological recordings from the ophthalmic nerve and the trigeminal ganglion of the bobolink (dolichonyx oryzivorus) indicate the presence of units (14% of the spontaneously active cells) that are sensitive to small changes in the magnetic field. the most common response was an increase in the rate of spontaneous activity. the most sensitive units responded to changes of 200 nt (less than 0.5% of the earth's total field). other responses included reaction to a 0.5 hz sinusoidal variatio ... | 1990 | 2289162 |
| behavioural evidence for the use of magnetic material in magnetoreception by a migratory bird | the biophysical mechanism of vertebrate magnetic sensory perception has not been completely resolved. we here provide evidence for the use of a magnetic material (probably magnetite) by a vertebrate to detect the earth's magnetic field. the role of magnetite in bobolink (dolichonyx oryzivorus) orientation was assessed by magnetizing the birds with a magnetic pulse in one of three orientations. bobolinks magnetized with different polarities were significantly oriented in directions different from ... | 1995 | 9317510 |
| does the avian ophthalmic nerve carry magnetic navigational information? | the bobolink (dolichonyx oryzivorus) uses the earth's magnetic field as one source of directional information for its migratory orientation. however, the location and structure of the magnetoreceptors that transduce the magnetic information to the nervous system are unknown. because treatment with a strong magnetic pulse results in a change in the direction of orientation, one of the receptors is thought to involve a magnetizable material such as magnetite. the effects of the magnetizing treatme ... | 1996 | 9319100 |
| grassland songbirds in a dynamic management landscape: behavioral responses and management strategies. | in recent decades, earlier and more frequent harvests of agricultural grasslands have been implicated as a major cause of population declines in grassland songbirds. from 2002 to 2005, in the champlain valley of vermont and new york, usa, we studied the reproductive success of savannah sparrows (passerculus sandwichensis) and bobolinks (dolichonyx oryzivorus) on four grassland treatments: (1) early-hayed fields cut before 11 june and again in early- to mid-july; (2) middle-hayed fields cut once ... | 2006 | 17205901 |
| visual pigment and oil droplet characteristics of the bobolink (dolichonyx oryzivorus), a new world migratory bird. | the retinal photoreceptors of a new world migratory bird, the bobolink (dolichonyx oryzivorus) were examined using microspectrophotometry. based on the absorbance spectra of their visual pigments and oil droplets, retinal photoreceptors include five classes of single cones, one double cone, and one rod. the single cones contain a long-wavelength pigment (lambda(max)=564nm) paired with a red or clear droplet, a medium-wavelength pigment (lambda(max)=505nm) with an orange or yellow droplet, and an ... | 2008 | 18054982 |
| grassland songbird survival and recruitment in agricultural landscapes: implications for source-sink demography. | population growth and decline are particularly sensitive to changes in three key life-history parameters: annual productivity, juvenile survival, and adult survival. however, for many species these parameters remain unknown. for example, although grassland songbirds are imperiled throughout north america, for this guild, only a small number of studies have assessed these parameters. from 2002 to 2006, in the agricultural landscape of the champlain valley of vermont and new york, usa, we studied ... | 2008 | 18705380 |
| assessing the use of genomic dna as a predictor of the maximum absorbance wavelength of avian sws1 opsin visual pigments. | recently, in vitro mutation studies have made it possible to predict the wavelengths of maximum absorbance (lambdamax) of avian uv/violet sensitive visual pigments (sws1) from the identity of a few key amino acid residues in the opsin gene. given that the absorbance spectrum of a cone's visual pigment and of its pigmented oil droplet can be predicted from just the lambdamax, it may become possible to predict the entire spectral sensitivity of a bird using genetic samples from live birds or museu ... | 2009 | 19048261 |
| testing the role of patch openness as a causal mechanism for apparent area sensitivity in a grassland specialist. | area sensitivity, species being disproportionately present on larger habitat patches, has been identified in many taxa. we propose that some apparently area-sensitive species are actually responding to how open a habitat patch is, rather than to patch size. we tested this hypothesis for bobolinks (dolichonyx oryzivorus) by comparing density and occupancy to a novel openness index, patch area, and edge effects. bobolink density and occupancy showed significant relationships with openness, but log ... | 2012 | 22159812 |
| multiple lineages of avian malaria parasites (plasmodium) in the galapagos islands and evidence for arrival via migratory birds. | haemosporidian parasites in the genus plasmodium were recently detected through molecular screening in the galapagos penguin (spheniscus mendiculus). we summarized results of an archipelago-wide screen of 3726 endemic birds representing 22 species for plasmodium spp. through a combination of molecular and microscopy techniques. three additional plasmodium lineages were present in galapagos. lineage a-infected penguins, yellow warblers (setophaga petechia aureola), and one medium ground finch (ge ... | 2013 | 24033638 |
| local parasite lineage sharing in temperate grassland birds provides clues about potential origins of galapagos avian plasmodium. | oceanic archipelagos are vulnerable to natural introduction of parasites via migratory birds. our aim was to characterize the geographic origins of two plasmodium parasite lineages detected in the galapagos islands and in north american breeding bobolinks (dolichonyx oryzivorus) that regularly stop in galapagos during migration to their south american overwintering sites. we used samples from a grassland breeding bird assemblage in nebraska, united states, and parasite dna sequences from the gal ... | 2016 | 26865960 |
| inadvertent social information in breeding site selection of natal dispersing birds. | several species use the number of young produced as public information (pi) to assess breeding site quality. pi is inaccessible for synchronously breeding birds because nests are empty by the time the young can collect this information. we investigate if location cues are the next best source of inadvertent social information (isi) used by young prospectors during breeding site choice. we experimentally deployed isi as decoys and song playbacks of breeding males in suitable and sub-optimal habit ... | 2006 | 16543178 |
| proximate and landscape factors influence grassland bird distributions. | ecologists increasingly recognize that birds can respond to features well beyond their normal areas of activity, but little is known about the relative importance of landscapes and proximate factors or about the scales of landscapes that influence bird distributions. we examined the influences of tree cover at both proximate and landscape scales on grassland birds, a group of birds of high conservation concern, in the sheyenne national grassland in north dakota, usa. the grassland contains a div ... | 2006 | 16827003 |