02097nas a2200205 4500008004100000245012600041210006900167300001400236490000700250520141900257653002101676653002501697653002201722653001801744653001901762100001401781700001701795700001601812856006301828 2016 eng d00aVocal matching and intensity of begging calls are associated with a forebrain song circuit in a generalist brood parasite0 aVocal matching and intensity of begging calls are associated wit a615 - 6250 v763 a

Vocalizations produced by developing young early in life have simple acoustic features and are thought to be innate. Complex forms of early vocal learning are less likely to evolve in young altricial songbirds because the forebrain vocal-learning circuit is underdeveloped during the period when early vocalizations are produced. However, selective pressure experienced in early postnatal life may lead to early vocal learning that is likely controlled by a simpler brain circuit. We found the food begging calls produced by fledglings of the brown-headed cowbird (Molothrus ater), a generalist avian brood parasite, induced the expression of several immediate early genes and early circuit innervation in a forebrain vocal-motor pathway that is later used for vocal imitation. The forebrain neural activity was correlated with vocal intensity and variability of begging calls that appears to allow cowbirds to vocally match host nestmates. The begging-induced forebrain circuits we observed in fledgling cowbirds were not detected in nonparasitic passerines, including species that are close relatives to the cowbird. The involvement of forebrain vocal circuits during fledgling begging and its association with vocal learning plasticity may be an adaptation that provides young generalist brood parasites with a flexible signaling strategy to procure food from a wide range of heterospecific host parents.

10abrood parasitism10abrown-headed cowbird10afood begging call10aparental care10avocal learning1 aLiu, W.C.1 aRivers, J.W.1 aWhite, D.J. uhttps://onlinelibrary.wiley.com/doi/abs/10.1002/dneu.2234802482nas a2200253 4500008004100000245009700041210006900138300001400207490000700221520169100228653002401919653001201943653001901955653002101974653002501995653001902020653002602039653002502065653001702090100001902107700001902126700002202145856006102167 2014 eng d00aMismatched begging displays between foreign and host offspring reduce brood parasite fitness0 aMismatched begging displays between foreign and host offspring r a785 - 7930 v253 a

Obligate brood parasites must obtain food from unrelated host parents during the developmental period, and this may be especially difficult when parasitic nestlings are raised alone. Unlike specialist brood parasites, generalist brood parasites use a single begging display for a range of host species. In this study, we 1) tested whether the begging display of the generalist brown-headed cowbird (Molothrus ater) was more exaggerated than the closely related, nonparasitic red-winged blackbird (Agelaius phoeniceus) and 2) examined how begging displays were linked to food provisioning when both foreign species were raised by the Bell’s vireo (Vireo bellii), a small cowbird host. We also quantified parental provisioning to unparasitized broods containing 1–4 vireo nestlings to provide a reference provisioning curve to provide context for assessing the feeding rate to foreign offspring. We found blackbirds begged as intensely as (or more intensely than) cowbird nestlings, vireo parents provisioned both species similarly, and the amount of food provisioned to unparasitized broods increased with brood size and maintained per-capita vireo growth. However, feeding of a single foreign nestling was significantly less than that of a modal brood of 4 vireos, indicating parents fed foreign nestlings at submaximal rates. Vireos did not respond to begging of foreign nestlings in the same manner as their own offspring, and this led to significant fitness costs for foreign nestlings. We conclude that a single foreign nestling provided an inadequate stimulus for vireos, probably because of a mismatch between the begging displays of foreign and host offspring.

10aAgelaius phoeniceus10abegging10aBell’s vireo10abrood parasitism10abrown-headed cowbird10aMolothrus ater10aprovisioning behavior10ared-winged blackbird10aVireo bellii1 aRivers, J., W.1 aBlundell, M.A.1 aRothstein, S., I. uhttps://academic.oup.com/beheco/article/25/4/785/290052802657nas a2200253 4500008004100000245011900041210006900160300001300229490000700242520186200249653002402111653001202135653002102147653002502168653001902193653002502212653002502237100001702262700001902279700001802298700001502316700002002331856005202351 2013 eng d00aThe exaggerated begging behaviour of an obligate avian brood parasite is shared with a nonparasitic close relative0 aexaggerated begging behaviour of an obligate avian brood parasit a529 -5360 v863 aOffspring signalling models predict that the begging displays of obligate brood parasites are more intense than nonparasitic species because parasitic young are never reared by their genetic parents and often compete against unrelated host young during development. The brown-headed cowbird, Molothrus ater, has been described as having exaggerated begging relative to nonparasitic species, but an effective test of this idea is lacking because previous studies have not controlled for evolutionary history while simultaneously standardizing rearing conditions. We quantified the begging intensity of cowbirds and the closely related, nonparasitic red-winged blackbird, Agelaius phoeniceus, when both species experienced identical rearing conditions in two distinct nest environments: reared alone by a small cowbird host, or reared with two host young by a moderate-sized cowbird host. Against theoretical predictions, we found that in both nest environments four components of the cowbird begging display were similar to (or less intense than) blackbird begging displays (i.e. latency to beg, begging score, call rate and call amplitude) when nestlings were tested across a gradient of short-term need. Our results provide the first experimental evidence that a closely related, yet nonparasitic, species shares an exaggerated begging display with a brood-parasitic species when reared under conditions typically experienced by parasitic offspring. We discuss three nonexclusive explanations for our findings: (1) relatedness among cowbird nestmates reduced cowbird begging intensity (kin selection hypothesis), (2) reduced body condition of blackbirds elevated their begging intensity (body condition hypothesis) and (3) intense competition in blackbird nest environments led to increased blackbird begging intensity (competitive environment hypothesis).10aAgelaius phoeniceus10abegging10abrood parasitism10abrown-headed cowbird10aMolothrus ater10aoffspring signalling10ared-winged blackbird1 aRivers, J.W.1 aBlundell, M.A.1 aLoughin, T.M.1 aPeer, B.D.1 aRothstein, S.I. uhttp://dx.doi.org/10.1016/j.anbehav.2013.06.00402542nas a2200289 4500008004100000245011500041210006900156300001300225490000800238520164800246653002401894653001701918653002101935653003101956653001501987653001302002653001902015653002402034653002502058653002002083653001702103100001702120700001702137700001902154700002002173856005902193 2010 eng d00aCommunity-level patterns of host use by the Brown-headed Cowbird (Molothrus ater), a generalist brood parasite0 aCommunitylevel patterns of host use by the Brownheaded Cowbird M a263 -2730 v1273 a

Quantifying community-level host use by generalist brood parasites is important because it provides a measure of the resources that parasites need for reproduction. During the 2002–2007 breeding seasons, we quantified host use by the Brown-headed Cowbird (Molothrus ater) at Konza Prairie Biological Station in northeast Kansas. Overall, 54.4% of nests (n = 2,621) of 22 passerine host species that typically accept parasitic eggs were parasitized, and parasitized nests contained an average of 1.9 ± 1.03 (SD) Brown-headed Cowbird eggs, nestlings, or both. Multiple parasitism was common on the study site in all years: 55.7% of parasitized nests (n = 1,425) received ≥2 Brown-headed Cowbird eggs. The Bell's Vireo (Vireo bellii; 70.5%) and the Dickcissel (Spiza americana; 69.6%) were parasitized at a significantly greater rate than the Red-winged Blackbird (Agelaius phoeniceus, 21.9%); collectively, these three species represented 85.8% of potential host nests found in all years. The host preference of Brown-headed Cowbirds did not appear to shift among the three species and instead they exhibited a consistent preference for Dickcissel nests over the course of the breeding season and among years. Both the rate and the intensity of parasitism on Dickcissels were significantly lower during the present study than in one conducted several decades earlier at the same site. Our results indicate that cowbirds in northeast Kansas differentially parasitize hosts, that most cowbird eggs are laid in the nests of a small number of host species, and that the Dickcissel appears to be preferred over other hosts.

10aAgelaius phoeniceus10aBell's Vireo10abrood parasitism10acommunity-level parasitism10aDickcissel10ahost use10aMolothrus ater10amultiple parasitism10ared-winged blackbird10aSpiza americana10aVireo bellii1 aRivers, J.W.1 aJensen, W.E.1 aKosciuch, K.L.1 aRothstein, S.I. uhttps://academic.oup.com/auk/article/127/2/263/514838202366nas a2200205 4500008004100000245014500041210006900186300001300255490000800268520160400276653002101880653002501901653001501926653002501941653001901966653002001985100001702005700001602022856012202038 2005 eng d00aGeographic variation in Brown-headed Cowbird (Molothrus ater) parasitism on Dickcisssels (Spiza americana) in Great Plains tallgrass prairie0 aGeographic variation in Brownheaded Cowbird Molothrus ater paras a648 -6600 v1223 aThe incidence of brood parasitism by Brown-headed Cowbirds (Molothrus ater; hereafter “cowbirds“) within host species typically reflects the continental pattern in cowbird abundance across North America, where parasitism is heaviest in the Great Plains. However, we found considerable variation in cowbird parasitism on Dickcissel (Spiza americana) nests within a subregion of the Great Plains (the Flint Hills), where the highest levels of cowbird parasitism on grassland bird nests had been previously reported. Local parasitism frequencies on Dickcissel nests varied latitudinally across the Flint Hills, ranging from 0% to 92% of nests parasitized. Interestingly, we found no obvious patterns in habitat or host attributes that were associated with this steep geographic gradient in brood parasitism. Cowbird parasitism on Dickcissel nests was not correlated with the vertical density of local prairie vegetation, mean nest distance to edge, proportion of forest to grassland habitat surrounding study sites (≤5 to 10 km), geographic variation in host abundance, or Dickcissel density or nest initiation dates. Parasitism frequencies and intensities (number of cowbird eggs per parasitized nest) on Dickissel nests were only significantly related to variation in local female cowbird density. Dickcissel clutch size and apparent fledging success were negatively correlated with local cowbird parasitism levels. Geographic patterns in cowbird abundance within and among regions should be considered when establishing conservation areas for grassland birds or other cowbird hosts of concern.10abrood parasitism10abrown-headed cowbird10aDickcissel10ageographic variation10aMolothrus ater10aSpiza americana1 aJensen, W.E.1 aCully, J.F. uhttp://knz.lternet.edu/content/geographic-variation-brown-headed-cowbird-molothrus-ater-parasitism-dickcisssels-spiza