scholarly journals Color Variation Among Nestling Brown-Headed Cowbirds (Molothrus Ater) Does Not Reflect Differential Success With Hosts in Texas

The Auk ◽  
2007 ◽  
Vol 124 (2) ◽  
pp. 526-536
Author(s):  
Kevin Ellison ◽  
Spencer G. Sealy ◽  
Hope R. McGaha
Keyword(s):  
United States ◽  
Interspecific Competition ◽  
Host Species ◽  
Molothrus Ater ◽  
Color Variation ◽  
Southern United States ◽  
Adult Care ◽  
Brood Parasites ◽  
Fledging Success ◽  
A Site

Abstract As brood parasites, nestling Brown-headed Cowbirds (Molothrus ater) may exhibit characters that improve their fledging success when reared alongside host young. The coloration of mouthparts of nestlings can influence adult care and, thus, the polymorphism of yellow or white rictal flanges among nestling Brown-headed Cowbirds may reflect differential success with different hosts on the basis of flange color. Moreover, because Brown-headed Cowbirds in the southern United States co-occur with Bronzed Cowbirds (M. aeneus), whose young have white flanges, cowbird nestlings' flange colors may reflect a means for reducing interspecific competition through partitioning of host species on the basis of nestling flange color. To determine whether flange color influences cowbird fledging success with hosts of either color, we recorded the flange colors of cowbirds and their hosts at a site in Texas. We also tested whether flange color was influenced by nestling sex. Most hosts of Brown-headed Cowbirds had young with yellow flanges (81%, n = 16 spp.), yet Brown-headed Cowbirds with white flanges were more common (61%, n = 107). Bronzed Cowbirds parasitized primarily species whose young had white flanges (86%, n = 348 eggs). Despite the differential use of hosts with regard to flange color, the frequencies of each were similar among nestling and juvenile Brown-headed Cowbirds. Likewise, the frequencies of each color did not differ significantly between the sexes. Therefore, we suggest that a flange color matching that of nestmates is not strongly selected for by hosts. La Variación del Color entre Polluelos de Molothrus ater no Refleja Éxito Diferencial al Ser Criados por Especies Hospederas en Texas

scholarly journals Digital epidemiologic research on multilevel risks for HIV acquisition and other health outcomes among transgender women in Eastern and Southern United States: A protocol for an online cohort (Preprint)

2021 ◽  
Author(s):  
Andrea L Wirtz ◽  
Erin E Cooney ◽  
Megan Stevenson ◽  
Asa Radix ◽  
Tonia Poteat ◽  
...  
Keyword(s):  
United States ◽  
Health Outcomes ◽  
Cohort Studies ◽  
The United States ◽  
Transgender Women ◽  
Southern United States ◽  
Epidemiologic Research ◽  
Hiv Epidemic ◽  
Hiv Acquisition ◽  
A Site

BACKGROUND The HIV epidemic disproportionately impacts transgender women in the United States. Cohort studies identify unique risks for affected populations, but use of facility-based methods may bias findings towards individuals living in research catchment areas, more engaged in health services, and/or, in the case of transgender populations, those who are open about their transgender identity. Digital clinical trials and other online research methods are increasingly common, providing opportunity to reach those not commonly engaged in research. Simultaneously, there is a need to understand potential biases associated with digital research, how these methods perform and whether they are accepted across populations. OBJECTIVE This study aims to assess the feasibility of developing and implementing an online cohort of transgender women to assess risks for HIV acquisition and other health experiences and to evaluate how an online cohort compares to a site-based, technology enhanced cohort for epidemiologic research. The overarching goal is to estimate incidence of HIV and other health outcomes among transgender women in eastern and southern United States. METHODS This sub-study is part of a larger multisite prospective cohort (LITE) conducted among transgender women, which also includes a site-based cohort of six eastern and southern US cities. The online cohort was launched to enroll and follow participants across 72 cities with similar demographic characteristics in the same regions as the site-based cohorts. Participants are followed for 24 months. Adult transgender women are recruited via convenience sampling (e.g., peer referrals, social media, and dating apps). Participants reporting negative or unknown HIV status are enrolled in a baseline study visit, complete a socio-behavioral survey, and provide oral fluid specimens to test for HIV. Participants not living with HIV (lab-confirmed) at baseline are offered enrollment into the cohort; follow-up assessments occur every six months. RESULTS Enrollment into the online cohort launched in January 2019. Active recruitment stopped in May 2019 and enrollment officially closed in August 2020. A total of 580 participants enrolled into and are followed in the cohort. A recruitment-enrollment cascade was observed across screening, consent, and completion of study activities. Implementation experiences with HIV test kits highlight the need for heavy staff engagement to support participant engagement, visit completion, and retention, even with automated digital procedures. CONCLUSIONS This study is responsive to increasing research interest in online cohort research, particularly for populations who are most affected by the HIV epidemic and for those who may otherwise not participate in-person. The progression across stages of the recruitment-enrollment cascade provides useful insight for implementation of cohort studies in the online environment.

scholarly journals Natural and artificial scents do not increase egg rejection rates of model brood parasitic eggs by American robins (Turdus migratorius)

2020 ◽  
Vol 66 (4) ◽  
Author(s):  
Mark Erno Hauber
Keyword(s):  
Host Species ◽  
Molothrus Ater ◽  
Egg Rejection ◽  
Turdus Migratorius ◽  
Data Set ◽  
Brood Parasites ◽  
American Robins ◽  
Tactile Cues ◽  
Do So ◽  
Rejection Rates

Hosts of obligate avian brood parasites can diminish or eliminate the costs of parasitism by rejecting foreign eggs from the nests. A vast literature demonstrates that visual and/or tactile cues can be used to recognize and reject natural or model eggs from the nests of diverse host species. However, data on olfaction-based potential egg recognition cues are both sparse and equivocal: experimentally-applied, naturally-relevant (heterospecific, including parasitic) scents do not appear to increase egg rejection rates in two host species, whereas unnatural scents (human and tobacco scents) do so in one host species. Here I assessed the predictions that (i) human handling of mimetically-painted model eggs would increase rejection rates, and (ii) applying unnatural or natural scents to mimetically or non-mimetically painted model eggs alters these eggs’ respective rejection rates relative to controls. I studied wild American Robins (Turdus migratorius), a robust rejecter species of the eggs of obligate brood parasitic Brown-headed Cowbirds (Molothrus ater). There was no statistical evidence to support either prediction, whereas poorer color-mimicry was still a predicted cause of greater egg rejection in this data set. Nonetheless, future studies could focus on this and other host species and using these and different methods to apply and maintain the scenting of model eggs to more directly test hosts’ use of potential olfactory cues in the foreign-egg rejection process.

Genetic elucidation of host use by individual sympatric bronzed cowbirds (Molothrus aeneus) and brown-headed cowbirds (M. ater)

2006 ◽  
Vol 84 (9) ◽  
pp. 1269-1280 ◽  
Author(s):  
K. Ellison ◽  
S.G. Sealy ◽  
H.L. Gibbs
Keyword(s):  
Dna Markers ◽  
Host Species ◽  
Microsatellite Dna ◽  
Molothrus Ater ◽  
Host Use ◽  
Suitable Host ◽  
Brood Parasites ◽  
Potential Host ◽  
Microsatellite Dna Markers ◽  
Molothrus Aeneus

Species of avian brood parasites that use one or several species of hosts are called host specialists and generalists, respectively. To determine host use of individual bronzed cowbirds, Molothrus aeneus (Wagler, 1829), and brown-headed cowbirds, Molothrus ater (Boddaert, 1783), we assigned maternity to eggs using microsatellite DNA markers. We measured patterns of host use by individual sympatric cowbirds. This allowed us to determine whether these species competed for host nests and the number of females laying at nests that were already parasitized by conspecifics. We monitored 1447 nests of 42 potential host species and found that each species of cowbird used primarily four host species, with minimal overlap in the species used, yet at least some individuals acted as generalists. Individual cowbirds tended to avoid laying again at nests each had already parasitized, and multiple parasitism was frequently due to same-day laying by more than one female (19% and 44% of 27 and 39 cases for brown-headed and bronzed cowbirds, respectively). Our results suggest that both cowbirds can differentially parasitize host species; however, host use does not appear to be refined, as many eggs were laid in already-parasitized nests when unparasitized nests of other suitable host species were available.

Developmental asynchrony and host species identity predict variability in nestling growth of an obligate brood parasite: a test of the “growth-tuning” hypothesis

2021 ◽  
Author(s):  
Sarah Katherine Winnicki ◽  
Bill M. Strausberger ◽  
Nick Antonson ◽  
Dirk E. Burhans ◽  
Justin Lock ◽  
...  
Keyword(s):  
Growth Rates ◽  
Host Species ◽  
Developmental Plasticity ◽  
Molothrus Ater ◽  
The Novel ◽  
Brood Parasite ◽  
Species Identity ◽  
Brood Parasites ◽  
Specific Growth Rates ◽  
Developmental Asynchrony

Generalist obligate brood parasites are excellent models for studies of developmental plasticity, as they experience a range of social and environmental variation when raised by one of their many hosts. Parasitic Brown-headed Cowbirds (Molothrus ater (Boddaert, 1783)) exhibit host-specific growth rates, yet cowbird growth rates are not predicted by hosts’ incubation or brooding periods. We tested the novel “growth-tuning” hypothesis which predicts that total asynchrony between cowbirds’ and hosts’ nesting periods results in faster parasitic growth in nests where host young fledge earlier than cowbirds. We tested this prediction using previously-published and newly-added nestling mass data across diverse host species. Total nesting period asynchrony (summed across incubation and brooding stages) predicted cowbird growth; 8-day old cowbirds were heavier in host nests with relatively shorter nesting periods. We further explored the drivers of variation in growth using mass measurements of cowbirds in Song Sparrow (Melospiza melodia (Wilson, 1810)) and Red-winged Blackbird (Agelaius phoeniceus (Linnaeus, 1766)) nests. Our top models included host species (cowbirds grew faster in sparrow nests), numbers of nestmates (slowest when raised alone), and sex (males grew faster). These results confirm that multiple social and environmental factors predict directional patterns of developmental plasticity in avian generalist brood parasites.

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