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

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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Clutch variation and egg rejection in three hosts of the pallid cuckoo, Cuculus pallidus

Behaviour ◽

10.1163/000579509x12483520922043 ◽

2010 ◽

Vol 147 (1) ◽

pp. 19-36 ◽

Cited By ~ 8

Author(s):

Naomi Langmore ◽

Michelle Landstrom ◽

Robert Heinsohn

Keyword(s):

Host Species ◽

Rejection Rate ◽

Objective Measures ◽

Egg Rejection ◽

Brood Parasite ◽

Reflectance Spectrophotometry ◽

Brood Parasites ◽

Parasitised Host

AbstractIn theory, hosts of avian brood parasites would benefit by modifying their egg appearance in two ways to help identify mimetic foreign eggs: (i) by laying clutches that are more uniform in appearance and (ii) by laying clutches that differ from those of other females in the population. Support for these theories is inconsistent, and few studies have used objective measures of clutch variation. Here we used reflectance spectrophotometry to quantify within-clutch and between-clutch variation of three host species of an Australian brood parasite, the pallid cuckoo (Cuculus pallidus). We used egg-swapping experiments in which subjects were presented with either a conspecific egg or a heterospecific egg to compare the egg rejection responses of a frequently parasitised host, the white-plumed honeyeater (Lichenostomus penicillatus), with two less frequently parasitised hosts, dusky woodswallows (Artamus cyanopterus) and willie wagtails (Rhipidura leucophrys). As predicted, rejection rate increased as contrast between foreign egg and host clutch increased. Further, the major host showed greater between-clutch variation than the occasional hosts, and also rejected more similar-looking eggs. Contrary to predictions however, within-clutch variation was not lower in the major host, nor was it important in predicting the rejection rate of foreign eggs by the three host species.

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

Acta Zoologica Academiae Scientiarum Hungaricae ◽

10.17109/azh.66.4.309.2020 ◽

2020 ◽

Vol 66 (4) ◽

Cited By ~ 1

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.

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

The Auk ◽

10.1093/auk/124.2.526 ◽

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

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

Canadian Journal of Zoology ◽

10.1139/z06-091 ◽

2006 ◽

Vol 84 (9) ◽

pp. 1269-1280 ◽

Cited By ~ 29

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.

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Shared transcriptional responses to con- and heterospecific behavioral antagonists in a wild songbird

10.1101/795757 ◽

2019 ◽

Author(s):

Matthew I. M. Louder ◽

Michael Lafayette ◽

Amber A. Louder ◽

Floria M. K. Uy ◽

Christopher N. Balakrishnan ◽

...

Keyword(s):

Behavioral Plasticity ◽

Molothrus Ater ◽

System Response ◽

Brood Parasite ◽

Functional Responses ◽

Transcriptional Responses ◽

Free Living ◽

Brood Parasites ◽

Singing Behavior ◽

Immune System Response

AbstractThe recognition of and differential responses to salient stimuli are among the main drivers of behavioral plasticity, yet, how animals evolve and modulate functional responses to novel classes of antagonistic stimuli remain poorly understood. We studied free-living male red-winged blackbirds (Agelaius phoeniceus) to test whether gene expression responses in blood are distinct or shared between patterns of aggressive behavioral responses directed at simulated conspecific versus heterospecific intruders. In this species, males defend territories against conspecific males and respond aggressively to female brown-headed cowbirds (Molothrus ater), a brood parasite that commonly lays eggs in blackbird nests. Both conspecific songs and parasitic calls elicited aggressive responses from focal subjects and caused a downregulation in genes associated with immune system response, relative to control calls of a second, harmless heterospecific species. In turn, only the conspecific song treatment elicited an increase in singing behavior and an upregulation of genes associated with metabolic processes relative to the two heterospecific calls. Our results suggest that aspects of antagonistic responses to both conspecifics and brood parasites can be based on similar physiological responses, suggestive of shared molecular and behavioral pathways involved in the recognition and reaction to both evolutionarily old and new enemies.

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Effects of Host Species Identity and Diet on the Biodiversity of the Microbiota in Puerto Rican Bats

Current Microbiology ◽

10.1007/s00284-021-02607-5 ◽

2021 ◽

Author(s):

Steven J. Presley ◽

Joerg Graf ◽

Ahmad F. Hassan ◽

Anna R. Sjodin ◽

Michael R. Willig

Keyword(s):

Puerto Rican ◽

Host Species ◽

Species Identity

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Host density predicts the probability of parasitism by avian brood parasites

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2018.0204 ◽

2019 ◽

Vol 374 (1769) ◽

pp. 20180204 ◽

Cited By ~ 3

Author(s):

Iliana Medina ◽

Naomi E. Langmore

Keyword(s):

Spatial Distribution ◽

Reproductive Success ◽

Host Species ◽

Field Data ◽

Host Density ◽

Brood Parasites ◽

Parasitism Rates ◽

Analyse Data ◽

First Time ◽

Determining Factor

The spatial distribution of hosts can be a determining factor in the reproductive success of parasites. Highly aggregated hosts may offer more opportunities for reproduction but can have better defences than isolated hosts. Here we connect macro- and micro-evolutionary processes to understand the link between host density and parasitism, using avian brood parasites as a model system. We analyse data across more than 200 host species using phylogenetic comparative analyses and quantify parasitism rate and host reproductive success in relation to spatial distribution using field data collected on one host species over 6 years. Our comparative analysis reveals that hosts occurring at intermediate densities are more likely to be parasitized than colonial or widely dispersed hosts. Correspondingly, our intraspecific field data show that individuals living at moderate densities experience higher parasitism rates than individuals at either low or high densities. Moreover, we show for the first time that the effect of host density on host reproductive success varies according to the intensity of parasitism; hosts have greater reproductive success when living at high densities if parasitism rates are high, but fare better at low densities when parasitism rates are low. We provide the first evidence of the trade-off between host density and parasitism at both macro- and micro-evolutionary scales in brood parasites. This article is part of the theme issue ‘The coevolutionary biology of brood parasitism: from mechanism to pattern’.

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Effects of turbidity on prey consumption and growth in brook trout and implications for bioenergetics modeling

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f00-260 ◽

2001 ◽

Vol 58 (2) ◽

pp. 386-393 ◽

Cited By ~ 38

Author(s):

John A Sweka ◽

Kyle J Hartman

Keyword(s):

Growth Rates ◽

Brook Trout ◽

Specific Growth ◽

Abiotic Factors ◽

Foraging Strategies ◽

Turbid Water ◽

Daily Consumption ◽

Consumption Rates ◽

The Difference ◽

Specific Growth Rates

Brook trout (Salvelinus fontinalis) were held in an artificial stream to observe the influence of turbidity on mean daily consumption and specific growth rates. Treatment turbidity levels ranged from clear (<3.0 nephelometric turbidity units (NTU)) to very turbid water (> 40 NTU). Observed mean daily specific consumption rates were standardized to the mean weight of all brook trout tested. Turbidity had no significant effect on mean daily consumption, but specific growth rates decreased significantly as turbidity increased. Brook trout in turbid water became more active and switched foraging strategies from drift feeding to active searching. This switch was energetically costly and resulted in lower specific growth rates in turbid water as compared with clear water. Bioenergetics simulations were run to compare observed growth with that predicted by the model. Observed growth values fell below those predicted by the model and the difference increased as turbidity increased. Abiotic factors, such as turbidity, which bring about changes in the activity rates of fish, can have implications for the accuracy of predicted growth by bioenergetics models.

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