Costs of multiple parasitism for an avian brood parasite, the Brown-headed Cowbird (Molothrus ater)

2011 ◽  
Vol 89 (12) ◽  
pp. 1237-1248 ◽  
Author(s):  
C.B. Goguen ◽  
D.R. Curson ◽  
N.E. Mathews
Keyword(s):  
New Mexico ◽  
Intraspecific Competition ◽  
Molothrus Ater ◽  
Brood Parasite ◽  
Egg Survival ◽  
Host Nest ◽  
Egg Mortality ◽  
Nest Desertion ◽  
Nestling Period ◽  
Polioptila Caerulea

The Brown-headed Cowbird ( Molothrus ater (Boddaert, 1783)) is a generalist brood parasite that often lays into nests that contain conspecific eggs. Although it has often been assumed that this multiple parasitism reduces Cowbird survival, this has rarely been evaluated. We measured Cowbird survival in nests of the Blue-gray Gnatcatcher ( Polioptila caerulea (L., 1766)), Plumbeous Vireo ( Vireo plumbeus Coues, 1866), and Western Tanager ( Piranga ludoviciana (A. Wilson, 1811)) in New Mexico, USA. Our objectives were to measure the costs of intraspecific competition on Cowbird survival in multiply-parasitized nests, evaluate if these costs were related to host size, and to compare the costs of multiple parasitism relative to other mortality sources that occur over the entire nesting cycle. Intraspecific competition reduced Cowbird survival during the nestling period in nests of all three hosts, and was of particular importance in nests of the two smaller hosts. When all sources of egg mortality were considered, however, the costs of multiple parasitism were small compared with the large effects of predation and nest desertion. Given that multiple parasitism reduces Cowbird egg survival, it is unclear why Cowbirds multiply-parasitize. Possible explanations depend on an improved understanding of fecundity and level of host nest selectivity by female Cowbirds.

Genetic and temporal patterns of multiple parasitism by brown-headed cowbirds (Molothrus ater) on song sparrows (Melospiza melodia)

2003 ◽  
Vol 81 (2) ◽  
pp. 281-286 ◽  
Author(s):  
C M McLaren ◽  
B E Woolfenden ◽  
H L Gibbs ◽  
S G Sealy
Keyword(s):  
Reproductive Success ◽  
High Frequency ◽  
Molothrus Ater ◽  
Host Choice ◽  
Melospiza Melodia ◽  
Song Sparrow ◽  
Brood Parasite ◽  
Host Nest ◽  
Song Sparrows ◽  
Genetic Techniques

Identifying the factors used by an avian brood parasite to select host nests is important in understanding the determinates of individual reproductive success, yet such factors are poorly known for most parasitic species. Insights into these factors may come from understanding the conditions under which female parasites lay more than one egg per host nest (multiple parasitism). Using genetic techniques we examined patterns of multiple parasitism on a preferred host, the song sparrow (Melospiza melodia), to determine some basic patterns of multiple parasitism. Multiple parasitism involved equal frequencies of the same female parasitizing the same nest again and two or more females parasitizing the same nest. The frequency of multiple parasitism increased as the season progressed. We also documented a high frequency of parasitism that was not synchronized with host laying. These laying patterns may be the result of cowbirds "making the best of a bad situation" or of suboptimal host choice by inexperienced, nonselective females.

Parasitism of House Wren nests by Brown-headed Cowbirds: why is it so rare?

1997 ◽  
Vol 75 (2) ◽  
pp. 302-307 ◽  
Author(s):  
Stanislav Pribil ◽  
Jaroslav Picman
Keyword(s):  
Field Experiments ◽  
Molothrus Ater ◽  
Low Frequency ◽  
Nest Material ◽  
Nest Structure ◽  
Troglodytes Aedon ◽  
House Wren ◽  
House Wrens ◽  
Nest Desertion ◽  
Cowbird Parasitism

We tested five hypotheses that may explain why House Wren (Troglodytes aedon) nests are rarely parasitized by Brown-headed Cowbirds (Molothrus ater). House Wrens may prevent parasitism in five ways: (1) by choosing to nest in cavities with small entrances (inaccessible-entrance hypothesis), (2) by restricting the size of the entrance with nest material (nest-structure hypothesis), (3) by puncturing and ejecting parasitic eggs (puncture–ejection hypothesis), (4) by burying the parasitized clutch under a new nest (egg-burial hypothesis), or (5) by abandoning the parasitized nest altogether (nest-desertion hypothesis). We tested these hypotheses in field experiments and found that (i) female cowbirds cannot enter circular entrances smaller than 38 mm in diameter, (ii) wrens prefer cavities with small entrances (inaccessible to cowbirds) to those with large entrances (accessible to cowbirds), (iii) when forced to breed in cavities with large entrances, wrens do not reduce the entrance size with nest material, (iv) despite the unusual strength of cowbird eggs, wrens are physically capable of puncture–ejecting them, (v) wrens do not puncture–eject cowbird eggs from their own nests, (vi) wrens do not abandon parasitized nests or bury the parasitized clutches under new nests. These results are consistent with the inaccessible-entrance hypothesis. We propose that additional nesting adaptations, as well as active cowbird avoidance of House Wrens, may contribute to the low frequency of cowbird parasitism.

STUDIES OF FECUNDITY AND BEHAVIOUR OF THE ORIENTAL FRUIT MOTH, GRAPHOLITHA MOLESTA (LEPIDOPTERA: TORTRICIDAE), ON THE NIAGARA PENINSULA OF ONTARIO

1969 ◽  
Vol 101 (10) ◽  
pp. 1024-1033 ◽  
Author(s):  
J. H. H. Phillips ◽  
Jean R. Proctor
Keyword(s):  
Intraspecific Competition ◽  
Experimental Studies ◽  
Oriental Fruit Moth ◽  
Apple Trees ◽  
Egg Mortality ◽  
Grapholitha Molesta ◽  
Three Generations ◽  
Newly Hatched Larvae ◽  
Peach Trees ◽  
Peach Orchard

AbstractUnsprayed apple trees measurably increased the numbers of the Oriental fruit moth, Grapholitha molesta (Busck), in adjacent peach trees in only 1 of 4 years, though the apples were rather heavily infested. The moth became evenly dispersed throughout a previously uninfected peach orchard within three generations. Caged orchard trees were unsatisfactory for studying behaviour because the environment within the cages differed from that in the orchard. Experimental studies indicated that fecundity of the females was variable between years and generations and a varying proportion laid no eggs. Intraspecific competition between newly hatched larvae occurred at low egg densities; egg mortality was small but mortality of newly hatched larvae was large.

The time of day of egg laying by the Brown-headed Cowbird and other icterines

1991 ◽  
Vol 69 (8) ◽  
pp. 2093-2099 ◽  
Author(s):  
David M. Scott
Keyword(s):  
Molothrus Ater ◽  
Time Of Day ◽  
Egg Laying ◽  
Agelaius Phoeniceus ◽  
Brood Parasite ◽  
Dendroica Petechia ◽  
Cardinalis Cardinalis ◽  
Vireo Olivaceus ◽  
Molothrus Bonariensis ◽  
Dumetella Carolinensis

I present data on the time of day of oviposition for 16 species of icterines to evaluate the idea that laying exceptionally early in the morning by the brood parasite, the Brown-headed Cowbird (Molothrus ater), is a specialization for parasitism. This cowbird, the earliest known layer among icterines, typically lays before sunrise (sunrise −9.14 ± 2.52 (SE) min, n = 36). Another brood parasite, the Shiny Cowbird (Molothrus bonariensis), also sometimes lays before sunrise. The best-known nonparasitic icterines, the Red-winged Blackbird (Agelaius phoeniceus) and the Common Grackle (Quisacalus quiscula), lay shortly after sunrise. Fragmentary records show that several other icterines lay within an hour or so after sunrise. Data are inadequate to conclude that early laying by Brown-headed Cowbirds has arisen as an adaptation for parasitism. The Brown-headed Cowbird at London, Ontario, lays earlier than most local passerines, as is shown by new data on oviposition by seven host species arranged in order of increasing lateness of oviposition: Agelaius phoeniceus, Dendroica petechia, Melospiza melodia, Cardinalis cardinalis, Vireo olivaceus, Dumetella carolinensis, and Turdus migratorius.

Stable isotopes identify the natal origins of a generalist brood parasite, the brown-headed cowbird Molothrus ater

2008 ◽  
Vol 39 (3) ◽  
pp. 364-367 ◽  
Author(s):  
Karl L. Kosciuch ◽  
James W. Rivers ◽  
Brett K. Sandercock
Keyword(s):  
Stable Isotopes ◽  
Molothrus Ater ◽  
Brood Parasite

scholarly journals Multiple parasitism promotes facultative host acceptance of cuckoo eggs and rejection of cuckoo chicks

2021 ◽  
Author(s):  
Hee-Jin Noh ◽  
Rosalyn Gloag ◽  
Naomi E. Langmore
Keyword(s):  
Dilution Effect ◽  
Host Acceptance ◽  
Brood Parasite ◽  
Egg Survival

Many hosts of brood parasitic cuckoos reject foreign eggs from the nest. Yet where nests commonly receive more than one cuckoo egg, hosts might benefit by instead accepting parasite eggs. This is because cuckoos remove an egg from the nest before adding their own, and keeping cuckoo eggs in the nest reduces the odds that further host eggs are removed by subsequent cuckoos. This 'clutch dilution effect' has been proposed as a precondition for the evolution of cuckoo nestling eviction by hosts, but no previous studies have tested this in a host that rejects cuckoo nestlings. We tested the clutch dilution hypothesis in large-billed gerygones (Gerygone magnirostris), which are multiply parasitized by little bronze-cuckoos (Chalcites minutillus). Gerygones evict cuckoo nestlings but accept cuckoo eggs. Consistent with multiple parasitism favouring egg acceptance, we found gerygone egg survival was higher under scenarios of cuckoo egg acceptance than rejection. Yet gerygones were also flexible in their egg acceptance, with 35% abandoning cuckoo-egg-only clutches. This novel demonstration of adaptive clutch dilution suggests that multiple parasitism can favour a facultative response to brood parasite eggs, whereby hosts accept or reject parasite eggs depending on clutch composition.

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