Yellow Warbler Research Articles

Are Nest Predation and Brood Parasitism Correlated in Yellow Warblers? A Test of the Cowbird Predation Hypothesis

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The response of yellow warblers to brown-headed cowbird models in Prince Edward Island

The response of yellow warblers to brown-headed cowbird models in Prince Edward Island

Migration-Induced Variation in Thermogenic Capacity in Migratory Passerines

Increases in maximal capacity for thermogenesis (or Peak Metabolic Rate, PMR) are typically associated with winter acclimatization in passerines showing marked seasonal changes in cold tolerance. Thermogenic capacity also increases in spring migrant Warbling Vireos Vireo gilvus, a Neotropical migrant, relative to summer acclimatized individuals, but a similar increase does not occur in fall migrants. We tested whether migratory disposition was associated with variation in thermogenic capacity in another Neotropical migrant passerine, the Yellow Warbler Dendroica petechia, and in two passerine species migrating to mild temperate regions in winter, Yellow-rumped Warbler Dendroica coronata and Ruby-crowned Kinglet Regulus calendula. PMR was elicited by cold exposure in an atmosphere of 79% helium:21% oxygen during spring and fall migration for all species, and also during summer for Yellow Warblers. Yellow and Yellow-rumped Warblers both exhibited significantly higher thermogenic capacity in spring than at other seasons (23.3% greater than pooled summer and fall values in Yellow Warblers, 19.8% greater than in fall Yellow-rumped Warblers). For kinglets, males showed significantly higher PMR in spring than in fall (10.9%), but PMR did not vary seasonally in females. Thus, these species conform to a pattern of elevated thermogenic capacity in spring relative to other seasons, at least in the sex establishing breeding territories, suggesting that this may be a common pattern in migratory passerines. Mild temperate migrants migrate earlier in spring and later in fall than Neotropical migrants and, as a consequence, experience less variation in temperature between spring and fall migrations. Nevertheless, PMR varied similarly on a seasonal basis among Neotropical and mild-temperate migrants, despite the greater seasonal variation in temperatures encountered by Neotropical migrants. Moreover, ANCOVA on log PMR with log mass as a covariate did not demonstrate systematically lower PMR in Neotropical migrants than in mild temperate migrants for the species in this study, despite the differences in temperatures encountered during migration. This suggests that seasonal changes in PMR during migration are not associated with temperature acclimatization, but instead vary with other features of migratory patterns.

Extrapair Paternity in a Far Northern Population of Yellow Warblers Dendroica petechia

The proportion of extrapair paternity is known to vary greatly among species, but differences between populations of the same species have rarely been considered. We used microsatellite DNA markers to assess parentage of offspring in a subarctic population of the socially monogamous Yellow Warbler Dendroica petechia nesting near Churchill, Manitoba. We found a significantly lower proportion of extrapair young in the Churchill population than in a temperate population nesting approximately 1500 km to the south near the Queen's University Biological Station (QUBS) in Ontario. We show that the Churchill population also had significantly lower nesting density and significantly higher breeding synchrony; both are factors that have been hypothesized to affect extrapair paternity negatively. We suggest that inter-population comparisons can be used to test proximate mechanisms affecting extrapair paternity and in some cases may be better than interspecific or inter-individual comparisons. Towards this end we list eight other species that have had extrapair paternity measured in different populations. Studies that use genetic markers to assess the parentage of offspring have shown that extrapair paternity occurs in a wide range of bird species and that there is considerable interspecific variation in the proportion of offspring fathered by extrapair males (see Westneat and Sherman 1997). Understanding the variation in extrapair paternity has become a focus of mating system research. Nearly all species studied to date, however, have had extrapair paternity measured in only one population. Thus, it is not known how much of the apparent interspecific variation in extrapair paternity might be due to variation between populations within a species. For example, in the Willow Warbler Phylloscopus trochilus, the proportion of extrapair paternity differs considerably between a population in Sweden (0%; Gyllensten et al. 1990) and one in Norway (33%; Bjornstad and Lifjeld 1997). In this study we use microsatellite DNA markers to assess the parentage of offspring in a far northern population of the socially monogamous Yellow Warbler Dendroica petechia. Our first aim was to test whether the proportion of extrapair paternity in this population at the northern edge of the species' range differs from the 33% extrapair paternity in a population 1500 km to the south (Yezerinac et al. 1995). Nesting density and breeding synchrony are the most likely proximate causes of variation in the proportion of extrapair paternity (Westneat and Sherman 1997). However, evidence is mixed regarding the effect of either factor. Between-species comparisons provide no evidence that density affects extrapair paternity, whereas comparison of individuals nesting at different densities in the same population does suggest that density sometimes positively affects extrapair paternity (see Westneat and Sherman 1997). The apparent effect of synchrony on extrapair paternity is also debatable based upon results of interspecific and intraspecific studies (see Westneat and Sherman 1997, Stutchbury 1998, Weatherhead and Yezerinac 1998). In this study we measured nesting density and breeding synchrony within each of the two populations for which extrapair paternity was measured. Our second aim was to determine if there were synchrony and density differences between the populations that might explain any differences in extrapair paternity.

Farmland birds in southern Ontario: field use, activity patterns and vulnerability to pesticide use

The use of cropfields by birds is largely unknown in southern Canada and consequently the risk incurred by pesticide use on bird populations cannot be adequately characterised. The activity patterns and relative interior to edge use of bird species were examined for four crops in southern Ontario to assess the susceptibility of different species to pesticide use. Altogether 138 species were identified in the four crops over the 2 year period but only 25 species were recorded during 50% of visits in at least 1 month: 14 in corn ( Zea mays L.), 16 in soybean ( Glycine max L. Merr.), 14 in apple ( Malus spp.) orchards and eight in vineyards ( Vitis spp.). Territorial behaviour was an important activity for several species from May through July in the four crops. Nesting was confirmed in May, June and July for most species, with the exception of American Goldfinch Carduelis tristis, Chipping Sparrow Spizella passerina and Cedar Waxwing Bombycilla cedrorum which nested in August/September. Foraging was the most important activity for most species in all months (7/10 species in May, 6/8 species in June, 4/8 species in July, 5/8 August/September). Few fledgling young were observed. Most species used field edges consistently more often than expected in corn and soybean fields, according to the edge/interior ratio, Yellow Warbler Dendroica petechia being the exception. In apple orchards, relatively few species differentiated between edge and interior. Based on their frequency of occurrence (>50%), behaviour and temporal coincidence with pesticide applications, 13 species were considered most at risk: Killdeer Charadrius vociferus, Horned Lark Eremophila alpestris, American Crow Corvus brachyrhynchos, American Robin Turdus migratorius, European Starling Sturnus vulgaris, Chipping Sparrow, Vesper Sparrow Pooecetes gramineus, Savannah Sparrow Passerculus sandwichensis, Song Sparrow Melospiza melodia, Red-winged Blackbird Agelaius phoeniceus, Common Grackle Quiscalus quiscala, Brown-headed Cowbird Molothrus ater and Barn Swallow Hirundo rustica. The latter species, because of its foraging habit, is less likely to be exposed to pesticides. This study was important to identify focal species that can be used for detailed investigations on exposure to pesticides.

Ecology and Behavior of Yellow Warblers Breeding in Rhode Island's Great Swamp

I examined breeding phenology, territoriality, social interactions, reproductive success, and survivorship in a population of yellow warblers (Dendroica petechia) breeding in the Great Swamp, Washington County, Rhode Island. In four seasons of study (1992-1995), males preceded females in arriving on the breeding grounds. Females began building nests in early May. Of 94 nests whose host plants were identified, 28 were in Rosa, 28 in Salix, 12 in Clethra alnifolia, and 26 in plants of 12 other species. Clutches were initiated between May 14 and June 14. Males defended territories and formed monogamous social pair bonds with the females nesting on these territories. The breeding density was approximately five pairs/ha of occupied habitat. Only females were observed building nests or incubating clutches. Both members of social pairs participated in provisioning nestlings, with no significant difference in provisioning rates between the sexes. The mean size of first clutches was 4.5 (SE = 0.09), and clutch size declined as the season progressed. The probability that a newly laid egg would yield a surviving fledgling was 0.46. One instance of brood parasitism by brown-headed cowbirds (Molothrus ater) was observed. The percentage of birds breeding in one year that returned to the study area the next year was 56% for males and 42% for females. These results provide an opportunity for comparison with populations in other regions and a baseline against which future environmental impacts in southern Rhode Island might be evaluated.

Parentage and kinship studies in an obligate brood parasitic bird, the brown-headed cowbird (Molothrus ater), using microsatellite DNA markers.

Recent studies suggest that single-locus microsatellite DNA markers have the potential to unambiguously resolve parentage among individuals in natural populations where maternity is known. However, their power for determining parentage when neither parent is known is unclear. Here we investigate the usefulness of microsatellite DNA markers to determine parentage in a brood parasitic bird, the brown-headed cowbird (Molothrus ater), where, for a given offspring, no a priori knowledge of either parent is available. Seven polymorphic microsatellite DNA markers isolated from brown-headed cowbirds and yellow warblers (Dendroica petechia) were used to genetically characterize an individually marked breeding population of male and female cowbirds at Delta Marsh, Manitoba. Forty-four males, 21 females, and 61 cowbird chicks were genotyped at seven loci using DNA amplified from blood and tissue samples. The mean exclusion probabilities pooled across all seven loci were 0.9964 for males and 0.9948 for females. Two null (non-amplifying) alleles at one locus were discovered and accounted for by constructing alternate nonoverlapping primer sets. Exclusion analyses performed using all individuals determined both paternity and maternity for 43 chicks and paternity only for 4 chicks. Another microsatellite locus was then used to determine paternity for three additional chicks. Relatedness analyses placed 12 of the 18 remaining chicks not assigned both maternity and paternity into four unique full sibling groups. Overall, 90.16% (55 of 61) of all offspring examined were placed into distinct parent/sibling groups, demonstrating that this marker set is extremely useful for parentage studies in this species.

Timing of Egg Laying in Yellow Warblers

Many aspects of the breeding biology of wild birds have been studied thoroughly, but surprisingly little information has been obtained on when birds lay their eggs. For instance, few data exist on the time of day eggs are laid (Scott 1991), and the factors that control laying time are uncertain even for domestic species (Sharp 1980). How long females spend in their nests while laying each egg (i.e. laying bout; Sealy et al. 1995) and the interval between successive eggs in a clutch (i.e. laying interval; Schubert and Cooke 1993) are also poorly known (Scott 1991, Ricklefs 1993). Laying time and interval are important aspects of a species' breeding biology because they have implications for the energetics of the laying female (Astheimer 1985), hatching asynchrony of the resulting clutch (Ricklefs 1993), timing of brood parasitism (Scott 1991, Meijer 1992, Neudorf and Sealy 1994), and timing of pair and extrapair copulations (Birkhead 1988; but see Birkhead et al. 1996). Repeated inspection of nests has been the technique most frequently employed to obtain an estimate of laying time (see Skutch 1952). Using this technique, the time a female lays her egg is bracketed by visits before and after the egg has been laid, thereby providing an estimate of laying time. Laying times may be determined more accurately by observing nests continuously, either from a blind or with a video camera (Muma 1986, Sealy et al. 1995, Haftorn 1996). Direct observation also allows researchers to record other behaviors at the nest (Sealy et al. 1999) and to determine details of the act of oviposition (Nolan 1978, Sealy et al. 1995, Haftorn 1996). Laying times of passerines vary among species from several hours before sunrise until afternoon or early evening (e.g. Rosengren 1993, Scott 1993, Frith 1994). Likewise, different species of passerines have characteristic intervals between successive eggs in a clutch, ranging from approximately one day (23 to 27 h) to 48 h (e.g. Astheimer 1985, Morton and Pereyra

Early Native American Writing: New Critical Essays

1. 'Honoratissimi Benefactores': Native American students and two seventeenth-century texts in the university tradition Wolfgang Hochbruck and Beatrix Dudensing Reichel 2. 'Pray, Sir, consider a little': rituals of subordination and strategies of resistance in the letters of Hezekiah Calvin and David Fowler to Eleazer Wheelock Laura J. Murray 3. '(I speak like a fool but I am constrained): Samson Occom's Short Narrative and economies of the racial self Dana D. Nelson 4. Where, Then, Shall We Place the Hero of the Wilderness?: William Apess's Eulogy on King Philip and doctrines of racial destiny Anne Marie Dannenberg 5. 'They ought to enjoy the home of their fathers': the Treaty of 1838, Seneca Intellectualism, and Literary Genesis Daniel F. Littlefield, Jr 6.' I am Joaquin!': Space and freedom in Yellow Bird's The Life and Adventures of Joaquin Murieta, the Celebrated California Bandit John Lowe 7. This Voluminous Unwritten Book of Ours: early Native American writers and oral tradition William M. Clements 8. 'A terrible sickness among them': Smallpox and stories of the Frontier Helen Jaskoski 9. 'A desirable citizen, a practical business man': G. W. Grayson - Creek mixed blood, nationalist, and autobiographer Robert F. Sayre 10. An Indian ... an American: ethnicity, assimilation and balance in Charles Eastman's From the Deep Woods to Civilization Eric Peterson 11. 'Overcoming all obstacles': the assimilation debate in Native American women's journalism of the Dawes era Carol Batker 12. 'My people ... my kind': Mourning Dove's Cogewa, the Half-Blood as a narrative of mixed descent Martha L. Viehmann 13. 'Because I understand the storytelling art': the evolution of D'Arcy McNicle's The Surrounded Birgit Hans.

Rapid decline of host defences in response to reduced cuckoo parasitism: behavioural flexibility of reed warblers in a changing world

On Wicken Fen and nearby watercourses eastern England, parasitism by cuckoos, Cuculus canorus, declined from 26 and 16 of reed warbler (Acrocephalus scirpaceus) nests in 1985 and 1986, respectively...

Parental-care responses by yellow warblers (Dendroica petechia) to simultaneous manipulations of food abundance and brood size

Theoretical models view biparental care as a state of equilibrium that can be maintained only when the amount of parental care provided by one parent depends on the amount provided by its mate. According to these models, biparental care results when a decrease in the contribution of one parent is partially, but not completely, compensated for by an increase in the contribution of the other parent. Furthermore, this equilibrium state can only be stable if any other external factor affects male and female effort equally. We used yellow warblers (Dendroica petechia) to examine whether changes in brood size and food abundance affect the parental contributions of the sexes equally. Supplemental food did not affect parental care by either sex, but brood size did. Both males and females provided more to larger broods, and in large broods only, their provisioning rates increased with nestling age. Parental effort per nestling was similar in the two sexes, being higher for smaller broods and increasing with nestling age. Based on brood biomass, parental effort was greater for smaller broods, and decreased with nestling age in females only. Therefore, in agreement with current models of the maintenance of biparental care, the effects of brood size and nestling age on parental care did not differ significantly between the sexes. Nonetheless, data from other species and theory indicate that the costs and benefits of providing parental care differ between the sexes, so it is unlikely that biparental care can be maintained solely by a partial compensation response.

Breeding Bird Community Composition in Relation to Riparian Vegetation Structure in the Western United States

Riparian zones, which are under increasing pressure by various users, provide sources of avian diversity in many landscapes of the semiarid West; however, there are few data available that address avian community composition in different riparian vegetation structures. We compared total abundance of diurnal breeding birds, individual bird species abundance, bird species richness, and vegetation composition and structure among streamside vegetation associations in Bear and Silvies valleys in eastern Oregon during 1993 and 1994. We collected bird and vegetation data along 4 replicate transects within each of 3 vegetation associations characterized by streamside vegetation structure: herbaceous xeric shrub, discontinuous mesic shrub, and continuous mesic shrub. Total bird abundance was greater (P < 0.001) in the continuous mesic shrub association than in the herbaceous xeric shrub and discontinuous mesic shrub associations during 1993 and 1994. Species richness was inconsistent between years among vegetation associations (P = 0.034); it was greatest (Ps ≤ 0.037) in the continuous and discontinuous mesic shrub associations in 1993, and greatest (Ps ≤ 0.003) in the continuous mesic shrub association in 1994. Yellow warbler (Dendroica petechia), song sparrow (Melospiza melodia), willow flycatcher (Empidonax traillii), American robin (Turdus migratorius), common snipe (Gallinago gallinago), bobolink (Dolichonyx oryzivorus), and Vaux's swift (Chaetura vauxi) were most abundant in the continuous mesic shrub association (Ps ≤ 0.088). Savannah sparrow (Passerculus sandwichensis), black tern (Chlidonias niger), and American wigeon (Anas americana) were most abundant in the herbaceous xeric shrub association (Ps ≤ 0.032). Yellow warblers, willow flycatchers, and song sparrows, which almost exclusively depend on hydrophytic shrub thickets for nesting in the semiarid western United States, are especially threatened by the elimination or simplification of continuous associations of mesic shrub vegetation. We recommend that continuous associations of mesic shrub vegetation be maintained'or restored where possible because this vegetation structure is associated with avian abundance, species richness, riparian-associate bird species abundance, and landscape-level biological diversity.

Nestling competition, rather than supernormal stimulus, explains the success of parasitic brown-headed cowbird chicks in yellow warbler nests

Interspecific parasitic chicks are usually fed more than the smaller host young with whom they share the nest. This could be due to parasitic chicks having evolved exaggerated features that are preferred by the adults to the features present in their own young (the supernormal stimulus hypothesis). Alternatively, the success of parasitic chicks could be due to them being better competitors. We tested these hypotheses by studying the interaction between brown-headed cowbird chicks, Molothrus ater , and a common small host, the yellow warbler, Dendroica petechia . Parasitic chicks begged more intensively than the host's young and received most of the feeds. The relative height reached by the begging chicks of both species was the most important variable in determining their feeding success. Being larger and begging intensively, brown-headed cowbirds were better able to reach higher than the host's young, but at equal heights parasitic chicks were no better than the host's young at gaining feeds. It is suggested that the success of the brown-headed cowbirds when parasitizing yellow warblers is due to them physically out-competing the smaller young of their hosts, and not to them evoking a stronger response from the hosts by being a supernormal stimulus.

Short Incubation Periods of Brown-Headed Cowbirds: How Do Cowbird Eggs Hatch before Yellow Warbler Eggs?

Brown-headed Cowbird (Molothrus ater) eggs in natural nests hatch either before or at the same time as Yellow Warbler (Dendroica petechia) eggs despite being almost twice the size. Cowbird eggs may hatch before Yellow Warbler eggs because they (1) prolong the incubation of host eggs, (2) have more rapid embryonic development, or (3) hatch in response to stimuli from host eggs. We tested these hypotheses by comparing the incubation periods of cowbird eggs incubated in natural nests, incubated artificially in isolation from other eggs, and incubated artificially in clutches of Yellow Warbler eggs. Cowbird eggs incubated artificially in isolation from other eggs took significantly longer to hatch than either artificially incubated warbler eggs or naturally incubated cowbird eggs. The ratio of incubation period to egg volume was less for cowbirds than warblers, which indicates that cowbird embryos develop more rapidly relative to their size. The presence of a cowbird egg in natural nests significantly prolonged the incubation period of warbler eggs. Therefore, cowbird eggs appear to disrupt the incubation of smaller host eggs. Finally, the incubation periods of cowbird eggs incubated artificially in contact with warbler eggs were shorter, but not significantly so, than cowbird eggs incubated in isolation from other eggs. These results suggest that in addition to rapid embryonic development, cowbirds hatch before many hosts by disrupting incubation of smaller eggs and, possibly hatching early in response to stimuli from host eggs.

Parental-care responses by yellow warblers (&lt;i&gt;Dendroica petechia&lt;/i&gt;) to simultaneous manipulations of food abundance and brood size

Parental-care responses by yellow warblers (&lt;i&gt;Dendroica petechia&lt;/i&gt;) to simultaneous manipulations of food abundance and brood size

Reproductive synchrony and extra-pair mating strategy in a socially monogamous bird,Dendroica petechia

Depending on the circumstances under which extra-pair mating occurs, theory makes opposing predictions about how reproductive synchrony should influence extra-pair paternity. This study investigated which sex initiated extra-pair mating in the yellow warbler, whether extra-pair behaviour and extra-pair paternity were related to reproductive synchrony, and whether synchrony affected the mating success of all males equally. Observations and captures of individuals making territorial intrusions indicated that males initiated extra-pair mating. Spatial patterns of male territorial intrusions and of extra-pair paternity were similar. Males’ extra-pair activity was reduced when their social partner was fertile. More offspring were sired by the extra-pair male when the female nested asynchronously with that sire's social mate. Neither population-wide synchrony, nor synchrony with neighbours, however, seemed to predict the incidence of extra-pair parentage or the identity of the sire, indicating factors other than synchrony were also important. Males with more breast streaking (a plumage ornament) were more successful as extra-pair sires, and were least affected by the constraint of synchrony. Larger males were less often cuckolded, and achieved extra-pair success mainly when their partner was not fertile. Thus, male yellow warblers apparently use different mating tactics depending on their plumage and size. More generally, the results suggest how mating strategies are affected by which sex initiates extra-pair mating and by the relative contributions of within-pair and extra-pair paternity to total reproductive success.

Isolation of microsatellite DNA markers from a passerine bird, Dendroica petechia (the yellow warbler), and their use in population studies.

We describe the isolation and genetic characterization of five microsatellite loci in a passerine bird, the yellow warbler Dendroica petechia, and assess their use for various types of population-level analysis using data from two breeding populations. All five loci show levels of variability comparable to those observed in other vertebrates (Hexp = 0.388-0.989). One locus, Dp mu 05, is highly variable with 46 alleles detected in 41 individuals. All loci appeared to segregate in a Mendelian fashion as judged by patterns of inheritance in known families. However, one locus showed a significant heterozygote deficiency in one population suggesting the possible presence of null alleles at this locus. These markers provide a highly accurate system for determination of parentage in this species: the probability of detecting extrapair fertilization by males given known maternity was 0.999 in each of two separate populations. Comparison of allele frequencies and genetic distances between the two populations showed no evidence for significant differences in allele frequencies at individual loci, whereas the overall genetic distance and FST-value are significantly different from zero suggesting weak differentiation. Finally, cross-species amplification experiments showed that at least one locus appears to amplify products in a wide range of birds including nonpasserine species. Thus, our results demonstrate that these loci will provide a useful set of genetic information for addressing a wide range of population-level analyses in this and other bird species.

Isolation of microsatellite DNA markers from a passerine bird, Dendroica petechia (the yellow warbler), and their use in population studies

We describe the isolation and genetic characterization of five microsatellite loci in a passerine bird, the yellow warbler Dendroica petechia, and assess their use for various types of population-level analysis using data from two breeding populations. All five loci show levels of variability comparable to those observed in other vertebrates (Hexp = 0.388 – 0.989). One locus, Dpµ05, is highly variable with 46 alleles detected in 41 individuals. All loci appeared to segregate in a Mendelian fashion as judged by patterns of inheritance in known families. However, one locus showed a significant heterozygote deficiency in one population suggesting the possible presence of null alleles at this locus. These markers provide a highly accurate system for determination of parentage in this species: the probability of detecting extrapair fertilization by males given known maternity was 0.999 in each of two separate populations. Comparison of allele frequencies and genetic distances between the two populations showed no evidence for significant differences in allele frequencies at individual loci, whereas the overall genetic distance and FST-value are significantly different from zero suggesting weak differentiation. Finally, cross-species amplification experiments showed that at least one locus appears to amplify products in a wide range of birds including nonpasserine species. Thus, our results demonstrate that these loci will provide a useful set of genetic information for addressing a wide range of population-level analyses in this and other bird species.

Host responses to cowbirds near the nest: cues for recognition

Two cues (bill shape and vocalizations) that yellow warblers,Dendroica petechiamay use to recognize brown-headed cowbirds,Molothrus aterwere examined experimentally. Female yellow warblers responded more intensely to a control cowbird than one with a longer, thinner bill, which suggests that bill shape was an important cue in recognition. Responses involved close approaches, ‘seet’ alarm calls and sitting in the nest. Female yellow warblers distinguished between vocalizations of male and female cowbirds and those of a song sparrow,Melospiza melodia(control). They responded most intensely to female cowbird ‘chatter calls’ and least intensely to the sparrow song; responses to male cowbird ‘perched song’ were intermediate in intensity. The results suggest that female yellow warblers recognize cowbirds on the basis of bill shape and vocalizations. Furthermore, these results, coupled with previous findings, suggest that female yellow warblers distinguish between male and female cowbirds by vocalizations but not appearance.

Extra–pair mating, male plumage coloration and sexual selection in yellow warblers (Dendroica petechia)

Extra-pair mating has been proposed as a source of sexual selection responsible for secondary sexual traits that are common among socially monogamous birds, although supporting evidence is scant. In the socially monogamous yellow warbler, males are larger than females, and unlike females, have extensive reddish streaking on their breasts. Using DNA fingerprinting we show that within-pair parentage was positively related to male size, and that extra-pair mating success was positively related to the amount of streaking on the breast. To our knowledge, this is the first intraspecific evidence of an association between a male plumage ornament and gains of extra-pair paternity that is apparently independent of age. This study confirms that extra-pair mating can be an important mechanism of sexual selection even when the most successful sires are commonly cuckolded, and refutes a previous hypothesis that the variation in plumage and behaviour among male yellow warblers is an example of alternative, equally successful, evolutionarily stable strategies (ESS). More generally, the demonstrated independence of within-pair and extra-pair success and their associated traits indicates that where animals have multiple secondary sexual traits, different traits may be selected by different mechanisms that contribute to total reproductive success.