Blue-winged Warbler Research Articles

Geographic variability in mitochondrial introgression among hybridizing populations of Golden-winged (Vermivora chrysoptera) and Blue-winged (V.opinus) Warblers

The rapidly declining Golden-winged Warbler (Vermivora chrysoptera) is of conservation concern owing in part to hybridization with the closely related Blue-winged Warbler (V. pinus). These species hybridize extensively in eastern North America and over the past century the Blue-winged Warbler has displaced the Golden-winged Warbler from substantial regions of its historic breeding range. A previous study suggested that these genetic interactions result in rapid and asymmetric introgression of Blue-winged Warbler mitochondrial DNA (mtDNA) into Golden-winged phenotype populations within the zones of contact, but more recent and extensive surveys have documented a more complex pattern of genetic interchange between these taxa. We surveyed mtDNA/phenotype associations in 104 individuals of known phenotype drawn from two locations with different histories of contact and found substantial variation between sites in the extent of introgression. Where both species have co-existed for more than a century, we found evidence of bi-directional introgression and the long-term persistence of Golden-winged mtDNA haplotypes. At the leading edge of the northward expansion of Blue-winged Warblers, we found predominantly Golden-winged Warbler mtDNA haplotypes in both Golden-winged and hybrid-phenotype individuals. Across both sites, genetic swamping does not appear to be occurring via the early immigration of Blue-winged Warbler females into populations dominated by Golden-winged Warbler phenotypes. Instead, the differing patterns of mitochondrial introgression may be driven by the relative local population sizes of the parental species coupled with subtle between-species differences in mate choice and habitat preferences.

EDGE- AND AREA-SENSITIVITY OF SHRUBLAND BIRDS

Populations of shrubland birds in eastern North America have consistently declined since the 1960s, but conservation is hampered by an inadequate understanding of the area requirements of most species. We examined the sensitivity of shrubland specialists to (a) the area of shrub stands and (b) proximity to mature-forest edges, and we evaluated whether habitat characteristics, food resources, or productivity of bird populations could have caused the relationships we identified. In 2002–2003, we used constant-effort mist-netting on 6 small (4–8 ha) and 6 large (13–16 ha) regenerating clearcuts that were 4–6 years post-harvest in southern Ohio, USA. We placed 3 nets at 20, 50, and 80 m from the mature-forest edge (n = 9 nets per site), and we sampled vegetation, fruit, and arthropods at each net. Seven of 8 shrubland specialists, particularly blue-winged warbler, prairie warbler, yellow-breasted chat, indigo bunting, and field sparrow, avoided mature-forest edges, with twice as many birds caught 80 m from edges compared to 20 m. Abundances of most species, especially yellow-breasted chats, were positively correlated with area, though the combined area effect was not statistically significant. We found no evidence of reduced avian productivity in small stands. Neither area nor edge was associated with habitat characteristics, fruit abundance, or arthropod biomass. Our results suggest shrubland birds avoid habitat edges. Thus, small or narrow cuts may not provide optimal habitat for this suite of declining species, and managers should consider options to minimize edge and provide larger patches of shrubland habitats in landscape-scale planning efforts.

Reciprocal Introgression Between Golden-Winged Warblers (Vermivora Chrysoptera) and Blue-Winged Warblers (V. Pinus) in Eastern North America

Abstract Golden-winged Warblers (Vermivora chrysoptera) and Blue-winged Warblers (V. pinus) are small, brightly colored Neotropical migrant birds that breed in eastern North America. Wherever the two species occur together, they hybridize to a limited degree, producing distinctive hybrid phenotypes. In recent decades, chrysoptera has experienced dramatic population declines across much of its range. Those declines have often been correlated with establishment and increase of pinus in the same areas, but it remains uncertain what, if any, role pinus has played in driving the decline of chrysoptera. In a first attempt at molecular genetic analysis of chrysoptera-pinus population dynamics, Gill (1997) reported cryptic, completely asymmetric, and possibly very rapid introgression of pinus mitochondrial DNA (mtDNA) into chrysoptera, causing what he termed “local cytonuclear extinction” of chrysoptera. As Gill (1997) noted, however, those results were based on relatively small samples from a single area in Pennsylvania. To begin to investigate the generality of Gill’s findings and to establish a baseline for long-term genetic and ecological studies, we intensively sampled one new study area (in southern West Virginia) and also sampled more broadly across two other areas (in Michigan and Ohio) that have experienced pinus invasions and chrysoptera declines. In southern West Virginia, introgression of mtDNA appeared to be roughly symmetrical: 15% (11 of 72) of pinus phenotypes possessed chrysoptera mtDNA, and 12% (17 of 137) of chrysoptera phenotypes possessed pinus mtDNA. Results from much smaller samples from Michigan and Ohio also failed to show any evidence of asymmetric mitochondrial introgression. The results we report here, based on mtDNA and plumage phenotype information for 337 birds representing much of the range of the two species, indicate that previous genetic results and inferences from Pennsylvania may not be broadly applicable to the many areas of contact between chrysoptera and pinus in eastern North America.

Reciprocal Introgression between Golden-Winged Warblers (Vermivora chrysoptera) and Blue-Winged Warblers (V. pinus) in Eastern North America

Reciprocal Introgression between Golden-Winged Warblers (Vermivora chrysoptera) and Blue-Winged Warblers (V. pinus) in Eastern North America

RECIPROCAL INTROGRESSION BETWEEN GOLDEN-WINGED WARBLERS (VERMIVORA CHRYSOPTERA) AND BLUE-WINGED WARBLERS (V. PINUS) IN EASTERN NORTH AMERICA

Abstract Golden-winged Warblers (Vermivora chrysoptera) and Blue-winged Warblers (V. pinus) are small, brightly colored Neotropical migrant birds that breed in eastern North America. Wherever the two species occur together, they hybridize to a limited degree, producing distinctive hybrid phenotypes. In recent decades, chrysoptera has experienced dramatic population declines across much of its range. Those declines have often been correlated with establishment and increase of pinus in the same areas, but it remains uncertain what, if any, role pinus has played in driving the decline of chrysoptera. In a first attempt at molecular genetic analysis of chrysoptera-pinus population dynamics, Gill (1997) reported cryptic, completely asymmetric, and possibly very rapid introgression of pinus mitochondrial DNA (mtDNA) into chrysoptera, causing what he termed “local cytonuclear extinction” of chrysoptera. As Gill (1997) noted, however, those results were based on relatively small samples from a single area in Penn...

Effects of Vegetation, Interspecific Competition, and Brood Parasitism on Golden-Winged Warbler (Vermivora Chrysoptera) Nesting Success

Abstract The recent decline of Golden-winged Warblers (Vermivora chrysoptera) correlates with the loss of suitable nesting habitat, range expansion by Blue-winged Warblers (V. pinus), and eastward expansion of Brown-headed Cowbirds (Molothrus ater). Multivariate statistics were used to examine effects of those factors on Golden-winged Warbler reproduction in north central New York. Herb and shrub cover were positively correlated with clutch size. Blue-winged Warbler proximity was negatively correlated with Golden-winged Warbler clutch size. Tree cover and perhaps herb cover, after adjusting for brood size, correlated with a reduced number of Golden-winged Warbler fledglings. Herbaceous cover correlated with a greater number of cowbird eggs in Golden-winged Warbler nests. Cowbird parasitism correlated with a reduction in the number of Golden-winged Warbler eggs incubated and proportion of incubated eggs that hatched. However, cowbird parasitism, after adjusting for brood size, did not significantly affect nestling success rate. Cowbirds parasitized 30% of Golden-winged Warbler nests, which reduced the number of Golden-winged Warblers fledged by ∼17%. Average herb and tree cover values were 69 and 22 in Golden-winged Warbler territories and 60 and 23 in Blue-winged Warbler territories, respectively, with herb cover significantly greater for Golden-winged Warblers. Territories in the earliest stages of succession used by Golden-winged Warblers supported larger clutches and a reduction in the strong, negative effect of Blue-winged Warbler proximity and an increase in the negative effect correlated with cowbirds, if cowbirds were locally abundant.

EFFECTS OF VEGETATION, INTERSPECIFIC COMPETITION, AND BROOD PARASITISM ON GOLDEN-WINGED WARBLER (VERMIVORA CHRYSOPTERA) NESTING SUCCESS

Abstract The recent decline of Golden-winged Warblers (Vermivora chrysoptera) correlates with the loss of suitable nesting habitat, range expansion by Blue-winged Warblers (V. pinus), and eastward expansion of Brown-headed Cowbirds (Molothrus ater). Multivariate statistics were used to examine effects of those factors on Golden-winged Warbler reproduction in north central New York. Herb and shrub cover were positively correlated with clutch size. Blue-winged Warbler proximity was negatively correlated with Golden-winged Warbler clutch size. Tree cover and perhaps herb cover, after adjusting for brood size, correlated with a reduced number of Golden-winged Warbler fledglings. Herbaceous cover correlated with a greater number of cowbird eggs in Golden-winged Warbler nests. Cowbird parasitism correlated with a reduction in the number of Golden-winged Warbler eggs incubated and proportion of incubated eggs that hatched. However, cowbird parasitism, after adjusting for brood size, did not significantly affect ...

Blue-winged Warbler (Vermivora cyanoptera)

Blue-winged Warbler (Vermivora cyanoptera)

Blue-winged Warbler (Vermivora cyanoptera)

Blue-winged Warbler (Vermivora cyanoptera)

A Reassessment of the Status of Golden-winged and Blue-winged Warblers in the Hudson Highlands of Southern New York

Populations of Golden-winged Warblers (Vermivora chrysoptera) and Blue-winged Warblers (V. pinus) have coexisted in the Hudson Highlands for a century. Previous researchers in our study area suggested this unusual coexistence might be due to a low frequency of hybrids. However, during the 1998–1999 breeding season we found that 10% of the males were hybrids, a value similar to many studies elsewhere. We observed that hybrid males ceased singing and other conspicuous behaviors early in the breeding season. Pair formation and nesting by hybrids appeared to be rare, perhaps because of the reduced vigor of their displays. Most of the fieldwork by previous researchers in this area was conducted after the date when hybrids cease singing, which may account for prior reports of the absence of hybrids.

Behavioral Interactions between Golden-Winged and Blue-Winged Warblers

The breeding range of the Golden-winged Warbler (Vermivora chrysoptera) has expanded in some regions and contracted in others for more than a century (Gill 1980). The decline of the Golden-winged Warbler often is attributed to loss of breeding habitat and/or interactions with the Blue-winged Warbler (V pinus; Confer and Knapp 1977, 1981; Will 1986; Hands at al. 1989; Confer 1992a,b). Golden-winged Warblers nest in early successional habitat. Abandoned farmland is the precursor of most its nesting habitat, although fires, lumbering, and powerline maintenance also create habitat (Hands et al. 1989). The decline of the Goldenwinged Warbler is part of a widespread reduction in early successional species (Sauer et al. 1997) that is correlated with habitat loss. For example, abandonment of farmland in New Hampshire peaked about a century ago, and early successional habitat was most abundant from 1900 to 1955 (Litvaitis 1993). Since 1955, early successional habitat has decreased to nearly zero. Similar loss of habitat has occurred throughout the reforested northeastern United States, and the abundance of Golden-winged Warblers and other early successional birds has declined (Hill and Hagan 1991, Witham and Hunter 1992, Smith et al. 1993). At the other extreme, the rate of farmland abandonment has increased in Pennsylvania, Minnesota, and Wisconsin from 72,000 ha per year during 1925 to 1960 to 185,000 ha per year from 1960 to 1990 (Census of Agriculture 1935, 1992). Numbers of Golden-winged Warblers increased from 1980 to 1996 (Sauer et al. 1997). Within forested habitats, bird species turnover may continue as young forests mature (Holmes et al. 1986). Rappole and McDonald (1994) speculated that Golden-winged Warblers (but not Blue-winged warblers) have been seriously reduced in numbers as a result of winter-habitat loss.... However, regional declines of Golden-winged Warblers began more than 90 years ago (Gill 1980), before loss of winter habitat was extensive, and their numbers are increasing in the northern portions of their range (Sauer et

Numts: A Challenge for Avian Systematics and Population Biology

CONFER, J. L. AND K. KNAPP. 1981. Golden-winged Warblers and Blue-winged Warblers: The relative success of a habitat specialist and a generalist. Auk 98:108-114. FICKEN, M. S., AND R. W. FICKEN. 1968. Territorial relationships of Blue-winged Warblers, Goldenwinged Warblers, and their hybrids. Wilson Bulletin 80:161-172. GILL, F. B. 1980. Historical aspects of hybridization between Blue-winged and Golden-winged warblers. Auk 97:1-18. GILL, F. B. 1997. Local cytonuclear extinction of the Golden-winged Warbler. Evolution 51:519-525. GILL, F. B., AND W. E. LANYON. 1964. Experiments on species discrimination in Blue-winged Warblers. Auk 81:53-64. GILL, F. B., AND B. G. MURRAY, JR. 1972. Discrimination behavior and hybridization of the Bluewinged and Golden-winged warblers. Evolution 26:282-293. HANDS, H. M., R. D. DROBNEY, AND M. R. RYAN. 1989. Status of the Golden-winged Warbler in the northcentral United States. United States Fish and Wildlife Service, Twin Cities, Minnesota. HILL, N. P., AND J. M. HAGAN III. 1991. Population trends of some northeastern North American landbirds: A half-century of data. Wilson Bulletin 103:165-182. HOLMES, R. T., T. W. SHERRY, AND F. W. STURGES. 1986. Bird community dynamics in a temperate deciduous forest: Long-term trends at Hubbard Brook. Ecological Monographs 50:201-220. LITVAITIS, J. A. 1993. Response of early successional vertebrates to historic changes in land use. Conservation Biology 7:866-873. MURRAY, B. G., JR., AND F. B. GILL. 1976. Behavioral interactions of Blue-winged and Golden-winged warblers. Wilson Bulletin 88:231-254. RAPPOLE, J. H., AND M. V. McDoNALD. 1994. Cause and effect in population declines of migratory birds. Auk 111:652-660. SAUER, J. R., J. E. HINES, G. GOUGH, I. THOMAS, AND B. G. PETERJOHN. 1997. The North American Breeding Bird Survey home page, version 96.3. Patuxent Wildlife Research Center, Laurel, Maryland. SCHEIDER, F. 1959. Warblers in southern New York. Kingbird 9:13-19. SMITH, C. R., D. M. PENCE, AND R. J. O'CONNOR. 1993. Status of Neotropical migratory birds in the northeast: A preliminary assessment. Pages 172-188 in Status and management of Neotropical migratory birds (D. M. Finch and P. W. Stangel, Eds.). United States Forest Service General Technical Report RM-229, Newton Corner, Massachusetts. WILL, T. C. 1986. The behavioral ecology of species replacement: Blue-winged and Golden-winged warblers in Michigan. Ph.D. dissertation, University of Michigan, Ann Arbor. WITHAM, J. W, AND M. L. HUNTER, JR. 1992. Population trends of Neotropical migrant landbirds in northern coastal New England. Pages 85-95 in Ecology and conservation of Neotropical migrant landbirds (J. M. Hagan III and D. W Johnston, Eds.). Smithsonian Institution Press, Washington, D.C.

LOCAL CYTONUCLEAR EXTINCTION OF THE GOLDEN-WINGED WARBLER.

I compared the mtDNA compositions of two adjacent populations of Vermivora chrysoptera (golden-winged warbler) at different stages of transient hybridization with its sister species V. pinus (blue-winged warbler). Pinus mtDNA introgresses asymmetrically and perhaps rapidly into chrysoptera phenotypes without comparable reverse introgression of chrysoptera mtDNA into replacing pinus populations. Pinus mtDNA was virtually fixed (98%) in an actively hybridizing lowland population with varied phenotypes. Pinus mtDNA increased from 27% (n = 11) in 1988 to 70% (n = 10) in 1992 in successive samples of a highland population in the initial stages of hybridization. This population comprised mostly pure and slightly introgressed chrysoptera phenotypes. The rapid pace of asymmetrical introgression may be the result of initial invasion of chrysoptera populations by pioneering female pinus and/or an unknown competitive advantage of pinus females and their daughters over chrysoptera females.

Forest Bird Response to Regeneration Practices in Central Hardwood Forests

We studied breeding songbird populations in a managed, predominantly forested landscape, in southeastern Missouri. We determined differences in the relative abundance of breeding birds in forest stands that had been harvested by the clearcut (n = 12), shelterwood (n = 12), group selection (n = 12), and singletree selection (n = 10) forest regeneration methods, and mature even-aged stands (n = 12). Five migrant songbirds, the blue-winged warbler (Vermivora pinus), prairie warbler (Dendroica discolor), rufous-sided towhee (Pipilo erythrophthalmus), white-eyed vireo (Vireo griseus), and yellow-breasted chat (Icteria virens), were more abundant in clearcut treatments than other treatments (P 0.30). Nest success of species nesting in clearcut and shelterwood treatments was 18-50%. The percent of the site in gaps, shrub stem density, and tree-diameter distribution differed among forest regeneration methods (P < 0.001). We believe habitat requirements of birds in managed forests can be best met by a mixture of evenand uneven-aged forest management that creates a range of disturbance sizes. J. WILDL. MANAGE. 61(1):159-171

New Approaches to the Analysis of Population Trends in Land Birds

Although there is strong evidence that a few Neotropical migrant land birds have severely declining populations, we know of no evidence of general overall declines. One widely cited analysis of data from the Breeding Bird Survey (BBS), the only continental—scale monitoring program for land birds in the breeding season, indicates declining populations in eastern forests in the 1980s, but other analyses conclude that most species have had stable or increasing populations in the last 25 yr. These conflicting results call for a new perspective. Here, we propose two approaches to the analysis of BBS data that emphasize the detection of temporal and geographic variation in population trends. The first approach uses nonlinear regression to detect temporal changes in population trends, and permits the construction of graphs that compare nonlinear trends among regions. The second approach provides statistical tests of multispecies patterns of geographic variation in population trends. We report analyses of BBS data for 1966 to 1992 for the 26 species of wood warblers (Parulinae) for which the most data are available and the chance of obtaining reliable estimates is best. Using pooled data for all 26 species for eastern and central North America, nonlinear regression indicated declining populations in the Appalachian Mountains and the Eastern Foothills in the 1970s, and stability elsewhere. As examples of the use of this first approach in single—species analyses, we give maps, graphs, and statistical tests to illustrate variation in population trends by physiographic strata in the Blue—winged Warbler (Vermivora pinus) and the Ovenbird (Seiurus aurocapillus). As an example of the second approach, we applied a probit—normal model to a matrix of increases and decreases in the 26 species in 37 geographic strata. The analysis identified specific highland areas as having unusually high proportions of declining populations. These results suggest that correlates of elevation should be considered as factors possibly regulating populations of warblers and other land birds. Our perspective is that focus on studies of temporal and geographic variation in population trends of all birds, including Neotropical migrants, could help conservation biologists identify where species and groups of species are in the most trouble.

Blue-Winged Warbler in Regina

Blue-Winged Warbler in Regina

First Record of the Blue-Winged Warbler in Manitoba

First Record of the Blue-Winged Warbler in Manitoba

Song Types and their Use: Developmental Flexibility of the Male Blue‐winged Warbler

AbstractHow does an animal know the appropriate context in which to use its different vocalizations? I studied this problem with a songbird, the blue‐winged warbler (Vermivora pinus). Mated males in nature tend to sing one song form (II) at dawn, under low light levels, and at a median rate of 15 songs/min. Their other song (I, the more familiar bee‐buzz) is used later in the day, under higher light levels, and at a median rate of 6 songs/min. In the laboratory I tutored different groups of hand‐reared males under normal circumstances (group 1: song II early in the morning, under low light, at a rapid rate; song I later, under high light, at a slow rate), under reversed circumstances (group 2: song I early, low light, rapid rate; etc.), and with no contextual cues (group 3: songs I and II both early and late, under both light levels, and at an intermediate rate). Few males developed entirely normal blue‐wing song, but males of group 2 clearly reversed the use of song forms and components. The relationship between signal form and function in the songs of this warbler appears flexible and to some extent learned by the males.

Allozymes and Genetic Similarity of Blue-Winged and Golden-Winged Warblers

I studied variation in plumage color and allozymes in Golden-winged Warblers (Vermivora chrysoptera) from Minnesota and in Blue-winged Warblers (V. pinus) from Missouri and from eastern Pennsylvania. Color character scores were less than 2 in Missouri pinus and greater than 26 in Minnesota chrysoptera. The level of genetic divergence (D = 0.001) is comparable to that of conspecific populations of other passerine birds. I found no fixed alleles that could serve as genetic markers for studies of the evolutionary genetics of these warblers.

Blue-winged warblers (Vermivora pinus) ?recognize? dialects in type II but not type I songs

Male blue-winged warblers (Vermivora pinus) sing two distinctly different song types (I and II). Type II songs from eastern New York and western Massachusetts, USA, are different (Fig. 1), and during playback experiments males respond stronger to local than to foreign songs (Fig. 2). Type I songs are more stereotyped geographically (Fig. 1), and males do not differentiate between local and foreign Type I songs (Fig. 3). Differing degrees of intra- and inter-sexual selection on these two forms may have promoted variability in Type II songs and stereotypy in Type I songs among locations.