American Goldfinches Research Articles

Host range and dynamics of mycoplasmal conjunctivitis among birds in North America.

An epidemic of conjunctivitis among house finches (Carpodacus mexicanus) caused by Mycoplasma gallisepticum (MG) bacterial infections was first described in 1994. The disease exhibits high primary host specificity, but has been isolated from a limited number of secondary avian hosts at various times and locations. We used records from the House Finch Disease Survey, a continent-wide, volunteer monitoring project, to document the host range of conjunctivitis in birds at feeding stations and to investigate how disease in house finches might influence the spread of conjunctivitis to other hosts. Between 1994 and 1998, participants recorded 675 cases of conjunctivitis in 31 species other than house finches in eastern North America. Seventy five % of these cases were observed among three species: American goldfinches (Carduelis tristis), purple finches (Carpodacus purpureus) and house sparrows (Passer domesticus). The proportion of sites with diseased wintering populations of the three species increased over the 4 yr study and coincided with range expansion of conjunctivitis in house finches. Sites with diseased house finches present were significantly more likely to report conjunctivitis in each of the three species during the same month. These observations are most consistent with transmission of an infectious agent (presumably MG) from house finches to these secondary hosts via spillover of localized epidemics, rather than sustained interspecific transmission.

Differential effects of endoparasitism on the expression of carotenoid- and melanin-based ornamental coloration.

The striking diversity of sexual dimorphisms in nature begs the question: Why are there so many signal types? One possibility is that ornamental traits convey different sets of information about the quality of the sender to the receiver. The colourful, pigmented feathers of male birds seem to meet the predictions of this hypothesis. Evidence suggests that carotenoid pigmentation reflects the nutritional condition of males during moult, whereas in many instances melanin pigmentation is a reliable indicator of social status. However, as of yet there have been no experimental tests to determine how these two ornament types respond to the same form of environmental stress. In this study, we tested the effect of endoparasitic infection by intestinal coccidians (Isospora sp.) on the expression of both carotenoid- and melanin-based ornamental coloration in captive male American goldfinches (Carduelis tristis). We found that the carotenoid-based plumage and bill coloration of parasitized males was less saturated than that developed by unparasitized males, but that the brightness and size of melanin-based black caps did not differ between the groups. These findings provide the most robust empirical support to date for the notion that carotenoid and melanin ornaments reveal different information to conspecifics.

Mycoplasmal conjunctivitis in songbirds from New York.

A field study was conducted to determine the prevalence of conjunctivitis and Mycoplasma gallisepticum (MG) infections in house finches (Carpodacus mexicanus) and other songbirds common to bird feeders in Tompkins County (New York, USA). Eight hundred two individuals of 23 species and nine families of birds were captured and given physical examinations during the 14 mo study beginning in February 1998. Clinical conjunctivitis (eyelid or conjunctival swelling, erythema, and discharge) was observed in 10% (19/196) of house finches examined, and only in the winter months from November to March. Unilateral conjunctivitis was observed in 79% (15/19) of affected house finches; one case developed bilateral disease between 8 and 18 days following initial examination. Conjunctivitis was observed in a similar proportion of males and females sampled, and body condition scores and wing chord lengths were not significantly different between diseased and non-diseased house finches. Mycoplasma gallisepticum was isolated from 76% (13/17) of finches with conjunctivitis and 2% (3/168) of clinically normal house finches sampled during the study. DNA fingerprints of 11 MG isolates using random amplification of polymorphic DNA (RAPD) techniques showed no apparent differences in banding patterns over the course of the study, suggesting persistence of a single MG strain in the study population. The prevalence of conjunctivitis and MG infections declined in house finches between February/March 1998 and February/March 1999 (23% to 6%, and 20% to 5%, respectively), but only the former was significant (P < 0.05). Conjunctivitis was also observed in four American goldfinches (Carduelis tristis) and one purple finch (Carpodacus purpureus). Mycoplasma gallisepticum infection was confirmed in the purple finch, the first documented case of MG-associated conjunctivitis in this species. The purple finch isolate was similar to house finch isolates from the study site by RAPD analysis. Positive plate agglutination (PA) tests were recorded in one other goldfinch and two purple finches, suggesting exposure of these individuals to MG. Positive PA tests were also obtained from two brown-headed cowbirds (Molothrus ater) and four tufted titmice (Parus bicolor), but MG infection could not be confirmed in these cases due to lack of samples. Based on these findings, the prevalence of MG infections in hosts other than house finches appear to be low in the population sampled. There is growing evidence, however, that songbird species other than house finches are susceptible to MG infection and disease.

Restoring Savanna Using Fire: Impact on the Breeding Bird Community

AbstractRestoration of many terrestrial plant communities involves the reintroduction of fire. However, there have been few studies of the effects of fire on the avifauna during the restoration process. To study the effects of oak savanna restoration on avian communities, breeding birds were censused and the vegetation structure documented in seven experimental burn units (8–18 ha) that had experienced different frequencies of controlled burns during the past 31 years (0–26 burns). Data were analyzed with both direct and indirect gradient analyses using multivariate techniques. The results showed that, as savanna restoration proceeded, there was a general decline in predominantly insectivorous species, particularly those that feed in the upper canopy region (leaves and air space), and a general increase in omnivorous species, particularly those that feed on the ground and in the lower canopy. Insectivorous bark gleaners (woodpeckers) also increased during restoration and were correlated with the increase in standing dead trees resulting from the fires. Overall, savanna restoration resulted in increases in the abundance of many open country bird species, including many species that have been declining in central and eastern North America, including red‐headed woodpecker, Baltimore oriole, eastern kingbird, vesper sparrow, field sparrow, lark sparrow, brown thrasher, American goldfinch, and brown‐headed cowbird. The shifts in species and guilds were correlated with changes in burn frequency and the macro vegetation structure—tree and shrub density, leaf area index, and relative proportion of standing dead trees. The findings show that savanna restoration can increase bird diversity and provide important habitat for uncommon or declining bird species. These birds are most likely attracted to one or more of the distinctive habitat features of the restored savanna environments, including scattered mature trees, standing dead trees and snags, and presence of both shrubby and grassland vegetation. The findings also suggest that restoration ecologists and wildlife biologists will need to work together to achieve desired goals, since different types of savanna restoration efforts may produce different effects on the breeding bird community.

Conservation Reserve Program: Source or Sink Habitat for Grassland Birds in Missouri?

The Conservation Reserve Program (CRP) has been eredited with contributing substantially to the conservation of grassland birds. Although many species have nested in grasslands established under the CRP, little evidence of positive effect on populations has been reported. We measured reproductive rates and estimated fecundity of 7 grassland bird species in CRP fields in northern Missouri and compared those rates to estimates of fecundity needed to maintain stable populations (λ = 1). Under conservative assumptions of survival, CRP fields seemingly were source habitats (fecundity exceeded levels necessary for λ = 1) for grasshopper sparrows (Ammodramus savannarum) and field sparrows (Spizella pusilla) in at least 2 of 3 years (1993: P = 0.02, 1995: P < 0.001) and pooled over 3 years (Ps < 0.001). Although evidence was less compelling, CRP fields were likely source habitat for eastern meadowlarks (Sturnella magna) and American goldfinches (Carduelis tristis). For American goldfinches, fecundity was greater than that necessary for λ = 1 in 1995 (P < 0.001), and pooled over 3 years (P < 0.001). Our pooled estimate of fecundity was greater than necessary for λ = 1 for eastern meadowlarks (Ps < 0.001), but only under a liberal assumption of survival in 2 of 3 years (1993: P = 0.001; 1995: P = 0.088). Fecundity of common yellowthroats (Geothlypis trichas) varied substantially; therefore, source-sink status alternated among years, although the pooled estimate of fecundity was less than required for λ = 1 (P < 0.001). Dickcissel (Spiza americano) fecundity was consistently less than necessary for λ = 1 (conservative survival assumption: all Ps < 0.001; liberal survival assumption: 1994 P - 0.008. pooled P = 0.014). For red-winged blackbirds (Agelaius phoeniceus), CRP fields were consistently a sink habitat (all Ps < 0.001). Based on our evidence, the CRP likely has contributed to the conservation of grasshopper sparrows, field sparrows. and eastern meadowlarks. Although large numbers of dickcissels and red-winged black-birds nested in CRP fields, there is little evidence that the CRP has contributed to populations of those species.

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.

Phylogeny and rapid northern and southern hemisphere speciation of goldfinches during the Miocene and Pliocene epochs.

Mitochondrial cytochrome b (cyt b) from 25 out of 31 extant goldfinches, siskins, greenfinches and redpolls (genus Carduelis) has been sequenced from living samples taken around the world, specimens have also been photographed. Phylogenetic analysis consistently gave the same groups of birds, and this grouping was generally related to geographical proximity. It has been supposed that Pleistocene glaciations played a crucial role in the origin of extant diversity and distribution of Northern Hemisphere vertebrates. Molecular comparison of most extant songbird species belonging to the genus Carduelis does not support this assertion. The fossil record of chicken and pheasant divergence time has been used to calibrate the molecular clock; cyt b DNA dendrograms suggest that speciation in Carduelinae birds occurred during the Miocene and Pliocene Epochs (9-2 million years ago) in both the Northern and Southern Hemispheres. Only about 4% average amount of nucleotide substitution per lineage is found between the most distant Carduelis species; this suggests a remarkably rapid radiation when compared with the radiation of other passerine songbird genera. In addition, a continuum of small songbird speciation may be found during the Miocene Epoch in parallel with speciation of other orders (i.e. Galliformes, chicken/pheasant). Pleistocene glaciations may have been important in subspeciation (i.e. Eastern European grey-headed goldfinches/Western European black-headed goldfinches) and also in ice-induced vicariance (isolation) (i.e. siskin in Western Europe vs. siskin in Far East Asia) around the world. European isolated Serinus citrinella (citril finch) is not a canary, but a true goldfinch. South American siskins have quickly radiated in the last 4 million years coinciding with the emergence of the Isthmus of Panama; probably, a North American siskin related to C. notata invaded a suitable and varied biotope (the South American island) for Carduelis birds. North American goldfinches may be renamed as siskins, because they have a distant genetic relationship with European goldfinches. Genus Acanthis could be dropped, and thus redpolls should be separated from twite and linnet, the latter (Europeans) probably being related to American goldfinches. Also, reproductive barriers are observed between closely related species and not between other more distant ones. Finally, a tentative classification for genus Carduelis species is suggested.

Mycoplasma sturni from blue jays and northern mockingbirds with conjunctivitis in Florida.

Northern mockingbirds (Mimus polyglottos) and blue jays (Cyanocitta cristata) in a Florida (USA) wildlife care facility developed clinical signs and gross lesions suggestive of the ongoing outbreak of Mycoplasma gallisepticum (MG) conjunctivitis in house finches (Carpodacus mexicanus) and American goldfinches (Carduelis tristis). Mycoplasmal organisms were cultured from conjunctival/corneal swabs of birds with sinusitis, conjunctivitis, and/or epiphora. All of the isolates tested were identified as Mycoplasma sturni by indirect immunofluorescence. Mycoplasma sturni as well as MG should be considered in the differential diagnosis of songbirds with conjunctivitis.

A New Isospora sp. from Carduelis tristis (Aves: Fringillidae) from Ontario, Canada

Isospora gryphoni n. sp. is described from oocysts found in the feces of the American goldfinch, Carduelis tristis, from Guelph, Ontario, Canada. The oocysts are spherical to subspherical, with a double-layered, smooth, colorless oocyst wall, 29.2 x 30.7 microm (25-33 x 28-34; n = 30) with 2-4 rice-grain-shaped polar bodies; no micropyle or residuum. Sporocysts are ovoid, 22.2 x 13.4 microm (15-25 x 12-14.5; n = 30) with a small Stieda body, indistinct substiedal body, and prominent sporocyst residuum. Sporozoites are vermiform, each with a large refractile body at the posterior end. Forty-nine of 52 (94%) wild-caught adult C. tristis and 1 juvenile bird (minimum 12 days old) were excreting oocysts of I. gryphoni. None of 36 nestlings (maximum 10 days old) was excreting oocysts. Fecal encrustations from 7 of 10 used nests were found to contain oocysts of I. gryphoni.

Extrapair Paternity Associated with Renesting in the American Goldfinch

Copulations outside of the social pair bond occur in a wide range of bird species (Westneat et al. 1990, Birkhead and M0ller 1992). However, the fitness consequences of this behavior have been established only recently (e.g. Westneat 1990, Kempenaers et al. 1992, Lifjeld et al. 1993, Dunn et al. 1994, Hill et al. 1994). Failing to account for extrapair copulations (EPCs) can result in measures of reproductive success that are overestimated for some individuals and underestimated for others (Gibbs et al. 1990). Therefore, to better understand the adaptive significance of extrapair mating behavior, the degree to which EPCs result in fertilization must be assessed. This is possible with the use of molecular techniques such as DNA fingerprinting (Jeffreys et al. 1985a,b). The present study was undertaken to determine the prevalence and correlates of extrapair paternity (EPP) in a population of American Goldfinches (Carduelis tristis) by combining behavioral observations with DNA fingerprinting. The American Goldfinch is a small (ca. 12 g), sexually dimorphic cardueline finch that exhibits social monogamy (Middleton 1993; but see Middleton 1988). Because of the late initiation of breeding and the occurrence of a postnuptial molt, egg laying in southern Ontario is confined primarily to July and August (Middleton 1993). The result is a relatively synchronous breeding season in which the majority of clutches are started in the latter half of July (Middleton 1979). Both male and female goldfinches provide high levels of preand posthatching parental care. During the incubation period, males contribute indirect parental care by feeding the incubating female. Initially, adult males and females feed the nestlings in approximately equal proportions, but males gradually assume the predominant role and contribute most of the parental care after fledging (Middleton 1993). Thus, the fitness costs of cuckoldry to a pair-bonded male are high, and males guard their mates immediately before and during egg laying (Middleton 1993). According to Westneat et al. (1990), this pattern of reproduction (i.e. synchronized breeding, mate guarding by males) should reduce the potential for extrapair copulations. However, behaviors such as

Molecular epidemiologic investigations of Mycoplasma gallisepticum conjunctivitis in songbirds by random amplified polymorphic DNA analyses.

An ongoing outbreak of conjunctivitis in free-ranging house finches (Carpodacus mexicanus) began in 1994 in the eastern United States. Bacterial organisms identified as Mycoplasma gallisepticum (MG) were isolated from lesions of infected birds. MG was also isolated from a blue jay (Cyanocitta cristata) that contracted conjunctivitis after being housed in a cage previously occupied by house finches with conjunctivitis, and from free-ranging American goldfinches (Carduelis tristis) in North Carolina in 1996. To investigate the molecular epidemiology of this outbreak, we produced DNA fingerprints of MG isolates by random amplification of polymorphic DNA (RAPD). We compared MG isolates from songbirds examined from 1994 through 1996 in 11 states, representing three host species, with vaccine and reference strains and with contemporary MG isolates from commercial poultry. All MG isolates from songbirds had RAPD banding patterns identical to each other but different from other strains and isolates tested. These results indicate that the outbreak of MG in songbirds is caused by the same strain, which suggests a single source; the outbreak is not caused by the vaccine or reference strains analyzed; and MG infection has not been shared between songbirds and commercial poultry.

Mycoplasmal conjunctivitis in wild songbirds: the spread of a new contagious disease in a mobile host population.

A new mycoplasmal conjunctivitis was first reported in wild house finches (Carpodacus mexicanus) in early 1994. The causative agent was identified as Mycoplasma gallisepticum (MG), a nonzoonotic pathogen of poultry that had not been associated with disease in wild songbirds. Since the initial observations of affected house finches in the mid-Atlantic region, the disease has become widespread and has been reported throughout the eastern United States and Canada. By late 1995, mycoplasmal conjunctivitis had spread to an additional species, the American goldfinch (Carduelis tristis). This new disease exemplifies the rapid spread of a pathogen following introduction into a mobile wildlife population and provides lessons that may apply to emerging human diseases.

Relationships between scan and interscan durations in three avian species

Foraging birds interrupt a feeding bout to scan the environment for potential predators; their behaviour can therefore be described as an alternating sequence of scans (S) and interscan intervals (I). The ratio of I to S oscillates rhythmically during a foraging period; this is consistent across three avian species (Barbary dove, Streptopelia risoria; chough, Pyrrhocorax pyrrhocorax; and goldfinch, Carduelis tristis) and in a variety of social and foraging contexts. Thus, although there are differences in the mean ratio (possibly related to differences in food-handling time), all samples show the same pattern of cycling in the ratio of I to S. In addition to these oscillations, the length of an interscan interval tends to vary in direct proportion to the length of the preceding scan in solitary individuals (Barbary doves); however, in flock foragers (choughs and goldfinches) there is an inverse relationship between I and S.

Preferences of female American goldfinches (Carduelis tristis) for natural and artificial male traits

Preferences of female American goldfinches <i>(Carduelis tristis)</i> for natural and artificial male traits

Early nesting by the American Goldfinch, Carduelis tristis, and subsequent parasitism by the Brown-headed Cowbird, Molothrus ater, in Ontario

Early nesting by the American Goldfinch, Carduelis tristis, and subsequent parasitism by the Brown-headed Cowbird, Molothrus ater, in Ontario

The impact of dimethoate on rhythms of three granivorous bird species

Dimethoate is a currently sprayed organophosphate on farmlands. Its effects on endogenous rhythms of three farmland bird species, Savannah Sparrow ( Passerculus sandwichensis), Song Sparrow ( Melospiza melodia) and American Goldfinch ( Carduelis tristis) was studied. Doses of 0.24 g of dimethoate m −2 of seeds were given on the morning of Day 16 of the experiment for treated birds, and removed the next morning. Rhythmic parameters were collected in the form of perch hopping activity for a period of at least 30 days per bird. The treatment reduced significantly the mean daily activity levels of all the treated birds. It was found that dimethoate ingested orally causes temporary rhythm alterations, the mean recovery time from intoxication being 10.0 days, 11.5 days and 9.0 days for Song Sparrows, Savannah Sparrows and American Goldfinches, respectively. Such effects might become critical, if not fatal, in terms of the food finding ability of the animal and the birds would also be more vulnerable to predators.

Metabolic Aspects of Shivering Thermogenesis in Passerines during Winter

Various passerines enhance their cold resistance in winter through a form of metabolic acclimatization. This involves an improved ability to sustain elevated rates of regulatory thermogenesis, primarily through shivering. This muscular activity depends principally on catabolism of fatty acids. Significantly, establishment and daily replenishment of substantial fat reserves are associated with winter acclimatization in many passerines. This acclimatization also appears linked with winter increases in the activities of certain catabolic enzymes in skeletal muscle, notably P-hydroxyacyl Co-A dehydrogenase and phosphofructokinase. The factors that initiate and regulate winter acclimatization in passerines are poorly understood. The metabolic character of this form of adjustment, which certainly involves processes affecting deposition, mobilization, and use of energy substrates assures that an array of hormones will be involved. We review several possible candidates, emphasizing glucagon, corticosterone, and the thyroid hormones. Recent studies indicate seasonal variation in levels of thyroid hormones, but not of corticosterone in free-living individuals of the American Goldfinch Carduelis tristis, a prominent species in studies of passerine winter acclimatization.

Effects of Wind and Illumination on Behavior and Metabolic Rate of American Goldfinches (Carduelis tristis)

We measured the metabolic rate of active-phase American Goldfinches (Carduelis tristis) with and without illumination at 10°C and four wind speeds. We observed the birds via closed-circuit television. Illumination alone increased metabolism 37%. Metabolic rate increased linearly with activity and wind speed. A decrease in activity as wind speed increased tended to counteract the increase in thermoregulatory metabolism caused by convection, and reduced the slope of metabolism-vs.-wind-speed plots. The increase of metabolism with activity was reduced by the presence of illumination, which suggests relatively more compensation for thermoregulatory metabolism by activity metabolism when illumination is present. Stepwise linear regression was used to correct for nonthermal effects of illumination and wind to improve estimates of their purely thermal effects.

An Experimental Test of the Brood-Reduction Hypothesis in European Starlings

An Experimental Test of the Brood-Reduction Hypothesis in European Starlings

The predictability and patterns of vigilant behaviour

While foraging, many animals alternate between feeding and scanning. Spectral analysis of continuous series of scan durations S and inter-scan intervals I for American Goldfinches Carduelis tristis, feeding either on small or large seeds, and choughs Pyrrhocorax pyrrhocorax showed that there were nonrandom fluctuations in the magnitude of S and I is all the examined series. Both the I and S showed cyclical oscillations between short and long events. Within individuals the sequential and temporal patterns in the I and S series were similar. However, the temporal patterns were more affected by variations in food-handling time than were the sequential ones. The predictability of the I and S series and the similarity, within individuals, of their sequential and temporal patterns seem general processes resistant to variations in behavioural constraints, and the temporal patterns in the I and S series fit to the method of handling food.