Dove Habitat Association Based on Remotely Sensed Land Cover Types in South Texas

Abstract: We tested whether presence of white-winged doves (Zenaida asiatica) and mourning doves (Z. macroura) in South Texas, USA, was associated with any of the land cover types recorded in the 2001 National Land Classification Database. We used the point-transect method to conduct presence—absence surveys for both species at 236 points encompassing 744 observations. Within predefined land cover types surrounding each survey point, we used Geographic Information Systems to determine the proportions of each land cover type present. We used randomization tests to compare proportions of land cover types present at points with and without doves. We used Program DISTANCE to estimate dove densities at survey points and to test whether certain land cover types were associated with greater dove densities. Our results indicated white-winged dove occurrence in South Texas was positively associated with urban land and cropland, whereas mourning dove occurrence was positively associated with cropland. For land cover types found to be associated with dove presence, estimated density for each dove species increased as the proportion of associated land cover type increased. These results can assist wildlife biologists in the development of a more efficient and targeted protocol for censusing doves. In addition, our methods can be applied to other species across several geographic areas and landscape scales.     

Experimental transfer of Trichomonas gallinae (Rivolta, 1878) from white-winged doves to mourning doves

Isolates of Trichomonas gallinae (Rivolta, 1878) from white-winged doves, Zenaida asiatica (L.), were transferred experimentally to young mourning doves, Zenaida macroura (L.). Twenty-three of 25 mourning doves developed infections with isolates of T. gallinae from 25 white-winged doves. In addition, eight of eight rock doves (Columba livia Gmelin) were infected with duplicate isolates. All infected recipient birds harbored avirulent isolates except for one mourning dove which died from extensive oral lesions. However, repeated attempts using this isolate of T. gallinae to produce lesions in additional recipients were unsuccessful. Despite the findings of this study, it was suggested that future dove management strategies consider the possibility of disease outbreaks involving white-winged doves and susceptible populations of mourning doves.     

Importance of Native Seeds in White-Winged Dove Diets Dominated by Agricultural Grains

ABSTRACT Agricultural intensification is a key factor in the decline of many avian populations throughout the world, yet the exact mechanisms that contribute to these declines are relatively unresolved, especially for seed-eating species. We tested the hypothesis that forage quality, particularly protein content, limits productivity in birds consuming diets dominated by agricultural grains and lacking in native forages. We used white-winged doves (Zenaida asiatica) because columbids are highly granivorous and white-winged doves have declined in areas dominated by grain agriculture. We randomly assigned 52 pairs of captive doves to 1 of 2 treatments: we fed one treatment sorghum (Sorghum bicolor) and the second sorghum plus native seeds (croton [Croton sp.] and native sunflower [Helianthus sp.]). Birds with access to native seeds fledged 123% more young per pair, with young weighing 32% more at fledging than those fed only sorghum. Doves with access to native seeds selected a diet consisting of 43% sorghum, 32% croton, and 25% sunflower. We conclude that agricultural grains, which typically have high metabolizable energy and low to moderate protein concentrations, are not sufficient for normal productivity of white-winged doves. The lack of native forages with sufficient metabolizable energy and protein content may be a factor in the declining productivity of white-winged doves in the lower Rio Grande Valley of Texas, USA, as well as other species in regions dominated by agriculture.     

Helminth community structure in an expanding white-winged dove (Zenaida asiatica asiatica) population

Helminth communities of 171 fledged white-winged doves (Zenaida asiatica asiatica) from the expanding eastern population in Texas (USA) were examined from hosts collected 11 June to 19 September 1997 within their historical range, new breeding periphery, and an intermediate area. Eleven helminth species, representing 435 individuals, were found. Helminths occurred in three microhabitats, of which the small intestine was the most commonly occupied. Nematodes dominated numerically (76% of total worms), followed by cestodes (17%), and trematodes (7%). Infracommunities were species-poor; the most complex infracommunity consisted of three helminth species, which occurred in three host individuals, followed by two species that occurred in 13 hosts. The remaining 155 doves had one (70) or no (85) species. The overall helminth component community was species-poor and was dominated by Ascaridia columbae which occurred in 26% of the white-winged doves and accounted for 65% of all helminth individuals. Prevalence and abundance of A. columbae varied by geographic region and host age, but not by host sex. Helminth component communities varied by geographic region, host age, and host sex. These differences were primarily attributable to unique occurrences of uncommon species within specific host subpopulations. Results suggest that the white-winged doves' multimodal regional abundance pattern, sympatry with other columbids, and granivorous diet may be more important in shaping helminth community structure than the influences often associated with geographic range expansion.     

Survival,fidelity, and recovery rates of white-winged doves in Texas

Management of migratory birds at the national level has historically relied on regulatory boundaries for definition of harvest restrictions and estimation of demographic parameters. Most species of migratory game birds are not expanding their ranges, so migratory corridors are approximately fixed. White-winged doves (Zenaida asiatica), however, have undergone significant variation in population structure with marked range expansion occurring in Texas, and range contraction in Arizona, during the last 30 years. Because >85% of white-winged dove harvest in the United States (approx. 1.3 million annually) now occurs in Texas, information on vital rates of expanding white-winged dove populations is necessary for informed management. We used band recovery and mark–recapture data to investigate variation in survival and harvest across 3 geographic strata for white-winged doves banded in the pre-hunting season in Texas during 2007–2010. We banded 60,742 white-winged doves, recovered 2,458 bands via harvest reporting, and recaptured 455 known-age birds between 2007 and 2010. The best supporting model found some evidence for geographic differences in survival rates among strata (A–C) in both hatch-year (juvenile; A = 0.205 [SE = 0.0476], B = 0.213 [SE = 0.0278], C = 0.364 [SE = 0.0254]) and after-hatch year (adult; A = 0.483 [SE = 0.0775], B = 0.465 [SE = 0.0366], C = 0.538 [SE = 0.251]) birds. White-winged doves had a low probability of moving among strata (0.009) or being recaptured (0.002) across all strata. Harvest recovery rates were concordant with estimates for other dove species, but were variable across geographic strata. Based on our results, harvest management strategies for white-winged doves in Texas and elsewhere should consider differences in population vital rates among geographic strata. © 2012 The Wildlife Society.     

Helminth community composition, structure, and pattern in six dove species (Columbiformes: Columbidae) of South Texas

The helminth community composition and structure of 6 species of columbids residing in south Texas are reported and compared herein. Sixty individuals of the following species, rock pigeons (Columba livia [RP]), mourning doves (Zenaida macroura [MD]), Eurasian collared-doves (Streptopelia decaocto [ECD]), white-winged doves (Zenaida asiatica [WWD]), and common ground doves (Columbina passerina [CGD]), and 48 Inca doves (Columbina inca [ID]) were collected during the summer of 2006 and examined for helminths. Twelve helminth species were found (9 nematodes and 3 cestodes), representing 486 individuals. Nematodes numerically dominated the component community in all host species. Overall, helminth prevalence was similar among host sex within all dove species. However, prevalence of Skrjabinia bonini and Hymenolepis sp. in RPs was significantly different among host age groups (P = 0.01, P = 0.0002, respectively). Likewise, prevalence of Killigrewia delafondi was higher (P = 0.0001) in adult WWDs. Based on percent similarity and Jaccard's coefficient of community indices, helminth component communities were dissimilar, and the number of shared helminth species varied among host species. Data from this study suggest that the environment surrounding preferred host habitat and foraging strategies of each host species is the driving force behind helminth component communities. This study emphasizes the importance of examining co-occurring hosts at both local and regional scales to elucidate helminth community structure and patterns.     

Parasitic helminths of Eurasian collared-doves (Streptopelia decaocto) from Florida

Sixty-three Eurasian collared-doves (ECDs) (Streptopelia decaocto) from Florida were examined for parasitic helminths from June to December 2001. Nine species of helminths were identified (5 nematodes, 2 cestodes, and 2 trematodes). The most prevalent helminths were Ascaridia columbae (73.0%), Fuhrmannetta crassula (28.6%), Ornithostrongylus quadriradiatus (12.7%), and Bruscapillaria obsignata (11.1%). The helminths with the greatest mean intensity were Tanaisia bragai (13.5), A. columbae (9.3), and O. quadriradiatus (7.1). In Florida, the mean intensity of A. columbae in ECDs (9.3) was similar to that found in white-winged doves (Zenaida asiatica) (9.1) (P = 0.461), and both the intensities were significantly higher than that in the native mourning doves (Zenaida macroura) (3.7) (P = 0.001 and 0.005, respectively). Fuhrmannetta crassula is reported for the first time in columbids from Florida.     

Survival of Trichomonas gallinae in white-winged dove carcasses

Survival of Trichomonas gallinae was examined in white-winged dove (Zenaida asiatica) carcasses to assess whether birds that have been dead up to 8 hr can be sampled reliably for this protozoan. Carcasses of 100 T. gallinae-positive white-winged doves were separated into four groups of 25 birds, representing 2, 4, 6, and 8 hr post mortem sampling intervals and placed into an environmental chamber maintained at 27 C and 75% relative humidity. Live T. gallinae were isolated in 96, 100, 100, and 92% of the carcasses at each of the respective post mortem intervals. The experiment was repeated with another 100 carcasses of T. gallinae-positive white-winged doves placed in the environmental chamber, this time maintained at 27 C and 40% relative humidity. Live T. gallinae occurred in 96, 100, 96, and 100% of the carcasses at each of the respective post mortem intervals. Across both trials, the overall ability to detect positive birds from sampling carcasses up to 8 hrs post mortem was 97%. An a posteriori experiment was conducted in which 23 and 18 carcasses from the second trial were maintained in the environmental chamber at 27 C and 40% relative humidity and resampled at 24 and 48 hr post mortem, respectively. Live trichomonads were isolated from 91 and 44% of the carcasses at 24 and 48 hr, respectively. Results suggest live T. gallinae can be obtained from dove carcasses reliably up to 8 hr and possibly up to 24 hr after host death. The ability for T. gallinae to survive within this time interval can aid wildlife personnel in monitoring this protozoan at hunter check stations or obtaining samples from recently killed birds.     

Poxvirus in scaled quail and prevalences of poxvirus-like lesions in northern bobwhites and scaled quail from Texas

Prevalences of poxvirus-like lesions were determined for 177 northern bobwhites (Colinus virginianus) and 24 scaled quail (Callipepla squamata) trapped in southern Texas from 1976 to 1979 and for 190 northern bobwhites and 105 scaled quail shot at five locations in southern Texas from 1980 to 1981. None of the northern bobwhites trapped in 1976-1977 was infected, but 54% of the trapped scaled quail were infected; 17% of the northern bobwhites and 34% of the scaled quail shot in 1980-1981 had pox lesions, primarily on the wings. Prevalence was unrelated to sex or age of birds. For both species, prevalence was greatest during late spring and early summer. Histologic and electron microscopic examination confirmed poxvirus in two scaled quail, which constituted the first report of poxvirus in this species.     

Pathogenicity of Eimeria lettyae Ruff, 1985 in the northern bobwhite (Colinus virginianus L.)

Sporulated oocysts of Eimeria lettyae were administered orally to 5-day-old or 18-day-old northern bobwhites (Colinus virginianus, L.). Five-day-old bobwhites were more susceptible based on higher mortality and reduced weight gain. A dose of 5 X 10(5) oocysts produced 25-43% mortality in 5-day-old bobwhites, but none in 18-day-old bobwhites. A dose of 1 X 10(6) oocysts/bobwhite produced 83-100% mortality in 5-day-old bobwhites, and 17-83% mortality in 18-day-old bobwhites. Body weight gain was reduced significantly with a dose of 1 X 10(5) oocysts or greater in 5-day-old bobwhites and with a dose of 5 X 10(5) oocysts or greater in 18-day-old bobwhites. Infection in all age groups reduced concentrations of plasma pigment and plasma protein, but did not affect packed cell volumes. No grossly visible lesions were present in the intestine although there was a shortening of the villi in the duodenum. In mature bobwhites, infection with E. lettyae did not cause mortality, but did reduce egg production and fertility.     

Learning Differences between Feral Pigeons and Zenaida Doves: The Role of Neophobia and Human Proximity

Learning differences predicted from ecological variables can be confounded with differences in wariness of novel stimuli (neophobia). Previous work on feral pigeons ( Columba livia ), as well as on group-feeding and territorial zenaida doves ( Zenaida aurita ), reported individual and social learning differences predicted from social foraging mode. In the present study, we show that speed of learning a foraging task covaries with neophobia and latency to feed from a familiar dish in the three types of columbids. Pigeons were much faster than either territorial or group-feeding zenaida doves on all tests conducted in captivity, but showed unexpectedly strong neophobia in some urban flocks during field tests. Human proximity strongly affected performance in group-feeding doves both in the field and in captivity. They were slightly faster at learning than their territorial conspecifics in cage tests. In multiple regressions, species identity, but not social foraging mode, significantly predicted individual variation in learning, as did individual variation in neophobia. Wariness of novel stimuli and species differences associated with artificial selection appear to be more important than foraging mode and wariness of humans in accounting for learning differences between these columbids.     

Foraging ecologies of giraffe (Giraffa camelopardalis reticulata) and camels (Camelus dromedarius) in northern Kenya: effects of habitat structure and possibilities for competition?

The foraging ecologies of reticulated giraffe (Giraffa camelopardalis reticulata) and domestic camels (Camelus dromedarius) were examined in the Laikipia District of Kenya, where these species have recently become sympatric. Camels increased popularity in the region has lead to concerns about their environmental impacts and possible competition with wild giraffe for resources. We gathered foraging data on both species using 2‐min group scans that recorded feeding heights and plant food preferences. Transects sampled the vegetation in areas where foraging observations were recorded. Giraffe females feed at lower elevations than males, while female camels feed below both sexes of giraffe. There was very little observed overlap in food preferences between the species. However, habitat type has an effect on foraging ecologies of both giraffe sexes, but habitat did not influence camel foraging. Camel herder husbandry techniques also influence camel foraging dynamics. These findings have important implications in achieving the twin objectives of wildlife conservation and pastoralist livestock production in northern Kenya.     

Species Differences in Spatial Memory Performance on a Three-dimensional Task

Three species of seed-caching corvids were tested in a spatial, three-dimensional analog of the radial maze. The apparatus consisted of five artificial trees, each with six branches. A wooden feeder could be attached to each branch. Each feeder contained a hole that could hold a pine seed. During the first 40 trials of acquisition testing, all three species improved rapidly with nutcrackers and pinyon jays performing at higher levels than scrub jays. Testing was then interrupted for 31 d. After the interruption, the two species of jays continued to improve but the nutcrackers did not. This species performed with only modest accuracy through the remainder of the experiment. Mixed-interval testing was done at 10, 60, 180, and 300 min. All species declined in accuracy with increased retention interval. However, at 10 and 180 min, pinyon jays performed significantly better than scrub jays. This is the fourth spatial memory task in which pinyon jays have out-performed scrub jays. The difference in performance between these two species provides more evidence for divergence in spatial cognition as a function of dependence on cached food.     

Management Implications of Cover Selection Data: Northern Bobwhite Example

Abstract: We derived a method of estimating the direction and magnitude of cover changes for potentially maximizing wildlife abundance on an area. We illustrate the method with data on cover selection by northern bobwhites (Colinus virginianus) collected in the Texas Panhandle from 2000 to 2003. We used radiotelemetry to determine use of cover associations, Geographic Information System analysis to determine their availability, and logic related to use-availability analysis to collapse 95% kernel home ranges to usable space. Bobwhites selected mixed-shrub cover consisting of sand plum (Prunus angustifolia) and fragrant sumac (Rhus aromatica), and they avoided or neutrally used 8 other cover associations. However, grass upland and sand sagebrush (Artemisia filifolia) associations occurred in ≥86% of home ranges (n = 96 bobwhites with ≥30 radiolocations). Usable space averaged 54.2% ± 1.72 SE of kernel home ranges. The data indicated that adding about 226 ha of mixed-shrub cover or a structural homologue while simultaneously reducing the quantity of most other cover associations would maximize bobwhite abundance. An area with 30–60% mixed-shrub cover, with the balance in grass upland and sand sagebrush, and with cover dispersed such that no point was >30 m from mixed-shrub cover was hypothetically optimal for bobwhites in our region. Within certain constraints (e.g., financial, social, edaphic), managers can apply this method by manipulating cover types through relevant management practices (e.g., planting, prescribed burning, mechanical removal of vegetation). This method, with minor modification, could also be used to decrease usable space on an area, and thus decrease wildlife densities, should that be the manager's objective.     

Oral Fimbriae and Papillae in Parasitic Lampreys (Petromyzontiformes)

There are 38 species of living lampreys, 18 parasitic and 20 nonparasitic. The parasitic species feed as adults, while the nonparasitic do not. The taxonomy and systematics of the living lampreys is based primarily on dentition characters. Since the number of oral fimbriae and oral papillae have never been systematically investigated in lampreys, we compared them in 17 of the 18 parasitic lampreys to assess their usefulness as taxonomic characters. Both showed little variation with total length and sex within a species, while exhibiting greater variation between species. Parasitic species belonging to the three lamprey families could be distinguished using the number of oral fimbriae: southern hemisphere Mordaciidae (0) and Geotriidae (55–65) and northern hemisphere Petromyzontidae (81–144). However, the taxonomic usefulness of the two characters at the species level was limited. Ten out of the 17 species of parasitic lampreys were placed into four distinct groups based on their numbers of oral fimbriae, and only in two of these was the character diagnostic. Twelve out of the 17 species were placed into two distinct groups based on their numbers of oral papillae and for none of these was the character diagnostic. Blood feeders and intermediate feeders (blood + flesh) were shown to have significantly higher numbers of oral fimbriae than flesh feeders. The higher numbers of oral fimbriae in the former two types of feeders were presumed to be linked to their greater need to create a good seal for feeding purposes. Blood feeders were also shown to have significantly higher numbers of oral papillae than either intermediates or flesh feeders. The higher numbers of oral papillae in the blood feeders were presumed to be linked to their greater need to find suitable attachment sites for feeding purposes.     

Ecology of helminth parasitism in bobwhites from northern Florida

Examination of 700 northern bobwhites (Colinus virginianus), 50 each February from 1971 through 1984, from Tall Timbers Research Station, Leon County, Florida, disclosed 15 species of helminth parasites. Nine species (Raillietina cesticillus, R. colinia, Aproctella stoddardi, Cheilospirura spinosa, Cyrnea colini, Dispharynx nasuta, Heterakis isolonche, Tetrameres pattersoni, and Trichostrongylus tenuis) generally were found on an annual basis and were considered characteristic components of the helminth fauna. Infrequently found species were Brachylecithum nanum, Rhabdometra odiosa, Capillaria sp., Gongylonema ingluvicola, H. gallinarum, and Oxyspirura matogrosensis. Intensities of C. colini and H. isolonche differed among host sex and age classes, and prevalences and/or intensities of A. stoddardi, C. spinosa, T. pattersoni, and T. tenuis differed between host age classes. Prevalences and/or abundances of seven species (R. cesticillus, R. colinia, C. spinosa, C. colini, H. isolonche, T. pattersoni, and T. tenuis) varied with bobwhite density, apparently because bobwhites were either the primary or only definitive host on the area. Two species (A. stoddardi and D. nasuta) did not vary with bobwhite density, apparently due to the buffering effect of a broad range of definitive hosts on the area. Prevalences and/or intensities of R. colinia, C. spinosa, and T. tenuis differed with agricultural fields status (cultivated versus fallow) suggesting that land use and its attendant habitat changes influenced transmission of these species. The occurrence of C. spinosa and T. pattersoni in individual bobwhites was not independent and was attributed to utilization of the same species of grasshoppers as intermediate hosts. Localized tissue damage and inflammation were associated with A. stoddardi, D. nasuta, C. spinosa, C. colini and T. pattersoni. Decreases in body weight in juvenile bobwhites were associated with increasing intensities of H. isolonche and T. tenuis. The observed relationships to bobwhite density and other variables are discussed with regard to known aspects of life histories of the nine most common species.     

Survey of aflatoxin concentrations in wild bird seed purchased in Texas.

The use of backyard feeders to attract avian wildlife is a common practice throughout the United States. However, feeding wildlife may create a problem due to aflatoxin, a harmful fungal metabolite, which can affect wildlife that are fed contaminated grain. Our study was initiated to determine if songbirds were being exposed to aflatoxin-contaminated feed throughout Texas. Bags of wild bird seed (n = 142) were purchased from grain cooperatives, grocery stores, and pet shops located in the panhandle, central, south, east, and west regions of Texas during spring and summer 1999. Aflatoxin concentrations in bird seed ranged from non-detectable to 2,780 micrograms/kg. Overall, 17% of samples had aflatoxin concentrations greater than 100 micrograms/kg, of which 83% contained corn as an ingredient. Retail establishment effects were noted in the southern and western regions of Texas, with average concentrations of aflatoxin greater from bags of bird seed purchased from grain cooperatives, followed by pet shops, then grocery stores. Regional differences in aflatoxin levels were not apparent from bags of seed purchased at pet shops: however, regional differences were noted in aflatoxin levels from seeds obtained at grocery stores and grain cooperatives. Average aflatoxin concentration from seed purchased at grocery stores was greatest in the panhandle region, followed by the remaining regions. Within grain cooperatives, the panhandle, south, and west regions of Texas exhibited higher levels of aflatoxin-contaminated bird seed than cooperatives within the east and central regions of Texas. Granivorous songbirds in Texas are exposed to aflatoxins at backyard feeders, which may be a significant morbidity and mortality factor.     

A multispecies approach to manage effects of land cover and weather on upland game birds

Loss and degradation of grasslands in the Great Plains region have resulted in major declines in abundance of grassland bird species. To ensure future viability of grassland bird populations, it is crucial to evaluate specific effects of environmental factors among species to determine drivers of population decline and develop effective conservation strategies. We used threshold models to quantify the effects of land cover and weather changes in "lesser prairie‐chicken" and "greater prairie‐chicken" (Tympanuchus pallidicinctus and T. cupido, respectively), northern bobwhites (Colinus virginianus), and ring‐necked pheasants (Phasianus colchicus). We demonstrated a novel approach for estimating landscape conditions needed to optimize abundance across multiple species at a variety of spatial scales. Abundance of all four species was highest following wet summers and dry winters. Prairie chicken and ring‐necked pheasant abundance was highest following cool winters, while northern bobwhite abundance was highest following warm winters. Greater prairie chicken and northern bobwhite abundance was also highest following cooler summers. Optimal abundance of each species occurred in landscapes that represented a grassland and cropland mosaic, though prairie chicken abundance was optimized in landscapes with more grassland and less edge habitat than northern bobwhites and ring‐necked pheasants. Because these effects differed among species, managing for an optimal landscape for multiple species may not be the optimal scenario for any one species.     

Aflatoxin production in supplemental feeders provided for northern bobwhite in Texas and Oklahoma

Mycotoxins are toxic metabolites produced by varous species of fungi. Aflatoxin (AF), a particular type of mycotoxin, can negatively impact many wildlife species in the laboratory; however, the magnitude of the problem in the field environment is unclear. Wild birds generally consume a combination of native foods and agricultural grains. A common practice in which birds, such as northern bobwhite (Colinus virginianus), contact stored agricultural grain is through supplemental feeding. This feeding practice may promote the production of AF. The objectives of this study were to (1) examine AF production in supplemental feeders and (2) examine the relationship between weather and AF production in supplemental feeders. Samples were collected from supplemental feeders from November through February of 1996-97 and 1997-98. Mean monthly AF concentration of samples from feeders ranged from 0.57+/-2.86 to 15.47+/-14.69 ppb. Aflatoxin concentration in supplemental feeders increased from pre-sample to one month after filling the feeders each year. AF production in supplemental feeders was highly variable among months with no real temporal pattern between years. Instead, AF production was related to the highly variable relative humidity of the study area which influences moisture content of grain. Average relative humidity can be used to predict AF production.     

Aflatoxin levels in corn available as wild turkey feed in Georgia

Samples of corn available as wildlife feed from retailers throughout Georgia (USA) were collected during April 1997 and analyzed for aflatoxin to determine if levels harmful to wild turkeys (Meleagris gallopavo) were present. Three of 31 (10%) samples collected from a 40-country area were positive. An enzyme-linked immunosorbent assay qualitatively determined that two samples contained from 0 to 20 ppb aflatoxin. A chromatography analysis of a third sample measured 380 ppb total aflatoxin. A small percentage of our sample of wildlife feed collected during one season contained levels of aflatoxin that may cause harm to turkeys, especially poults. However, because aflatoxin levels ranging from 100 to 400 ppb may cause liver dysfunction and immunosuppression in turkey poults and other wildlife, grains known to be contaminated with aflatoxin at levels unacceptable for domestic animal feeds (> or =100 ppb) should not be sold as wildlife feed. Further analyses of grains sold as wildlife feed should be conducted to address this potential problem.