Michael F. Small

A comparison of effects of radiotransmitter attachment techniques on captive white-winged doves

Abstract We experimentally evaluated alternative techniques of attaching radiotransmitters to captive white-winged doves (Zenaida asiatica) in Kingsville, Texas during 1998. Our evaluation consisted of monitoring physiological, pathological, and behavioral parameters in doves subjected to 6 radiotransmitter attachments (backpack harnesses, adhesive, subcutaneous implants, intracoelomic implants, subcutaneous surgeries without implantation, intracoelomic surgeries without implantation). We analyzed physiological parameters across 2 pretreatment and 4 post-treatment periods using a model-selection approach of mixed-effect models. Birds did not differ in physiological variables among treatment groups and a control. Time-activity budgets analyzed using nonparametric Friedmans tests did not differ in any activity category among treatment groups and a control. Subcutaneous implants were the most effective method of attachment based on retention rates, lack of mechanical difficulties associated with external attachment techniques, and minimum levels of pathology reported following necropsies.

BREEDING ECOLOGY OF WHITE-WINGED DOVES IN A RECENTLY COLONIZED URBAN ENVIRONMENT

Abstract Using field-implanted subcutaneous radio transmitters, we monitored the breeding biology of White-winged Doves (Zenaida asiatica) in a recently colonized urban area (Waco, Texas). We implanted transmitters in June 2002 (n = 39; 16 males, 23 females) and February and March 2003 (n = 40; 17 males, 17 females, 6 unknown sex), and tracked radio-tagged doves every 3rd day until transmitters no longer functioned (90–120 days). We tracked 26 doves to 36 nests in nine tree species. The maximum number of nesting attempts was four. Nest success of first and second nesting attempts was 62 and 24%, respectively, and overall nest success for both years combined was 52%. Mean nest height—as a proportion of tree height—ranged from 0.31 to 0.75. Urban White-winged Doves had an extended breeding season; nesting attempts occurred both before and after the traditional dove breeding period in native brush habitats of the lower Rio Grande Valley of Texas. Field-implantation of subcutaneous radio transmitters was a viable technique for monitoring nesting activities of White-winged Doves.

Toward increasing avian diversity: urban wildscapes programs

Residential development in urban and suburban settings is a major cause of habitat change affecting avian communities. The effects from land-clearing prior to initiation of construction followed by landscaping focused on traditional aesthetics has reduced habitat diversity at multiple levels. These residential developments generally emphasize the use of ornamental, nonindigenous vegetation with little to no concern for native species and natural vegetation parameters. As a result, avian community composition and diversity is changed. We compared avian communities at three sites in Bexar County, Texas; two residential neighborhoods in the city of San Antonio and an unincorporated undeveloped site, Government Canyon State Natural Area. The residential neighborhoods were a Texas Parks and Wildlife Department certified wildscapes development and a traditionally developed neighborhood. Bird abundance and species richness in the neighborhoods were greater than at Government Canyon State Natural Area (P < 0.01), but no differences existed between the neighborhoods. Bird diversity was greatest at the wildscapes neighborhood (P < 0.01). Further, bird diversity did not differ between the traditional neighborhood and the natural area. Evenness differed among sites (P = 0.006) with the natural area having the greatest value. Bird diversity measures correlated with woody plant density and vertical cover (r = 0.358 to 0.673, P < 0.05) at residential sites. Residential areas incorporating natural landscapes into their design attracted a greater variety of birds than traditionally landscaped residential areas.

Effects of Methyl Parathion on White-Winged Dove Productivity and Reproductive Behavior

Recent analyses suggest that exposure to cholinesterase (ChE)-inhibiting pesticides may be a factor contributing to declines of white-winged dove (Zenaida asiatica) populations in the Lower Rio Grande Valley (LRGV) of Texas, USA. Because irrigated cotton fields are regularly sprayed with organophosphorus (OP) pesticides (known ChE inhibitors) and doves drink irrigation water, we conducted a series of experiments to determine effects of OP pesticides in drinking water on productivity and reproductive behavior of white-winged doves. During the breeding seasons of 1996-1998, we exposed captive breeding pairs of white-winged doves to various concentrations of methyl parathion (MP), an OP pesticide widely used in the LRGV. Exposure to drinking water with 1.0 ppm MP did not significantly affect reproduction. Exposure to ≥4.5 ppm MP primarily affected egg laying and incubation stages of the reproductive cycle. Specifically, both chronic and periodic exposure to MP-contaminated water reduced number of eggs laid/pair, time incubating, and number of chicks fledged/pair. Food and water consumption declined with exposure to MP. Responses of white-winged doves to MP exposure were consistent with the hypothesis that declines in dove populations in the LRGV are influenced by pesticide exposure. However, field evidence of direct exposure is required to support the hypothesis of a pesticide-related decline.

Representativeness of Land Cover Composition along Routes of the North American Breeding Bird Survey

ABSTRACT. The North American Breeding Bird Survey (BBS) is an annual transect point-count survey of >500 species and >3,500 survey routes (transects). Observers drive and record birds seen and heard within a radius of 400 m of 50 survey points (“stops”) evenly spaced along a 39.4-km survey route. Thus, the land area along both sides of a route composes a linear or curvilinear landscape. Although BBS data have been used in many studies and conservation plans, there have been few attempts to determine how well the landscapes along BBS routes represent landscapes at larger spatial extents, particularly with regard to land-cover composition. Using data from the 2001 National Land Cover Database, we conducted a study of representativeness of 3,230 routes by comparing the differences in percent cover of 15 land-cover types in BBS landscapes (buffer width of 0.4 km surrounding a route) to larger local landscapes (10 km buffer width) and regions. At the local level, BBS landscapes were representative for most of the cover types except open water, which was underrepresented, and lightly developed open space, which was overrepresented. At the regional level, the collective composition of BBS landscapes was very similar to the composition within entire Bird Conservation Regions. Overall, these results should encourage the continued use of BBS data in ornithological and ecological research and in conservation planning.

MOBILE ANESTHESIA UNIT FOR IMPLANTING RADIOTRANSMITTERS IN BIRDS IN THE FIELD

Abstract We designed a mobile anesthesia unit for surgically implanting radio transmitters in birds in the field. This minimizes the amount of time individuals undergoing the procedure are kept from their normal activities. Two units were designed and tested. In 2000, we successfully implanted radio transmitters in 40 white-winged doves in Kingsville, Texas, using a surgical unit carried in the bed of a truck. In 2002, we successfully implanted 39 white-winged doves in Waco, Texas, using a surgical unit carried in the cargo area of a minivan. The success of both trials indicates this method has great potential for use for numerous avian species while minimizing impacts to individuals being studied.

MITOCHONDRIAL DNA AND MORPHOLOGICAL VARIATION OF WHITE-WINGED DOVES IN TEXAS

Abstract White-winged Doves (Zenaida asiatica) in Texas are separated into four subspecies primarily based on morphological variation. However, problems differentiating the subspecies by morphological measurements alone and a recent range expansion have led to questions about their systematic status and population structure. We evaluated both morphological characters and a 289 base-pair segment of the mitochondrial control region from 183 White-winged Doves taken from 31 locations in Texas, New Mexico, and Arizona. Twenty-seven variable base changes were observed, which resulted in 44 haplotypes. An analysis of haplotypes yielded little phylogenetic signal; however, analyses of haplotype frequencies indicated geographic heterogeneity between doves collected in the four historic subspecies ranges. Doves from the range expansion areas were intermediate in size and genetically homogenous. Morphological analyses suggested congruency between control region variation and body size. Our data support the recognition of two subspecies of White-winged Doves with a zone of intergradation in the range expansion areas. The dispersal of White-winged Doves into the expansion areas appears to be a congruent process by both subspecies.

CHOLINESTERASE ACTIVITY IN WHITE-WINGED DOVES EXPOSED TO METHYL PARATHION

Captive white-winged doves (Zenaida asiatica) were exposed to various levels of methyl parathion (MP) in drinking water to determine effects on brain and blood cholinesterase (ChE) activity. We conducted two experiments to test the influence of MP dose (the amount of MP actually ingested), MP concentration (the amount of MP per unit water), and exposure duration (number of days exposed to a constant MP concentration) on ChE activity. Plasma ChE activity was not useful in predicting brain ChE activity. Methyl parathion concentration had a greater influence on plasma and brain ChE activity levels than dose or time of exposure. These results contribute to the evaluation of irrigation water as a route of exposure of wildlife to pesticides.

CHARACTERISTICS OF THE HAEMOPROTEID COMMUNITY IN AN EXPANDING WHITE-WINGED DOVE POPULATION

The haemoproteid community of 171 eastern white-winged doves (Zenaida asiatica asiatica) from the expanding Texas population was examined using thin blood smears. During summer 1997, heart blood was taken from doves within their historical breeding range (Lower Rio Grande Valley of Texas), an intermediate region (San Antonio and surrounding area), and the new breeding periphery (north central to southeast Texas). Two species were found: Haemoproteus columbae and Haemoproteus sacharovi. Infracommunities rarely occurred in heart blood, as only 20 of 132 infected doves demonstrated gametocytes of both species. Overall prevalence of H. columbae and H. sacharovi was 77 and 15%, respectively. Prevalence of H. columbae was higher in the Lower Rio Grande Valley (LRGV) and intermediate regions than at the periphery, higher in adults than juveniles, and similar between males and females. Prevalence of H. sacharovi was lower in the LRGV than intermediate and peripheral regions, similar between juveniles and adults, and higher in females than males. Mean density of H. columbae and H. sacharovi was 15.9 ± 2.7 and 0.3 ± 0.1 (mean ± SE per 3,000 erythrocytes), respectively. Overall mean abundance of H. columbae and H. sacharovi was 12.2 ± 2.2 and 0.04 ± 0.02, respectively. Mean abundance of H. columbae was higher in the LRGV and intermediate regions than at the periphery and was similar between host age and between host sex; H. sacharovi was similar among regions, host age, and host sex. This study emphasizes the importance of using prevalence, density, and abundance data to assess haemoproteid community structure and pattern.

Nesting Home Range and Movements of an Urban White-winged Dove Population

Abstract We monitored nesting home ranges of White-winged Doves (Zenaida asiatica) in Waco, Texas using field-implanted, subcutaneous radio transmitters. Mean nesting home-range size differed by gender (75.7 km2 for females, 31.9 km2 for males, P = 0.17). Mean nesting home-range for all individuals of known gender differed by year (75.6 km2 for 2002, 32.0 km2 for 2003, P < 0.001). Within-year mean nesting home ranges for individuals differed by gender for 2002 but did not for 2003. We received reports of 35 band recoveries (2.3% of those banded) through March 2004. Distance moved did not differ by year, gender for adults, or for gender by age. Distances of recoveries from banding sites ranged from 0 to 477.4 km.