Proceedings of the Vertebrate Pest Conference, 2004
Through accidental and intentional introductions, the monk parakeet, native to South America, is ... more Through accidental and intentional introductions, the monk parakeet, native to South America, is now established in several parts of the United States. In Florida, it occurs in 21 of 67 counties. Monk parakeets build a bulky nest structure of sticks, and they often build on electric utility substations and support S1IUctures for distnbution and ~ion lines. This nesting activity is incompatl1>le with reliable electric service because nest material creates short ciicuits that cause power outages. Nest removal by electric utility peisonnel is ongoing but provides only short-term relic~ as birds readily rebuild their nests. In this study, we evaluated pasmre and active methods to trap monk parakeets, and we documented the effectivcn~ of trapping to reduce rates of nest rebuilding on distnbution poles. At electric substations, we ~ two pasmre trap designs: a drop-in style trap, and a walk-. in style trap. Monk parakeets were wary of traps, however, and were not easily captured even with extensive pro-baiting and the use of decoy birds. At distnbution poles, we actively trapped birds at 47 nest sites using specially designed nets placed over nest entrances at night while birds roosted. Birds were then caught as they flew out of the nests into the net. Capture suc:ccss at individual nest sites ranged from 0 to lOOo/o with an overall average of 51%. Of the 47 sites where birds were trapped at night, 43 nests were removed immediately or shortly after netting. Subsequent monitoring revealed that higher nest site capture rates resulted in slower rates of nest rebuilding. We conclude that while more research is needed to design an effective pasmre tmpping system, monk parakeets can be readily trapped from distnbution pole nests at night thereby enhancing nest removal efforts.
Invasive black spiny-tailed iguanas (Ctenosaura similis) on Invasive black spiny-tailed iguanas (... more Invasive black spiny-tailed iguanas (Ctenosaura similis) on Invasive black spiny-tailed iguanas (Ctenosaura similis) on
Recent increases in turkey vulture (Cathartes aura) and black vulture (Coragyps atratus) populati... more Recent increases in turkey vulture (Cathartes aura) and black vulture (Coragyps atratus) populations in North America have been attributed in part to their success adapting to human-modified landscapes. However, the capacity for such landscapes to generate favorable roosting conditions for these species has not been thoroughly investigated. We assessed the role of anthropogenic and natural landscape elements on roosting habitat selection of 11 black and 7 turkey vultures in coastal South Carolina, USA using a GPS satellite transmitter dataset derived from previous research. Our dataset spanned 2006-2012 and contained data from 7916 nights of roosting. Landscape fragmentation, as measured by land cover richness, influenced roosting probability for both species in all seasons, showing either a positive relationship or peaking at intermediate values. Roosting probability of turkey vultures was maximized at intermediate road densities in three of four seasons, and black vultures showed a positive relationship with roads in fall, but no relationship throughout the rest of the year. Roosting probability of both species declined with increasing high density urban cover throughout most of the year. We suggest that landscape transformations lead to favorable roosting conditions for turkey vultures and black vultures, which has likely contributed to their recent proliferations across much of the Western Hemisphere. More than three quarters of Earth's terrestrial surface is impacted by the presence of humans 1 . Since the industrial era, buildings and paved land have collectively increased to a global expanse exceeding 2.47 million km 2 , while total forest and wetland cover concurrently declined by 30% and 55%, respectively 2,3 . Converting land to suit the needs of humans not only reduces natural habitat, but often fragments the remaining habitat into isolated patches that exist within a matrix of human development 4 . Land conversions have been detrimental to many bird species due to factors such as reduced resource availability, the spread of invasive species, and increased human-wildlife conflict 5 . As a result, nearly one quarter of the global bird population has been lost since the advent of agriculture 6 . Some species, however, have been able to thrive across landscapes modified by humans. Human presence can result in novel food items that birds exploit 7 , and in structures like buildings or communication towers that can serve as suitable nesting or roosting sites 8 . Increases in edge habitat resulting from habitat fragmentation may be advantageous for edge specialists, and some species can exploit resources provided by agricultural landscapes . Two avian species that have seemingly benefited from human landscape modifications are turkey vultures (Cathartes aura) and black vultures (Coragyps atratus). Between 1966 and 2015, population indexes for these species in the United States increased each year by 2.19% and 4.77% on average, respectively 11 . Concurrently, the geographic ranges of both species across North and South America have also expanded dramatically . These trends pose a marked contrast to vulture populations in other parts of the world, many of which have declined precipitously over the past few decades 15 . Compared to species on other continents, turkey vultures and black vultures have a better conservation status due in part to ecological traits such as faster life-history strategies . Additionally, they are to exposed to more favorable social and political conditions including greater
In Dade County, Florida, the production of tropical fruit is a major component of the agricultura... more In Dade County, Florida, the production of tropical fruit is a major component of the agricultural industry with total sales amounting to $73.5 million in the 1997-1998 season. Two types of fruit in particular, lychee (Litchi chinensis) and longan (Euphoria longana), are rapidly emerging in economic importance with a combined annual value of over $19 million. For many lychee and longan growers, bird damage is perceived to be a significant constraint to production, yet there is no published information on the extent of damage caused by birds. In 1999, we initiated research to identify the bird species responsible for longan damage, quantify the extent of bird damage, and estimate monetary losses. Estimates of fruit loss in 3 longan orchards ranged from 4% to 64% which resulted in losses of $536 to $ 18,182 per hectare. Common grackles (Quiscalus quiscula) were the most prevalent pest birds, but monk parakeets (Myiopsitta monachus) were equally if not more destructive, resulting in 30 times more damage at the orchard where they were present. In 2000, we expanded the study to include lychee. Estimates of bird damage to longan ranged from 1% to 28% ($259/ha to $17,623/ha) with the greatest damage occurring in the orchard subject to grackle and monk parakeet depredation. Bird damage to lychee was substantial (11%, $477/ha) in only lof 4 the groves studied. Monk parakeets were not observed to feed on lychee. We conclude that damage to longan and lychee by grackles is common but usually not great. In longan orchards frequented by monk parakeets, however, damage increases dramatically. Long-term bird management strategies should include exclusion with netting in high-damage areas as well as consideration of reduction in monk parakeet populations.
In Venezuela, lethal control of wintering Dickcissels (Spiza americana) is considered a threat to... more In Venezuela, lethal control of wintering Dickcissels (Spiza americana) is considered a threat to the species survival. To help farmers protect their rice and sorghum crops from depredations by Dickcisse ls and to minimize the killing of large numbers of these birds, alternative non-lethal crop protection measures are needed. To that end, the responses of captive Dickcissels to three bird-repellent chemicals applied to rice seed were evaluated. In one-cup feeding trials, treatments of methiocarb (0.05% g g 71 , applied as Mesurol Ò 75% wettable powder) and anthraquinone (0.5%, applied as Flight Control Ò ) reduced consumption of rice by 70% relative to pretreatment consumption. Other anthraquinone treatments (0.05, 0.1%) and methyl anthranilate (0.05%) were ineffective. In two-cup trials, with untreated millet as the alternative food, consumption of rice treated with 0.05 and 0.1% anthraquinone was reduced by 90% relative to pretreatment levels. Overall, Dickcissels responded to the repellents similarly to the red-winged blackbird (Agelaius phoeniceus). Because Flight Control Ò has been used successfully to reduce blackbird use of rice fields in the USA, the prospect is good for successful reduction of damage to ripening rice by Dickcisse ls in Venezuela, particularly if repellent use is coupled with the establishment of alternative feeding sites.
Proceedings of the Vertebrate Pest Conference, 2004
Black vulture depredations to newborn livestock, poultry, and other captive animals have been rep... more Black vulture depredations to newborn livestock, poultry, and other captive animals have been reported from at least 15 states, and during the 1990s, reports of depredations increased annually by an average of 18%. In response to this mue, we initiated a study at Buck Island Ranch of the MacArthm Agro-Ecology Research Center in central Florida to examine interactions between cattle and vultures. Based on previous reports, we hypothesized that vulture predation selectively targets calves of young, inexperienced cows. To document vulture activity, we conducted point counts of vultures in pastures throughout the ranch. from Janwuy 2000 to March 2001. During point counts, turkey vultures accounted for 78% of the observations compared to 22% for black vultures. We noted that vultures used certain pastures preferentially, with over 70% of the vultures in 3 pastures where heifers were calving and the remainder spread among 7 pastures containing yearling heifers only or cows and calves. Turlccy and black vultures were often present during the 19 calving events we observed, but usually neither species exlu'bited threatening behavior toward calves or calving heifers. Imtead, the birds seemed intent on gaining access to the afterbirth. On one occasion, however, we observed an attempted depredation by black vultures on a calf as it was being born. The cow was able to chase the birds oft however, and the birth proceeded successfully. We conclude that predation by black vultures occurs when the birds identify and then exploit vulnerable animals, although there is still much to be leamcd regarding the circumstances that promote such activity. Current management recommendations include dispersing nearby black vulture roosts and providing careful oversight to protect inexperienced cows that arc first-time breeders.
In Executive Order 13112 "Invasive Species", an alien species is defined as one "that is not nati... more In Executive Order 13112 "Invasive Species", an alien species is defined as one "that is not native" to a particular ecosystem. In North America today, there are nearly 100 alien bird species with self-sustaining populations. These include numerous game birds (primarily gallinaceous birds) and escaped pet birds (primarily psittacine species). Others, such as house sparrows (Passer domesticus), European starlings (Sturnus vulgaris), and mute swan (Cygnus olor), were originally introduced for aesthetic reasons or to control agricultural insect pests. The establishment of alien bird populations through purposeful or accidental introductions has resulted in numerous problems including crop damage, transmission of disease, adverse impacts to native species, and aircraft safety concerns. The estimated cost associated with alien bird species in North America approaches $2 billion annually. Although many alien bird species apparently cause minimal or no harm, others are considered persistent and destructive pest species. The challenge for wildlife managers often is one of public opinion and education rather than identifying effective management and control strategies. For many bird damage situations, techniques currently exist for addressing the specific problem, and ongoing research is providing new tools. Many times, however, the will of the public overrides the scientific and economic need to manage aggressively to reduce detrimental alien bird populations. Specific examples of this dilemma for wildlife managers are provided by case studies featuring monk parakeets (Myiopsitta monachus), and mute swan.
Animals communicate with potential mates using species-specific signals, and pheromones are power... more Animals communicate with potential mates using species-specific signals, and pheromones are powerful sexual signals that modify conspecific behavior to facilitate mate location. Among the vertebrates, snakes are especially adept in mate searching via chemical trailing, which is particularly relevant given that many snake species are invasive outside their native ranges. Chemical signals used in mate choice are, thus, potentially valuable tools for management of invasive snake species. The Burmese python (Python bivittatus) is an invasive snake in the Florida Everglades where it is negatively impacting native fauna. In this study, we sought to: (i) determine if males can follow conspecific chemical trails in a Y-maze; and (ii) describe the mate searching behaviors exhibited by males while trailing. All males consistently followed a single female scent trail in the maze, but when only a male scent trail was present they did not discriminate between the male and blank arms. Rate of tongue-flicking, a proxy for chemosensory sampling, was also marginally higher when males were following female versus male scent trails. However, when both female and male scent trails were simultaneously present in the Y-maze, males did not show a preference for the female arm, although the tongue-flick rate was higher in the female-only trial compared to female versus male. Analyses of multiple male behaviors individually and using an ethogram revealed that behaviors were more frequent and complex in the female-only trials compared to male-only trials. Additional behavioral trials are needed to determine if an effective pheromonal approach to Burmese python management is possible.
Throughout its North American range, the turkey vulture (Cathartes aura) appears to be thriving. ... more Throughout its North American range, the turkey vulture (Cathartes aura) appears to be thriving. Turkey vulture populations wintering at Key West Naval Air Station (KWNAS), Florida are no exception to this trend. As vulture numbers continue to increase, so do potential conflicts with human activities. Abundant feeding opportunities and ample roost sites create ideal circumstances for wintering vultures. The increasing TUVU winter population is of particular concern because of the potential interaction with aircraft using the landing facility at KWNAS. Prior to developing vulture management recommendations at KWNAS, we needed to learn more about TUVU activity and movement patterns. Here we present results from 2013-2014 on trapping and marking efforts, with emphasis on vulture movement data acquired using GSM transmitters.
In the United States, black vulture (Coragyps atratus) and turkey vulture (Cathartes aura) pose s... more In the United States, black vulture (Coragyps atratus) and turkey vulture (Cathartes aura) pose significant birdstrike risks to aircraft. Understanding flight behaviors of vultures in and around military and civilian airfields is necessary to alleviate these risks. Using satellite telemetry data collected from 11 black vultures and 7 turkey vultures equipped with Global Positioning System backpack harness technology, we collected data on location and altitude near the Marine Corps Air Station (MCAS) in Beaufort, South Carolina from September 2006 to September 2008. We used military aircraft flight landing patterns to visualize a new concept, a flight altitude cone of depression (FACOD), which models a three-dimensional flight pattern over the airfield. We then identified areas in and around MCAS where vulture flight paths penetrated the FACOD and locations of vultures were proximate to flight approach routes that posed potential risk to aircraft for a birdstrike. Combining altitude of in-flight locations of vultures or other species with three-dimensional flight patterns of aircraft provides a novel method for managers of military and domestic airfields to assess birdstrike risk and to focus corrective actions.
Growing vulture populations represent increasing hazards to civil and military aircraft. To asses... more Growing vulture populations represent increasing hazards to civil and military aircraft. To assess vulture flight behavior and activity patterns at the Marine Corps Air Station in Beaufort, South Carolina, we equipped 11 black vultures (Coragyps atratus) and 11 turkey vultures (Cathartes aura) with solarpowered Global Positioning System (GPS) satellite transmitters during a 2-year study (1 Oct 2006-30 Sep 2008). Turkey vultures had larger seasonal home ranges than did black vultures, and 2 turkey vultures made round-trips to Florida. Black vultures consistently spent less time in flight (8.4%) than did turkey vultures (18.9%), and black vultures flew at higher altitudes than did turkey vultures in all seasons except summer when altitudinal distributions (above ground level) did not differ. Although we recorded maximum altitudes of 1,578 m for black vultures and 1,378 for turkey vultures, most flights were low altitude. A matrix of vulture flight altitude versus time of day revealed that >60% of vulture flight activity occurred from 4 hr to 9 hr after sunrise at altitudes below 200 m. Continuation of aggressive harassment coupled with flexible training schedules to avoid times and altitudes of high vulture activity will decrease hazards to aircraft posed by these birds.
Depredations to livestock by black vultures are a concern for many producers, and there is an inc... more Depredations to livestock by black vultures are a concern for many producers, and there is an increasing need for effective means to alleviate conflicts between livestock and vultures. One approach to this problem is to identify the roost site that is the source of the offending birds and then disperse that roost. We evaluated this approach in southwestern Virginia, where sheep and cattle operations in the New River Valley have historically experienced depredations by black vultures. During February 2004, we trapped and tagged 200 vultures and equipped 20 of them with radio transmitters. We established data-logger receiving stations at the main roost site in Radford, VA and at 4 nearby livestock operations. We monitored vulture use of the roost and the livestock sites for 2 weeks and then we dispersed the Radford roost using vulture effigies and hand-held lasers. We continued to monitor vulture activity at the livestock study sites for 8 weeks. Our findings showed that although the roost in Radford was dispersed, vulture use of the livestock operations after roost dispersal did not differ from pre-dispersal activity. Vultures in the area apparently shifted to alternate roost sites with no noticeable disruption to their foraging activities. For roost management to be effective against livestock depredations, dispersal activity must include the ancillary roosts as well as the main roost. Furthermore, prompt removal and proper disposal of livestock carcasses should greatly reduce the attractiveness of cattle and sheep operations for foraging black vultures.
One component of brown tree snake (Boiga irregularis) management on Guam is the use of a toxic ba... more One component of brown tree snake (Boiga irregularis) management on Guam is the use of a toxic bait that consists of acetaminophen tablets inserted into a dead neonatal mouse (DNM), which in turn is placed within a cylindrical polyvinyl chloride (PVC) bait station suspended above ground. Whereas this technique is effective in killing snakes, possible hazards to nontarget species, especially the Mariana crow (Corvus kubaryi), are of concern. We used the fish crow (C. ossifragus) as a surrogate for the Mariana crow to evaluate (1) oral toxicity of acetaminophen, (2) behavior of crows exposed to DNM containing acetaminophen tablets, and (3) ability of crows to remove DNM from cylindrical bait stations. In the oral toxicity test, all five crows that were each force-fed two 40-mg acetaminophen tablets survived and at least two birds regurgitated the tablets. Five additional crows received a double dose (four 40-mg tablets); each regurgitated all of its tablets, but one bird died. Crows g...
Proceedings of the Vertebrate Pest Conference, 2004
Through accidental and intentional introductions, the monk parakeet, native to South America, is ... more Through accidental and intentional introductions, the monk parakeet, native to South America, is now established in several parts of the United States. In Florida, it occurs in 21 of 67 counties. Monk parakeets build a bulky nest structure of sticks, and they often build on electric utility substations and support S1IUctures for distnbution and ~ion lines. This nesting activity is incompatl1>le with reliable electric service because nest material creates short ciicuits that cause power outages. Nest removal by electric utility peisonnel is ongoing but provides only short-term relic~ as birds readily rebuild their nests. In this study, we evaluated pasmre and active methods to trap monk parakeets, and we documented the effectivcn~ of trapping to reduce rates of nest rebuilding on distnbution poles. At electric substations, we ~ two pasmre trap designs: a drop-in style trap, and a walk-. in style trap. Monk parakeets were wary of traps, however, and were not easily captured even with extensive pro-baiting and the use of decoy birds. At distnbution poles, we actively trapped birds at 47 nest sites using specially designed nets placed over nest entrances at night while birds roosted. Birds were then caught as they flew out of the nests into the net. Capture suc:ccss at individual nest sites ranged from 0 to lOOo/o with an overall average of 51%. Of the 47 sites where birds were trapped at night, 43 nests were removed immediately or shortly after netting. Subsequent monitoring revealed that higher nest site capture rates resulted in slower rates of nest rebuilding. We conclude that while more research is needed to design an effective pasmre tmpping system, monk parakeets can be readily trapped from distnbution pole nests at night thereby enhancing nest removal efforts.
Invasive black spiny-tailed iguanas (Ctenosaura similis) on Invasive black spiny-tailed iguanas (... more Invasive black spiny-tailed iguanas (Ctenosaura similis) on Invasive black spiny-tailed iguanas (Ctenosaura similis) on
Recent increases in turkey vulture (Cathartes aura) and black vulture (Coragyps atratus) populati... more Recent increases in turkey vulture (Cathartes aura) and black vulture (Coragyps atratus) populations in North America have been attributed in part to their success adapting to human-modified landscapes. However, the capacity for such landscapes to generate favorable roosting conditions for these species has not been thoroughly investigated. We assessed the role of anthropogenic and natural landscape elements on roosting habitat selection of 11 black and 7 turkey vultures in coastal South Carolina, USA using a GPS satellite transmitter dataset derived from previous research. Our dataset spanned 2006-2012 and contained data from 7916 nights of roosting. Landscape fragmentation, as measured by land cover richness, influenced roosting probability for both species in all seasons, showing either a positive relationship or peaking at intermediate values. Roosting probability of turkey vultures was maximized at intermediate road densities in three of four seasons, and black vultures showed a positive relationship with roads in fall, but no relationship throughout the rest of the year. Roosting probability of both species declined with increasing high density urban cover throughout most of the year. We suggest that landscape transformations lead to favorable roosting conditions for turkey vultures and black vultures, which has likely contributed to their recent proliferations across much of the Western Hemisphere. More than three quarters of Earth's terrestrial surface is impacted by the presence of humans 1 . Since the industrial era, buildings and paved land have collectively increased to a global expanse exceeding 2.47 million km 2 , while total forest and wetland cover concurrently declined by 30% and 55%, respectively 2,3 . Converting land to suit the needs of humans not only reduces natural habitat, but often fragments the remaining habitat into isolated patches that exist within a matrix of human development 4 . Land conversions have been detrimental to many bird species due to factors such as reduced resource availability, the spread of invasive species, and increased human-wildlife conflict 5 . As a result, nearly one quarter of the global bird population has been lost since the advent of agriculture 6 . Some species, however, have been able to thrive across landscapes modified by humans. Human presence can result in novel food items that birds exploit 7 , and in structures like buildings or communication towers that can serve as suitable nesting or roosting sites 8 . Increases in edge habitat resulting from habitat fragmentation may be advantageous for edge specialists, and some species can exploit resources provided by agricultural landscapes . Two avian species that have seemingly benefited from human landscape modifications are turkey vultures (Cathartes aura) and black vultures (Coragyps atratus). Between 1966 and 2015, population indexes for these species in the United States increased each year by 2.19% and 4.77% on average, respectively 11 . Concurrently, the geographic ranges of both species across North and South America have also expanded dramatically . These trends pose a marked contrast to vulture populations in other parts of the world, many of which have declined precipitously over the past few decades 15 . Compared to species on other continents, turkey vultures and black vultures have a better conservation status due in part to ecological traits such as faster life-history strategies . Additionally, they are to exposed to more favorable social and political conditions including greater
In Dade County, Florida, the production of tropical fruit is a major component of the agricultura... more In Dade County, Florida, the production of tropical fruit is a major component of the agricultural industry with total sales amounting to $73.5 million in the 1997-1998 season. Two types of fruit in particular, lychee (Litchi chinensis) and longan (Euphoria longana), are rapidly emerging in economic importance with a combined annual value of over $19 million. For many lychee and longan growers, bird damage is perceived to be a significant constraint to production, yet there is no published information on the extent of damage caused by birds. In 1999, we initiated research to identify the bird species responsible for longan damage, quantify the extent of bird damage, and estimate monetary losses. Estimates of fruit loss in 3 longan orchards ranged from 4% to 64% which resulted in losses of $536 to $ 18,182 per hectare. Common grackles (Quiscalus quiscula) were the most prevalent pest birds, but monk parakeets (Myiopsitta monachus) were equally if not more destructive, resulting in 30 times more damage at the orchard where they were present. In 2000, we expanded the study to include lychee. Estimates of bird damage to longan ranged from 1% to 28% ($259/ha to $17,623/ha) with the greatest damage occurring in the orchard subject to grackle and monk parakeet depredation. Bird damage to lychee was substantial (11%, $477/ha) in only lof 4 the groves studied. Monk parakeets were not observed to feed on lychee. We conclude that damage to longan and lychee by grackles is common but usually not great. In longan orchards frequented by monk parakeets, however, damage increases dramatically. Long-term bird management strategies should include exclusion with netting in high-damage areas as well as consideration of reduction in monk parakeet populations.
In Venezuela, lethal control of wintering Dickcissels (Spiza americana) is considered a threat to... more In Venezuela, lethal control of wintering Dickcissels (Spiza americana) is considered a threat to the species survival. To help farmers protect their rice and sorghum crops from depredations by Dickcisse ls and to minimize the killing of large numbers of these birds, alternative non-lethal crop protection measures are needed. To that end, the responses of captive Dickcissels to three bird-repellent chemicals applied to rice seed were evaluated. In one-cup feeding trials, treatments of methiocarb (0.05% g g 71 , applied as Mesurol Ò 75% wettable powder) and anthraquinone (0.5%, applied as Flight Control Ò ) reduced consumption of rice by 70% relative to pretreatment consumption. Other anthraquinone treatments (0.05, 0.1%) and methyl anthranilate (0.05%) were ineffective. In two-cup trials, with untreated millet as the alternative food, consumption of rice treated with 0.05 and 0.1% anthraquinone was reduced by 90% relative to pretreatment levels. Overall, Dickcissels responded to the repellents similarly to the red-winged blackbird (Agelaius phoeniceus). Because Flight Control Ò has been used successfully to reduce blackbird use of rice fields in the USA, the prospect is good for successful reduction of damage to ripening rice by Dickcisse ls in Venezuela, particularly if repellent use is coupled with the establishment of alternative feeding sites.
Proceedings of the Vertebrate Pest Conference, 2004
Black vulture depredations to newborn livestock, poultry, and other captive animals have been rep... more Black vulture depredations to newborn livestock, poultry, and other captive animals have been reported from at least 15 states, and during the 1990s, reports of depredations increased annually by an average of 18%. In response to this mue, we initiated a study at Buck Island Ranch of the MacArthm Agro-Ecology Research Center in central Florida to examine interactions between cattle and vultures. Based on previous reports, we hypothesized that vulture predation selectively targets calves of young, inexperienced cows. To document vulture activity, we conducted point counts of vultures in pastures throughout the ranch. from Janwuy 2000 to March 2001. During point counts, turkey vultures accounted for 78% of the observations compared to 22% for black vultures. We noted that vultures used certain pastures preferentially, with over 70% of the vultures in 3 pastures where heifers were calving and the remainder spread among 7 pastures containing yearling heifers only or cows and calves. Turlccy and black vultures were often present during the 19 calving events we observed, but usually neither species exlu'bited threatening behavior toward calves or calving heifers. Imtead, the birds seemed intent on gaining access to the afterbirth. On one occasion, however, we observed an attempted depredation by black vultures on a calf as it was being born. The cow was able to chase the birds oft however, and the birth proceeded successfully. We conclude that predation by black vultures occurs when the birds identify and then exploit vulnerable animals, although there is still much to be leamcd regarding the circumstances that promote such activity. Current management recommendations include dispersing nearby black vulture roosts and providing careful oversight to protect inexperienced cows that arc first-time breeders.
In Executive Order 13112 "Invasive Species", an alien species is defined as one "that is not nati... more In Executive Order 13112 "Invasive Species", an alien species is defined as one "that is not native" to a particular ecosystem. In North America today, there are nearly 100 alien bird species with self-sustaining populations. These include numerous game birds (primarily gallinaceous birds) and escaped pet birds (primarily psittacine species). Others, such as house sparrows (Passer domesticus), European starlings (Sturnus vulgaris), and mute swan (Cygnus olor), were originally introduced for aesthetic reasons or to control agricultural insect pests. The establishment of alien bird populations through purposeful or accidental introductions has resulted in numerous problems including crop damage, transmission of disease, adverse impacts to native species, and aircraft safety concerns. The estimated cost associated with alien bird species in North America approaches $2 billion annually. Although many alien bird species apparently cause minimal or no harm, others are considered persistent and destructive pest species. The challenge for wildlife managers often is one of public opinion and education rather than identifying effective management and control strategies. For many bird damage situations, techniques currently exist for addressing the specific problem, and ongoing research is providing new tools. Many times, however, the will of the public overrides the scientific and economic need to manage aggressively to reduce detrimental alien bird populations. Specific examples of this dilemma for wildlife managers are provided by case studies featuring monk parakeets (Myiopsitta monachus), and mute swan.
Animals communicate with potential mates using species-specific signals, and pheromones are power... more Animals communicate with potential mates using species-specific signals, and pheromones are powerful sexual signals that modify conspecific behavior to facilitate mate location. Among the vertebrates, snakes are especially adept in mate searching via chemical trailing, which is particularly relevant given that many snake species are invasive outside their native ranges. Chemical signals used in mate choice are, thus, potentially valuable tools for management of invasive snake species. The Burmese python (Python bivittatus) is an invasive snake in the Florida Everglades where it is negatively impacting native fauna. In this study, we sought to: (i) determine if males can follow conspecific chemical trails in a Y-maze; and (ii) describe the mate searching behaviors exhibited by males while trailing. All males consistently followed a single female scent trail in the maze, but when only a male scent trail was present they did not discriminate between the male and blank arms. Rate of tongue-flicking, a proxy for chemosensory sampling, was also marginally higher when males were following female versus male scent trails. However, when both female and male scent trails were simultaneously present in the Y-maze, males did not show a preference for the female arm, although the tongue-flick rate was higher in the female-only trial compared to female versus male. Analyses of multiple male behaviors individually and using an ethogram revealed that behaviors were more frequent and complex in the female-only trials compared to male-only trials. Additional behavioral trials are needed to determine if an effective pheromonal approach to Burmese python management is possible.
Throughout its North American range, the turkey vulture (Cathartes aura) appears to be thriving. ... more Throughout its North American range, the turkey vulture (Cathartes aura) appears to be thriving. Turkey vulture populations wintering at Key West Naval Air Station (KWNAS), Florida are no exception to this trend. As vulture numbers continue to increase, so do potential conflicts with human activities. Abundant feeding opportunities and ample roost sites create ideal circumstances for wintering vultures. The increasing TUVU winter population is of particular concern because of the potential interaction with aircraft using the landing facility at KWNAS. Prior to developing vulture management recommendations at KWNAS, we needed to learn more about TUVU activity and movement patterns. Here we present results from 2013-2014 on trapping and marking efforts, with emphasis on vulture movement data acquired using GSM transmitters.
In the United States, black vulture (Coragyps atratus) and turkey vulture (Cathartes aura) pose s... more In the United States, black vulture (Coragyps atratus) and turkey vulture (Cathartes aura) pose significant birdstrike risks to aircraft. Understanding flight behaviors of vultures in and around military and civilian airfields is necessary to alleviate these risks. Using satellite telemetry data collected from 11 black vultures and 7 turkey vultures equipped with Global Positioning System backpack harness technology, we collected data on location and altitude near the Marine Corps Air Station (MCAS) in Beaufort, South Carolina from September 2006 to September 2008. We used military aircraft flight landing patterns to visualize a new concept, a flight altitude cone of depression (FACOD), which models a three-dimensional flight pattern over the airfield. We then identified areas in and around MCAS where vulture flight paths penetrated the FACOD and locations of vultures were proximate to flight approach routes that posed potential risk to aircraft for a birdstrike. Combining altitude of in-flight locations of vultures or other species with three-dimensional flight patterns of aircraft provides a novel method for managers of military and domestic airfields to assess birdstrike risk and to focus corrective actions.
Growing vulture populations represent increasing hazards to civil and military aircraft. To asses... more Growing vulture populations represent increasing hazards to civil and military aircraft. To assess vulture flight behavior and activity patterns at the Marine Corps Air Station in Beaufort, South Carolina, we equipped 11 black vultures (Coragyps atratus) and 11 turkey vultures (Cathartes aura) with solarpowered Global Positioning System (GPS) satellite transmitters during a 2-year study (1 Oct 2006-30 Sep 2008). Turkey vultures had larger seasonal home ranges than did black vultures, and 2 turkey vultures made round-trips to Florida. Black vultures consistently spent less time in flight (8.4%) than did turkey vultures (18.9%), and black vultures flew at higher altitudes than did turkey vultures in all seasons except summer when altitudinal distributions (above ground level) did not differ. Although we recorded maximum altitudes of 1,578 m for black vultures and 1,378 for turkey vultures, most flights were low altitude. A matrix of vulture flight altitude versus time of day revealed that >60% of vulture flight activity occurred from 4 hr to 9 hr after sunrise at altitudes below 200 m. Continuation of aggressive harassment coupled with flexible training schedules to avoid times and altitudes of high vulture activity will decrease hazards to aircraft posed by these birds.
Depredations to livestock by black vultures are a concern for many producers, and there is an inc... more Depredations to livestock by black vultures are a concern for many producers, and there is an increasing need for effective means to alleviate conflicts between livestock and vultures. One approach to this problem is to identify the roost site that is the source of the offending birds and then disperse that roost. We evaluated this approach in southwestern Virginia, where sheep and cattle operations in the New River Valley have historically experienced depredations by black vultures. During February 2004, we trapped and tagged 200 vultures and equipped 20 of them with radio transmitters. We established data-logger receiving stations at the main roost site in Radford, VA and at 4 nearby livestock operations. We monitored vulture use of the roost and the livestock sites for 2 weeks and then we dispersed the Radford roost using vulture effigies and hand-held lasers. We continued to monitor vulture activity at the livestock study sites for 8 weeks. Our findings showed that although the roost in Radford was dispersed, vulture use of the livestock operations after roost dispersal did not differ from pre-dispersal activity. Vultures in the area apparently shifted to alternate roost sites with no noticeable disruption to their foraging activities. For roost management to be effective against livestock depredations, dispersal activity must include the ancillary roosts as well as the main roost. Furthermore, prompt removal and proper disposal of livestock carcasses should greatly reduce the attractiveness of cattle and sheep operations for foraging black vultures.
One component of brown tree snake (Boiga irregularis) management on Guam is the use of a toxic ba... more One component of brown tree snake (Boiga irregularis) management on Guam is the use of a toxic bait that consists of acetaminophen tablets inserted into a dead neonatal mouse (DNM), which in turn is placed within a cylindrical polyvinyl chloride (PVC) bait station suspended above ground. Whereas this technique is effective in killing snakes, possible hazards to nontarget species, especially the Mariana crow (Corvus kubaryi), are of concern. We used the fish crow (C. ossifragus) as a surrogate for the Mariana crow to evaluate (1) oral toxicity of acetaminophen, (2) behavior of crows exposed to DNM containing acetaminophen tablets, and (3) ability of crows to remove DNM from cylindrical bait stations. In the oral toxicity test, all five crows that were each force-fed two 40-mg acetaminophen tablets survived and at least two birds regurgitated the tablets. Five additional crows received a double dose (four 40-mg tablets); each regurgitated all of its tablets, but one bird died. Crows g...
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