\u3ci\u3eGopherus polyphemus\u3c/i\u3e (Gopher Tortoise), \u3ci\u3eCtenosaura similis\u3c/i\u3e (Gray\u27s Spiny-Tailed Iguana) Predation

Gopherus polyphemus is currently listed as a threatened and protected species in the state of Florida (Mushinsky et al. 2006. In Meylan led.], Biology and Conservation of Florida Turtles, pp. 350-375. Chelonian Research Monographs 3). Documented natural predators of Gopherus polyphemus include the Raccoon (Procyon lotor), Gray Fox (Urocyon cinereoargenteris), Striped Skunk (Mephitus mephitis), Opposum (Didelphis virginianus), Armadillo (Dasypus novemcinctus),and crows (Corvus sp.) (Mushinsky et al., op. cit. ), and the introduced Savaunah Monitor (Varanus exanthematicus) (Owens et al. 2005. Herpetol. Rev. 3657-58). Herein, we augment this list to include the nonindigenous Gray\u27s Spiny-tailed Iguana (Ctenosaura similis)

Vulture-Cattle Interactions at a Central Florida Ranch

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 issue, we initiated a study at Buck Island Ranch of the MacArthur 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 January 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. Turkey and black vultures were often present during the 19 calving events we observed, but usually neither species exhibited threatening behavior toward calves or calving heifers. Instead, 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 buds off, however, and the birth proceeded successfully. We conclude that predation by black vultures occurs when the buds identify and then exploit vulnerable animals, although there is still much to be learned regarding the circumstances that promote such activity. b e n t management recommendations include dispersing nearby black vulture roosts and providing careful oversight to protect inexperienced cows that are first-time breeders

Evaluation of Trapping to Reduce Monk Parakeet Populations at Electric Utility Facilities

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 structures for distribution and transmission lines. This nesting activity is incompatible with reliable electric service because nest material creates short circuits that cause power outages. Nest removal by electric utility personnel is ongoing but provides only short-term relief, as buds readily rebuild their nests. In h s study, we evaluated passive and active methods to trap monk parakeets, and we documented the effectiveness of trapping to reduce rates of nest rebuilding on distribution poles. At electric substations, we tested two passive 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 pre-baiting and the use of decoy birds. At distribution 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 success at individual nest sites ranged from 0 to 100% 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 passive trapping system, monk parakeets can be readily trapped from distribution pole nests at night thereby enhancing nest removal efforts

Bird Damage to Tropical Fruit in South Florida

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 1 of 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

Feral swine damage to globally imperiled wetland plant communities in a significant biodiversity hotspot in Florida

We studied rooting damage during five-years of feral swine control at Avon Park Air Force Range, a significant botanical biodiversity hotspot in peninsular Florida with many globally imperiled plant species and communities. While control reduced swine abundance, remaining animals consistently rooted the 49 studied sites in both middle-dry season (MDS) and late-dry season (LDS) each year. At each study site, we measured rooting with sub-meter accuracy. Neither total nor proportional area rooted differed in either season, across study years, or among plant community types: herbaceous seepage slopes, wet pine savannas, wet grasslands. The proportion of sites with damage during MDS was at least 25 % less than pre-control baseline. During LDS, the proportion of sites with damage increased over years but remained below the initial 2 years’ MDS results. Fresh rooting frequency (rooting \u3c1 \u3eweek-old) across sites dropped precipitously from baseline and remained low for MDS. Fresh rooting frequency among sites during LDS was lower than MDS for all but year two of the study. Canopied habitatwetlands, integrating swine control into other compatible land use practices, and improving swine control efficacy. While we measured damage amounts at each site very accurately, our approach of also considering frequency of rooting and frequency of fresh rooting across sites offers low-labor means to broadly assess swine damage and control efficacy at large geographic scales because in-field measurements of damage amounts are not needed

Feral swine damage to globally imperiled wetland plant communities in a significant biodiversity hotspot in Florida

We studied rooting damage during five-years of feral swine control at Avon Park Air Force Range, a significant botanical biodiversity hotspot in peninsular Florida with many globally imperiled plant species and communities. While control reduced swine abundance, remaining animals consistently rooted the 49 studied sites in both middle-dry season (MDS) and late-dry season (LDS) each year. At each study site, we measured rooting with sub-meter accuracy. Neither total nor proportional area rooted differed in either season, across study years, or among plant community types: herbaceous seepage slopes, wet pine savannas, wet grasslands. The proportion of sites with damage during MDS was at least 25 % less than pre-control baseline. During LDS, the proportion of sites with damage increased over years but remained below the initial 2 years’ MDS results. Fresh rooting frequency (rooting \u3c1 \u3eweek-old) across sites dropped precipitously from baseline and remained low for MDS. Fresh rooting frequency among sites during LDS was lower than MDS for all but year two of the study. Canopied habitatwetlands, integrating swine control into other compatible land use practices, and improving swine control efficacy. While we measured damage amounts at each site very accurately, our approach of also considering frequency of rooting and frequency of fresh rooting across sites offers low-labor means to broadly assess swine damage and control efficacy at large geographic scales because in-field measurements of damage amounts are not needed

Evaluation of Bird Shield as a blackbird repellent in ripening rice and sunflower fields

Chemical repellents sometimes can provide a nonlethal alternative for reducing wildlife impacts to agricultural production. In late summer and autumn 2002, we evaluated Bird Shield™ (active ingredient: methyl anthranilate, Bird Shield Repellent Corporation, Spokane, Wash.) as a blackbird (Icteridae) repellent in Missouri rice fields and North Dakota sunflower fields. We selected 5 pairs of ripening rice fields in southeastern Missouri and randomly allocated treatments (treated and control) within pairs. The repellent was aerially applied by fixed-winged aircraft at the recommended label rate and volume (1.17 L Bird Shield/ha and 46.7 L/ha, respectively); 1 field received 2X the label rate. We observed no difference in average bird activity (birds/minute) between treated and control fields over the 3-day posttreatment period (P = 0.503). We used reversed-phase liquid chromatography to quantify methyl anthranilate residues in treated fields. The maximum concentration of methyl anthranilate in rice samples was 4.71 μg/g. This concentration was below reported threshold values that irritate birds. In North Dakota we selected 6 pairs of sunflower fields used by foraging blackbirds. We randomly selected 1 field from each pair for 2 aerial applications of Bird Shield at the label-recommended rate ~1 week apart. The remaining 6 fields served as controls. Daily bird counts, starting the first day of application and continuing for 5–7 days after the second application, showed similar numbers of blackbirds within treated and control fields (P = 0.964). We observed no difference in sunflower damage within treated and control fields (P = 0.172) prior and subsequent to the treatment. Bird Shield was not effective for repelling blackbirds from ripening rice and sunflower fields

Evaluation of Bird Shield as a blackbird repellent in ripening rice and sunflower fields

Chemical repellents sometimes can provide a nonlethal alternative for reducing wildlife impacts to agricultural production. In late summer and autumn 2002, we evaluated Bird Shield™ (active ingredient: methyl anthranilate, Bird Shield Repellent Corporation, Spokane, Wash.) as a blackbird (Icteridae) repellent in Missouri rice fields and North Dakota sunflower fields. We selected 5 pairs of ripening rice fields in southeastern Missouri and randomly allocated treatments (treated and control) within pairs. The repellent was aerially applied by fixed-winged aircraft at the recommended label rate and volume (1.17 L Bird Shield/ha and 46.7 L/ha, respectively); 1 field received 2X the label rate. We observed no difference in average bird activity (birds/minute) between treated and control fields over the 3-day posttreatment period (P = 0.503). We used reversed-phase liquid chromatography to quantify methyl anthranilate residues in treated fields. The maximum concentration of methyl anthranilate in rice samples was 4.71 μg/g. This concentration was below reported threshold values that irritate birds. In North Dakota we selected 6 pairs of sunflower fields used by foraging blackbirds. We randomly selected 1 field from each pair for 2 aerial applications of Bird Shield at the label-recommended rate ~1 week apart. The remaining 6 fields served as controls. Daily bird counts, starting the first day of application and continuing for 5–7 days after the second application, showed similar numbers of blackbirds within treated and control fields (P = 0.964). We observed no difference in sunflower damage within treated and control fields (P = 0.172) prior and subsequent to the treatment. Bird Shield was not effective for repelling blackbirds from ripening rice and sunflower fields

Landscape transformations produce favorable roosting conditions for turkey vultures and black vultures

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

Relevance of large litter bag burial for the study of leaf breakdown in the hyporheic zone

Particulate organic matter is the major source of energy for most low-order streams, but a large part of this litter is buried within bed sediment during floods and thus become poorly available for benthic food webs. The fate of this buried litter is little studied. In most cases, measures of breakdown rates consist of burying a known mass of litter within the stream sediment and following its breakdown over time. We tested this method using large litter bags (15 x 15 cm) and two field experiments. First, we used litter large bags filled with Alnus glutinosa leaves (buried at 20 cm depth with a shovel) in six stations within different land-use contexts and with different sediment grain sizes. Breakdown rates were surprisingly high (0.0011–0.0188 day-1) and neither correlate with most of the physico-chemical characteristics measured in the interstitial habitats nor with the land-use around the stream. In contrast, the rates were negatively correlated with a decrease in oxygen concentrations between surface and buried bags and positively correlated with both the percentage of coarse particles (20–40 mm) in the sediment and benthic macro-invertebrate richness. These results suggest that the vertical exchanges with surface water in the hyporheic zone play a crucial role in litter breakdown. Second, an experimental modification of local sediment (removing fine particles with a shovel to increase vertical exchanges) highlighted the influence of grain size on water and oxygen exchanges, but had no effect on hyporheic breakdown rates. Burying large litter bags within sediments may thus not be a relevant method, especially in clogged conditions, due to changes induced through the burial process in the vertical connectivity between surface and interstitial habitats that modify organic matter processing