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James Dwyer
Archbold Biological Station / MAERC |
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| Adult Crested Caracara Photo Courtesy Steve Schubert, USFWS | |
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Virginia Tech Department of Fisheries and Wildlife |
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Juvenile Crested Caracara, and Me. I'm the one in the green shirt. PhotoCourtesy Justin Styer, WilsonMiller Consulting |
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HABITAT, SURVIVAL, AND FLOCKING OF NON-BREEDING CRESTED CARACARAS (CARACARA CHERIWAY) IN FLORIDA Dissertation Working Plan Major Advisor Dr. James (Jim) D. Fraser ABSTRACT
Florida contains an isolated population of crested caracaras (Caracara cheriway, hereafter caracara) listed as Threatened by the U.S. Fish and Wildlife Service (Federal Register, 1987) and the state of Florida (Logan 1997), and a conservation and recovery plan has been constructed (US Fish and Wildlife Service 1999, Federal Register 2004). Caracaras in Florida were formerly identified as Florida crested caracara (Caracara plancus) (American Ornithologists’ Union 2000), and before that as Audubon’s crested caracara (Polyborus plancus audubonii) (American Ornithologists’ Union 1993). Some citations and legal documents retain these names. The conversion of much of the open areas (native prairie, improved pasture, and grassland) preferred by caracaras to more closed environments (citrus, sugar cane, and urban development) may be causing declines in territory occupancy (Millsap 1989), and lead to a long-term population decline (Layne 1996, Millsap et al. 1990). The persistence of Florida’s caracara population depends not only on maintaining a breeding population, and protecting nesting habitat, but also on ensuring the survival and recruitment of non-breeding caracaras, since the survival on non-breeding birds can affect population persistence (Penteriani et al 2005a). Recent research has indicated that caracaras do not breed until they are at least three years old (Morrison 1999, Nemeth and Morrison 2002), and that in Florida non-breeding birds form flocks of up to 60 individuals in Florida (Morrison 2003). These flocks appear to occur year-round in particular areas that may be critical to the species’ survival. In this project, I will identify the extent of those areas (variously called settling areas (Ferrer 1993a and 1993b, Ferrer and Harte 1997, Penteriani et al. 2005b), temporary home ranges (Forsman et al. 2002), or juvenile home ranges (Belthoff et al. 1993). I will also identify the particular habitats used by non-breeding caracaras within those areas. Morrison (2003) provided estimates of both adult and juvenile survival. The best model possible (selected via AIC) grouped all non-breeding caracaras into a single class, but it is likely that survival probabilities actually differ among ages of non-breeding caracaras (Morrison 2003). I will provide information focused on the survival of > 1 year old non-breeding caracaras. Because an understanding of the behavior of non-breeding caracaras may be critical to their conservation, I will identify the most likely hypotheses on why caracaras form flocks. These hypotheses range from hypotheses easily relatable to raptors (i.e, various foraging benefits) to hypotheses not often considered in raptors (i.e, social learning and alternative mating strategies). This project will pursue a variety of widely disparate objectives, and because of the potential for confusion, more comprehensive literature reviews have been included in the opening discussion of each objective rather than discussed here. In this project I will provide important new information on habitat use, survival, and the function of flocking in non-breeding caracaras. Each of these datasets will evaluate the ecology of non-breeding crested caracaras in Florida from different viewpoints. The combined perspectives of these independent datasets will create a synthesis of understanding that will be used to inform and maximize the effectiveness of the USFWS and the state of Florida in creating and implementing the best possible conservation and recovery plans possible for crested caracaras in Florida. Due to the value of long-term data sets, I will also evaluate the current occupancy status of nesting areas identified during the 1990s. The overall goal of this project is to describe as many of the details of the ecology of non-breeding caracaras as possible, to contribute to the species’ conservation, and to advance scientific knowledge.
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PREVENTING THE ELECTROCUTION OF RAPTORS IN AN URBAN ENVIRONMENT Dwyer, J.F and R. W. Mannan1 ABSTRACT Electrocution of raptors in the United States has been a cause of concern since the early 1970s when it was first identified as a significant source of mortality. Since then, biologists and industry personnel have developed an understanding of how and why raptors are killed more often on some pole types, and have developed techniques to identify those poles and to modify them to prevent a raptor from simultaneously contacting multiple, differentially energized conductors. Doing so has enabled the electric industry to focus limited resources on the most lethal poles. This work has been conducted primarily in rural areas, but raptors are found in urban areas also. Since previous research indicated that Harris' hawks living in urban Tucson, Arizona were affected by electrocution, I investigated: 1) whether poles close to nests were more likely to electrocute a hawk than poles of the same configuration farther away; and 2) whether pole modifications intended to prevent the electrocution of raptors were effective. I was also able to asses the extent of raptor electrocution in Tucson. Over 18 months of study, I found 133 electrocuted raptors, 9 electrocuted corvids, 15 raptors suffering from electric shock injuries, and evidence to suggest that I failed to detect 1 out of every 3 electrocutions, even in the areas I searched most intensively. All electrocutions on monitored poles around Harris' hawk nests occurred within 300 m of nests, suggesting that poles close to nests are more likely to electrocute a raptor. In early 2003, prior to any nest-specific retrofitting, I detected 1.4 electrocutions per monitored nest. In 2004, after roughly half of poles within 300 m of nests were retrofitted, I detected 0.2 electrocutions per nest. Retrofitting utility poles does reduce electrocutions. 1 R.W. (Bill) Mannan, School of Natural Resources, University of Arizona, Tucson, AZ, 85721, USA
*********************************************************************************** DISAPPEARANCE OF RAPTOR CARCASSES IN AN URBAN ENVIRONMENT Dwyer, J.F. and R.W. Mannan1 ABSTRACT Mortality is an important aspect of population dynamics, and carcass necropsies can be an effective way of evaluating mortality factors. In human-dominated landscapes the persistence and disposition of carcasses is likely to be different than in natural areas. As part of an investigation of raptor electrocution in Tucson, Arizona, USA, we evaluated the persistence and disposition of carcasses of birds of prey (raptors) in an urban area. We placed the carcasses of 23 raptors at the bases of the nearest "safe" utility poles to 23 Harris's Hawk nests. We revisited those carcasses daily for one week, and every other day for another week, to determine whether and how the carcasses were removed. Six to eight weeks prior to placing each carcass, we delivered letters to all properties within 300 meters of nests to inform residents that there were Harris's hawks in the area, and to request that we be contacted if a dead raptor was discovered. Residents reported 22% of carcasses within 1 day, and 30% within 3.5 days. Carcasses that were not reported within 3.5 days were never reported. Another 17% of carcasses were definitely removed by humans (e.g., buried with a wooden cross over the grave), but not reported. Twenty-seven percent of carcasses disappeared, but we could not determine how that disappearance occurred, and 4% were definitely scavenged by non-humans. The remaining 26% were never removed. Participating residents often conveyed that they had encountered carcasses previously, but had not recognized their value, and had disposed of them with household garbage. We suggest that carcasses in urban environments disappear in large part via humans, and that projects investigating animal populations in human-dominated landscapes should avail themselves of the public's willingness to contribute to conservation studies. 1 R.W. (Bill) Mannan, School of Natural Resources, University of Arizona, Tucson, AZ, 85721, USA *********************************************************************************** AVIAN BUCCAL SWABS YIELD AMPLIFIABLE DNA Dwyer, J.F. and M. Culver1 ABSTRACT Sex ratios of avian populations are regularly assessed via molecular methods in sexually monomorphic or overlapping dimorphic species or age classes. Genetic analyses can be difficult to implement however, if blood or feather collection is disallowed. We found that buccal swabs provided an alternative method of collecting amplifiable DNA from Harris's Hawks, and suggest that the method may be useful in other species. Buccal swabs may be especially useful in assessing primary sex ratio in nestlings whose large gapes may facilitate the technique in all but the smallest species. 1 Melanie Culver, Arizona Cooperative Fish and Wildlife Research Unit, USGS, (BRD), School of Natural Resources, University of Arizona, Tucson, AZ, 85721, USA PDF OF POSTER (under construction)
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Top Left: There's no way Chris N is going to catch him from there but that's all right, Chris K rarely needs a spotter anyway. All photos courtesy of Chris K. |
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Here are a couple of links to sites with online climbing videos. Content there changes every couple of weeks, so check back! |
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