Implications of goat eradication on the survivorship of the Galapagos hawk

Non-native mammals cause ecological disasters in island ecosystems and their eradication is usually considered beneficial to native biodiversity. Goats (Capra hircus) were introduced to Santiago Island, Galapagos, Ecuador, in the early 1800s, and their numbers increased to about 100,000 by 1970. A goat eradication campaign initiated in 2002 was successful, eliminating the last individuals in 2006. To evaluate the effects of goat eradication, between 1998 and 2010 we studied the Galapagos hawk (Buteo galapagoensis) population on Santiago Island before, during, and after eradication. We used a 12-year data set in a capture–mark–recapture analysis to estimate the apparent survivorship of territorial adults in 33 breeding territories, and a 5-year data set to estimate the population sizes of the floater (non-territorial) fraction of the population. Juvenile floaters showed a drastic decline starting in 2006 and continuing in 2007, 2008, and 2010, which we attribute to the completion of goat eradication in 2006, and subsequent habitat changes. We found a significant decline in adult survivorship after the goat eradication program. Additionally, group size positively affected adult survivorship in this cooperatively polyandrous raptor, presumably reflecting the benefit of shared defense and offspring provisioning during harsher conditions. The changes in the hawk population after goat eradication are an example of unforeseen consequences of a restoration program, and we hypothesize that these changes are adjustments towards a new equilibrium under the current ecosystem characteristics and capacity. © 2012 The Wildlife Society.     

Management-related stress in the red-shouldered hawk

Disturbance stress can prevent or disrupt successful management of captive birds of prey. Using heart rate as an indicator of stress, two female red-shouldered hawks (Buteo lineatus) were monitored via radio telemetry. Spontaneous heart rate fluctuations in response to stressors involved in management-related activities, as well as some in response to naturally occurring activities, were recorded. In nearly every case, stressors caused dramatic increases in the heart rate of each bird, the magnitude of which was directly related to the degree of human contact involved. The increased heart rates occurred in response to stressors whether or not any behavioral stress symptoms were exhibited. Under the conditions of this study, the use of a falconer's hood did not completely eliminate stress in restrained hawks.     

Development of 19 microsatellite loci for Swainson's hawks (Buteo swainsoni) and other buteos

We developed 26 Swainson's hawk (Buteo swainsoni) microsatellite primers from CA, AAT, CATC and GAGAA enriched genomic libraries. Primers were tested in 357 Swainson's hawks from western North America as well as seven other Buteo species. These markers will have broad application in investigations of Buteo population structure and genetic diversity.     

Site-Specific Assessments of Environmental Risk and Natural Resource Damage Based on Great Horned Owls

Selection of receptors is a key element of ecological risk and natural resource damage assessments. The great horned owl (Bubo virginianus; GHO) has advantages as a tertiary terrestrial receptor and integrated measure of exposure to chemical residues in a multiple-lines-of-evidence approach that includes elucidation of contaminant exposure by measured (tissue-based) and predicted (dietary) methodologies, and population-level measures of potential adverse effects (i.e., productivity, abundance). Methods described herein exploited attributes of GHO behavior, including its propensity to nest in artificial nesting platforms. This approach allowed better control of experimental conditions, minimized uncertainty in assessment endpoints, and maximized data utility for testing hypotheses. During 5 years, 54 GHO nests (14 active territories) along 38 km of river floodplain were monitored at the Kalamazoo River Superfund Site (Kalamazoo/Allegan Counties, Michigan). Concentrations of polychlorinated biphenyls (PCBs) and otho-, para-substituted isomers of dichlorodiphenyltrichloroethane (DDT), including DDD/DDE (Σ DDTs), were measured in 24 eggs and 16 samples of nestling blood plasma. Dietary PCB exposure was predicted by determining site-specific dietary composition and sampling and quantifying PCB concentrations in 171 prey items collected within active GHO territories. The convergence of exposure and effects assessments improved confidence in resulting predictions of minimal risk to resident GHO populations (Hazard Quotients ≤1.5). Repeated GHO use of nesting platforms minimized temporal and spatial variability.     

A mtDNA phylogeny of sea eagles (genus Haliaeetus) based on nucleotide sequences of the cytochrome b-gene

The mitochondrial cytochrome b gene of seven species of sea eagles H. albicilla, H. leucocephalus, H. leucoryphus, H. leucogaster, H. sanfordi, H. pelagicus and H. vocifer was amplified by PCR and sequenced (1026 bp). Phylogeny reconstructions by the Maximum Parsimony and Neighbour-Joining methods produced similar trees in which sea eagles represent a monophyletic group. In addition, the clade H. albicilla/H. leucocephalus groups with the clade H. pelagicus/H. leucoryphus in a monophyletic boreal group while H. vocifer clusters with the H. leucogaster/H. sanfordi clade in a monophyletic tropical clade. The nearest relatives of sea eagles are the kites (genus Milvus) and buzzards (genus Buteo), whereas ‘booted’ eagles (genus Aquila) and vultures (genera Gyps and Aegypius) have diverged earlier from the accipitrid branch. Honey bussards (genus Pernis) and vultures of the genera Gypaetus and Neophron represent basal taxa of the accipitrid lineage. Falcons, New World vultures and the secretary bird (Sagittarius) appear in separate clades outside the Accipitridae.     

Extra‐pair paternity in Swainson's Hawks

ABSTRACT Although passerines have been relatively well studied and many species found to exhibit relatively high rates of extra‐pair paternity (EPP), less is known about the frequency of EPP in other avian taxa, including raptors. From 2008 to 2010, we examined the frequency of EPP in a population of Swainson's Hawks (Buteo swainsoni) in Butte Valley, California. We examined paternity of 56 nestlings from 19 pairs and 27 broods and found that only three nestlings (5%) in two (7%) broods were the result of extrapair fertilizations. This relatively low frequency of EPP may be the result of mechanisms that reduce the likelihood of extra‐pair fertilization (e.g., mate guarding and frequent copulation), or could result from females limiting EPP to assure paternity of the social male and ensure paternal investment in offspring.