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TwitterThe Maxent modeling algorithm was used to build the species distribution model at 270 m spatial resolution using species occurrence points and environmental layers as predictors (Phillips et al. 2006). Species occurrence points were primarily obtained from CNDDB (California Natural Diversity Database) and other CDFW sources, GBIF (Global Biodiversity Information Facility), PRBO (Point Blue Conservation Science) and Arctos museum databases. Vegetation, distance to water, elevation, and bioclimatic variables (Franklin et al. 2013) were used as predictor variables. The models were run at 270 m spatial resolution with five replications using cross-validation as a method of sample evaluation. Cross-validation involved the partitioning of the sample data into n subsets, fitting the models to n-1subsets, and testing the model on the one subset not used in fitting the model. Initial model runs showed that our models converged around 2,000 iterations and for this reason we ran all models with 2,500 maximum iterations. Maxent was implemented in R using the ‘dismo''package (Hijmans et al. 2011). Model evaluation was carried out using the ‘PresenceAbsence''package in R (Freeman and Moisen 2008). We used AUC as a metric to evaluate model performance. The package also computes threshold values using several accuracy metrics to translate predicted probability maps into binary suitable and unsuitable habitats. We selected the MeanProb, a threshold set based on the mean predicted probability of species occurrences. The output from Maxent are grid datasets in a multiband ‘tif''format with one band for each replication. We averaged the five replicated maps and created a mean grid for each species. The grid was then symbolized to represent low (threshold-50), medium (50-75) and high (75-100) habitat suitability, with pixel values that are below the threshold excluded. Models were reviewed by CDFW species experts; please review the use limitations.For more information see the project report at [https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=85358].
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These data are point locations where hawks and owls (raptors) were detected during playback surveys conducted between 28 March 2005 and 21 July 2005 along 36 randomly selected watercourses in the foothills of the Sierra Nevada Mountain Range. These data represent 260 positive responses for several species of hawks and owls to the playback surveys. This study was done by the North Central Region of the California Department of Fish and Game with support from the Resource Assessment Program. These data represent the point locations where individual hawks and owls were detected based on geographic algorithms using estimated distances and compass bearings from fixed points along public roads. Methodology: Playback surveys using MP3 players and battery-powered speakers were done to elicit vocal or behavioral responses from hawks and owls from fixed points along public roads in the foothills of the Sierra Nevada. The surveys were done along 36 randomly selected watercourses, and one or three surveys were done at the points between March and July 2005. Seventeen watercourses had one survey while 19 watercourses had three surveys. Survey periods were (1) March to mid-April, (2) late April to late May, and (3) June to July. Watercourses with one survey were surveyed during the March to mid-April period; watercourses with one survey were dropped from the study after the first survey due to logistic and manpower constraints. Each watercourse had 3-5 fixed points that were between 500-1,000 meters apart to ensure spatial independence. Hawk surveys were conducted between 8:00 am and 5:00 pm, while owl surveys were conducted between 8:30 pm and 4:15 am. Playback surveys were done with fixed sequences of species calls as follows: (1) for hawks, sharp-shinned hawks, Cooper's hawks, and red-shouldered hawks; and (2) for owls, flammulated owl (starting in May), northern saw-whet owl, northern pygmy-owl, western screech-owl, long-eared owl, and great-horned owl. No calls were done for red-tailed hawks, osprey, Swainson's hawks, or barn owls which were detected during the surveys and included in these data. The duration of the playbacks for each species consisted of a 1-minute silent period, a 4-minute playback period with 4 repeated sequences of 30 seconds of vocalizations followed by 30 seconds of silence, and a 1-minute silent period. The speaker initially faced North, and was then rotated South, West, and East with successive 30-second playback/30-second silence periods. Detected animals were visually or aurally located and identified. Laser rangefinders were used to estimate distances, while compasses were used to derive compass bearings. Habitats of detected animals were determined from field observations during the day for hawks or from aerial photographs with owls based on knowledge of field conditions at the fixed points. A GIS algorithm was used to locate the estimated field locations based on the estimated distances and compass bearings, and then habitats were verified with aerial photographs. The sex and age of each detected individual was determined if possible, and observers rated the confidence of their determination of the number of individuals, species type, sex and age of each detection.
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Species and abundances of soaring birds identified from the hawk-watch monitoring station.
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TwitterOrthomosaic of Billy Hawk Caye, Belize. Images were collected in October 2016 as part of the Open Reef Mapping Society using DJI Phantom 4 quadcopters. Quadcopters were flown at an altitude of 150m with a picture frequency of 7 seconds. Flight time for Billy Hawk Caye was 2 minutes. Images were processed using Esri’s Drone2Map to create this orthomosaic. The spatial resolution of this orthomosaic is 6.42cm per pixel.This orthomosaic is open-source, freely available, and is not intended to be used for nefarious or illegal purposes. Our goal is to provide the imagery to stimulate citizen science and greater scientific discovery of the islands of Belize. This orthomosaic is not guaranteed to be 100% spatially accurate and should not be used for nautical/charting purposes. Differences in location may be due to errors in processing or previously outdated imagery.Images for this orthomosaic were collected in collaboration with Open Reef Mapping Society, Citizen Science GIS, Coastal Zone Management Authority and Institute (CZMAI), University of Central Florida, and University of Belize.When using this orthomosaic please cite Open Reef Mapping Society, Citizen Science GIS, Coastal Zone Management Authority and Institute (CZMAI), University of Central Florida, and University of Belize in the credits section.
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Habitat loss causes population declines, but the mechanisms are rarely known. In the European Boreal Zone, loss of old forest due to intensive forestry is suspected to cause declines in forest-dwelling raptors by reducing their breeding performance. We studied the boreal breeding habitat and habitat-associated breeding performance of the northern goshawk (Accipiter gentilis), common buzzard (Buteo buteo) and European honey buzzard (Pernis apivorus). We combined long-term Finnish bird-of-prey data with multi-source national forest inventory data at various distances (100–4000 m) around the hawk nests. We found that breeding success of the goshawk was best explained by the habitat within a 2000-m radius around the nests; breeding was more successful with increasing proportions of old spruce forest and water, and decreasing proportions of young thinning forest. None of the habitat variables affected significantly the breeding success of the common buzzard or the honey buzzard, or the brood size of any of the species. The amount of old spruce forest decreased both around goshawk and common buzzard nests and throughout southern Finland in 1992–2010. In contrast, the area of young forest increased in southern Finland but not around hawk nests. We emphasize the importance of studying habitats at several spatial and temporal scales to determine the relevant species-specific scale and to detect environmental changes. Further effort is needed to reconcile the socioeconomic and ecological functions of forests and habitat requirements of old forest specialists.
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TwitterThe Maxent modeling algorithm was used to build the species distribution model at 270 m spatial resolution using species occurrence points and environmental layers as predictors (Phillips et al. 2006). Species occurrence points were primarily obtained from CNDDB (California Natural Diversity Database) and other CDFW sources, GBIF (Global Biodiversity Information Facility), PRBO (Point Blue Conservation Science) and Arctos museum databases. Vegetation, distance to water, elevation, and bioclimatic variables (Franklin et al. 2013) were used as predictor variables. The models were run at 270 m spatial resolution with five replications using cross-validation as a method of sample evaluation. Cross-validation involved the partitioning of the sample data into n subsets, fitting the models to n-1subsets, and testing the model on the one subset not used in fitting the model. Initial model runs showed that our models converged around 2,000 iterations and for this reason we ran all models with 2,500 maximum iterations. Maxent was implemented in R using the ‘dismo''package (Hijmans et al. 2011). Model evaluation was carried out using the ‘PresenceAbsence''package in R (Freeman and Moisen 2008). We used AUC as a metric to evaluate model performance. The package also computes threshold values using several accuracy metrics to translate predicted probability maps into binary suitable and unsuitable habitats. We selected the MeanProb, a threshold set based on the mean predicted probability of species occurrences. The output from Maxent are grid datasets in a multiband ‘tif''format with one band for each replication. We averaged the five replicated maps and created a mean grid for each species. The grid was then symbolized to represent low (threshold-50), medium (50-75) and high (75-100) habitat suitability, with pixel values that are below the threshold excluded. Models were reviewed by CDFW species experts; please review the use limitations.For more information see the project report at [https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=85358].