Using this map and assumptions about the likely occupancy of Barred Owls, we examined potential S... more Using this map and assumptions about the likely occupancy of Barred Owls, we examined potential Spotted Owl responses to the different hypotheses via adjustments to vital rates, and dispersion of adults and sub-adults. For this study we re-developed an earlier spatially explicit population demographics model for Spotted Owls into a state-transition-based demographics model for Spotted Owl territories based on the location and attributes of potential territories (as identified by the resource location model), cumulative cost distances measured between all pairs of these territories (estimated by the connectivity model), and the effects of Barred Owls modifying the demographic rates for Spotted Owls within those territories. The model reports on population-level indicators, which we then import into a Bayesian Belief Network post-processor. Indicators were produced using a reference landscape condition (termed AgingOnly) in which no disturbances affect forest structure, and compared r...
Red Knots Calidris canutus that migrate along the Pacific Flyway during spring are believed to be... more Red Knots Calidris canutus that migrate along the Pacific Flyway during spring are believed to belong to the roselaari subspecies, and in coastal Washington, USA, these knots aggregate in numbers not exceeded elsewhere in the flyway south of Alaska. In May 2010, as part of a continuing effort to investigate knot migration, including an effort to develop an estimate of abundance, we searched the northern areas of Grays Harbor and Willapa Bay, Washington, from airboats for flagged Red Knots originating from Baja California Sur, Mexico. We observed Red Knots roosting on sand or dredge-spoil islands, on estuarine shorelines, and at primary foraging areas. Red Knots were observed roosting primarily at shoreline and island locations, including sites that would not be available to them during extreme high tides or during storm events. The peak abundance of Red Knots occurred on 8 May, when 5,665 were in Grays Harbor and 1,314 in Willapa Bay. We documented 157 individually-marked Red Knots ...
The influence of different probability cutpoints and associated variations in sample size on popu... more The influence of different probability cutpoints and associated variations in sample size on population sex ratios were inferred with birds sexed by discriminant function analysis (DFA). Using two data sets from Dunlins (Calidris alpina) collected in western Washington state as examples, it was observed that selection of high probability (-0.95) cutpoints resulted in biased population sex ratio estimates. Overall, approximately
Interactions between Merlins (Falco columbarius) and Dunlins (Calidris al- pina) were studied at ... more Interactions between Merlins (Falco columbarius) and Dunlins (Calidris al- pina) were studied at estuarine areas in western Washington during winter, 1979 to 1985. Twenty-five of 111 hunting flights by Merlins were successful (22.5%). Five of seven capture attempt techniques were used successfully with a success rate of 4.9%. The most common capture techniques were the stoop at a flock and
Red Knots Calidris canutus believed to be of the subspecies roselaari, migrate along the Pacific ... more Red Knots Calidris canutus believed to be of the subspecies roselaari, migrate along the Pacific coast of North America and use localized areas of Grays Harbor and Willapa Bay, Washington, as stopover sites. As part of an effort to estimate the population size of Red Knots that use Grays Harbor and Willapa Bay during spring, we used airboats as observation platforms to facilitate making counts of knots and to search for leg flags during the 2009 spring migration. We made several site counts of >1,000 Red Knots and recorded a peak of about 4,000 birds at the Grays Harbor study area on 4 May. The peak of migration at Willapa Bay occurred on 30 April. Most of the higher counts of knots were made after the peak than before. We saw 146 leg flags and made positive flag code identifications of 91 individuals on 132 occasions. All flagged birds were marked in Guerrero Negro, Mexico, except for two birds marked on Wrangel Island, Russia. Aggregations of Red Knots were observed near the mo...
Red Knots Calidris canutus that migrate along the Pacific Flyway during spring are believed to be... more Red Knots Calidris canutus that migrate along the Pacific Flyway during spring are believed to belong to the roselaari subspecies, and in coastal Washington, USA, these knots aggregate in numbers not exceeded elsewhere in the flyway south of Alaska. In May 2010, as part of a continuing effort to investigate knot migration, including an effort to develop an estimate of abundance, we searched the northern areas of Grays Harbor and Willapa Bay, Washington, from airboats for flagged Red Knots originating from Baja California Sur, Mexico. We observed Red Knots roosting on sand or dredge-spoil islands, on estuarine shorelines, and at primary foraging areas. Red Knots were observed roosting primarily at shoreline and island locations, including sites that would not be available to them during extreme high tides or during storm events. The peak abundance of Red Knots occurred on 8 May, when 5,665 were in Grays Harbor and 1,314 in Willapa Bay. We documented 157 individually-marked Red Knots ...
Red Knots Calidris canutus roselaari occur along the Pacific coast of the Americas and may use as... more Red Knots Calidris canutus roselaari occur along the Pacific coast of the Americas and may use as few as four stopover or staging sites during spring migration. There are key information gaps regarding this population’s status and non-breeding distribution because of its localized distribution during migration, relatively small population size (estimated population of 17,000) and a poor understanding of the location of major overwintering sites. Based on resightings of marked birds, we assessed migratory connectivity of Red Knots along the Pacific coast. Knots captured and marked at two sites in NW Mexico have been observed at several locations, including migration areas in coastal Washington and the Yukon-Kuskokwim Delta in W Alaska and breeding areas in NW Alaska. The greatest connectivity was between Guerrero Negro/Ojo de Liebre and Golfo de Santa Clara, Mexico, and during northbound migration, between those two sites and coastal Washington, USA. Much less is known about the sout...
... Further, zones of breeding sympatry are likely to occur across this re-gion where lowland tun... more ... Further, zones of breeding sympatry are likely to occur across this re-gion where lowland tundra near the coastal plain changes to more alpine landscapes. ... 1993. Spe-ciation in golden-plovers, Pluvialis dominica and P. fulva: evidence from the breeding grounds. ...
Using this map and assumptions about the likely occupancy of Barred Owls, we examined potential S... more Using this map and assumptions about the likely occupancy of Barred Owls, we examined potential Spotted Owl responses to the different hypotheses via adjustments to vital rates, and dispersion of adults and sub-adults. For this study we re-developed an earlier spatially explicit population demographics model for Spotted Owls into a state-transition-based demographics model for Spotted Owl territories based on the location and attributes of potential territories (as identified by the resource location model), cumulative cost distances measured between all pairs of these territories (estimated by the connectivity model), and the effects of Barred Owls modifying the demographic rates for Spotted Owls within those territories. The model reports on population-level indicators, which we then import into a Bayesian Belief Network post-processor. Indicators were produced using a reference landscape condition (termed AgingOnly) in which no disturbances affect forest structure, and compared r...
Red Knots Calidris canutus that migrate along the Pacific Flyway during spring are believed to be... more Red Knots Calidris canutus that migrate along the Pacific Flyway during spring are believed to belong to the roselaari subspecies, and in coastal Washington, USA, these knots aggregate in numbers not exceeded elsewhere in the flyway south of Alaska. In May 2010, as part of a continuing effort to investigate knot migration, including an effort to develop an estimate of abundance, we searched the northern areas of Grays Harbor and Willapa Bay, Washington, from airboats for flagged Red Knots originating from Baja California Sur, Mexico. We observed Red Knots roosting on sand or dredge-spoil islands, on estuarine shorelines, and at primary foraging areas. Red Knots were observed roosting primarily at shoreline and island locations, including sites that would not be available to them during extreme high tides or during storm events. The peak abundance of Red Knots occurred on 8 May, when 5,665 were in Grays Harbor and 1,314 in Willapa Bay. We documented 157 individually-marked Red Knots ...
The influence of different probability cutpoints and associated variations in sample size on popu... more The influence of different probability cutpoints and associated variations in sample size on population sex ratios were inferred with birds sexed by discriminant function analysis (DFA). Using two data sets from Dunlins (Calidris alpina) collected in western Washington state as examples, it was observed that selection of high probability (-0.95) cutpoints resulted in biased population sex ratio estimates. Overall, approximately
Interactions between Merlins (Falco columbarius) and Dunlins (Calidris al- pina) were studied at ... more Interactions between Merlins (Falco columbarius) and Dunlins (Calidris al- pina) were studied at estuarine areas in western Washington during winter, 1979 to 1985. Twenty-five of 111 hunting flights by Merlins were successful (22.5%). Five of seven capture attempt techniques were used successfully with a success rate of 4.9%. The most common capture techniques were the stoop at a flock and
Red Knots Calidris canutus believed to be of the subspecies roselaari, migrate along the Pacific ... more Red Knots Calidris canutus believed to be of the subspecies roselaari, migrate along the Pacific coast of North America and use localized areas of Grays Harbor and Willapa Bay, Washington, as stopover sites. As part of an effort to estimate the population size of Red Knots that use Grays Harbor and Willapa Bay during spring, we used airboats as observation platforms to facilitate making counts of knots and to search for leg flags during the 2009 spring migration. We made several site counts of >1,000 Red Knots and recorded a peak of about 4,000 birds at the Grays Harbor study area on 4 May. The peak of migration at Willapa Bay occurred on 30 April. Most of the higher counts of knots were made after the peak than before. We saw 146 leg flags and made positive flag code identifications of 91 individuals on 132 occasions. All flagged birds were marked in Guerrero Negro, Mexico, except for two birds marked on Wrangel Island, Russia. Aggregations of Red Knots were observed near the mo...
Red Knots Calidris canutus that migrate along the Pacific Flyway during spring are believed to be... more Red Knots Calidris canutus that migrate along the Pacific Flyway during spring are believed to belong to the roselaari subspecies, and in coastal Washington, USA, these knots aggregate in numbers not exceeded elsewhere in the flyway south of Alaska. In May 2010, as part of a continuing effort to investigate knot migration, including an effort to develop an estimate of abundance, we searched the northern areas of Grays Harbor and Willapa Bay, Washington, from airboats for flagged Red Knots originating from Baja California Sur, Mexico. We observed Red Knots roosting on sand or dredge-spoil islands, on estuarine shorelines, and at primary foraging areas. Red Knots were observed roosting primarily at shoreline and island locations, including sites that would not be available to them during extreme high tides or during storm events. The peak abundance of Red Knots occurred on 8 May, when 5,665 were in Grays Harbor and 1,314 in Willapa Bay. We documented 157 individually-marked Red Knots ...
Red Knots Calidris canutus roselaari occur along the Pacific coast of the Americas and may use as... more Red Knots Calidris canutus roselaari occur along the Pacific coast of the Americas and may use as few as four stopover or staging sites during spring migration. There are key information gaps regarding this population’s status and non-breeding distribution because of its localized distribution during migration, relatively small population size (estimated population of 17,000) and a poor understanding of the location of major overwintering sites. Based on resightings of marked birds, we assessed migratory connectivity of Red Knots along the Pacific coast. Knots captured and marked at two sites in NW Mexico have been observed at several locations, including migration areas in coastal Washington and the Yukon-Kuskokwim Delta in W Alaska and breeding areas in NW Alaska. The greatest connectivity was between Guerrero Negro/Ojo de Liebre and Golfo de Santa Clara, Mexico, and during northbound migration, between those two sites and coastal Washington, USA. Much less is known about the sout...
... Further, zones of breeding sympatry are likely to occur across this re-gion where lowland tun... more ... Further, zones of breeding sympatry are likely to occur across this re-gion where lowland tundra near the coastal plain changes to more alpine landscapes. ... 1993. Spe-ciation in golden-plovers, Pluvialis dominica and P. fulva: evidence from the breeding grounds. ...
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Papers by Joseph Buchanan