Predation by Ermine and Long-tailed Weasels on Duck Eggs

Ermine (Mustela erminea) and long-tailed weasel (M. frenata) predation on duck eggs was studied at Union Slough National Wildlife Refuge, Kossuth County, Iowa, 1984-85. Captive individuals of both species ate 2-4 duck eggs at a rate of 0.5-2 eggs per trial day. All eggs were moved but some were not opened. One hole, ringed with small fragments and bite-outs\u27\u27, was made in all eggs opened by captive weasels. In the field, the appearance of opened eggs, the pattern of egg loss and the amount of nest bowl disturbance were used to determine the number of nests depreciated by weasels. Egg loss at nests depredated by weasels generally occurred over several days; nest bowl disturbance was minimal and most hens did not abandon their nests until over half their eggs were taken. Of 263 upland duck nests that failed due co predation, 38 had eggs taken by weasels and 27 of the 38 failed solely because of weasels. Weasels also took eggs from at least 5 of 20 nests that lost 1-7 eggs before ≥1 remaining egg hatched. Because 12 of 13 weasels captured were ermine, most depredation of nests by weasels during the study probably was by ermine

CHARACTERISTICS OF SANDHILL CRANE ROOSTS IN THE SACRAMENTO-SAN JOAQUIN DELTA OF CALIFORNIA

The Sacramento-San Joaquin Delta (Delta) region of California is an important wintering region for 2 subspecies of Pacific Flyway sandhill cranes (Grus canadensis): the Central Valley Population of the greater sandhill crane (G. c. tabida) and the Pacific Flyway Population of the lesser sandhill crane (G. c. canadensis). During the winters of 2007-08 and 2008-09 we conducted roost counts, roadside surveys, aerial surveys, and tracked radio-marked birds to locate and assess important habitats for roosting cranes in the Delta. Of the 69 crane night roosts we identified, 35 were flooded cropland sites and 34 were wetland sites. We found that both larger individual roost sites and larger complexes of roost sites supported larger peak numbers of cranes. Water depth used by roosting cranes averaged 10 cm (range 3-21 cm, mode 7 cm) and was similar between subspecies. We found that cranes avoided sites that were regularly hunted or had high densities of hunting blinds. We suggest that managers could decide on the size of roost sites to provide for a given crane population objective using a ratio of 1.5 cranes/ha. The fact that cranes readily use undisturbed flooded cropland sites makes this a viable option for creation of roost habitat. Because hunting disturbance can limit crane use of roost sites we suggest these 2 uses should not be considered readily compatible. However, if the management objective of an area includes waterfowl hunting, limiting hunting to low blind densities and restricting hunting to early morning may be viable options for creating a crane-compatible waterfowl hunt program

Avian influenza at both ends of a migratory flyway: characterizing viral genomic diversity to optimize surveillance plans for North America

Although continental populations of avian influenza viruses are genetically distinct, transcontinental reassortment in low pathogenic avian influenza (LPAI) viruses has been detected in migratory birds. Thus, genomic analyses of LPAI viruses could serve as an approach to prioritize species and regions targeted by North American surveillance activities for foreign origin highly pathogenic avian influenza (HPAI). To assess the applicability of this approach, we conducted a phylogenetic and population genetic analysis of 68 viral genomes isolated from the northern pintail (Anas acuta) at opposite ends of the Pacific migratory flyway in North America. We found limited evidence for Asian LPAI lineages on wintering areas used by northern pintails in California in contrast to a higher frequency on breeding locales of Alaska. Our results indicate that the number of Asian LPAI lineages observed in Alaskan northern pintails, and the nucleotide composition of LPAI lineages, is not maintained through fall migration. Accordingly, our data indicate that surveillance of Pacific Flyway northern pintails to detect foreign avian influenza viruses would be most effective in Alaska. North American surveillance plans could be optimized through an analysis of LPAI genomics from species that demonstrate evolutionary linkages with European or Asian lineages and in regions that have overlapping migratory flyways with areas of HPAI outbreaks

Presence of Avian Influenza Viruses in Waterfowl and Wetlands during Summer 2010 in California: Are Resident Birds a Potential Reservoir?

Although wild waterfowl are the main reservoir for low pathogenic avian influenza viruses (LPAIv), the environment plays a critical role for the circulation and persistence of AIv. LPAIv may persist for extended periods in cold environments, suggesting that waterfowl breeding areas in the northern hemisphere may be an important reservoir for AIv in contrast to the warmer southern wintering areas. We evaluated whether southern wetlands, with relatively small populations (thousands) of resident waterfowl, maintain AIv in the summer, prior to the arrival of millions of migratory birds. We collected water and fecal samples at ten wetlands in two regions (Yolo Bypass and Sacramento Valley) of the California Central Valley during three bi-weekly intervals beginning in late July, 2010. We detected AIv in 29/367 fecal samples (7.9%) and 12/597 water samples (2.0%) by matrix real time Reverse Transcription Polymerase Chain Reaction (rRT-PCR). We isolated two H3N8, two H2N3, and one H4N8 among rRT-PCR positive fecal samples but no live virus from water samples. Detection of AIv RNA in fecal samples was higher from wetlands in the Sacramento Valley (11.9%) than in the Yolo Bypass (0.0%), but no difference was found for water samples (2.7 vs. 1.7%, respectively). Our study showed that low densities of hosts and unfavorable environmental conditions did not prevent LPAIv circulation during summer in California wetlands. Our findings justify further investigations to understand AIv dynamics in resident waterfowl populations, compare AIv subtypes between migratory and resident waterfowl, and assess the importance of local AIv as a source of infection for migratory birds

Ecology of female northern pintails during winter in the San Joaquin Valley, California

I radio-tagged 191 Hatch-Year (HY) and After-Hatch-Year (AHY) female northern pintails (Anas acuta) in the San Joaquin Valley (SJV), California and studied their movements, habitat use and survival during August March, 1991-94. Overall, 94.3% wintered in central California; the highest percentage left during the 1991 drought. Tulare Basin and Mendota Wildlife Area (WA) pintails moved to the Grassland Ecological Area (EA) vicinity when hunting began. Of those wintering in central California, 83% went to the Sacramento Valley, most during December. AHY pintails tended to leave earliest but the effect of age varied with body condition. Loss of Tulare Basin habitat has contributed to the late-winter decline of pintails throughout the SJV. Local distribution and movements differed most among seasons, day and night periods and shoot and nonshoot days. Overall, 64% of the day and 85% of the night locations in the Grassland EA vicinity were on private wetlands. Habitat availability and use varied greatly among SJV areas and during the winter. Pintails selected shallow and avoided deepwater habitats. Swamp timothy wetlands were the most abundant and most highly selected habitat in Grassland EA and Mendota WA. In Tulare Basin, preirrigated fields were the most abundant and selected habitat during PREHUNT, but managed wetlands were most abundant and selected thereafter. Selection of watergrass wetlands during night was low in the Grassland EA vicinity but high in Mendota WA. In Tulare Basin, pintails selected preirrigated fallow and safflower fields; selection of barley-wheat fields varied greatly. The exodus of most pintails from the SJV during December implies that preferred late-winter habitats were lacking. Winter survival was lower for HY (0.67) than AHY (0.76) pintails. Survival was similar to Louisiana and Suisun Marsh but lower than in the Sacramento Valley. Hunting caused 83%, avian predators 7.6%, collisions 1%, and disease or other non-hunting factors 8.7% of the mortalities. Hunting mortality was related to fall body condition for HY but not AHY pintails. The retrieval rate for shot radio-tagged pintails was 80.3%. This study indicates that inter-related factors influenced female pintail ecology during winter in California but availability of productive habitat was especially important

Projected Impacts of Climate, Urbanization, Water Management, and Wetland Restoration on Waterbird Habitat in California's Central Valley.

The Central Valley of California is one of the most important regions for wintering waterbirds in North America despite extensive anthropogenic landscape modification and decline of historical wetlands there. Like many other mediterranean-climate ecosystems across the globe, the Central Valley has been subject to a burgeoning human population and expansion and intensification of agricultural and urban development that have impacted wildlife habitats. Future effects of urban development, changes in water supply management, and precipitation and air temperature related to global climate change on area of waterbird habitat in the Central Valley are uncertain, yet potentially substantial. Therefore, we modeled area of waterbird habitats for 17 climate, urbanization, water supply management, and wetland restoration scenarios for years 2006-2099 using a water resources and scenario modeling framework. Planned wetland restoration largely compensated for adverse effects of climate, urbanization, and water supply management changes on habitat areas through 2065, but fell short thereafter for all except one scenario. Projected habitat reductions due to climate models were more frequent and greater than under the recent historical climate and their magnitude increased through time. After 2065, area of waterbird habitat in all scenarios that included severe warmer, drier climate was projected to be >15% less than in the "existing" landscape most years. The greatest reduction in waterbird habitat occurred in scenarios that combined warmer, drier climate and plausible water supply management options affecting priority and delivery of water available for waterbird habitats. This scenario modeling addresses the complexity and uncertainties in the Central Valley landscape, use and management of related water supplies, and climate to inform waterbird habitat conservation and other resource management planning. Results indicate that increased wetland restoration and additional conservation and climate change adaptation strategies may be warranted to maintain habitat adequate to support waterbirds in the Central Valley

Waterbird habitat projected for 17 scenarios, years 2006–2099.

<p>Area (km²) and proportion of existing (3,183 km² in 2005) wintering waterbird habitat projected to be available in the Central Valley of California during 2006–99 for 17 scenarios (A. 1–5, B. 6–9, C. 10–13, D. 14–17) comprised of various climate, urbanization, water management, and wetland restoration levels (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0169780#pone.0169780.t001" target="_blank">Table 1</a> for scenario descriptions).</p

CHARACTERISTICS OF SANDHILL CRANE ROOSTS IN THE SACRAMENTO-SAN JOAQUIN DELTA OF CALIFORNIA

The Sacramento-San Joaquin Delta (Delta) region of California is an important wintering region for 2 subspecies of Pacific Flyway sandhill cranes (Grus canadensis): the Central Valley Population of the greater sandhill crane (G. c. tabida) and the Pacific Flyway Population of the lesser sandhill crane (G. c. canadensis). During the winters of 2007-08 and 2008-09 we conducted roost counts, roadside surveys, aerial surveys, and tracked radio-marked birds to locate and assess important habitats for roosting cranes in the Delta. Of the 69 crane night roosts we identified, 35 were flooded cropland sites and 34 were wetland sites. We found that both larger individual roost sites and larger complexes of roost sites supported larger peak numbers of cranes. Water depth used by roosting cranes averaged 10 cm (range 3-21 cm, mode 7 cm) and was similar between subspecies. We found that cranes avoided sites that were regularly hunted or had high densities of hunting blinds. We suggest that managers could decide on the size of roost sites to provide for a given crane population objective using a ratio of 1.5 cranes/ha. The fact that cranes readily use undisturbed flooded cropland sites makes this a viable option for creation of roost habitat. Because hunting disturbance can limit crane use of roost sites we suggest these 2 uses should not be considered readily compatible. However, if the management objective of an area includes waterfowl hunting, limiting hunting to low blind densities and restricting hunting to early morning may be viable options for creating a crane-compatible waterfowl hunt program

Median and worst-year area and percent of existing wintering waterbird habitat for 17 scenarios.

<p>Median and worst-year area (km²) and percent (%) of existing wintering waterbird habitat projected to be available in the Central Valley of California during 2006–35, 2036–65 and 2066–99 for 17 scenarios comprised of various climate, urbanization, water management, and wetland restoration levels (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0169780#pone.0169780.t001" target="_blank">Table 1</a> for scenario descriptions). Existing habitat is the approximate area of waterbird habitat (3,183 km²) that existed in the Central Valley in 2005.</p

Data from: Bird use of fields treated post-harvest with two types of flooding in Tulare Basin, California

We surveyed birds on grain and non-grain fields in the Tulare Basin of California treated post-harvest with two types of flooding that varied in duration and depth of water applied (Flooded-type fields [FLD]: 1 week; Irrigated-type fields [IRG]: 1 week) flooding increased waterbird use of grain fields in the Tulare Basin more than in the northern Central Valley. Thus, even though water costs are high in the Tulare Basin, if net benefit to waterbirds is considered, management programs that increase availability of FLD-type fields (especially grain) in the Tulare Basin may be a cost-effective option to help meet waterbird habitat conservation goals in the Central Valley of California