Yukon Delta National Wildlife Refuge Research Articles

Migratory Timing and Rates of Chinook Salmon Bound for the Kwethluk and Kisaralik Rivers

Abstract Detailed information regarding migratory behavior (i.e., phenology and rate of travel) of specific Pacific salmon Oncorhynchus spp. substocks can be used to design management strategies focused on protecting substocks from harvest when desired; however, this information is often lacking. The Kwethluk and Kisaralik rivers are two tributaries of the lower Kuskokwim River that originate and flow through the Yukon Delta National Wildlife Refuge in western Alaska. Although these two systems are the primary Chinook Salmon–producing tributaries within the Yukon Delta National Wildlife Refuge, little is known about migratory behavior of Chinook Salmon destined for these rivers. In 2015 and 2016, 119 Chinook Salmon tagged with radio telemetry transmitters entered either the Kwethluk or Kisaralik Rivers and were tracked throughout their migration to their assumed final spawning location using both ground- and aerial-based tracking methods. We compared migration timing and swim speeds between fish bound for these two rivers and between fish of different sizes and compared the consistency among the 2 y. In general, we found that fish bound for the Kwethluk and Kisaralik rivers exhibited similar migration behaviors in 2015 and 2016, including entry timing into the Kuskokwim River and migration rates once in the tributaries. A key finding was that Chinook Salmon swam fastest (range of means between years: 20–45 km/d) in the main-stem Kuskokwim River and slowed significantly (4–15 km/d) upon entry into lower portions of the tributaries. Our findings have relevance for harvest management strategies; for example, temporal fishery closures will impact Chinook Salmon bound for both the Kwethluk and Kisaralik rivers equally given their broad overlap in entry timing, and individuals will remain vulnerable to harvest for longer periods when located in tributaries rather than the portion of the main-stem directly below the tributary confluences.

Habitat Selection By Bristle-Thighed Curlews (Numenius tahitiensis) Breeding Within The Southern Nulato Hills, Alaska

ABSTRACT Bristle-thighed Curlews (Numenius tahitiensis, hereafter ‘curlews') breed only on low Arctic tundra in the southern Nulato Hills of the Yukon Delta National Wildlife Refuge (NWR) and on the Seward Peninsula, Alaska. Curlews use several distinct habitat types on the breeding grounds; however, quantified data of habitat use by curlews exist only for the Seward Peninsula. We investigated which available habitats on the breeding grounds were used most often by curlews in the Nulato Hills and compared availability with use to determine habitat selection using a land cover layer created in ArcGIS based on aerial photography and ground referenced locations. We also compared curlew habitat usage at our study site to habitats used on the Seward Peninsula. We used vegetation quadrats to determine plant composition within each habitat. We also determined percentage of habitat and plant composition within curlew territories. Curlews preferred shrub meadow tundra which consisted primarily of lichens (>50%), m...

Nest-Site Fidelity and Dispersal of Gyrfalcons Estimated by Noninvasive Genetic Sampling

Abstract. We used feathers from adult Gyrfalcons (Falco rusticolus) molted in breeding territories and blood samples from nestlings to document nest-site fidelity and dispersal of breeding adults and juveniles at three areas 100– 350 km apart in Yukon Delta National Wildlife Refuge, Alaska, 2003–2007. We used genotypes from seven polymorphic microsatellite loci that provided a mean probability of identity of 0.91 × 10-5. Breeding Gyrfalcons were highly faithful to study area and territory; we documented no dispersals of breeding birds among study areas and only one dispersal between territories. But their fidelity to nest sites was low; 22% of birds returned to the same nest site the following year. Distance among alternate nests within a territory averaged 750 m and was similar for both sexes. Mean tenure in a territory was 2.8 years, similar for both sexes, and distributed bimodally with peaks at 1 and 4 years. Mean annual turnover rate at the Ingakslugwat Hills (Volcanoes) study area was 20%. We detect...

Detection Probability of Cliff-Nesting Raptors During Helicopter and Fixed-Wing Aircraft Surveys in Western Alaska

Abstract We conducted repeated aerial surveys for breeding cliff-nesting raptors on the Yukon Delta National Wildlife Refuge (YDNWR) in western Alaska to estimate detection probabilities of Gyrfalcons (Falco rusticolus), Golden Eagles (Aquila chrysaetos), Rough-legged Hawks (Buteo lagopus), and also Common Ravens (Corvus corax). Using the program PRESENCE, we modeled detection histories of each species based on single species occupancy modeling. We used different observers during four helicopter replicate surveys in the Kilbuck Mountains and five fixed-wing replicate surveys in the Ingakslugwat Hills near Bethel, AK. During helicopter surveys, Gyrfalcons had the highest detection probability estimate (; = 0.79; SE 0.05), followed by Golden Eagles ( = 0.68; SE 0.05), Common Ravens ( = 0.45; SE 0.17), and Rough-legged Hawks ( = 0.10; SE 0.11). Detection probabilities from fixed-wing aircraft in the Ingakslugwat Hills were similar to those from the helicopter in the Kilbuck Mountains for Gyrfalcons a...

Demography of Eastern Yellow Wagtails at Cape Romanzof, Alaska

We quantified demographic parameters of Eastern Yellow Wagtails (Motacilla tschutschensis) breeding at Cape Romanzof, Yukon Delta National Wildlife Refuge, Alaska. We monitored 79 nests in an 837-ha area during 1997–1999 and banded 160 individuals. Mayfield nest success differed among years and ranged from 0.14 to 0.63/year. Most nest failures were attributed to predation. Annual fecundity (mean number of fledglings/female) ranged from 0.7 to 3.7. At least 8.8% of nests had polygynous males; females paired with polygynous males had the same fecundity as monogamous females. Forty-two to 100% of the breeding males returned the following year, usually to the same territory while no adult females returned. Four nestlings banded in the study area returned to nest the following year. The best model for annual survival accounted for differences between both age groups and years. The demography of Eastern Yellow Wagtails at Cape Romanzof varied and was characterized by relatively high adult male survival and site fidelity, female-biased dispersal, and weak natal philopatry. The absence of returning females is significant and possible differences in migration stopovers and wintering locations should be investigated. Moderate levels of male immigration may be necessary in periodic pulses to maintain a local population, but female immigration would need to be massive and sustained.

Blood Lead Concentrations of Spectacled Eiders Near the Kashunuk River, Yukon Delta National Wildlife Refuge, Alaska

We collected, 342 blood samples from spectacled eiders (Somateria fischeri) on their breeding grounds in western Alaska from late May through to early August 1993–1995. Lead concentrations of ≥0.50 p.p.m. wet weight were found in the blood of 20% of the adult female eiders, 2% of the adult males and 6% of the ducklings. Lead was detected (≥0.02 p.p.m.) more frequently in the blood of adult females than in adult males or ducklings and the maximum concentrations were 14.37, 0.50 and 4.28 p.p.m. wet weight, respectively. In adult females, there was a significant difference in the proportion of detectable blood lead concentrations between three collection times (arrival/nesting, hatch and brood rearing), with the highest proportion (92%) occurring at hatch. Nine hens with blood lead concentrations of ≥0.50 p.p.m. were captured a second time several weeks to 1 year later. In the hens sampled twice at intervals of several weeks, the blood lead concentrations increased and declined at mean daily rates of 1.10 and 0.94, respectively. The lead concentrations in the blood of adults were not correlated with body weights. Radiographs were taken of 119 eiders and corresponding blood samples from 98 of these birds were analysed for lead. Ingested shot was seen in X-rays of 12 adults and three ducklings and, of the 13 blood samples tested, all had detectable lead concentrations. Of the birds without radiographic evidence of ingested shot, 84% of the adult females, 19% of the adult males and 17% of the ducklings had detectable lead concentrations in their blood. Breeding ground exposure of waterfowl to lead shot is unusual and is of particular concern in spectacled eiders because of their threatened status and declining numbers in western Alaska.

Behavior of Cackling Canada Geese during Brood Rearing

We studied behavior of Cackling Canada Goose (Branta canadensis minima, cacklers) broods between 1992 and 1996 on the Yukon Delta National Wildlife Refuge in western Alaska. An increase in time spent foraging by goslings during our study was weakly correlated with an increase in the size of the local breeding population. Amount of time spent feeding by adults and goslings increased throughout the brood rearing period. Overall, goslings spent more time feeding than either adult females or males, and adult males spent the most time alert. Time alert varied among brood rearing areas and increased with brood size, but there was no variation in time spent alert among years. Increases in feeding or alert behaviors were at a cost to time spent in all other behaviors. We suggest that there is not a simple trade-off between feeding and alert behavior in cacklers, but instead that time spent feeding and alert are optimized against all other behaviors. We suggest that forage quality and availability determines the amount of time spent feeding, whereas the threat of predation or disturbance determines the amount of time spent alert.

Lead poisoning of spectacled eiders (Somateria fischeri) and of a common eider (Somateria mollissima) in Alaska.

Lead poisoning was diagnosed in four spectacled eiders (Somateria fischeri) and one common eider (Somateria mollissima) found dead or moribund at the Yukon Delta National Wildlife Refuge, Alaska (USA) in 1992, 1993, and 1994. Ingested lead shot was found in the lower esophagus of one spectacled eider and in the gizzard of the common eider. Lead concentrations in the livers of the spectacled eiders were 26 to 38 ppm wet weight, and 52 ppm wet weight in the liver of the common eider. A blood sample collected from one of the spectacled eiders before it was euthanized had a lead concentration of 8.5 ppm wet weight. This is the first known report of lead poisoning in the spectacled eider, recently listed as a threatened species by the U.S. Fish and Wildlife Service.

Decline in a Population of Spectacled Eiders Nesting on the Yukon-Kuskokwim Delta, Alaska

The number of spectacled eiders (Somateria fischeri) nesting on two study areas near the Kashunuk River, on the central Yukon-Kuskokwim (Y-K) Delta, Alaska, declined by over 75% in the last 20 years. Nesting densities have remained low, but have not significantly declined since 1985. There has been no decrease in the reproductive effort of individual females as indicated by average clutch sizes. There has been a significant decline in the proportion of nests located on islands on one of the two study areas. Nesting success declined significantly during the 1970's. Success was not monitored in recent years, but has likely been low, based on the poor nesting success and declining numbers of cackling Canada geese (Branta canadensis minima) and black brant (B. bernicla nigricans) nesting on the area. Nest predation by arctic foxes (Alopex lagopus) severely limited the productivity of cackling Canada geese, and foxes were likely the major predators of eider nests. Persistent high predation rates may lead to local extirpation in highly philopatric species such as eiders. The spectacled eider (Somateria fischeri) breeds along the coasts of the Bering and Chukchi seas in western and northern Alaska, and northern and eastern Russia (Bellrose 1980). The population on the Yukon-Kuskokwim (Y-K) Delta is in decline (Stehn et al. 1993), and is listed by the U. S. Fish and Wildlife Service (1993) as a threatened species. Evidence for the decline is based on changes in the number of eiders counted during aerial surveys, and current estimates of nesting density (Stehn et al. 1993), relative to an extrapolated estimate derived from the number of eiders nesting on small study sites on the Y-K Delta in the early 1970's (Dau and Kistchinski 1977). Here we present evidence of a long-term decline in the number of nesting eiders based on changes in the number of birds on two study sites monitored for up to 20 years. STUDY AREA AND METHODS The study areas were located in the Yukon Delta National Wildlife Refuge, along the Kashunuk River on the central Y-K Delta, Alaska (61°26'N, 165°27'W), approximately 20 km upriver from the Bering Sea (Fig. 1). Habitat at the sites is described in detail elsewhere (Ely and Raveling 1984, Babcock and Ely 1994). Both study areas were covered with numerous small lakes, ponds, and tidal sloughs and dominated by moist tundra vegetation (mixed sedges and grasses) interspersed with intermediate and upland dry tundra (lichens, mosses, and dwarf shrubs). Portions of the Old Chevak study site were slightly higher in elevation and more inland than the Onumtuk site, and were characterized by more intermediate and upland habitat. Habitat used by nesting spectacled eiders on the Y-K Delta lies within an estimated 9300 km2 of wet sedge/grass meadows categorized as the vegetated intertidal zone (King and Dau 1981). This zone is essentially the lowland terrain between the outer edge of vascular plant growth (i.e. normal high tide line) and the maximum inland extent of storm surges identified by the driftwood line. All of the Onumtuk area, and the southern and eastern portions of the Old Chevak area were within this vegetated intertidal zone. Eider work on the 11.1-km2 Onumtuk study area began in 1969 (Mickelson 1975), and was continued through 1973 (Dau 1974). In 1975, two 2.8-km2 sites were selected within the original study area. Investigations at these plots were conducted by CPD untiI 1980; refuge biologists lead research activities there untiI 1985, when CRE took over the work. The 12-km2 Old Chevak study site is adjacent to the Kashunuk River just north of the Onumtuk plots. The Old Chevak plots were initially searched in 1977 and 1978, when CRE was conducting work on nesting geese (Ely and Raveling 1984). Field methods used here were exactly the same during all years. Although we did

Effects of Carrying Radio Transmitters on Energy Expenditure of Pacific Black Brant

We compared daily energy expenditure and body mass changes of captive yearling black brant (Branta bernicla nigricans) with and without backpack-mounted radio transmitters in a repeated measures design. Daily energy expenditure was estimated by continuously monitoring 0, consumption and CO2 production for 24 hours. Carrying transmitters had no effect on daily energy expenditure (P > 0.10) or mass loss (P > 0.3). We detected no temporal variation in daily energy expenditure after attachment of transmitters, an indication that any acclimation occurred within the first 24 hours. Because experimental birds were confined to a small (45 x 60 x 74 cm) chamber during metabolism measurements, our results do not address the influence of transmitters on the cost of locomotion. J. WILDL. MANAGE. 54(1):42-45 Radio telemetry has played a significant role in studies of waterfowl movements (Ringelman and Longcore 1982) and of mortality (Ball et al. 1975). However, results of studies relying on radio telemetry may be biased if the radio packages influence the individuals carrying them. Changes in waterfowl behavior have been associated with the application of radio packages (Gilmer et al. 1974), and Gilmer et al. (1974) detected an increased recovery rate for birds carrying radios compared to normally banded controls. However, Gilmer et al. (1974) could not separate the effects of harvest rate from a potentially higher reporting rate for radiomarked birds. Survival rate may be affected by application of radio packages if the energy budgets of marked individuals are sufficiently altered by the packages and harnesses. Such changes in energy budgets could result from behavioral changes (e.g., time spent feeding), changes in the costs of locomotion, including work required to carry the mass of the radio packages, or changes in metabolism associated with the stress of carrying a radio package. For example, birds secrete corticosterone in response to short term stressors, such as handling (Wingfield et al. 1982), and chronic factors such as social environment or climate (Assenmacher 1973, Wingfield et al. 1982). Corticosterone has a marked influence on metabolism (Assenmacher 1973) and, therefore, potentially on energy balance. No study has assessed the impact of carrying radio transmitters on daily energy expenditure of waterfowl. We had 2 goals: (1) assess whether attachment of backpack-mounted radio transmitters increased metabolic rate, and (2) determine whether black brant acclimated after attachment of transmitters, causing a temporal pattern in metabolic rate. To achieve our goals, metabolic rate was monitored periodically before application of radio transmitters and from 1 to 35 days after attachment. Our study does not address changes in energy expenditure associated with increased locomotory costs (Gessaman and Nagy 1988) in free-living black brant because our measurements were made on brant confined to metabolism cages. Black brant were reared in their natal areas during studies supported by the Alaska Fish and Wildlife Research Center and Yukon Delta National Wildlife Refuge, U.S. Fish and Wildlife Service. We thank M. R. Peterson, P. L. Flint, and K. Laing for assistance in rearing goslings in the field. N. A. Gundlach assisted with maintenance of brant in Fairbanks. K. J. Kokjer provided essential help with the maintenance of the data acquisition system. M. C. Perry, K. L. Parker, and K. J. Reinecke provided very constructive comments on the manuscript. Funding was provided by the Alaska Fish and Wildlife