Mark S. Lindberg

Environmental Influence on Life-History Traits: Growth, Survival, and Fecundity in Black Brant (Branta Bernicla)

We studied relationships between body size of female Black Brant goslings (Branta bernicla nigricans) late in their growth period and first year survival, eventual adult body size, breeding propensity, and size and volume of clutches they eventually produced to examine the relationship between growth and fitness in this population. We indexed body size by calculating PC1 scores based on either culmen and tarsus, or culmen, tarsus, and mass. Gosling (PC scores based on culmen and tarsus) size was positively correlated with resighting rate (P = 0.005), indicating that larger goslings survived at a higher rate than did smaller goslings. Gosling size was correlated with adult size of the same individuals (P = 0.0004). Larger goslings were more likely to breed as 2- or 3-yr-olds than were medium or small goslings (P = 0.008). Larger adult brant laid more eggs (P = 0.03) and produced clutches with greater total volume (P = 0.03) than did smaller brant. Given the important role of foraging environment in growth of goslings, these data suggest an important role of early environment in determining life-history traits.

DUCK NEST SURVIVAL IN THE MISSOURI COTEAU OF NORTH DAKOTA: LANDSCAPE EFFECTS AT MULTIPLE SPATIAL SCALES

Nest survival is one of the most important parameters in the population dynamics of grassland-nesting ducks (Anas and Aythya spp.) that breed in the Prairie Pothole Region of North America. Grassland habitats used by these species are increasingly threatened by habitat loss and the coincident fragmentation, which may indirectly alter nest survival through effects on predators. Although predators are the dominant cause of nest loss, they are difficult to monitor directly. Thus, indirect analyses of habitat variables are required. Many studies have attempted to address the relationship between fragmentation and nest survival; however, few studies have examined the influence of fragmentation at multiple spatial scales. Understanding how landscape characteristics at multiple spatial scales explain variation in nest survival is important, because no single correct scale is likely to exist for a diversity of landscape metrics. We examined the relationships between habitat variables and duck nest survival (n ≈ 4...

EFFECTS OF DISPERSAL ON SURVIVAL PROBABILITY OF ADULT YELLOW WARBLERS (DENDROICA PETECHIA)

Abstract Annual survival probability estimates for songbirds are generally biased low because dispersal is not differentiated from mortality. Presently, knowledge of between-year breeding dispersal is lacking for most songbirds. To assess adult survival probabilities and dispersal, we color-banded and resighted 436 Yellow Warblers (Dendroica petechia) over five breeding seasons at 11 study sites in the Bitterroot Valley, Montana. During the last two of those seasons, we searched extensively for marked warblers between and surrounding those sites. We compared survival probabilities estimated with and without this added dispersal information and assessed the effectiveness of adjusting survival probabilities with transient-type models. Survival probabilities were calculated using open population models, and model selection was based on Akaikes Information Criterion (AIC) within program MARK. The best model indicated that survival probabilities differed between males and females and varied among years. We found that dispersal off the study site was common (in 1999, 30% of resighted birds were found off their original study site), and survival probabilities increased by 6.5–22.9% (0.02 ± 0.07−0.106 ± 0.06) with the inclusion of dispersed birds. We suggest that emigration can have substantial effect on survival probabilities and advise against the use of return rates from small study areas or spatial or temporal comparisons of return rates because of spatial and temporal variation in extent of emigration. In addition, our results suggest that additional assessments of the reliability of transient-type models under some sampling schemes may be warranted.

NATAL AND BREEDING PHILOPATRY IN A BLACK BRANT, BRANTA BERNICLA NIGRICANS, METAPOPULATION

We estimated natal and breeding philopatry and dispersal probabilities for a metapopulation of Black Brant (Branta bernicla nigricans) based on observations of marked birds at six breeding colonies in Alaska, 1986–1994. Both adult females and males exhibited high (>0.90) probability of philopatry to breeding colonies. Probability of natal philopatry was significantly higher for females than males. Natal dispersal of males was recorded between every pair of colonies, whereas natal dispersal of females was observed between only half of the colony pairs. We suggest that female-biased philopatry was the result of timing of pair formation and characteristics of the mating system of brant, rather than factors related to inbreeding avoidance or optimal discrepancy. Probability of natal philopatry of females increased with age but declined with year of banding. Age-related increase in natal philopatry was positively related to higher breeding probability of older females. Declines in natal philopatry with year of banding corresponded negatively to a period of increasing population density; therefore, local population density may influence the probability of nonbreeding and gene flow among colonies.

Breeding-season survival of mallard females in the prairie pothole region of Canada

As part of the Prairie Habitat Joint Venture (PHJV) Habitat Assessment Project, we radiomarked and tracked daily 2,249 female mallard ducks (Anas platyrhynchos) in the Prairie Pothole Region (PPR) of Canada. We conducted our study at 19 different 54- to 78-km 2 sites for 1 year per site from 1993 to 1998. We estimated female survival probability during the 90-day period following arrival on the breeding area and employed information-theoretic approaches to select among competing models that described factors affecting survival probability. We investigated the relationship between female survival and 3 periods of the nesting season, female age (yearling vs. older), upland habitat treatments, longitude, and habitat variables. Our model estimates of female survival probability ranged between 0.62 (SE = 0.028) and 0.84 (SE = 0.018) and averaged 0.76 (SE = 0.004) for the 90-day period. The best approximating model indicated that female survival was (1) lowest when most females were nesting, and (2) depended on longitude and percent wetland habitat such that survival was lowest at western sites with low wetland densities. Management efforts to reduce wetland loss, especially in western regions of the Canadian PPR, may positively influence female survival. Upland habitat restorations designed to improve nest survival may not have a concurrent impact on female survival unless a significant portion of the nesting population is affected.

Seasonal and annual survival of adult Pacific brant

Declining mid-winter counts of Pacific brant (Branta bernicla nigricans) and reduced numbers of nesting birds on their main breeding grounds prompted us to assess factors that may be limiting recovery of this population. We estimated seasonal and annual survival rates of adult brant in 1986-93 from resightings of leg-banded birds. Brant were banded at a major colony on the Yukon-Kuskokwim Delta, Alaska (Y-K Delta) in 1986-92, and resighted there in 1987-93 as well as at major fall and spring migration and wintering areas in 1990-93. Seasonal survival was the same for males and females. Mean monthly survival rate was lowest (P ≤ 0.05) in late spring migration (15 Apr-1 Jun), the period of greatest subsistence harvest on the breeding grounds, and highest in winter (1 Jan-1 Mar), the period of greatest sport harvest. Annual survival rate did not vary among years (F = 0.51; 5, 718 df; P = 0.91) and averaged 0.840 (SE = 0.031) from 1986 to 1993. Subsistence harvest has contributed to low population levels of Pacific brant.

Earlier migration timing, decreasing phenotypic variation, and biocomplexity in multiple salmonid species.

Climate-induced phenological shifts can influence population, evolutionary, and ecological dynamics, but our understanding of these phenomena is hampered by a lack of long-term demographic data. We use a multi-decade census of 5 salmonid species representing 14 life histories in a warming Alaskan stream to address the following key questions about climate change and phenology: How consistent are temporal patterns and drivers of phenology for similar species and alternative life histories? Are shifts in phenology associated with changes in phenotypic variation? How do phenological changes influence the availability of resource subsidies? For most salmonid species, life stages, and life histories, freshwater temperature influences migration timing – migration events are occurring earlier in time (mean = 1.7 days earlier per decade over the 3–5 decades), and the number of days over which migration events occur is decreasing (mean = 1.5 days per decade). Temporal trends in migration timing were not correlated with changes in intra-annual phenotypic variation, suggesting that these components of the phenotypic distribution have responded to environmental change independently. Despite commonalities across species and life histories, there was important biocomplexity in the form of disparate shifts in migration timing and variation in the environmental factors influencing migration timing for alternative life history strategies in the same population. Overall, adult populations have been stable during these phenotypic and environmental changes (λ ≈1.0), but the temporal availability of salmon as a resource in freshwater has decreased by nearly 30 days since 1971 due to changes in the median date of migration timing and decreases in intra-annual variation in migration timing. These novel observations advance our understanding of phenological change in response to climate warming, and indicate that climate change has influenced the ecology of salmon populations, which will have important consequences for the numerous species that depend on this resource.

Satellite Telemetry in Avian Research and Management: Sample Size Considerations

Abstract Satellite tracking is currently used to make inferences to avian populations. Cost of transmitters and logistical challenges of working with some species can limit sample size and strength of inferences. Therefore, careful study design including consideration of sample size is important. We used simulations to examine how sample size, population size, and population variance affected probability of making reliable inferences from a sample and the precision of estimates of population parameters. For populations of >100 individuals, a sample >20 birds was needed to make reliable inferences about questions with simple outcomes (i.e., 2 possible outcomes). Sample size demands increased rapidly for more complex problems. For example, in a problem with 3 outcomes, a sample of >75 individuals will be needed for proper inference to the population. Combining data from satellite telemetry studies with data from surveys or other types of sampling may improve inference strength.

Density-dependent effects on growth, body size, and clutch size in black brant

-We documented gosling size in late summer, adult body size, and clutch size of known-age Black Brant (Branta bernicla nigricans) females nesting on the Tutakoke River colony between 1986 and 1995. During this period, the colony increased from 1,100 to >5,000 nesting pairs. Gosling mass at 30 days of age declined from 764 + SE of 13 g and 723 ? 15 g for males and females, respectively, in the 1986 cohort, to 665 + 18 g and 579 ? 18 g in the 1994 cohort. Gosling size was directly negatively correlated with number of Black Brant broods. We detected no trend in adult body size for individuals from these cohorts; in fact, adults from the 1992 and 1994 cohorts had the largest overall masses. Clutch size increased with age from 3.4 eggs for 2-year-old females to 4.4 eggs for 5-year-old females. Clutch size declined during the study by 0.20 (3-year-old females) to 0.45 (2-year-old females) eggs. Clutch size did not decline between the 1986 and 1990 cohorts for females that were >5 years old. Our results for clutch size and gosling size are similar to those recorded for Lesser Snow Geese (Chen caerulescens caerulescens). Our failure to detect a trend in adult body size, however, differs from the response of other geese to increasing population density. We interpret this difference in effects of density on adult size between Black Brant and other geese as an indication of stronger selection against the smallest individuals in Black Brant relative to other species of geese. Received 19 May 1997, accepted 17 November 1997. ARCTIC-NESTING GEESE are strictly herbivorous during the breeding season (Owen 1980, Sedinger 1992) and are selective of the most nutritious foods and habitats containing these foods (Lieff 1973, Harwood 1975, Sedinger and Raveling 1984, Gadallah and Jefferies 1995a, b). Despite these strong preferences, substantial variation exists in growth rates of goslings, which likely is associated with temporal and spatial variation in habitat quality (Cooch et al. 1991a, Larsson and Forslund 1991, Sedinger and Flint 1991, Aubin et al. 1993). Because gosling growth is associated with future survival and fecundity (Larsson and Forslund 1991, 1992, Francis et al. 1992, Rockwell et al. 1993, Sedinger et al. 1995b), habitat quality likely is directly linked to processes determining population dynamics. Sedinger and Raveling (1986) argued that seasonal declines in nutrient I E-mail: ffjss@aurora.alaska.edu 2 Present Address: Institute for Wetland and Waterfowl Research, Ducks Unlimited Inc., One Waterfowl Way, Memphis, Tennessee 38120, USA. 3Present Address: Alaska Science Center, Division of Biological Resources, U.S. Geological Survey, 1011 East Tudor Road, Anchorage, Alaska 99503, USA. concentration in the diet of Cackling Canada Geese (B. canadensis minima) resulted from reduced availability of the highest-quality foods because of grazing by geese. Lesser Snow Geese (Chen caerulescens caerulescens) substantially reduce the abundance of preferred food plants (Cargill and Jefferies 1984, Hik and Jefferies 1990), as do some Black Brant (B. bernicla nigricans; hereafter brant; Person et al. 1998). The relationship between nutrient intake by goslings and demographic parameters creates the potential for per capita availability of foods of sufficient quality during brood rearing to influence population dynamics. Long-term declines in body size and fecundity have been associated with increased size of a colony of Lesser Snow Geese, and Cooch et al. (1991a, b) and Francis et al. (1992) demonstrated a decline in juvenile survival for this colony over the same period. The number of brant nesting on the YukonKuskokwim (Y-K) Delta declined by more than 60% in the 1970s and early 1980s (Sedinger et al. 1993), likely as a result of human harvest (Sedinger 1996) and predation by arctic foxes (Alopex lagopus; Anthony et al. 1991, Sedinger et al. 1993). Reduced predation and harvest were as-

NEST‐SITE SELECTION OF PASSERINES: EFFECTS OF GEOGRAPHIC SCALE AND PUBLIC AND PERSONAL INFORMATION

Nest-site selection is an important determinant of individual fitness in birds. Understanding what information individuals use to choose nest sites is therefore important for understanding the evolution of nest-site selection, the dynamics of populations, and the conservation of species. We used five years of mark-recapture data for Mountain Bluebirds (Sialia currucoides) to examine how dispersal probability and nest-site selection vary with potential cues of nest-site quality. Dispersal distance between breeding seasons and nest-site selection were modeled as a function of personal reproductive success, conspecific density, conspecific reproductive success, and habitat type. Between years, the dispersal probability was related to personal reproductive success, not conspecific information, and individuals fledging fewer young dispersed longer distances. For dispersing individuals, the probability that a nest site was selected in year i was negatively related to distance from the nest site selected in year i - 1 for all age and sex classes, and positively related to conspecific density and reproductive success in year i - 1 for both second-year (SY) and after-hatch-year (AHY) females. However, nest-site selection in year i was more strongly related to conspecific density in year i- 1 for hatch-year (HY) females and was much more strongly related to the reproductive success of conspecifics in year i - 1 for AHY females. Nest-site selection of HY and AHY males was not consistently related to the metrics of conspecific information, but we suspect that relationships were obscured by competitive interactions. We found no evidence indicating that individuals respond differently to conspecific information at longer distances, suggesting that individuals limit dispersal to areas where they have prior knowledge. We predict that these patterns of nest-site selection will allow birds to loosely track nest-site quality and maintain an ideal free distribution, where average fitness is equal in all habitat types.