S. Kim Nelson

FORAGING DISTANCES OF RADIO-MARKED MARBLED MURRELETS FROM INLAND AREAS IN SOUTHEAST ALASKA

Abstract We radiotagged seven female and two male Marbled Murrelets (Brachyramphus marmoratus) of undetermined breeding status and followed their movements through the inner passages of northern southeast Alaska during the breeding season (May–July) in 1998. Six of the nine murrelets were detected inland in the early morning hours from 24 June to 17 July. Inland visits for each individual were consistent to a particular location, but short in duration, which precluded locating nest sites. We recorded 46 locations at sea up to 124 km (x̄ = 78 ± 27 km) from inland sites during the period 19 June to 16 July. We detected murrelets at inland sites and at sea on the same day on 20 occasions with a mean distance between these locations of 75 ± 42 km. The majority of murrelets were located at sea in western Icy Strait, a productive feeding area at the mouth of Glacier Bay, Alaska. This study provides the first direct evidence that Marbled Murrelets in southeast Alaska are consistently traveling considerable distances between potential nesting and foraging areas. These findings have important implications for murrelet conservation and management efforts in southeast Alaska.

Characterizing dispersal patterns in a threatened seabird with limited genetic structure.

Genetic assignment methods provide an appealing approach for characterizing dispersal patterns on ecological time scales, but require sufficient genetic differentiation to accurately identify migrants and a large enough sample size of migrants to, for example, compare dispersal between sexes or age classes. We demonstrate that assignment methods can be rigorously used to characterize dispersal patterns in a marbled murrelet (Brachyramphus marmoratus) population from central California that numbers approximately 600 individuals and is only moderately differentiated (FST∼ 0.03) from larger populations to the north. We used coalescent simulations to select a significance level that resulted in a low and approximately equal expected number of type I and II errors and then used this significance level to identify a population of origin for 589 individuals genotyped at 13 microsatellite loci. The proportion of migrants in central California was greatest during winter when 83% of individuals were classified as migrants compared to lower proportions during the breeding (6%) and post‐breeding (8%) seasons. Dispersal was also biased toward young and female individuals, as is typical in birds. Migrants were rarely members of parent‐offspring pairs, suggesting that they contributed few young to the central California population. A greater number of migrants than expected under equilibrium conditions, a lack of individuals with mixed ancestry, and a small number of potential source populations (two), likely allowed us to use assignment methods to rigorously characterize dispersal patterns for a population that was larger and less differentiated than typically thought required for the identification of migrants.

Nesting ecology of Marbled Murrelets at a remote mainland fjord in southeast Alaska

ABSTRACT Studying the ecology of endangered species in portions of their range where the population remains abundant can provide fundamental information for conservation planners. We studied nesting by radio-tagged Marbled Murrelets (Brachyramphus marmoratus) during 2007 and 2008 in Port Snettisham, a relatively pristine, remote mainland fjord in southeast Alaska with high at-sea densities of Marbled Murrelets during the breeding season. Of 33 active Marbled Murrelet nest sites located during the study, we found 15 within forested habitat (tree nest sites), 16 in nonforested habitat (ground nest sites), and 2 that could not be determined. Some nests were located farther inland from the coast (range: 1–52 km) and at higher elevations (range: 42–1,100 m) than previously documented in Alaska. Nesting success to ≥20 days posthatch (0.20 ± 0.07 [SE]) was less than half of similar estimates in British Columbia and more comparable to estimates from California and Washington. A logistic regression found that nesting success did not differ between years, but nesting success was higher for tree nests than for ground nests. Conservation planners should consider that Marbled Murrelets will use certain nonforest habitat types for nesting in mainland southeast Alaska. Our reported nesting success was likely a maximum, and our results indicate that nesting success can be low even when nesting habitat is seemingly abundant and marine habitat appears excellent.

Northwest Forest Plan—the first 10 years (1994-2003): status and trends of populations and nesting habitat for the marbled murrelet.

The Northwest Forest Plan (the Plan) is a large-scale ecosystem management plan for federal land in the Pacific Northwest. Marbled murrelet (Brachyramphus marmoratus) populations and habitat were monitored to evaluate effectiveness of the Plan. The chapters in this volume summarize information on marbled murrelet ecology and present the monitoring results for marbled murrelets over the first 10 years of the Plan, 1994 to 2003. The marbled murrelet was federally listed in 1992 as threatened in Washington, Oregon, and California. The Plan identified the marbled murrelet as a major objective in the Plan design and hence the status of the murrelet is a key indicator of the Plan’s potential success. Effectiveness monitoring for the marbled murrelet has two facets: (1) assess population trends at sea by using a unified sampling design and standardized survey methods, and (2) establish a credible estimate of baseline nesting-habitat data by modeling habitat relations, and use the baseline to track habitat changes over time. Our primary monitoring objective was to determine the status and trends of marbled murrelet populations and nesting habitat in the Plan area.

FOREST LANDSCAPE PATTERNS AROUND MARBLED MURRELET NEST SITES IN THE OREGON COAST RANGE

We analyzed forest composition and landscape preferences of marbled murrelets (Brachyramphus marmoratus). Using dawn surrreys and tree climbing, we found 41 murrelet nest sites on state and federal lands in the Oregon Coast Range Province in western Oregon between 1990 and 1998. Landscapes in 0.5- and 1.0-km-radius plots at these nest sites were compared to patterns in similar plots around a set of points randomly selected from stands of mature or old- growth trees on public lands in the same province. We found less open-sapling and hardwood forests in the plots at nest sites than at random sites for both plot sizes. Conversely, the pro- portion of pole-young conifer habitat was greater at nest sites than at random sites for both plot sizes. Landscape pattern analysis showed that the amount of edge-perimeter density, nest-patch perimeter, and high-contrast edge of nest patches was lower in the 1.0-km-radius plots at nest sites than at random sites. Our best multivariate logistic regression model indicated that greater amounts of pole-young and mature-old-growth forests, less edge (perimeter density and high- contrast edge at nest patches), and more cohesive nest-patch shape best distinguished murrelet nest sites from random sites. We hypothesize that murrelet nest-site selection at the landscape scale may be the result of an antipredator strategy to reduce predation risks on eggs and juvenile murrelets. Young (simple-structure) conifer stands adjacent to nesting areas may decrease pre- dation rates at murrelet nests. Land managers should consider limiting clearcut harvest units both adjacent to murrelet nest patches and within at least 1 km of murrelet nests, as clearcuts increase high-contrast edge in addition to increasing fragmentation levels.

Diel Shifts in the Marine Distribution of Marbled Murrelets Near Port Snettisham, Southeast Alaska

Abstract. Little is known about seabird distributions at night. Densities of Marbled Murrelets (Brachyramphus marmoratus, hereafter “murrelets”) and potential prey were determined along fixed-width transects in spring and summer of 2007 and 2008, and compared during night and day in two regions of Port Snettisham, near Juneau, Southeast Alaska. Murrelets moved from a shallower, more sheltered inner region, used during the day for foraging and staging for inland flights (2007 night densities = 15 ± 13 murrelets·km-2; 2007 day densities = 172 ± 67 murrelets·km-2), to a deeper, more exposed outer region, further from shore, during dark hours (2007 night densities = 113 ± 61 murrelets·km-2; 2007 day densities = 41 ± 23 murrelets·km-2). Prey school density and relative prey density were significantly higher at night in the inner region compared with the outer region (2.2 times higher prey school density and 3.8 times higher relative prey density), suggesting that murrelets were not redistributing themselves to forage on fish prey. A more likely explanation for why murrelets move from day use areas to night use areas is to avoid predators such as Bald Eagles (Haliaeetus leucocephalus), Great Horned Owls (Bubo virginianus) and various mammals.

Trends in Caspian Tern Nesting and Diet in San Francisco Bay: Conservation Implications for Terns and Salmonids

Abstract. Colony size, nesting ecology and diet of Caspian Terns (Hydroprogne caspia) were investigated in the San Francisco Bay area (SFBA) during 2003–2009 to assess the potential for conservation of the tern breeding population and possible negative effects of predation on survival of juvenile salmonids (Oncorhynchus spp.). Numbers of breeding Caspian Terns declined 36% from 2003 to 2009, mostly due to abandonment of the Knight Island colony and decline of the Brooks Island colony, the two largest colonies in the SFBA. Concurrently, nesting success declined 69% associated with colony site characteristics such as (a) quality and quantity of nesting substrate, (b) vulnerability to nest predators, (c) displacement by other colonial waterbirds and (d) human disturbance. Marine fishes were the predominant prey in tern diets from the SFBA; however, diet composition varied among colonies. Juvenile salmonids comprised 22.9% of the diet of terns nesting in the North Bay, 5.3% of diet of terns nesting in the Central Bay, and 0.1% in the South Bay. Construction or restoration of nesting islands in the South Bay may help maintain and restore breeding Caspian Terns without enhancing mortality of salmonid stocks of conservation concern.