Search

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...

The Kittlitz's Murrelet (Brachyramphus brevirostris) is a poorly-known species of alcid and a seabird of conservation concern. Nesting murrelets were discovered at Agattu Island in the western Aleutian Islands, and a field study provided new information on nest site selection, chick growth rates and reproductive success. Twelve ground nests were located in upland habitats (441 masl) at inland areas of Agattu (2.3 km from shore). All nests contained one egg or chick. Murrelets tended to nest in association with a ground cover of orange crustose lichens, bare ground, small rocks and graminoids. Estimates of growth rates for the body mass of nestling Kittlitz's Murrelets were lower (KL < 0.10) than published estimates for other small-bodied alcids with semiprecocial young (KL = 0.14 to 0.23). Murrelet young departed from nests after 30 days of growth at 47% of adult mass but at 80% of adult wing length. Optimal wing-loading may ensure successful dispersal flights from terrestrial nest sites to ocea...

Radio-telemetry was used to continuously monitor the at-sea activity of an adult Marbled Murrelet (Brachyramphus marmoratus) nesting in Santa Cruz County, California. From 05.39 h on 28 May 1997, to 05.14 h on 29 May 1997, the murrelet was followed by tracking teams at Ano Nuevo Bay. Between 05.44 h and 20.19 h on 28 May, the bird engaged in eleven dive bouts, with a mean duration of 18.8 ± 5.4 min. Mean dive duration was 24.8 ± 15.7 s; mean surface between dives was 15.2 ± 12.7 s. No dives were initiated after 20.19 h. The bird spent 12.3% of the at-sea period and 23.4% of daylight hours engaged in diving bouts. This relatively small amount of time spent diving allows for considerable flexibility in activity budget.

Unlike other alcids, laying of replacement eggs has not been well documented in Brachyramphus murrelets. Observations of two radio-marked Marbled Murrelets (Brachyramphus marmoratus) in northern California during 2001 and 2002 suggested that they can re-lay in the same breeding season. In 2001, aircraft telemetry first detected a male Marbled Murrelet at a forested inland location on 17 May. This bird alternated 24h incubation bouts with 24h at sea periods until 29 May, when data logger recordings indicated that the bird arrived at the nest at 05.17 h (PDT), but left at 05.32 h. This nesting effort had apparently failed. Sixteen days later, on 14 June this murrelet arrived in the vicinity of the first nest site at 05.19 h and remained there until 18.57 h that same evening and then left. We suspected that this event represented a second breeding effort that also failed, either near or at the site of the first effort. In 2002 a female Marbled Murrelet, first detected inland on 13 June by aircraft t...

We surveyed Marbled Murrelets (Brachyramphus marmoratus) daily from small boats in Auke Bay and Fritz Cove, Alaska, from May through August 1992 and 1993. Differences in numbers of juveniles and in the timing of their presence in the study area between the two years indicated that breeding phenology was late and productivity was low in 1992 compared to 1993. This difference was consistent with variability in the physical environment. Of 99 fish identified in the bills of fish-holding adult murrelets, 81 (82%) were Pacific Sand Lance (Ammodytes hexapterus). Counts of fish-holding adult murrelets were significantly higher in the evening than at any other time of day. Time of day had no significant effects on counts of fledglings, indicating that juveniles were moving into and out of the study area during the day. Murrelets were predominantly found in groups of two or more, even during incubation, suggesting that murrelets incur an appreciable benefit, such as increased foraging efficiency, from for...

The assumption that brood patches identify incubating birds is a pervasive one in avian literature, and as a result, brood patches are often used to infer breeding status. Although the developmental stages of the brood patch with specific reproductive stages in passerines have been described, this information for seabirds is not often reported. Thus, for birds whose breeding activities are not easily observed, it is difficult to confirm (1) that it is valid to assume that a bird which has some stage of brood patch is a nester or putative nester, and (2) whether specific stages of brood patch development reflect specific stages of the breeding cycle. We tested the utility of brood patch scores to infer breeding status in a non-colonial seabird, the Marbled Murrelet (Brachyramphus marmoratus), a species always captured away from the nest site. We confirmed the breeding status of murrelets with brood patches, and assessed the specific stages of brood patch development to the timing of egg-production...

We measured offshore Marbled Murrelet (Brachyramphus marmoratus) abundance from April through October between 1989 and 1998, in northern California and southern Oregon and investigated its relationships with marine and terrestrial habitats. We found that higher murrelet abundance offshore was strongly related to the presence of large, clustered and unfragmented old-growth forests on nearby inland areas. Murrelets were most abundant offshore of contiguous old-growth forest adjacent to relatively abundant medium-sized, second-growth coniferous forests. Compared to the forest habitat, marine habitat was relatively unimportant in determining murrelet abundance offshore; high marine primary productivity and nutrients were not associated with high murrelet numbers. Tidal flat shorelines were weakly associated with more murrelets, independent of inland habitat. Our findings suggest management efforts to conserve the Marbled Murrelet should focus on protecting or creating large, contiguous blocks of old-...

Sea ducks have been captured with mist nets set across breeding streams and in drive traps at sea during the flightless period, but capture of flying birds on staging and wintering coastal areas presents a challenge. Here, we describe a highly successful technique for capturing Harlequin Ducks (Histrionicus histrionicus) at sea, modified from a mistnet set developed to capture Marbled Murrelets (Brachyramphus marmoratus) at sea. While the original method was passive, decoys were added to attract birds and occasionally birds were driven toward the nets using small boats. The capture technique proved to be safe and effective. Three hundred and seventy-eight birds were captured during 28 d of effort and no birds died in the nets or during handling. The technique has been further modified to capture molting Harlequin Ducks. The technique and its modified version could be easily used to capture other sea ducks on their staging, wintering and molting areas.