Search

For longer-lived species, individuals hedge their bets by skipping breeding when conditions are poor to preserve the opportunity for future breeding attempts. Thus, understanding the ecological drivers behind the 'choice' to reproduce or not is a key step in identifying and diagnosing causes of population change. We investigated both marine and terrestrial factors that might influence whether Kittlitz's Murrelets Brachyramphus brevirostris--a long-lived seabird of conservation concern that is often associated with glacially-influenced habitats--choose to breed in a given year. We used a suite of proxies to explain variation in reproductive metrics of radio-tagged Kittlitz's Murrelets, exploring three hypotheses related to prey availability, nest depredation risk, and energetic costs of nesting in Icy Bay, Alaska, 2007-2012. In two of the years, we compared results with the locally co-occurring, closely-related Marbled Murrelet B. marmoraus. Across the six-year period of our study, the posterior mean breeding propensity of Kittlitz's Murrelets was 0.21 (95% credible interval [CrI] = 0.15-0.27), nesting success was 0.41 (CrI = 0.25-0.57), and fecundity was 0.04 (CrI = 0.02-0.06). Although none of our three hypotheses were strongly supported by the data, our results collectively suggest that successful nesters expended greater effort than failed nesters and non-nesters to acquire sufficient prey--they stayed longer in the study area, had larger marine core use areas, spent slightly less time diving, and had shorter commuting distances and longer incubation shifts. Also, in years when fecundity was highest, overlap of individual marine core use areas was greatest, suggesting predictable foraging hotspots for murrelets in those years. Importantly, when comparing Brachyramphus species, we found that Marbled Murrelets outperformed Kittlitz's Murrelets reproductively by three to four times in overlapping years, suggesting different drivers of reproduction. From our collective results, we posit that the limitation to reproduction of Kittlitz's Murrelets may not be prey abundance or quality, but instead efficient access to prey. While our associations with indices of prey availability, depredation risk, and energetic costs to nesting did not explain much of the variation in fitness metrics, our study demonstrates the value of using a comparative approach and multiple metrics to diagnose factors limiting a population, especially when data are sparse. For bet-hedging species with complex life histories, we recommend using a combination of integrated modeling and a monitoring framework designed to accumulate evidence across studies to estimate population dynamics and improve inferences about ecological drivers. [ABSTRACT FROM AUTHOR]

The Kittlitz's Murrelet Brachyramphus brevirostris is an uncommon, dispersed-nesting seabird endemic to coastal waters of Alaska and eastern Russia. While the range-wide status of this species is unclear, proximate concerns regarding its viability are driven by low breeding propensity and nesting success. We studied individual and environmental factors associated with the decision to breed and timing of nest initiation of Kittlitz's Murrelets in Icy Bay, Alaska, over a 6-year period between 2007 and 2012. We radio-tagged 191 of 569 individuals captured during the spring pre-breeding period. At the time of capture, nearly all murrelets were exhibiting signs of breeding; most were in alternate plumage, paired, in apparently good body condition, and developing a brood patch. Yet an average of only 20% (range 5%-45%) of the radio-tagged murrelets nested annually. More individuals chose to breed during years with an intense Aleutian low-pressure system (i.e. low North Pacific Index) and low average wind speeds in the spring, with such conditions apparently leading to an earlier and stronger phytoplankton bloom. Our results also indicated a weak, positive association between the peak magnitude of chlorophyll-a and delayed nest initiation. While we infer that the decision to breed and timing of nest initiation are related in part to factors that reflect spring bloom dynamics, we encourage more directed studies on the relationship between environmental conditions during the spring pre-breeding period and the chronically low reproductive output exhibited by this species. [ABSTRACT FROM AUTHOR]

The article discusses findings of a study to quantify inland activity patterns and flight altitudes of Marbled Murrelets or Brachyramphus marmoratus in Northern California. It notes the threatened species status of the Marbled Murrelet and the effectiveness of using marine radar to measure passage rates and altitudes of murrelets. The research shows that 2,780 murrelets were detected flying towards land during 78 dawn surveys conducted in February to December 2012.

The article evaluates Kittlitz's Murrelet Brachyramphus brevirostris population trend for the initial time frame, from 1986 to 2012, for Prince William Sound, Alaska. It reveals that Prince William Sound had factors that would make the population estimates to be sensitive to misidentification of species. It offers evidence that misidentification took place, and re-analyzes the population trend censoring two years with suspected misidentification. It also explains that analyses made suggest no significant drop of Kittlitz's Murrelets in Prince William Sound.

The article presents a study on whether at-sea distributions of Marbled Murrelets BRachyramphus marmoratus on the southwest coast of Vancouver Island in British Columbia are spatially associated with Gray Whales Eschrichtius robustus. The researchers performed surveys of Marbled Murrelets and whales from a 10.6 meter passenger vessel along a 105 kilometer transect from Bamfield to Port Renfrew. They used the Pythagorean theorem to measure the distance to the nearest whale for every transect segment. They found that varying oceanic conditions may cause changes in the abundance and distribution of Marbled Murrelets.

The article presents a study on the habitat use and spatial distribution of Marbled Murrelets Brachyramphus marmoratus at Port Snettisham in Juneau, Alaska. The researchers used voice recorders to note the numbers of birds sitting on the water within 50 meters on either side of the boat as well as the observation times. They used the Classification and Regression Tree (CART) methods to analyze murrelet distribution with respect to habitat features. They found that Port Snettisham is important for murrelets because they occurred at higher densities than studies of other areas have found.

The article discusses a study of the distribution, abundance and trend estimates of the Kittlitz's Murrelet Brachyramphus brevirostris in Prince William Sound (PWS), Alaska from 1972 and 2007. A population model was developed for the study using the field estimates and variances for Marbled, Kittlitz's and unidentified murrelets. The populations of Brachyramphus murrelets were found to be declining based on field and model estimates. The possible role of a regional, contemporaneous alteration in the environment in the long-term decline of the two species is mentioned. Also emphasized is the need to include the Brachyramphus species in a list of conservation priorities.

The article focuses on a study that analyzed survey data as a part of the Symposium on Population Status and Trends of Kittlitz's Murrelet in Prince William Sound (PWS), Alaska, between 1989 and 2007. The study showed that Brachyramphus murrelets in PWS declined by about 68 percent between 1989 and 2007.