COEXISTENCE AND SPATIAL DISTRIBUTIONS OF MARBLED MURRELETS (<i>BRACHYRAMPHUS MARMORATUS</i>) AND OTHER ALCIDS OFF SOUTHWEST VANCOUVER ISLAND, BRITISH COLUMBIA

Burger, Alan E.; Hitchcock, Caitlin; Stewart, Edmund; Davoren, Gail K.

doi:10.1525/auk.2008.125.1.192

Cited by 15 publications

(15 citation statements)

References 33 publications

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“…Although murrelets are typically solitary or occur in pairs (Nelson 1997), they also partake in mixed-species feeding flocks. Alternatively, larger alcids may act as competitors for smaller alcids (Piatt 1990, Burger et al 2008. We saw neither negative nor positive correlations between foraging activity and densities of other murrelets or murres, which might be due to murrelets in this area avoiding close proximity to murres (Burger et al 2008).…”

Section: Factors Influencing Diving Activitymentioning

confidence: 62%

“…Alternatively, larger alcids may act as competitors for smaller alcids (Piatt 1990, Burger et al 2008. We saw neither negative nor positive correlations between foraging activity and densities of other murrelets or murres, which might be due to murrelets in this area avoiding close proximity to murres (Burger et al 2008). Thus, murrelets may forage effectively regardless of local enhancement or potential competitors.…”

Section: Factors Influencing Diving Activitymentioning

confidence: 62%

“…We were only able to conduct observations during daylight hours; therefore, we considered primary chick-feeding periods as the first h after sunrise and the last 2 h before sunset. To test whether the presence/ absence of conspecifics and other seabird species influenced the diving activity of murrelets, we calculated densities (number of birds divided by number of 1 min scans) of murrelets and common murres Uria aalge, the 2 most common diving piscivores and possible competitors (Burger et al 2008), for each observation hour.…”

Section: Methodsmentioning

confidence: 99%

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Limited foraging flexibility: increased foraging effort by a marine predator does not buffer against scarce prey

Ronconi¹,

Burger²

2008

Mar. Ecol. Prog. Ser.

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Flexibility in activity time budgets allows animals to cope with heterogeneous and changing environments. Many marine predators, such as seabirds, exhibit flexibility in their foraging behaviour to buffer reproductive success against periods of low prey availability. Over 3 years, 2004 to 2006, we studied the foraging behaviour of a threatened seabird, the marbled murrelet Brachyramphus marmoratus in southwestern Vancouver Island, British Columbia, Canada. An information-theoretic approach was used to compare among factors (temporal, spatial, environmental, and competitors) that may influence diving activity. We also quantified local prey availability by hydroacoustic surveys and regional oceanographic conditions (chlorophyll a concentrations and upwelling indices) to investigate relationships between diving activity, food supply and environmental conditions. Prey indices varied spatially, seasonally, and annually, showing reduced prey availability during incubation and chick-rearing of 2005. Upwelling indices and chlorophyll a concentrations, as an index of primary productivity, were delayed in 2005. Year and breeding phase had the greatest impact on diving activity, with additional variation among sites. Murrelets increased diving activity in years and seasons with scarce prey and poor oceanographic conditions (incubation and chick-rearing 2005) and decreased diving activity at sites with high prey availability. There was a linear relationship between diving activity and food availability, suggesting no clear thresholds in response to decreases in prey. Despite their flexible activity budgets, increased foraging effort by murrelets in 2005 was inadequate to ensure average levels of reproductive success. Thus, flexible foraging behaviour by murrelets may be ineffective to buffer reproductive success when environmental conditions are extremely poor. KEY WORDS: Activity budgets · Prey availability · Foraging ecology · Thresholds · Seabirds · Brachyramphus marmoratusResale or republication not permitted without written consent of the publisher

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Section: Factors Influencing Diving Activitymentioning

confidence: 62%

Section: Factors Influencing Diving Activitymentioning

confidence: 62%

Section: Methodsmentioning

confidence: 99%

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Limited foraging flexibility: increased foraging effort by a marine predator does not buffer against scarce prey

Ronconi¹,

Burger²

2008

Mar. Ecol. Prog. Ser.

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“…These smaller species may have avoided other larger species, particularly members of their own guilds, to avoid interference competition with larger animals. Although marbled murrelets regularly occur in mixed-species flocks elsewhere (Sealy 1973, Vermeer et al 1992, Ostrand 1999, they may avoid flocks, or regions, in which larger common murres are present (Chilton & Sealy 1987, Burger et al 2008. Between the 2 marine mammal species, the smaller (harbor porpoise) also had only negative or neutral associations, potentially in response to avoidance of the larger California sea lion due to competition.…”

Section: Body Sizementioning

confidence: 99%

“…For birds that partake in flocks, the benefits (ability to find prey; aggregation of prey) presumably outweigh any costs of competition (Sealy 1973, Göt-mark et al 1986). However, interference competition has been proposed as a mechanism reducing the likelihood of certain species co-occurring in the same flock (Hoffman et al 1981, Ballance et al 1997, Maniscalco et al 2001, Burger et al 2008.…”

Section: Introductionmentioning

confidence: 99%

Co-occurrence and aggregation of marine birds and mammals in Monterey Bay, California, USA

Henkel¹

2009

Mar. Ecol. Prog. Ser.

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Patterns of spatial and temporal co-occurrence or avoidance among different species of marine birds and mammals can provide insights into the degree to which these top predators compete for prey. I conducted at-sea surveys in nearshore waters of Monterey Bay, California, USA, and used a randomization technique to assess co-occurrence patterns of marine birds and mammals in 1 km transect segments. As expected, strongest positive associations were among members of 3 different foraging guilds: pursuit-divers, surface-feeders, and plunge-divers. Within guilds, pursuitdivers exhibited marked avoidance of one another (negative co-occurrence), although surfacefeeders often co-occurred with each other. The study was conducted during 2 yr, 1999 and 2000; during 2000, when predator abundance was greater and prey abundance may have been decreased, pursuit-divers exhibited more avoidance of one another than in 1999. These data suggest that competition reduces foraging ability for pursuit-diving species, making it more profitable for them to disperse more widely, whereas surface-feeding species (primarily gulls) benefit from flock foraging under most conditions. Larger animals tended to frequently co-occur, while the smallest member of each guild tended to avoid other species, indicating competitive exclusion of smaller predators.

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Low breeding propensity and wide‐ranging movements by marbled murrelets in Washington

et al. 2016

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The marbled murrelet (Brachyramphus marmoratus) is a threatened seabird that forages in nearshore marine waters but nests inland, commonly in older coniferous forests. Information on ranging behavior and breeding propensity can be useful for informing management, especially when comparisons can be made between declining or threatened populations and more stable, unthreatened populations. Over 5 years, we measured ranging behavior and breeding propensity of marbled murrelets in Washington, USA where murrelets are considered threatened. Our primary objective was to compare space use and breeding by murrelets in Washington with those from other regions and where the species is not considered threatened. We radio tracked 157 murrelets from 2004 to 2008. Median marine 95% kernel ranges were 487 km2 (truex¯=938±1,348 [SD]) and larger than those reported for non‐threatened populations in Alaska, USA in other studies. Ranges computed from minimum convex polygons (MCPs; median = 404 km2; truex¯=708±847) were on average similar to those reported for threatened populations in California, USA, although larger than those reported for Alaska. Distances traveled between consecutive marine telemetry locations were greater than reported previously in Alaska. Variation in movements in our study were not associated with oceanographic conditions although appeared greater for murrelets captured along the Pacific Coast compared to those occupying interior marine waters in the Salish Sea. Twenty individuals (12.7%) attempted to breed in our study, and we estimated breeding propensity was 13.1–20.0%. This is the lowest breeding propensity reported for a population of murrelets to date. For breeders, nest‐sea commuting distances were greater than reported previously, with 4 breeders traveling farther than the previously reported maximum of 125 km. The low breeding propensity, large marine ranges, and long nest‐sea commutes in this study may point to poor‐quality marine habitat in Washington compared to other parts of the murrelet's range. In combination with reported declines in terrestrial nesting habitat from other studies, this indicates that additional management is needed to improve murrelet breeding habitat in Washington. Future management actions should focus on improving both terrestrial and marine habitat. © 2016 The Wildlife Society.

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COEXISTENCE AND SPATIAL DISTRIBUTIONS OF MARBLED MURRELETS (BRACHYRAMPHUS MARMORATUS) AND OTHER ALCIDS OFF SOUTHWEST VANCOUVER ISLAND, BRITISH COLUMBIA

Cited by 15 publications

References 33 publications

Limited foraging flexibility: increased foraging effort by a marine predator does not buffer against scarce prey

Limited foraging flexibility: increased foraging effort by a marine predator does not buffer against scarce prey

Co-occurrence and aggregation of marine birds and mammals in Monterey Bay, California, USA

Low breeding propensity and wide‐ranging movements by marbled murrelets in Washington

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