Behavioral and Physiological Responses of Eared Grebes (Podiceps Nigricollis) to Variations in Brine Shrimp (Artemia Franciscana) Densities

Caudell, Joe N.; Conover, Michael R.

doi:10.3398/1527-0904(2006)66[12:baproe]2.0.co;2

Cited by 23 publications

(31 citation statements)

References 8 publications

(9 reference statements)

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“…One can question our conclusion that brine shrimp are food-limited given predation by corixids (Wurtsbaugh andBerry 1990, Wurtsbaugh 1992) and the abundant Eared Grebes (Caudell and Conover 2006) might limit brine shrimp. However, when corixid and Eared Grebe numbers were correlated with the residuals of the above relationships or were included in the relationships, predator impacts were not negative as expected if it is limiting, but exhibited a weak positive effect for corixids (p , 0.02) and no effect for Eared Grebes (p , 0.24).…”

Section: Brine Shrimpmentioning

confidence: 89%

“…Jehl (1988Jehl ( , 2007 concluded that Eared Grebe migration from Mono Lake in California was influenced by comparable brine shrimp densities. In contrast, a smaller value of 0.04-1.0/l was estimated to provide basal and foraging energetic needs for Eared Grebes in Great Salt Lake (Caudell 2001, Caudell and Conover 2006, Conover and Caudell 2009), but this does not include the greater demands of migration, survival in the wild, and reproduction. Finally, our estimated minimum brine shrimp density for maintenance of grebe populations (5.85/l) is not much smaller than average observed brine shrimp density during our study (6.97/l), which suggests that grebe numbers may be sensitive to brine shrimp populations.…”

Section: Predatorsmentioning

confidence: 97%

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The Great Salt Lake Ecosystem (Utah, USA): long term data and a structural equation approach

et al. 2011

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Abstract. Great Salt Lake (Utah, USA) is one of the world's largest hypersaline lakes, supporting many of the western U.S.'s migratory waterbirds. This unique ecosystem is threatened, but it and other large hypersaline lakes are not well understood. The ecosystem consists of two weakly linked food webs: one phytoplankton-based, the other organic particle/benthic algae-based.Seventeen years of data on the phytoplankton-based food web are presented: abundances of nutrients (N and P), phytoplankton (Chlorophyta, Bacillariophyta, Cyanophyta), brine shrimp (Artemia franciscana), corixids (Trichocorixa verticalis), and Eared Grebes (Podiceps nigricollis). Abundances of less common species, as well as brine fly larvae (Ephydra cinerea and hians) from the organic particle/benthic algae-based food web are also presented. Abiotic parameters were monitored: lake elevation, temperature, salinity, PAR, light penetration, and DO. We use these data to test hypotheses about the phytoplankton-based food web and its weak linkage with the organic particle/benthic algae-based food web via structural equation modeling.Counter to common perceptions, the phytoplankton-based food web is not limited by high salinity, but principally through phytoplankton production, which is limited by N and grazing by brine shrimp. Annual N abundance is highly variable and depends on lake volume, complex mixing given thermo-and chemo-clines, and recycling by brine shrimp. Brine shrimp are food-limited, and predation by corixids and Eared Grebes does not depress their numbers. Eared Grebe numbers appear to be limited by brine shrimp abundance. Finally, there is little interaction of brine fly larvae with brine shrimp through competition, or with corixids or grebes through predation, indicating that the lake's two food webs are weakly connected.Results are used to examine some general concepts regarding food web structure and dynamics, as well as the lake's future given expected anthropogenic impacts.

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Section: Brine Shrimpmentioning

confidence: 89%

Section: Predatorsmentioning

confidence: 97%

The Great Salt Lake Ecosystem (Utah, USA): long term data and a structural equation approach

et al. 2011

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“…Feeding behaviour might also be affected by other factors such as wind speed (Green et al, 1999;Heath et al, 2008), or the time of day when data were recorded (Heath et al, 2008), but in our study all foraging observations were conducted at the same time and on days without wind. In the Great Salt Lake, grebes also increased their time spent foraging when brine shrimp densities were low (Caudell & Conover, 2006b). Our analysis of gizzard contents confirmed the dominance of brine shrimps in the grebe diet at the Odiel marshes.…”

Section: Discussionmentioning

confidence: 96%

“…It is likely that moulting grebes are only able to adjust foraging effort within certain limits, given the number of daylight hours and the need to spend time in other activities (Caudell & Conover, 2006b). At the end of moulting period when thermal stress is greatest and food supply is lowest in the Odiel marshes, grebes may not be able to meet their energy requirements.…”

Section: Discussionmentioning

confidence: 98%

Behavioural and population responses to changing availability of Artemia prey by moulting black-necked grebes, Podiceps nigricollis

et al. 2011

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We examined how availability of brine shrimps, Artemia parthenogenetica, influenced temporal aspects of foraging behaviour and population dynamics of moulting black-necked grebes, Podiceps nigricollis, from late August to early December in four salt ponds in the Odiel marshes, southern Spain, in 2008 and 2009. The moulting grebe population was higher in 2009, coinciding with an increase in shrimp biomass, with a peak of 2,500 birds in October. Grebes increased their time spent foraging as the season progressed, coinciding with decreases in shrimp biomass and water temperature. Foraging activity was lower in 2009, when shrimp biomass was greater. Diving was the most frequent feeding method, especially as the season progressed. Brine shrimps at the bottom of the water column were larger than those near the surface. Differences between years in grebe body mass suggest that changing shrimp availability and water temperature had an influence on body condition. The grebe population consumed an estimated 0.2-2.0% of the standing crop of Artemia per day, with this fraction increasing as the season progresses, thus contributing to the decline in the Artemia population. Our results suggest that moulting grebes are probably only able to adjust foraging effort within certain limits, especially at the end of moulting period when thermal stress is greatest and food supply is lowest. They may leave the study area when they can no longer meet their energy requirements.

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“…Moreover, there is an upper limit to the time that grebes can spend foraging each day, because they must spend a certain amount of time for preening and resting (Caudell and Conover 2006). Most of the feeding occurs during daylight hours (Cooper, Winkler, and Lenz 1984;Fox 1994) because they locate food by sight (Caudell and Conover 2006). Flight exercises marked the end of the wintering period when the assemblage of moulting individuals trained the wings to leave the study site.…”

Section: Discussionmentioning

confidence: 99%

Abundance and diurnal activity budget of sympatric Podicipedidae species at a Ramsar site in north-east Algeria

Abdellioui

Bensouilah

Houhamdi

2015

Zoology and Ecology

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In order to evaluate the number of Podicipedidae and to monitor their diurnal behaviour for the first time in North Africa, bimonthly outings were conducted from September 2013 to August 2014 in Garaet Hadj-Tahar, a Ramsar site. The population size varied significantly between three investigated species. The peak numbers observed during the whole study period were 484 and 86 individuals of the Little Grebe and the Great Crested Grebe, respectively. These two species were present all year. The maximum for the Black-necked Grebe was 13 individuals observed during January 2014. This last species was a rare winter visitor to Garaet Hadj-Tahar. The analysis of the diurnal time budget revealed that feeding was the major activity of the Little Grebe and swimming was the major activity of the Great Crested Grebe. The latter devoted more time to preening, resting and parading than the former did. The total time spent for agonistic behaviour and flight accounted for a minimal budget for both species. Pirmą kartą Šiaurės Afrikoje, Garaet Hadj-Tahar pelkių komplekse (Ramsaro konvencijos saugomoje teritorijoje) buvo įvertintas Podicipedidae šeimos paukščių gausumas ir elgsena dienos metu. Tyrimai atlikti kas du mėnesiai stebint šiuos paukščius 2013 m. rugsėjį -2014 m. rugpjūtį. Nustatyti ženklūs tiriamų rūšių populiacijų dydžių skirtumai. Mažieji kragai (daugiausiai -484 individai) ir ausuotieji kragai (86 individai) buvo aptinkami pelkėse per visus metus. Didžiausias juodakaklių kragų skaičius (13 paukščių) užfiksuotas 2014 m. sausio mėn. Į Garaet Hadj-Tahar pelkes juodakakliai kragai žiemojimui užklysta retai. Dieninės elgsenos stebėjimai parodė, kad mažieji kragai daugiausia laiko maitinosi, ausuotieji kragai -plaukiojo. Mažieji kragai daugiau laiko nei ausuotieji kragai skyrė plunksnų valymui, poilsiui ir ritualinei elgsenai. Mažiausiai abiejų rūšių paukščių laiko užėmė agonistinė elgsena ir skraidymas.

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Behavioral and Physiological Responses of Eared Grebes (Podiceps Nigricollis) to Variations in Brine Shrimp (Artemia Franciscana) Densities

Cited by 23 publications

References 8 publications

The Great Salt Lake Ecosystem (Utah, USA): long term data and a structural equation approach

The Great Salt Lake Ecosystem (Utah, USA): long term data and a structural equation approach

Behavioural and population responses to changing availability of Artemia prey by moulting black-necked grebes, Podiceps nigricollis

Abundance and diurnal activity budget of sympatric Podicipedidae species at a Ramsar site in north-east Algeria

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