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Beverly A. Gingras - One of the best experts on this subject based on the ideXlab platform.
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Trophic relationships of two species of Grebe on a prairie lake based on stable isotope analysis
Hydrobiologia, 2012Co-Authors: Jennifer L Newbrey, Cynthia A. Paszkowski, Beverly A. GingrasAbstract:We used stable isotope analysis of carbon and nitrogen to investigate the trophic relationships of Western (Aechmophorus occidentalis (Lawrence)) and Red-necked (Podiceps grisegena (Boddaert)) Grebes from Lake Wabamun, a large prairie lake in north-central Alberta, Canada. We collected tissue samples (i.e., pectoralis muscles and primary feathers) from 42 Western and 22 Red-necked Grebes (adults and juveniles) that had died in captivity after an oil spill on Lake Wabamun on 3 August, 2005. We also collected fish and invertebrates, focusing on taxa known to serve as prey for Grebes. Based on comparisons of 15N enrichment in muscle tissue, Western Grebes, northern pike (Esox lucius Linnaeus), yellow perch (Perca flavescens (Mitchill)), and lake whitefish (Coregonus clupeaformis (Mitchill)) were top consumers in Lake Wabamun, as were Red-necked Grebes. Adult Western Grebe muscle was more enriched with 15N than adult Red-necked Grebe muscle by 1.5‰, indicating that Western Grebes foraged at a slightly higher trophic position on Lake Wabamun than Red-necked Grebes. Red-necked Grebe muscles and feathers were also less depleted in 13C than Western Grebe muscle, indicating that Red-necked Grebes likely spent more time foraging in the littoral zone than Western Grebes. There were no differences in muscle or feather isotopic signals between juvenile and adult Western Grebes, suggesting that both age groups fed on similar prey items and in similar habitats. Muscle tissues and primary feathers of larger Red-necked Grebes were more enriched in both 15N and 13C than smaller Grebes likely because larger Grebes consume more or larger fish.
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TROPHIC RELATIONS OF THE RED-NECKED Grebe ON LAKES IN THE WESTERN BOREAL FOREST: A STABLE-ISOTOPE ANALYSIS
The Condor, 2004Co-Authors: Cynthia A. Paszkowski, Beverly A. Gingras, Paul H. Klatt, Kayedon Wilcox, William M. TonnAbstract:Abstract We compared trophic ecology of Grebes inferred from stable-isotope analysis to that from gut contents, and compared isotopic ratios of Red-necked Grebes (Podiceps grisegena) from lakes differing in their food webs. Analyses of different Grebe tissues (egg yolk and albumen, pectoral and leg muscle, breast and primary feathers) also allowed us to assess the effectiveness of these tissues at representing Grebe trophic relations. Isotopic ratios from pectoral and leg muscles were similar, based on comparisons within individual birds. Enriched values of δ15N and δ13C suggested that breast and primary feathers were molted over winter, and therefore reflected a marine food web. Albumen and yolk of Grebe eggs and muscle tissues from downy chicks, however, matched isotopic characteristics of the local food web, indicating that female Red-necked Grebes use nutrients from the breeding lake for egg formation. Eggs, therefore, can provide excellent material for isotopic analysis aimed at assessing trophic rel...
Julio L. Lancelotti - One of the best experts on this subject based on the ideXlab platform.
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rainbow trout effects on zooplankton in the reproductive area of the critically endangered hooded Grebe
Aquatic Conservation-marine and Freshwater Ecosystems, 2017Co-Authors: Julio L. Lancelotti, Maria Cristina Marinone, Ignacio RoeslerAbstract:Aquaculture in arid Patagonia is potentially affecting the hooded Grebe (Podiceps gallardoi), a critically endangered endemic waterbird. Exotic rainbow trout (Oncorhynchus mykiss) were stocked from 1994 in naturally fishless lakes, the primary reproductive habitat of this Grebe. Trout and Grebes are visual predators, whose diets overlap. Consequently, trout could reduce the abundance of prey of the hooded Grebe. This study compared the size distribution and abundance of the pelagic zooplankton fraction preyed upon by trout in four fishless lakes and three lakes stocked with trout, including vegetated and unvegetated lakes. The mean size of Daphnia spp. was 45% and 35% larger in fishless lakes than in stocked lakes, for unvegetated and vegetated lakes, respectively. Boeckella spp. were larger in fishless than in stocked vegetated lakes. Fishless and stocked lakes had highly contrasting biomasses of large pelagic crustaceans. Amphipods were absent from the water column of all stocked lakes analysed, and were abundant in fishless lakes. Parabroteas sarsi was absent from the two large unvegetated lakes, stocked with trout. These shifts in the abundance and size spectrum of the zooplankton may reflect competition between trout and hooded Grebe, affecting the survival of the latter species. The current conservation status of this rare aquatic bird demands the application of management tools to reduce the detrimental effects of aquaculture on their primary reproductive habitat. Copyright © 2016 John Wiley & Sons, Ltd.
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Precautionary rules for exotic trout aquaculture in fishless shallow lakes of Patagonia: minimizing impacts on the threatened hooded Grebe (Podiceps gallardoi).
Aquatic Conservation-marine and Freshwater Ecosystems, 2009Co-Authors: Julio L. Lancelotti, Luciana M. Pozzi, Pablo Yorio, María Del Carmen Diéguez, Miguel A. PascualAbstract:1. Conflicts between habitat use and conservation are inherent to the management of wetlands. A major challenge for their management is to preserve habitat while addressing the demands from multiple users. In southern Patagonia (Argentina), a growing aquaculture activity based on rainbow trout introductions in shallow lakes is generating concerns about the effects on the waterbird fauna, including some endemic species. 2. Generalized linear models (GLM) were used to analyse data on the endemic hooded Grebe (Podiceps gallardoi) collected over a diverse set of lakes to: (1) build presence-absence models as a function of environmental variables; (2) assess current and potential overlap with trout aquaculture; (3) explore the power of alternative lake assignment algorithms based on habitat variables to segregate critical habitat and aquaculture activities; and (4) explore the correlation between the probability of Grebe presence and their abundance in given lakes. 3. Hooded Grebe presence is clearly correlated with macrophyte cover, lake area, and water conductivity. Medium size lakes, with a combination of emerging macrophytes, adjacent to open water areas had the highest probability of both hooded Grebe presence and abundance. 4. Different lake allocation scenarios are identified that could grant significant protection to hooded Grebes without substantial losses for trout producers. The a priori probability to hold hooded Grebe, assigned by the model based on lake characteristics, provides a tool that can be used by managing authorities to derive precautionary management rules to regulate aquaculture and to preserve primary hooded Grebe habitat. Copyright © 2009 John Wiley & Sons, Ltd.
Cynthia A. Paszkowski - One of the best experts on this subject based on the ideXlab platform.
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Horned Grebe habitat use of constructed wetlands in Alberta, Canada
The Journal of Wildlife Management, 2012Co-Authors: Eva C. Kuczynski, Cynthia A. Paszkowski, Bev A. GingrasAbstract:Wetland degradation has resulted in declines in populations of aquatic birds throughout North America. Horned Grebe (Podiceps auritus), a migratory diving bird experiencing population decline, may benefit from wetland construction. We examined horned Grebe use of borrow pits (ponds created during highway construction) in Alberta, Canada. Our goals were to document patterns of occurrence and breeding success of Grebes on borrow pits and to determine if occupied and unoccupied sites differed in local habitat or landscape characteristics. In May 2003 and 2007, 330 constructed ponds were surveyed for horned Grebes. We chose 100 occupied and 100 unoccupied ponds for additional surveys in 2007 and 2008, and collected habitat and landscape data for these sites. We used generalized linear mixed model and generalized linear model regression, coupled with Akaike's Information Criterion, to determine which environmental variables were most effective in explaining occurrence of horned Grebes. The best model included all measured local and landscape habitat features. Horned Grebes occurred on 36% of ponds in May 2003 and 2007, and chicks were produced on 74.5–81.3% of occupied ponds in 2007 and 2008. Grebes occupied larger ponds with more emergent and riparian vegetation and avoided ponds that supported beavers, contained human structures, and were primarily surrounded by forest within 1 km. On ponds with Grebe pairs, chicks were produced more often on sites surrounded by more riparian vegetation. We conclude that the construction of small wetlands offers a promising means of increasing breeding habitat for horned Grebes and present specific recommendations for breeding pond construction. © 2012 The Wildlife Society.
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Trophic relationships of two species of Grebe on a prairie lake based on stable isotope analysis
Hydrobiologia, 2012Co-Authors: Jennifer L Newbrey, Cynthia A. Paszkowski, Beverly A. GingrasAbstract:We used stable isotope analysis of carbon and nitrogen to investigate the trophic relationships of Western (Aechmophorus occidentalis (Lawrence)) and Red-necked (Podiceps grisegena (Boddaert)) Grebes from Lake Wabamun, a large prairie lake in north-central Alberta, Canada. We collected tissue samples (i.e., pectoralis muscles and primary feathers) from 42 Western and 22 Red-necked Grebes (adults and juveniles) that had died in captivity after an oil spill on Lake Wabamun on 3 August, 2005. We also collected fish and invertebrates, focusing on taxa known to serve as prey for Grebes. Based on comparisons of 15N enrichment in muscle tissue, Western Grebes, northern pike (Esox lucius Linnaeus), yellow perch (Perca flavescens (Mitchill)), and lake whitefish (Coregonus clupeaformis (Mitchill)) were top consumers in Lake Wabamun, as were Red-necked Grebes. Adult Western Grebe muscle was more enriched with 15N than adult Red-necked Grebe muscle by 1.5‰, indicating that Western Grebes foraged at a slightly higher trophic position on Lake Wabamun than Red-necked Grebes. Red-necked Grebe muscles and feathers were also less depleted in 13C than Western Grebe muscle, indicating that Red-necked Grebes likely spent more time foraging in the littoral zone than Western Grebes. There were no differences in muscle or feather isotopic signals between juvenile and adult Western Grebes, suggesting that both age groups fed on similar prey items and in similar habitats. Muscle tissues and primary feathers of larger Red-necked Grebes were more enriched in both 15N and 13C than smaller Grebes likely because larger Grebes consume more or larger fish.
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Food-Web Relations of the Horned Grebe (Podiceps auritus) on Constructed Ponds in the Peace Parkland, Canada
Wetlands, 2010Co-Authors: Eva C. Kuczynski, Cynthia A. PaszkowskiAbstract:Borrow-pit constructed ponds, formed during road building, are common along highways that run through the Peace Parkland, Alberta, Canada, providing habitat for a variety of aquatic birds. The horned Grebe ( Podiceps auritus ) is a migratory diving bird that is in decline, likely due to native habitat destruction; however, it readily nests on roadside borrow pits. We conducted stable isotope analysis (SIA), based on carbon and nitrogen, of the food-webs of 14 borrow pits in the Peace Parkland, half occupied and half unoccupied by nesting horned Grebes, to determine if food-web structure differed between ponds where breeding Grebes were present versus ponds where Grebes were absent. Grebe eggs were collected from seven ponds and suspected vertebrate and invertebrate prey were collected from all ponds. Borrow pits had simple, consistent food-webs. No difference in food-web structure or invertebrate biomass was detected between occupied and unoccupied ponds. When present, horned Grebes were top predators, as determined by nitrogen signatures of egg albumen, and held the same trophic position as small-bodied fish. Grebes use nutrients acquired from the breeding pond for egg formation. SIA indicated that horned Grebes were generalists, feeding on organisms from a variety of trophic positions including odonates, leeches, and amphipods.
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Intruder pressure explains more of the variation in territory size than fish abundance for Red-necked Grebes (Podiceps grisegena) breeding on small boreal lakes
2005Co-Authors: Paul H. Klatt, Cynthia A. PaszkowskiAbstract:In the Red-necked Grebe (Podiceps grisegena), breeding pairs use both overt aggression and ritualistic behavior to defend territories for breeding and feeding. Examining the influence of factors determining territory size simultaneously continues to be stressed in studies of territorial systems. The behavior of Grebes breeding on small boreal lakes (15– 240 ha) was examined in relation to several environmental variables through three stages of the breeding season (pre-nesting, nesting, and post-nesting). Territory size was shown to be inversely related to Grebe density and fish abundance during the pre-nesting and nesting stages of the breeding season. In addition, Grebe density was more strongly associated with territory size than was fish abundance. The costs and benefits that balance economic decisions for breeding Grebes rigorously defending areas are discussed.
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TROPHIC RELATIONS OF THE RED-NECKED Grebe ON LAKES IN THE WESTERN BOREAL FOREST: A STABLE-ISOTOPE ANALYSIS
The Condor, 2004Co-Authors: Cynthia A. Paszkowski, Beverly A. Gingras, Paul H. Klatt, Kayedon Wilcox, William M. TonnAbstract:Abstract We compared trophic ecology of Grebes inferred from stable-isotope analysis to that from gut contents, and compared isotopic ratios of Red-necked Grebes (Podiceps grisegena) from lakes differing in their food webs. Analyses of different Grebe tissues (egg yolk and albumen, pectoral and leg muscle, breast and primary feathers) also allowed us to assess the effectiveness of these tissues at representing Grebe trophic relations. Isotopic ratios from pectoral and leg muscles were similar, based on comparisons within individual birds. Enriched values of δ15N and δ13C suggested that breast and primary feathers were molted over winter, and therefore reflected a marine food web. Albumen and yolk of Grebe eggs and muscle tissues from downy chicks, however, matched isotopic characteristics of the local food web, indicating that female Red-necked Grebes use nutrients from the breeding lake for egg formation. Eggs, therefore, can provide excellent material for isotopic analysis aimed at assessing trophic rel...
Michel D. Houseman - One of the best experts on this subject based on the ideXlab platform.
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Fossil Grebes from the Truckee Formation (Miocene) of Nevada and a new phylogenetic analysis of Podicipediformes (Aves)
Palaeontology, 2013Co-Authors: Daniel T. Ksepka, Amy M. Balanoff, Michael A. Bell, Michel D. HousemanAbstract:Podicipediformes is a cosmopolitan clade of foot-propelled diving birds that, despite inhabiting marine and lacustrine environments, have a poor fossil record. In this contribution, we describe three new Grebe fossils from the diatomite beds of the Late Miocene Truckee Formation (10.2 ± 0.2 Ma) of Nevada (USA). Two postcranial skeletons and an associated set of wing elements indicate that at least two distinct Grebe species occupied the large, shallow Lake Truckee during the Miocene. Phylogenetic analysis of morphological data supports a basal divergence between a clade uniting the dabchicks (Tachybaptus, Limnodytes, Poliocephalus) and a clade uniting Podilymbus, Rollandia, Podiceps and Aechmophorus. Missing data, combined with a paucity of informative skeletal characters, make it difficult to place the Truckee Grebes within either of these major clades. Given the weak projection of the cnemial crests compared with extant Grebes, it also remains plausible that these specimens represent stem lineage Grebes. Although more material is needed to resolve the phylogenetic position of the Truckee Grebes, our analysis offers insight into the tempo of Grebe evolution by placing the Miocene taxon Thiornis sociata within the dabchick clade. Thiornis sociata provides a minimum age calibration of 8.7 Ma for the basal divergence among dabchicks. Based on the recovery of a nonmonophyletic Tachybaptus and placement of the Western Hemisphere ‘Tachybaptus’ dominicus as the basal member of the otherwise exclusively Eastern Hemisphere dabchick clade, we resurrect the genus Limnodytes for this extant species (Limnodytes dominicus). Our results also nest the large, long-necked Aechmophorus Grebes within the genus Podiceps, as the sister taxon to Podiceps major.
Ignacio Roesler - One of the best experts on this subject based on the ideXlab platform.
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rainbow trout effects on zooplankton in the reproductive area of the critically endangered hooded Grebe
Aquatic Conservation-marine and Freshwater Ecosystems, 2017Co-Authors: Julio L. Lancelotti, Maria Cristina Marinone, Ignacio RoeslerAbstract:Aquaculture in arid Patagonia is potentially affecting the hooded Grebe (Podiceps gallardoi), a critically endangered endemic waterbird. Exotic rainbow trout (Oncorhynchus mykiss) were stocked from 1994 in naturally fishless lakes, the primary reproductive habitat of this Grebe. Trout and Grebes are visual predators, whose diets overlap. Consequently, trout could reduce the abundance of prey of the hooded Grebe. This study compared the size distribution and abundance of the pelagic zooplankton fraction preyed upon by trout in four fishless lakes and three lakes stocked with trout, including vegetated and unvegetated lakes. The mean size of Daphnia spp. was 45% and 35% larger in fishless lakes than in stocked lakes, for unvegetated and vegetated lakes, respectively. Boeckella spp. were larger in fishless than in stocked vegetated lakes. Fishless and stocked lakes had highly contrasting biomasses of large pelagic crustaceans. Amphipods were absent from the water column of all stocked lakes analysed, and were abundant in fishless lakes. Parabroteas sarsi was absent from the two large unvegetated lakes, stocked with trout. These shifts in the abundance and size spectrum of the zooplankton may reflect competition between trout and hooded Grebe, affecting the survival of the latter species. The current conservation status of this rare aquatic bird demands the application of management tools to reduce the detrimental effects of aquaculture on their primary reproductive habitat. Copyright © 2016 John Wiley & Sons, Ltd.
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Hooded Grebe Podiceps gallardoi population decreased by eighty per cent in the last twenty-five years
Bird Conservation International, 2012Co-Authors: Ignacio Roesler, Santiago Imberti, Hernán Casañas, Bettina Mahler, Juan C. ReboredaAbstract:We estimated the present population size of the Hooded Grebe Podiceps gallardoi and compared it with the population in 1985. During the breeding seasons 2009/2010 and 2010/2011 we monitored 251 lakes on the main plateaus of Santa Cruz province, southern Patagonia, Argentina, where the entire population of Hooded Grebes spends the breeding season. During 2009/2010 we monitored 131 lakes and observed 521 Hooded Grebes in 16 lakes, while during 2010/2011 we monitored 186 lakes and observed 535 individuals in 14 lakes. At both breeding seasons five lakes contained near 85% of the population. We only observed 6 breeding colonies, two in 2009/2010 and four in 2010/2011, totalling 242 nesting attempts. Nearly 90% of the nests failed during egg stage, mainly due to strong winds and depredation by American mink Neovison vison . Only 28 nests hatched chicks, but none of the young survived to independence due to low temperatures. We compared the results of our 2010/2011 survey with one conducted during 1984/1985 and detected that the population diminished by approximately 80%. This decline was observed on all but one plateau (“Buenos Aires”) where most breeding attempts occurred. Our results show that at present Hooded Grebes are highly dependent on a few suitable lakes where they congregate to breed. We analyse possible causes for the decline of the population and propose conservation actions to protect this species.
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A new threat for the globally Endangered Hooded Grebe Podiceps gallardoi: the American mink Neovison vison.
Bird Conservation International, 2012Co-Authors: Ignacio Roesler, Santiago Imberti, Hernán Casañas, Noelia VolpeAbstract:Summary The Hooded Grebe Podiceps gallardoi has been uplisted to globally ‘Endangered’ recently mainly because of the rapid population decline suffered within the last 20 years due to factors such as nest depredation by Kelp Gull Larus dominicanus as well as destruction of colonies by wind and lake desiccation. During a census of Hooded Grebes during the 2010/2011 breeding season we found a new predator that has not previously been mentioned, the American mink Neovison vison. One individual mink killed 33 Hooded Grebes and consequently destroyed one of the five colonies found in that breeding season. Due to the characteristics of the waterbird assemblage in the area, the impact of mink could be catastrophic.
