Tracing nutrient sources to lipid production in insects using stable isotope (δ13C, δ2H) tracers: Implications for nutritional physiology of migratory species.

Using stable isotope measurements of insect tissues to determine origin and migratory patterns is well established. However, isotopically determining nutritional origins of lipids, the primary fuel of migration, has not been as thoroughly researched. We explored isotopic links between diet and stored lipids in laboratory raised True armyworm moths (Mythimna unipuncta) using δ13C and δ2H measurements. Pupae were randomly separated into four groups (n=20) and fed isotopically distinct nectar, each consisting of a combination of high δ13C (C4 sugar), or low δ13C (C3 sugar) carbohydrate, with high δ2H (deuterium spiked), or low δ2H (tap) water. After 6 days of feeding, lipids were extracted for isotopic analysis using CF-IRMS. The carbohydrate contributed to approximately 80% of the δ13C and water contributed to approximately 13% of the δ2H in lipids. Lipids from C4 fed moths had higher δ13C values compared to C3 fed moths (-29.1 vs -16.6 ‰, P2H values compared to moths given tap water (-187.3 vs -254.6 ‰, P13C which can be used to provide continental isoscapes for tracking sources of stored lipids

Observations of Foraging Northern Fulmars (Fulmarus Glacialis) in the Canadian High Arctic

We summarize observations of foraging northern fulmars (Fulmarus glacialis) in the Barrow Strait-Lancaster Sound region of the Northwest Territories from June to September 1984-90 and in Admiralty Inlet, N.W.T., in July 1989. In each year, fulmars scavenged hunter-killed marine mammal remains in the vicinity of Resolute Bay. Large feeding flocks, aggregated primarily along tide lines and at upwelling sites, exploited primarily calanoid copepods by surface seizing and diving. Late-season onshore movement of Arctic cod (Boreogadus saida) resulted in flocks of several thousand fulmars capturing cod by surface and pursuit diving. We determined experimentally that northern fulmars are capable of diving to 3 m to retrieve cod.Key words: northern fulmar, Fulrmarus glacialis, feeding behaviour, diving, Barrow Strait, Lancaster SoundRÉSUMÉ. On résume les observations faites sur des fulmars boréaux (Fulmarus glacialis) en train de se ravitailler dans la région du détroit de Barrow et du détroit de Lancaster dans les Territoires du Nord-Ouest, de juin à septembre 1984 à 1990, et dans l'inlet de l'Amirauté (T.N.-O.) en juillet1989. Chaque année, les fulmars se repaissaient des restes de mammifères marins tués par des chasseurs à proximité de la baie Resolute. De grandes volées s'attroupaient pour se nourrir, surtout le long des laisses de marée et aux sites d'émergence, et pêchaient principalement des calanus,en les saisissant à la surface et en plongée. La migration de fin de saison de la morue polaire (Boreogadus saida) vers le rivage attirait des volées composées de plusieurs milliers de fulmars qui capturaient la morue en piquant à la surface et en la poursuivant sous l'eau. On a déterminé expérimentalement que le fulmar boréal est capable de plonger à 3 m sous la surface pour retrouver la morue.Mots clés: fulmar boréal, Fulrnarus glacialis, comportement alimentaire, plongée, détroit de Barrow, détroit de Lancaste

Origins of Late-Breeding Nomadic Sedge Wrens in North America: Limitations and Potential of Hydrogen-Isotope Analyses of Soft Tissue

This is the published version. Copyright Central Ornithology Publication OfficeThe nomadic Sedge Wren (Cistothorus platensis) breeds primarily in mesic grasslands in north-central North America. Following breeding in these regions from late May to early July, however, the species then “appears” en masse in the tallgrass prairie region farther south (e.g., Missouri and Kansas) and to the east to breed again from mid-July to early August (Herkert et al. 2001). The provenance of birds appearing in late summer to breed in these areas remains unknown because of problems inherent in mark—recapture surveys. Recent studies have shown how endogenous markers may be used to infer origins of individual birds. We analyzed levels of the stable hydrogen isotope 2H (δD) from liver, muscle, and claws of Sedge Wrens from known northern breeding locations first to establish the relationships between δD in the wrens' tissue and mean δD in precipitation during the growing season (δDp ). From these relationships we derived expected values (mean and 95% CI) for three sites in Kansas and Missouri where late breeders colonized. The observed values of δD in these late breeders were primarily within the range expected for those locations, but more individuals than expected had δD values higher than expected. In addition, in birds apparently originating from north or south of Kansas and Missouri, the values of δD in claws were positively correlated with those in other tissues, in contrast to those with the “local” signal. This supports the idea that the isotopic outliers at these sites were more recent arrivals. For small-bodied birds like the Sedge Wren, however, the isotopic approach based on soft tissues is limited to a very narrow temporal window of inference because of rapid elemental turnover. This greatly restricts the use of this technique in inferring origins of small nomadic species

A 10 500-Year Sequence of Bird Remains from the Southern Boreal Forest Region of Western Canada

The prehistoric avian fauna from the Charlie Lake Cave site, Peace River District, British Columbia, spans the last 10,500 years and includes birds from eleven orders. Prior to about 10,000 B.P. the fauna is sparse and the most common species is Cliff Swallow (Hirundo pyrrhonota), which probably nested at the site. The avian fauna from 10,000 B.P. to the present is dominated by wetland associated birds (mainly grebes and ducks) of the same species found in the area today and is consistent with the establishment of boreal forest by 10,000 B.P. From about 8000 B.P. Passenger Pigeon (Ectopistes migratorius) occurs and appears to have been a regular component of the local fauna. The assemblages demonstrate rapid colonization of boreal environments by bird populations by 10,000 B.P. and probably indicate that the modern patterns of migration were established early in the Holocene.Key words: British Columbia, fossil birds, Holocene, Passenger PigeonL’avifaune préhistorique du site de Charlie Lake Cave, dans le district de Peace River en Colombie-Britannique, couvre les 10 500 dernières années et comprend des oiseaux appartenant à onze ordres différents. Antérieurement à environ 10 000 BP, la faune est clairsemée et l’espèce la plus courante est l’hirondelle à front blanc (Hirundo pyrrhonota), qui nidifie probablement sur le site. L’avifaune couvrant de 10 000 BP au présent est dominée par des oiseaux associés aux terres humides (surtout des grèbes et des canards) appartenant aux mêmes espèces que l’on trouve actuellement dans la région, et cette prédominance correspond à l’établissement d’une forêt boréale d’ici 10 000 BP. A partir d’environ 8000 BP, la tourte (Ectopistes migratorius) fait son apparition et semble avoir été une composante régulière de la faune locale. Les assemblages indiquent une colonisation rapide des milieux boréaux par les populations d’oiseaux d’ici 10 000 BP et semblent indiquer que les schémas de migration actuels se sont établis au début de l’holocène.Mots clés: Colombie-Britannique, oiseaux fossiles, holocène, tourt

Does Removal of Duck Nest Predators Affect the Temporal Patterns of Predation for Simulated Nests of Grassland Songbirds?

We tested whether the temporal patterns of songbird nest predation changed following removal of predators of duck nests in North Dakota, USA, 1995-1996. Overall, 2286 simulated nests were deployed of which 951 were equipped with depredation timing devices that recorded the time of day of nest destruction. Predators destroyed 242 timer nests, and 155 depredation events were recorded. Temporal distribution of predation events was uniform over a 24-h period. However, predator groups, identified by using marks left on modeling clay eggs, depredated nests at different times. Mean times of depredation were 07h41, 12h57, 17h50, and 22h47 for small mammals, ground squirrels, birds, and medium-sized mammals, respectively. Daily depredation events occurred earlier on removal versus non-removal sites. However, within each predator group, there was no difference in depredation times between removal and non-removal sites. We suggest that the difference in time of depredation is caused by the differential importance of each predator group on removal versus removal sites, and thus conclude that removing duck nest predators does not affect temporal foraging patterns of smaller predators

Environmental Contaminants in Colonial Waterbirds from Great Slave Lake, NWT: Spatial, Temporal and Food-chain Considerations

Great Slave Lake in the Northwest Territories, Canada, differs regionally in trophic status and local and regional inputs of contaminants. Spatial and temporal trends in contaminant levels in bioindicator species such as colonial waterbirds could offer insights into the potential for contaminant bioaccumulation in Great Slave Lake. Persistent chlorinated hydrocarbon contaminants, mercury (Hg), and selenium (Se) were examined in herring gull (Larus argentatus) eggs and livers collected from various locations on Great Slave Lake in 1995. Eggs were collected in May and June, and livers in May and August. Also, the relationship between contaminants and trophic level, as inferred from stable-nitrogen isotope analysis (delta 15N), was examined in four colonial waterbird species: herring gull, mew gull (L. canus), Caspian tern (Sterna caspia), and black tern (Chlidonias niger). Finally, the co-accumulation of mercury and selenium was examined in eggs of these birds. There were no differences in chlorinated hydrocarbon concentrations among four sampling sites (colonies). Concentrations did not differ between herring gull adults collected in early May and those collected in early August. Chlorinated hydrocarbon concentrations in eggs of herring gull, mew gull, Caspian tern, and black tern were related to their trophic positions as inferred from their delta 15N values in their lipid-free egg yolks. Concentrations in these colonial waterbirds were much higher than those in fish from Great Slave Lake, but lower than those in their conspecifics from the Great Lakes. It is probable that a relatively large proportion of the chlorinated hydrocarbon contaminant load in colonial waterbird eggs on Great Slave Lake results from exposure to and storage of such contaminants at more heavily contaminated wintering and staging areas. This possibility limits the usefulness of colonial waterbirds as indicators of chlorinated hydrocarbon bioaccumulation in Great Slave Lake. Selenium and mercury concentrations in herring gull eggs differed significantly among the four breeding colonies, and concentrations in adults declined between May and August. Selenium and mercury were positively correlated in eggs of all species.Le Grand lac des Esclaves situé dans les Territoires du Nord-Ouest, au Canada, diffère au niveau régional quant à l'état trophique et à l'apport local et régional de contaminants. Les tendances spatiales et temporelles dans les niveaux de contaminants chez des espèces considérées comme indicateurs biologiques, telles que les oiseaux aquatiques coloniaux, pourraient donner un aperçu du potentiel de bioaccumulation des contaminants dans le Grand lac des Esclaves. On a examiné les contaminants d'hydrocarbures chlorés rémanents, le mercure (Hg) et le sélénium (Se) dans les œufs et le foie du goéland argenté (Larus argentatus) prélevés en 1995 à divers endroits du Grand lac des Esclaves. Les œufs ont été prélevés en mai et juin, et les foies en mai et août. On a en outre étudié le rapport entre les contaminants et l'état trophique, déduit de l'analyse de l'isotope d'azote stable (delta 15N) chez quatre espèces d'oiseaux aquatiques coloniaux: le goéland argenté, le goéland cendré (L. canus), la sterne caspienne (Sterna caspia) et la guifette noire (Chlidonias niger). Pour finir, on a étudié l'accumulation conjointe de mercure et de sélénium dans les œufs de ces oiseaux. Il n'y avait pas de différence dans les concentrations d'hydrocarbures chlorés entre les quatre sites (colonies) échantillonnés. Les concentrations ne différaient pas entre les goélands argentés adultes prélevés début mai et ceux prélevés début août. Les concentrations en hydrocarbures chlorés dans les œufs du goéland argenté, du goéland cendré, de la sterne caspienne et de la guifette noire étaient reliées à leurs positions trophiques déduites des valeurs (delta 15N) trouvées dans le jaune des œufs sans lipides. Les concentrations chez ces oiseaux aquatiques coloniaux étaient beaucoup plus élevées que chez les poissons du Grand lac des Esclaves, mais inférieures à celles trouvées chez leurs congénères des Grands Lacs. Il est probable qu'une proportion relativement importante de la charge de contaminants d'hydrocarbures chlorés dans les œufs des oiseaux aquatiques coloniaux du Grand lac des Esclaves résulte de l'exposition à ces contaminants dans les aires d'hivernage et les points d'escale fortement contaminés, et de leur emmagasinage subséquent. Cette possibilité limite l'utilité des oiseaux aquatiques coloniaux comme indicateurs de bioaccumulation des hydrocarbures chlorés dans le Grand lac des Esclaves. Les concentrations de sélénium et de mercure dans des œufs du goéland argenté diffèrent nettement entre les quatre colonies reproductrices, et les concentrations chez les adultes ont baissé entre mai et août. Le sélénium et le mercure étaient corrélés de façon positive dans les œufs de toutes les espèces

Multi-isotopic (δ2H, δ13C, δ15N) tracing of molt origin for European starlings associated with U.S. dairies and feedlots

Introduced bird species can become invasive in agroecosystems and their management is inhibited if their origin and movements are not well understood. Stable isotope measurements of feathers can be used to infer molt origins and interstate movements in North America. We analyzed stable-hydrogen (δ2H), carbon (δ13C) and nitrogen (δ 15N) isotope ratios in feathers to better understand the molt origin of European starlings (Sturnus vulgaris) collected at dairies and feedlots throughout the United States. Primary feathers were used from 596 adult and 90 juvenile starlings collected during winter at dairies and feedlots that experience starling damages in Arizona, California, Colorado, Idaho, Illinois, Iowa, Kansas, Minnesota, Missouri, Nebraska, Nevada, New Hampshire, New Mexico, New York, North Carolina, Oregon, Texas, Vermont, Washington and Wisconsin. The best-fit model indicated that the combination of feather δ2H, δ13C and δ15N values best predicted the state where samples were collected and thus supported use of this approach for tracing molt origins in European starlings. Interestingly, molt origins of starlings collected at dairies and feedlots generally west of −90˚ longitude (i.e. 11 of 15 states west of the Mississippi River, including Wisconsin) were assigned to the collection state and/or the state adjacent to the collection state. In contrast, molt origins of starlings collected generally east of −90˚ longitude (four of five eastern states) were not assigned to the collection state and/or the state adjacent to the collection state. Among all starlings (N = 686), 23% were assigned to the collection state and 19% were assigned to the state adjacent to the collection state. Among all males (N = 489) and all females (N = 197), 23% and 26% were assigned to the collection state and 19% and 13% were assigned to the state adjacent to the collection state, respectively. We observed a greater proportion (88%) of juvenile starlings assigned to states other than their collection state (i.e. potentially a result of natal dispersal) than that proportion (76%) in adult starlings. This study included an unprecedented sample of feather isotopes from European starlings throughout the United States. As a novel contribution to the ecology and management of invasive and migratory passerines, we demonstrate how such feather isoscapes can be used to predict molt origin and, potentially, interstate movements of European starlings for subsequent ecological and management investigations

Changes in diet and trophic position of a top predator 10 years after a mass mortality of a key prey

After the disappearance of primary prey, seabirds exhibit gradually decreased breeding performance, and eventually the population size drops. Results are presented of an investigation into the diet of little penguins (Eudyptula minor) at Phillip Island, Australia, during a period when their key prey, pilchard (Sardinops sagax), declined dramatically. Data from stomach flushing (1982-2006) were used, supported by stable isotope (δ 15N, δ13C) analyses of blood samples (2003, 2004, and 2006). The effect of the pilchard mortality on penguin diet was immediate, the birds shifting to a diet almost devoid of pilchard, and this was followed by 2 years of low breeding success, with considerably fewer penguins coming ashore. During periods when pilchard was not part of the diet, penguins consumed prey of a higher trophic level, e.g. higher values of δ15N. Variability in penguin blood δ15N coincided with years of low prey diversity. The disappearance of pilchard resulted in a decrease in prey diversity and led penguins to >fish up> the foodweb, possibly because of the simplified trophic structure. After 1998, however, breeding success re-attained average levels and the numbers of penguins coming ashore increased, probably because of increased abundance of prey other than pilchard after a 3-year period of food scarcity. Although little penguins apparently compensated over time, a less-flexible diet could make them ultimately vulnerable to further changes in their foodweb. © 2010 International Council for the Exploration of the Sea.Peer Reviewe