scholarly journals Late-Summer Feeding and Migration Behaviour and Numerical Trends of Common Nighthawks, Chordeiles minor, near Pinawa, Manitoba, 1976-2009

2009 ◽  
Vol 123 (4) ◽  
pp. 338 ◽  
Author(s):  
Peter Taylor
Keyword(s):  
Long Range ◽  
Survey Methods ◽  
Late Summer ◽  
Breeding Population ◽  
Migratory Behaviour ◽  
Single Location ◽  
Local Breeding ◽  
And Migration ◽  
Sewage Lagoons ◽  
Summer Feeding

Feeding concentrations of Common Nighthawks, Chordeiles minor, during the evening in late summer were observed and counted near the Pinawa, Manitoba, sewage lagoons during 28 of the 34 years from 1976 to 2009. Counts were frequent but non-systematic in 1976-1981, infrequent in 1982-1991, and both frequent and systematic in most years during the period 1992-2009. Results of 226 counts are analysed and interpreted as showing a major decline in the local breeding population during the 1980s but more stable numbers of transient birds, assumed to originate farther north. The timing and other characteristics of feeding and migratory behaviour are discussed. The limitations of interpreting data from a single location are acknowledged and some systematic survey methods are recommended, emphasizing the importance of all-round, long-range visibility to help distinguish between migration and foraging.

Isonymy and population structure of Irish isolates during the 1890s

1982 ◽  
Vol 14 (2) ◽  
pp. 241-247 ◽  
Author(s):  
John H. Relethford
Keyword(s):  
Population Structure ◽  
Genetic Variation ◽  
Isolation By Distance ◽  
Breeding Population ◽  
Isolated Populations ◽  
Estimated Parameters ◽  
Distance Model ◽  
Local Breeding ◽  
And Migration ◽  
Close Fit

SummaryThe estimation of genetic similarity from correspondence of surnames (isonymy) allows investigation of historical population structure. This study uses surname data from seven isolates located along the west coast of Ireland during the 1890s to assess geographic and historic influences on population structure. Observed genetic variation among populations shows a close fit with the expected isolation by distance model, with estimated parameters of isolation and migration being similar to those obtained in other studies of isolated populations. Local genetic variation appears to be due primarily to the size of the local breeding population, with deviations being explained in terms of recent emigration.

Renewing hope: the rediscovery of Atelopus varius in Costa Rica

2013 ◽  
Vol 34 (4) ◽  
pp. 573-578 ◽  
Author(s):  
José F. González-Maya ◽  
Jerrold L. Belant ◽  
Sarah A. Wyatt ◽  
Jan Schipper ◽  
Josué Cardenal ◽  
...  
Keyword(s):  
Costa Rica ◽  
Resource Use ◽  
Private Property ◽  
Breeding Population ◽  
Critically Endangered ◽  
Single Location ◽  
Frog Species ◽  
Conservation Actions ◽  
Remnant Population ◽  
Protected Zone

More than 90% of harlequin frog species (Atelopus spp.), endemic to the Americas, are currently threatened with extinction. We report the discovery of the only currently known breeding population of the Critically Endangered A. varius in Costa Rica. This population was located in 2008 on a private property in Las Tablas Protected Zone near San Vito, Coto Brus at 1300 m elevation. Previously, the only known remaining/remnant population of this species and genus was a single location near Manuel Antonio, Puntarenas, Costa Rica, where two individuals were documented in 2004. Subsequent searches at this location have yielded no additional sightings. Delineating the spatial limits of this population, quantifying demographics and resource use, and implementing conservation actions are necessary to ensure persistence of this population. Conducting additional surveys in this region to ascertain occurrence of additional populations is warranted.

Longitudinal clines in the frequency distribution of ‘super-clones’ in an aphid crop pest

2015 ◽  
Vol 105 (6) ◽  
pp. 694-703 ◽  
Author(s):  
A. Gilabert ◽  
C.-A. Dedryver ◽  
S. Stoeckel ◽  
M. Plantegenest ◽  
J.-C. Simon
Keyword(s):  
Frequency Distribution ◽  
Rhopalosiphum Padi ◽  
Late Summer ◽  
Cereal Aphid ◽  
Main Mode ◽  
Frequency Distributions ◽  
Cropping Season ◽  
Northern Half ◽  
And Migration ◽  
Open Question

AbstractParthenogenesis is the main mode of reproduction of aphids. Their populations are therefore composed of clones whose frequency distribution varies in space and time. Previous population genetic studies on aphids have highlighted the existence of highly abundant clones (‘super-clones’), distributed over large geographic areas and persisting over time. Whether the abundance of ‘super-clones’ results from their ecological success or from stochastic forces, such as drift and migration, is an open question. Here, we looked for the existence of clines in clonal frequency along a climatic gradient in the cereal aphid Rhopalosiphum padi (Linnaeus, 1758) and examined the possible influence of geographical distance and environmental variables in the buildup and maintenance of such clonal clines. We investigated the spatial distribution of the commonest genotypes of R. padi by sampling populations along an east–west transect in maize fields in the northern half of France in both spring and late summer. Individual aphids were genotyped at several polymorphic loci, allowing the assessment of frequency distributions of multilocus genotypes (MLGs) across the cropping season. We found several MLGs showing longitudinal clines in their frequency distribution in both spring and summer. In particular, two dominant asexual genotypes of R. padi showed inverted geographical clines, which could suggest divergent adaptations to environmental conditions. We concluded that while the distribution of some ‘super-clones’ of R. padi seems most likely driven by the action of migration and genetic drift, selection could be also involved in the establishment of longitudinal clines of others.

scholarly journals Some of them came home: the Cayman Turtle Farm headstarting project for the green turtle Chelonia mydas

Oryx ◽  
2005 ◽  
Vol 39 (2) ◽  
pp. 137-148 ◽  
Author(s):  
Catherine D.L. Bell ◽  
Joe Parsons ◽  
Timothy J. Austin ◽  
Annette C. Broderick ◽  
Gina Ebanks-Petrie ◽  
...  
Keyword(s):  
Chelonia Mydas ◽  
Breeding Population ◽  
Marine Turtle ◽  
Management Technique ◽  
Cayman Islands ◽  
Age At Maturity ◽  
Green Turtles ◽  
Local Breeding ◽  
The Caribbean ◽  
Cayman Turtle Farm

Headstarting is a management technique employed to enhance recruitment of turtles into diminished or extirpated marine turtle populations. Although there have been numerous projects worldwide, there has been a paucity of detailed investigations into its efficacy. Between 1980 and 2001, 16,422 captive-raised hatchlings and 14,347 yearling green marine turtles Chelonia mydas were released from the Cayman Turtle Farm. Approximately 80% of all turtles released were subject to some form of tagging, including living tags. A total of 392 tagged animals have been recaptured at intervals of up to 19 years. Of this total, 160 individuals were captured in the Cayman Islands and 232 were recorded from other locations within the wider Caribbean and southeastern USA. There was significant variation in the release-recapture intervals at the three countries with most returns (Cayman, Cuba and Nicaragua). A positive relationship exists between time at large and size at recapture and data suggest growth rates comparable to those of wild green turtles in the region. There have been at least six living tag returns, four involving turtles released as yearlings and two involving turtles released as hatchlings. This demonstrates an age at maturity that may be as short as 15–19 years, depending on stage of release. Results show that some headstarted turtles are moving around the Caribbean, surviving for long periods of time, contributing to the local breeding population, and are possibly displaying shifts in habitat utilization with age similar to those recorded by wild individuals.

scholarly journals Effects of Hatching Date and Egg Size on Growth, Recruitment, and Adult Size of Lesser Scaup

The Condor ◽  
2000 ◽  
Vol 102 (4) ◽  
pp. 930-935 ◽  
Author(s):  
Russell D. Dawson ◽  
Robert G. Clark
Keyword(s):  
Selective Advantage ◽  
Breeding Population ◽  
Adult Size ◽  
Hatching Date ◽  
Egg Volume ◽  
Brood Rearing ◽  
Aythya Affinis ◽  
Lesser Scaup ◽  
Local Breeding ◽  
Nutrient Reserves

AbstractEvidence suggests that birds breeding early in the season or laying larger eggs are at a selective advantage because quality and survival of their offspring are higher. We tested whether wild Lesser Scaup (Aythya affinis) hatching early in the season or from larger eggs had enhanced growth as ducklings and larger size or higher probability of recruiting to the local breeding population in years after hatching. After correcting for age at capture, body mass, head length, and culmen of ducklings were inversely related to hatching date, but were unrelated to egg volume. As adults, late-hatched birds had shorter wing lengths (second-year birds only) and tended to have smaller head lengths (all after-hatch year birds) than early hatching birds. We suggest that later-hatching birds are smaller due to increased competition for food during brood rearing. Recruitment probability increased as natal egg volume increased and decreased among birds with later natal hatching dates. We speculate these results are due to higher mortality of ducklings hatched from small eggs, and because early-hatched birds have more time to acquire nutrient reserves that would reduce vulnerability to costs of migration.

Social-Behavior and Colony Formation in a Population of Crested Terns, Sterna-Bergii, in Southwestern Australia

1987 ◽  
Vol 14 (4) ◽  
pp. 529 ◽  
Author(s):  
JN Dunlop
Keyword(s):  
Social Behavior ◽  
Breeding Season ◽  
Small Groups ◽  
Social Behaviour ◽  
Colony Formation ◽  
Late Summer ◽  
Breeding Population ◽  
Southwestern Australia ◽  
Nest Sites ◽  
The Social

In a breeding population of crested terns near Fremantle, W.A., social behaviour involved complex patterns of social displays and paired behaviour. The social phase was probably truncated over much of the extended breeding season by the presence of incubating conspecifics, and may serve to synchronise laying in their absence. The responses of pre-laying crested terns to incubating conspecifics were studied by means of artificial 'colonies' of polyurethane models. These proved to be most attractive to prebreeding pairs searching for nest sites, and the earliest eggs were invariably laid among the decoys. Pre-breeding terns in the social phase were not attracted to the decoys. It is suggested that loose groups of incubating conspecifics acted as a key stimulus, releasing settlement and laying in birds in an advanced state of reproductive readiness. This key stimulus could change the learned location of colonies but during late summer and early autumn other factors, probably related to food availability, controlled the onset of laying. Small, spatially distinct, nesting groups were less synchronous in their laying than larger colonies. Such small groups are thought to result from discontinuities in reproductive phase between groups of terns, which are not apparent when the number of pre-laying birds is large.

Comparison of breeding population survey methods for the Auckland Island shag (Phalacrocorax colensoi)

Polar Biology ◽  
2015 ◽  
Vol 38 (11) ◽  
pp. 1847-1852 ◽  
Author(s):  
B. L. Chilvers ◽  
G. B. Baker ◽  
J. A. Hiscock ◽  
P. J. McClelland ◽  
M. Holdsworth ◽  
...  
Keyword(s):  
Population Survey ◽  
Survey Methods ◽  
Breeding Population ◽  
Auckland Island

Viewpoint: Population projections and migration commissions

2014 ◽  
Vol 11 (1) ◽  
pp. 54-64
Author(s):  
Michael S Teitelbaum
Keyword(s):  
Long Range ◽  
Quantitative Methods ◽  
Population Projections ◽  
Demographic Projection ◽  
Demographic Projections ◽  
And Migration ◽  
The One

On the one hand the techniques of demographic projection are essential: they offer powerful and objective quantitative methods that, implemented and interpreted properly, can provide a hypothetical migration commission with critical insights into possible futures - futures that might otherwise not be apparent by examining contem-poraneous data. At the same time, if implemented improperly or interpreted naively, such long range demographic projections could represent instruments of confusion, exaggeration, and even deliberate distortion. Both the strengths and weaknesses in-herent in the use of demographic projections need to be understood by any immigra-tion commission that might emerge.

In vitro studies in Tubularia: a morphological role for digestive cells

Development ◽  
1973 ◽  
Vol 29 (1) ◽  
pp. 1-13
Author(s):  
Marc H. Glickman ◽  
Georgia E. Lesh-Laurie
Keyword(s):  
Interstitial Cell ◽  
Cell Attachment ◽  
Cell Monolayer ◽  
Leading Edge ◽  
Late Summer ◽  
Autoradiographic Study ◽  
Digestive Cell ◽  
Digestive Cells ◽  
And Migration

A chemically defined in vitro system for Tubularia has been developed. At 24 h after explantation of coenosarc, digestive cells attached to the substrate and migrated from the explant. The digestive cells migrated by a gliding motion with a fan-like membrane acting as a leading edge. Within 48 h a digestive cell monolayer was formed and invasion of this area by epithelio-muscular, gland and interstitial cells occurred. Autoradiographic study of 48–72 h cultures treated with [3H]thymidine showed nuclear incorporation of the label in digestive, epithelio-muscular, interstitial, cnidoblast and gland cells. When explants were grown on collagen-coated coverslips, accelerated attachment and migration of digestive cells was observed. Explants were also grown on Millipore filters. No digestive cell attachment occurred but epithelio-muscular, gland and interstitial cell attachments to the filter were observed. From these experiments, a morphological role for the digestive cells as a substrate for other cells of the coenosarc is postulated. Hydranth extract was supplemented to the culture medium. Studies with this material were performed with coenosarc from ‘late summer’ animals in which only 10–15% of the explants normally entered culture. However, with the addition of the extract, 100% of the explants went into culture. Interstitial cell populations increased 2–3 times in extract-treated explants.

An examination of stable hydrogen isotope (δD) variation in adult and juvenile feathers from a migratory songbird

2012 ◽  
Vol 90 (5) ◽  
pp. 585-594 ◽  
Author(s):  
Elizabeth A. Gow ◽  
Bridget J.M. Stutchbury ◽  
T. Done ◽  
T.K. Kyser
Keyword(s):  
Geographic Origin ◽  
Breeding Population ◽  
Tissue Growth ◽  
Hylocichla Mustelina ◽  
Intraindividual Variation ◽  
Single Location ◽  
Site Variation ◽  
Breeding Grounds ◽  
Spatio Temporal ◽  
Migratory Songbird

Stable hydrogen isotopes (δD) can help predict geographic origin of tissue growth but within-site variation of feather δD (δDf) exists. Multiple hypotheses explain δDf variation: moult timing, physiology, and spatio-temporal differences in source deuterium, but there have been few direct tests of these factors. We assessed δDf variation within a breeding population of Wood Thrush ( Hylocichla mustelina (Gmelin, 1789)), by sampling feathers from hatch-year birds, returning adults (after migration), and to eliminate confounding variables from newly grown adult primary feathers during moult. We evaluated potential mechanisms explaining δDf variation by examining intraindividual variation (different feather types), precipitation δD, prey δD, corticosterone (CORT), and breeding productivity. In addition, we directly compared δDf of newly grown primary feathers to δD blood hematocrit (δDb). We found significant differences in δDf between years and age classes and observed no significant intraindividual variation. δDf and δDb were not significantly correlated. CORT weakly contributed to δDf, but there are other factors influencing δDf. Ten percent of all feather samples had outlying δDf values, and were likely grown away from the breeding grounds. Our results document intrapopulation and intraindividual variation of δDf at a single location and indicated that age class and year-to-year differences contributed to high δDf variance.

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