Breeding Ecology of Sympatric Greater and Lesser Scaup (Aythya marila and Aythya affinis) in the Subarctic Northwest Territories

We studied the breeding ecology of greater and lesser scaup on islands of the North Arm of Great Slave Lake, Northwest Territories, and on the nearby mainland during 1990-98. The occurrence of nests of both species on the North Arm islands was determined primarily by the distribution of nesting gulls and terns and secondarily by habitat features. Nest parasitism was frequent on the islands, but not on the mainland. Average clutch size was 8.99 ± 0.12 (n = 169) for greater scaup and 9.20 ± 0.17 (n = 93) for lesser scaup on the North Arm, and 8.71 ± 0.18 (n = 55) for lesser scaup on the mainland. No greater scaup nests were found on the mainland. Apparent nest success on the islands was higher (greater scaup 75%, n = 271; lesser scaup 77%, n = 158) than on the mainland (lesser scaup 37%, n = 59). Apparent egg success was 63% (n = 1485) for greater scaup and 67% (n = 934) for lesser scaup on the islands, and 40% (n = 435) for lesser scaup on the mainland. Hatchability of eggs was 98% (n = 556) for greater scaup and 94% (n = 416) for lesser scaup on islands, and 98% (n = 435) for lesser scaup on the mainland. Our findings, when compared to those of previous studies, do not indicate that either clutch size or egg hatchability has declined in recent years. Therefore, it seems unlikely that broad changes in these reproductive parameters are responsible for local or continental declines in lesser scaup populations. However, nest success on our mainland study area may have been too low to maintain the local population.De 1990 à 1998, on a étudié l'écologie de reproduction du fuligule milouinan et du petit fuligule sur des îles situées dans le Bras-Nord du Grand Lac des Esclaves (Territoires du Nord-Ouest) ainsi que sur la terre ferme avoisinante. La présence, dans les îles du Bras-Nord, de nids appartenant aux deux espèces était surtout déterminée par la distribution des mouettes et des sternes, et en second lieu par les caractéristiques de l'habitat. Le piratage des nids était fréquent sur les îles, mais pas sur la terre ferme. La taille moyenne des couvées était de 8,99 ± 0,12 (n = 169) pour le fuligule milouinan et de 9,20 ± 0,17 (n = 93) pour le petit fuligule dans le Bras-Nord, et de 8,71 ± 0,18 (n = 55) pour le petit fuligule sur la terre ferme. On n'a pas trouvé de nids de fuligule milouinan sur la terre ferme. Le succès apparent de la nidification sur les îles était plus grand (fuligule milouinan: 75 p. cent, n = 271; petit fuligule: 77 p. cent, n = 158) que sur la terre ferme (petit fuligule: 37 p. cent, n = 59). Le succès apparent de la ponte était de 63 p. cent (n = 1485) pour le fuligule milouinan et de 67 p. cent (n = 934) pour le petit fuligule sur les îles, et de 40 p. cent (n = 435) pour le petit fuligule sur la terre ferme. L'éclosabilité était de 98 p. cent (n = 556) pour le fuligule milouinan et de 94 p. cent (n = 416) pour le petit fuligule sur les îles, et de 98 p. cent (n = 435) pour le petit fuligule sur la terre ferme. Quand on les compare à ceux d'études antérieures, nos résultats ne révèlent aucun déclin au cours des dernières années quant à la taille de la couvée ou l'éclosabilité. Il semble donc peu probable que des changements majeurs dans ces paramètres de reproduction soient responsables des déclins au niveau local ou continental dans les populations du petit fuligule. Le succès de la nidification dans la zone couverte par notre étude située sur la terre ferme peut toutefois avoir été trop faible pour maintenir le niveau de population locale

Breeding Biology of Brant on Banks Island, Northwest Territories, Canada

The numbers of brant (Branta bernicla) in the Pacific Flyway are relatively small compared to other populations of arctic geese and have declined from historic levels. Little information is available on brant from Banks Island, although the size of the island and its location in the western Canadian Arctic make it a potentially important nesting area for this species. In 1992-93, we documented the distribution of nesting brant on the southern half of Banks Island through aerial surveys and carried out ground studies at the colonies to document nesting chronology and reproductive parameters. Ten colonies were found in 1992 (n = 159 nests) and 42 colonies (including seven colonies that had been active in 1992) and five solitary nests were found in 1993 (n = 514 nests). Two-thirds (67%) of the nesting locations supported 10 or fewer nests. Most colonies (36 of 45) were located on small islands (mean = 248 m²) in inland lakes or large ponds, and the remaining colonies (n = 9) were located on the mainland near active snowy owl (Nyctea scandiaca) nests. In 1993, when June temperatures were milder and snow melted sooner than in 1992, mean date of clutch initiation was significantly earlier (12 June vs. 20 June in 1992; p < 0.001) and mean clutch size was significantly larger (3.8 vs. 3.5 in 1992; p = 0.02). An index of productivity for the 21 414 km² area surveyed in both years was much higher in 1993 (1339 young) than in the very late spring of 1992 (347 young). The number of adult brant on the survey area was similar in both years, and the lower productivity in 1992 was due primarily to fewer pairs' nesting that year. Smaller clutch size and lower nesting success may also have lowered productivity in 1992, but their effects appeared to be secondary. No correlation was found between colony size and clutch size, mean number of goslings hatched, or the percentage of nests that proved successful.Le nombre de bernaches cravants (Branta bernicla) dans la voie migratoire du Pacifique est relativement faible quand on le compare aux autres populations d'oies de l'Arctique, et il a diminué par rapport à ses niveaux historiques. On a peu de renseignements sur la bernache de l'île Banks, même si la taille de l'île et son emplacement dans l'Arctique canadien occidental pourraient en faire une aire de nidification importante pour cette espèce. En 1992 et 1993, on a consigné au moyen de relevés aériens la distribution des bernaches qui nichaient dans la moitié sud de l'île Banks, et on a effectué des études sur le terrain, là où se trouvaient les colonies, afin de consigner la chronologie de nidification et les paramètres de reproduction. En 1992, on a trouvé 10 colonies (n = 159 nids) et, en 1993, 42 colonies (y compris sept qui avaient été actives en 1992), ainsi que cinq nids solitaires (n = 514 nids). Deux tiers (67 p. cent) des sites de nidification accueillaient 10 nids ou moins. La plupart des colonies (36 sur 45) se trouvaient sur des îlots (moyenne = 248 m²) situés dans des lacs ou de grands étangs de l'île, tandis que le reste (n = 9) étaient situées sur la terre ferme près de nids actifs de harfangs des neiges (Nyctea scandiaca). En 1993, avec des températures en juin plus douces et une fonte nivale plus rapide qu'en 1992, la date moyenne du début de la couvée a été nettement plus hâtive (le 12 juin par rapport au 20 juin en 1992; p < 0,001) et la taille moyenne de la couvée a été nettement plus grande (3,8 par rapport à 3,5 en 1992; p = 0,02). Un index de productivité pour les 21 414 km² de la zone de relevés des deux années était beaucoup plus élevé en 1993 (1339 petits) qu'au cours du printemps très tardif de 1992 (347 petits). Le nombre de bernaches cravants adultes dans la zone des relevés était semblable dans les deux années, et la productivité plus faible en 1992 était surtout due à un nombre moindre de paires ayant fait un nid cette année-là. La taille plus petite de la couvée et le taux de réussite plus faible quant à l'établissement du nid pourraient aussi expliquer la baisse de productivité de 1992, mais ces effets paraissent secondaires. On n'a trouvé aucune corrélation entre la taille de la colonie et la taille de la couvée, le nombre moyen d'oisons éclos, ou le pourcentage de nids où la reproduction a réussi

The Last Best Hope for Progressivity in Tax

We argue that a spending tax, as opposed to an income or wage tax, is the “last best hope” for a return to significantly more progressive marginal tax rates than obtain today. The simple explanation for this central claim looks to incentive effects, especially for “rich people,” as both economists and commentators are inclined to focus. High marginal tax rates under an income tax fall on and hence deter the socially productive activities of work and savings. High marginal rates under a wage tax fall on and hence deter the socially productive activity of work alone. But high marginal rates under a spending tax fall on and hence deter high-end spending, which is arguably a social “bad,” and do not necessarily deter the social goods of work and savings. This is a possible empirical result. In this Article, we present the analytic arguments for it and sketch out a research agenda that might verify it. The idea is that because one can escape or defer paying taxes under a progressive spending tax by saving, an activity with positive social externalities, the efficiency costs of high marginal rates under a spending tax can be mitigated. Unless people work only in order to be able to spend on themselves, and even then only if they fully internalize in their present labor supply decisions the ultimate tax they will pay - and we argue that each of these assumptions is unlikely to hold in the extreme - a spending tax can bear more steeply progressive rates with less cost in efficiency or social wealth than can an income or wage tax. A progressive spending tax also holds out the possibility of sorting the rich or high ability into two groups, elastic savers and inelastic spenders, which could yield welfare gains unavailable under income or wage taxes, which under current technologies can only sort the high ability into workers and non-workers. Progressive spending taxes also fall on consumption financed by windfall gains, as to which unexpected good fortune exante incentive effects are likely to be weak

Testing metapopulation concepts: effects of patch characteristics and neighborhood occupancy on the dynamics of an endangered lagomorph

Metapopulation ecology is a field that is richer in theory than in empirical results. Many existing empirical studies use an incidence function approach based on spatial patterns and key assumptions about extinction and colonization rates. Here we recast these assumptions as hypotheses to be tested using 18 years of historic detection survey data combined with four years of data from a new monitoring program for the Lower Keys marsh rabbit. We developed a new model to estimate probabilities of local extinction and colonization in the presence of nondetection, while accounting for estimated occupancy levels of neighboring patches. We used model selection to identify important drivers of population turnover and estimate the effective neighborhood size for this system. Several key relationships related to patch size and isolation that are often assumed in metapopulation models were supported: patch size was negatively related to the probability of extinction and positively related to colonization, and estimated occupancy of neighboring patches was positively related to colonization and negatively related to extinction probabilities. This latter relationship suggested the existence of rescue effects. In our study system, we inferred that coastal patches experienced higher probabilities of extinction and colonization than interior patches. Interior patches exhibited higher occupancy probabilities and may serve as refugia, permitting colonization of coastal patches following disturbances such as hurricanes and storm surges. Our modeling approach should be useful for incorporating neighbor occupancy into future metapopulation analyses and in dealing with other historic occupancy surveys that may not include the recommended levels of sampling replication

Testing metapopulation concepts: effects of patch characteristics and neighborhood occupancy on the dynamics of an endangered lagomorph

Metapopulation ecology is a field that is richer in theory than in empirical results. Many existing empirical studies use an incidence function approach based on spatial patterns and key assumptions about extinction and colonization rates. Here we recast these assumptions as hypotheses to be tested using 18 years of historic detection survey data combined with four years of data from a new monitoring program for the Lower Keys marsh rabbit. We developed a new model to estimate probabilities of local extinction and colonization in the presence of nondetection, while accounting for estimated occupancy levels of neighboring patches. We used model selection to identify important drivers of population turnover and estimate the effective neighborhood size for this system. Several key relationships related to patch size and isolation that are often assumed in metapopulation models were supported: patch size was negatively related to the probability of extinction and positively related to colonization, and estimated occupancy of neighboring patches was positively related to colonization and negatively related to extinction probabilities. This latter relationship suggested the existence of rescue effects. In our study system, we inferred that coastal patches experienced higher probabilities of extinction and colonization than interior patches. Interior patches exhibited higher occupancy probabilities and may serve as refugia, permitting colonization of coastal patches following disturbances such as hurricanes and storm surges. Our modeling approach should be useful for incorporating neighbor occupancy into future metapopulation analyses and in dealing with other historic occupancy surveys that may not include the recommended levels of sampling replication

Annual Survival of Snail Kites in Florida: Radio Telemetry versus Capture-Resighting Data

We estimated annual survival of Snail Kites (Rostrhamus sociabilis) in Florida using the Kaplan-Meier estimator with data from 271 radio-tagged birds over a three-year period and capture-recapture (resighting) models with data from 1,319 banded birds over a six-year period. We tested the hypothesis that survival differed among three age classes using both data sources. We tested additional hypotheses about spatial and temporal variation using a combination of data from radio telemetry and single- and multistrata capture-recapture models. Results from these data sets were similar in their indications of the sources of variation in survival, but they differed in some parameter estimates. Both data sources indicated that survival was higher for adults than for juveniles, but they did not support delineation of a subadult age class. Our data also indicated that survival differed among years and regions for juveniles but not for adults. Estimates of juvenile survival using radio telemetry data were higher than estimates using capture-recapture models for two of three years (1992 and 1993). Ancillary evidence based on censored birds indicated that some mortality of radio-tagged juveniles went undetected during those years, resulting in biased estimates. Thus, we have greater confidence in our estimates of juvenile survival using capture-recapture models. Precision of estimates reflected the number of parameters estimated and was surprisingly similar between radio telemetry and single-stratum capture-recapture models, given the substantial differences in sample sizes. Not having to estimate resighting probability likely offsets, to some degree, the smaller sample sizes from our radio telemetry data. Precision of capture-recapture models was lower using multistrata models where region-specific parameters were estimated than using single-stratum models, where spatial variation in parameters was not taken into account

Lesser Snow Geese, Chen caerulescens caerulescens, and Ross's Geese, Chen rossii, of Jenny Lind Island, Nunavut

We surveyed the Lesser Snow (Chen caerulescens caerulescens) and Ross’s geese (Chen rossii) of Jenny Lind Island, Nunavut, using aerial photography in June 1988, 1998, and 2006, and a visual helicopter transect survey in July 1990. The estimated number of nesting geese was 39 154 ± SE 2238 in 1988, 19 253 ± 2323 in 1998, and 21 572 ± 1898 in 2006. In 1988 an estimated 2.7% of the nesting geese were Ross’s. The July 1990 population of adult-plumaged birds was 25 020 ± 3114. The estimated percentage blue morph among Snow and Ross’s geese was 19.0% in 1988, 25.1% in 1989, 23.0% in 1990 and 21.1% in 2006. Estimated pre-fledged Snow Goose productivity was 47% young in 1989 and 46% in 1990. Combined numbers of Snow and Ross’s geese on Jenny Lind Island grew over 250 fold, from 210 adults in 1962-1966 to 54 100 adults in 1985. Numbers subsequently declined, to 42 200 in 1988, 25 000 in 1990, 20 300 in 1998, and 26 400 in 2006. Population decline between 1985 and 1990 was consistent with anecdotal reports by others that die-offs of Snow Geese occurred in 1984, 1985 and 1989, and with our August 1989 fieldwork which found evidence of habitat degradation and malnourishment of young geese. In spite of limited food resources on Jenny Lind Island, the colony continued to exist in 2006 at near its 1990 and 1998 levels. Further studies there could provide insights for management of the overabundant mid-continent Snow Goose population and its arctic habitats

Men at risk The Physical, Mental and Social Health of Men in Massachusetts

In 2009, Clark University was accepted as the university to represent Massachusetts in the National Policy Institute for Family Impact Seminars at the University of Wisconsin – Madison (http://familyimpactseminars.org). Family Impact Seminars are a series of annual seminars, briefing reports, and discussion sessions that provide up-to-date, solution-oriented research on current issues for state legislators, their aides, and legislative support bureau personnel. The seminars provide objective, nonpartisan research on current issues and do not lobby for particular policies. Seminar participants discuss policy options and identify common ground where it exists

Change in Abundance of Pacific Brant Wintering in Alaska: Evidence of a Climate Warming Effect?

Winter distribution of Pacific Flyway brant (Branta bernicla nigricans) has shifted northward from low-temperate areas to sub-Arctic areas over the last 42 years. We assessed the winter abundance and distribution of brant in Alaska to evaluate whether climate warming may be contributing to positive trends in the most northern of the wintering populations. Mean surface air temperatures during winter at the end of the Alaska Peninsula increased about 1°C between 1963 and 2004, resulting in a 23% reduction in freezing degree days and a 34% decline in the number of days when ice cover prevents birds from accessing food resources. Trends in the wintering population fluctuated with states of the Pacific Decadal Oscillation, increasing during positive (warm) phases and decreasing during negative (cold) phases, and this correlation provides support for the hypothesis that growth in the wintering population of brant in Alaska is linked to climate warming. The size of the wintering population was negatively correlated with the number of days of strong northwesterly winds in November, which suggests that the occurrence of tailwinds favorable for migration before the onset of winter was a key factor in whether brant migrated from Alaska or remained there during winter. Winter distribution of brant on the Alaska Peninsula was highly variable and influenced by ice cover, particularly at the heavily used Izembek Lagoon. Observations of previously marked brant indicated that the Alaska wintering population was composed primarily of birds originating from Arctic breeding colonies that appear to be growing. Numbers of brant in Alaska during winter will likely increase as temperatures rise and ice cover decreases at high latitudes in response to climate warming.Au cours des 42 dernières années, la répartition de la bernache cravant du Pacifique (Branta bernicla nigricans) s’est déplacée vers le nord en hiver, passant ainsi de régions faiblement tempérées à des régions subarctiques. Nous avons évalué l’abondance et la répartition de la bernache en Alaska l’hiver afin de tenter de déterminer si le réchauffement climatique contribue aux tendances positives au sein des populations d’hivernage les plus au nord. Les températures moyennes de l’air à la surface en hiver se sont accrues d’environ 1°C entre 1963 et 2004, ce qui s’est traduit par une réduction de 23 % du nombre de jours atteignant le point de congélation et d’une diminution de 34 % du nombre de jours pendant lesquels la couverture de glace empêche les oiseaux d’avoir accès aux ressources alimentaires. Les tendances caractérisant la population d’hivernage fluctuaient en fonction des états de l’oscillation pacifique décennale en ce sens qu’elles augmentaient pendant les phases positives (tièdes) et qu’elles baissaient pendant les phases négatives (froides). Cette corrélation vient appuyer l’hypothèse selon laquelle la croissance de la population d’hivernage de la bernache en Alaska est liée au réchauffement climatique. L’effectif de la population d’hivernage a été négativement corrélé au nombre de jours de vents forts en provenance du nord-ouest en novembre, ce qui laisse croire que l’occurrence de vents arrières favorables à la migration avant le début de l’hiver constituait un facteur-clé déterminant si une bernache migrait de l’Alaska ou y restait pendant l’hiver. Dans la péninsule de l’Alaska, la répartition de la bernache en hiver variait énormément et dépendait de la couverture de glace, surtout à la lagune Izembek particulièrement achalandée. Les observations de bernaches déjà marquées ont permis de constater que la population d’hivernage de l’Alaska était principalement composée d’oiseaux provenant des colonies de reproduction de l’Arctique qui semblent prendre de l’ampleur. Le nombre de bernaches en Alaska pendant l’hiver augmentera vraisemblablement au fur et à mesure que les températures augmenteront et que les couvertures de glace diminueront en haute latitude en raison du réchauffement climatique