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In long-lived animals, survival rate is a key demographic parameter affecting population dynamics. The objective of this study was to estimate the apparent survival rate of adult Long-tailed Jaegers (Stercorarius longicaudus) breeding at one of the most northerly sites on earth, northern Ellesmere Island, Canada. Because of the large temporal fluctuations in numbers of lemmings, their primary food source during the summer, we also investigated the effect of annual variations in lemming abundance on survival rate. Analysis was based on 336 individuals marked as adults over 11 years with metal and color bands and capture-mark--recapture techniques. There was strong support for a model with two age classes, as survival of newly marked birds was 18% lower than that of previously marked ones. This difference could be due to a true age effect (if a high proportion of young adults was present in our initial samples) or, perhaps more likely, to the presence of transient individuals in the population. The estimated probability of apparent annual survival of local birds (corrected for color-band loss) was 0.91, comparable to values for other seabirds, and was constant overtime. We detected a weak trend for a decrease in apparent survival rate of newly marked birds in years of high lemming abundance but no effect on the survival of previously marked birds. This suggests that conditions at sea during the nonbreeding season may be more important in affecting annual survival. A new longevity record of 22 years was established for the species. [ABSTRACT FROM AUTHOR]

The Dunlin (Calidris alpina) is a polytypic shorebird with complex patterns of distribution and migration throughout its holarctic range. We analyzed mark-resighting data obtained between 1977 and 2010 from birds captured at two major staging areas in western Alaska to test the hypothesis that the migration patterns of Alaskan populations are a mixture ofparallel and chain, similar to those of Dunlin populations in the western Palearctic. Birds marked on the Yukon-Kuskokwim Delta were found wintering in both Asia and North America, which documented the unexpected mixing of C. a. arcticola from northern Alaska and C. a. pacifica from western Alaska and contradicted our initial prediction ofparallel migration pathways for these two subspecies. In its North American winter range C. a. pac~/ica segregated according to location of marking, confirming our prediction of a chain migration pattern within this population. Individuals of C. a. pac~fica marked on the delta were resighted significantly farther north, mostly in southern British Columbia and Washington, than birds marked on the second, more southerly staging area on the Alaska Peninsula, which were resighted primarily in the San Francisco Bay area of northern California. We recommend additional studies use a combination of intrinsic and extrinsic markers to quantify the strength of migratory connectivity between breeding, staging, and wintering areas. Such information is needed to guide conservation efforts because the Dunlin and other waterbirds are losing intertidal habitats at an unprecedented rate and scale, particularly in the Yellow Sea and other parts of Asia. [ABSTRACT FROM AUTHOR]

The basic assumption in the morphology of avian migrants is that longer, more pointed and concave wings are well adapted for long-distance migratory flights. We investigated how wingtip morphology of the Common Snipe was associated with aspects of its migration, such as amount of accumulated fat, refueling rates, length of stay at the stopover site, and timing of post-juvenile molt. Our study took place at the Jeziorsko reservoir, central Poland, where over 400 first-year Common Snipe (Gallinago gallinago) were caught in 2008 and 2009. Wing shape was found to correlate with different components of the species' stopover strategies. After controlling for the date of capture we found that first-year birds with wings adapted for efficient migration (pointed/concave wingtips) refueled more quickly and stayed for shorter times at the stopover site. Pointed/concave wing shape was also associated with accumulation of smaller fat reserves and later initiation of post-juvenile molt during the period of migration. By contrast, snipe having a wing shape adapted for predator evasion (rounded/convex wingtips) refueled more slowly, remained longer, and accumulated greater amounts of fat, which in turn facilitated earlier molting. [ABSTRACT FROM AUTHOR]

Stable isotopes of hydrogen have been used as a tool to determine migratory connectivity, or to link breeding and wintering grounds. Because isotopes serve as intrinsic markers, eliminating the need for birds to be relocated after an initial marking, they hold the potential to be an extremely useful tool. From 1998 to 2003 we gathered feathers from juvenile Merlins (Falco columbarius) and Northern Harriers (Circus cyaneus) during their fall migration in the Florida Keys and analyzed them isotopically in an attempt to determine their natal origins. Our results failed to reveal the natal origins of at least one of these two birds of prey. [ABSTRACT FROM AUTHOR]

Marine radar is a tool widely used in the study of bird migration, but in most cases it cannot identify detected objects to species. For this reason airspeed is used as one of the main criteria to separate birdlike from insectlike targets, but this criterion has not been tested outside the temperate regions where it was developed. We used a theoretical approach for calculating minimum-power speeds (Vmp) and maximum-range speeds (Vmrr ) of birds and insects to estimate an interval of airspeeds from which an appropriate value of the criterion can be selected and to propose a criterion based on flight speed for the Isthmus of Tehuantepec in southern Mexico. This approach, with data from 36 species of insects and 60 of passerines either known to occur or similar to species occurring in southern Mexico, found that although Vmp of insects and birds overlaps at 5.5 m sec-1, birds generally fly faster than insects. After combining our results with data from the literature, we conclude that the best airspeed to be used as criterion for distinguishing birdlike from insectlike targets lies within the range of 5.5-9.0 m sec-1 and that 7 m sec-1 is an appropriate airspeed for our study area. These airspeeds are applicable in southern Mexico and in regions where birds and insects have physical dimensions similar to the species addressed in our study. [ABSTRACT FROM AUTHOR]

The article presents a study which identifies patterns through DNA sequencing of prey selection in migrant sharp-shinned hawks from Capilla Peak in Manzano Mountains in New Mexico. The study compares a section of 16S rRNA mitochondrial gene of the specie's feathers. Results show that hawks took most of its preys in proportion to their availability along the migration route.

The article presents a study which uses radar and satellite land-cover data to determine the habitats with which birds are associated during migration stopover habitat in the southwestern U.S. The data has been used to study geographical patterns in densities of migrant passerines and quantifying its associations between migrants and their stopover habitats. Results of the study show that it is too simplistic to consider the arid West as inhospitable landscape which has small habitat resources.

The article presents a study on the broad scale movements of juvenile songbirds prior to migration. The study used radio telemetry and the topographical characteristics of the study sites to assess four hypothesis including the beginning of migration, habitat optimization, and the selection of breeding territory. The result showed that the movement of Yellow-rumped Warbler (Dendroica coronata) was directed toward down river valleys while Balckpoll Warbler (D. striata) moved toward the southeast.

The article presents new research development in avian migration which associated with the landbird migration in the western North America. Migration is considered as the most dangerous period for the migratory birds annual cycle because it resulted to high mortality rates. The recognition given to the stopover ecology, habitats and migration routes of the landbirds in the diverse and changing landscapes of American West, as well as the expanded use of radars, genetic data, plasma metabolites and multi-investigator collaborations have contributed to better and significant understanding of migration patterns of the birds in the region. These new information about the migration of the landbirds have led to advances and future research directions for migratory birds.