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At least 199 records · Page 11Linked to original sources
USGS2008

Extensive monitoring programmes viewed as long-term population studies: The case of North American waterfowl

Several long-running and geographically extensive survey programmes provide information used to make annual management decisions for North American waterfowl populations. Data from these programmes can also be viewed as resulting from long-term population studies and have formed the basis for a number of retrospective analyses. Short-term studies have been used to investigate mechanisms underlying results of the retrospective analyses. Results of the long-term and short-term studies complement each other nicely and have led to many useful inferences about North American waterfowl population dynamics. However, important questions remain unanswered, and it is suggested that many of these could best be addressed using an experimental approach.

Ibis↗
USGS2008

Adult survival of Black-legged Kittiwakes Rissa tridactyla in a Pacific colony

Breeding Black-legged Kittiwakes Rissa tridactyla survived at a mean annual rate of 0.926 in four years at a colony in Alaska. Survival rates observed in sexed males (0.930) and females (0.937) did not differ significantly. The rate of return among nonbreeding Kittiwakes (0.839) was lower than that of known breeders, presumably because more nonbreeders moved away from the study plots where they were marked. Individual nonbreeders frequented sites up to 5 km apart on the same island, while a few established breeders moved up to 2.5 km between years. Mate retention in breeding Kittiwakes averaged 69% in three years. Among pairs that split, the cause of changing mates was about equally divided between death (46%) and divorce (54%). Average adult life expectancy was estimated at 13.0 years. Combined with annual productivity averaging 0.17 chick per nest, the observed survival was insufficient for maintaining population size. Rather, an irregular decline observed in the study colony since 1981 is consistent with the model of a closed population with little or no recruitment. Compared to their Atlantic counterparts, Pacific Kittiwakes have low productivity and high survival. The question arises whether differences reflect phenotypic plasticity or genetically determined variation in population parameters.

Alaska↗
USGS2008

Survival, site and mate fidelity in South Polar Skuas Catharacta maccormicki at Anvers Island, Antarctica

In 1974–1975, 34 adult South Polar Skuas Catharacta maccormicki were colour-ringed on 18 nest territories at Bonaparte Point, Anvers Island, near Palmer Station along the Antarctic Peninsula. Subsequently, the area was searched for these birds during the austral summers of 1975–1976 to 1984–1985 and in 1987–1988 and 1989–1990. Fifty-three percent were seen in 1984–1985, 32% in 1987–1988 and 21% in 1989–1990. Annual survival rate averaged 95% from 1974–1975 to 1984–1985; no sexual differences were detected (n = 28 of known sex). Strong territory and mate fidelity were apparent: 34 skuas averaged 1.1 nest territories and 1.7 mates each in 16 years. Only 4 of 34 individuals (all females) were known to change territories, and each territory change involved a change of mates. Although males showed higher territory fidelity than females (P < 0.01), most females (four of five) retained their territories when previous mates failed to return. Seventeen of 34 birds changed mates a total of 24 times; at least 20 mate changes followed the death or disappearance of the former mate. Males showed slightly higher mate fidelity than females (P < 0.04). Female South Polar and Brown Skuas Catharacta lonnbergi did not differ in territory or mate fidelity. From 1974–1975 to 1984–1985, 120 South Polar Skua chicks were ringed on 18 nest territories on Bonaparte Point: 17 were resighted in the Palmer area when they were 3–10 years old. All 15 returnecs were found within 3 km of their natal nest sites, and four of them occupied nest territories on Bonaparte Point.

Ibis↗
USGS2008

Brood amalgamation in the Bristle-thighed Curlew Numenius tahitiensis : process and function

Alloparental care in birds generally involves nonbreeding adults that help at nests or breeding adults that help raise young in communal nests. A less often reported form involves the amalgamation of broods, where one or more adults care for young that are not their own. We observed this phenomenon among Bristle-thighed Curlew Numenius tahitiensis broods in western Alaska during 1990–1992. Amalgamation of broods generally involved the formation of temporary and extended associations. Temporary associations were formed by the incidental convergence of broods soon after they left their nests. During this period, parents defended distinct brood-rearing areas, were antagonistic to conspecifics and remained together for less than 3 days. Extended associations formed when chicks were 1–2 weeks old. Here, parents and their broods occupied distinct, but adjacent, brood-rearing areas and moved around as a unit. Whether a brood participated in either temporary or extended associations or remained solitary appeared to depend on brood density in the immediate area and on hatching date. When chicks were 3–4 weeks old, aggregations of up to ten broods formed wherein young mixed and parents defended a common brood-rearing area. All broods (n = 48) that survived to fledging joined such aggregations. Alloparental care involved only antipredator defence and was not associated with activities such as feeding and brooding. Most female parents abandoned their broods shortly after the young could fly and when aggregations were forming. The female parent of a pair always deserted its young before or on the same day as the male parent and, in every aggregation, one or two males continued to tend young for about 5 days longer than other male parents. In most cases, adults deserted the young 2–6 days before the young departed the area when about 38 days old. Bristle-thighed Curlews also formed temporary associations with American and Pacific Golden Plover Pluvialis dominica and Pluvialis fulva, Whimbrel Numenius phaeopus, Bar-tailed Godwit Limosa lapponica, Western Sandpiper Cal-idris mauri and Long-tailed Skua Stercorarius longicaudus. Curlews and other larger bodied species commonly attack-mobbed predators together, whereas smaller bodied species generally gave alarm calls and circled the predators. For all species, the intensity of antipredator defence by attending adults gradually decreased as young became older and aggregations formed. We suggest that amalgamation of broods among Bristle-thighed Curlew enhances predator defence, aids in the process of flock formation for migrating young, and allows females and some males to desert their young earlier.

Alaska↗
USGS2008

Wintering site fidelity and movement patterns of Western Sandpipers Calidris mauri in the San Francisco Bay estuary

Western Sandpipers Calidris mauri are the most numerous shorebird species in the San Francisco Bay estuary during winter. A sample of 106 Western Sandpipers was captured in mist nets and radio-marked with 1-g transmitters to examine their wintering site fidelity and movements. Differences in distances moved, home range extent and core area size were examined by age, sex, season, site, time of day and tide. All birds remained in the south San Francisco Bay region during winter and exhibited strong site fidelity, with a mean home range of 22.0 km 2 or only 8% of the study area. First-year birds had larger home ranges (26.6 ± 3.6 km 2 ) than adults (17.2 ± 2.5 km 2 ) in winter, but home range sizes of males and females were not significantly different in any period. Home range sizes were similar between seasons, but core areas were smaller in spring (6.3 ± 1.2 km 2 ) than in early (9.6 ± 4.0 km 2 ) or late (11.6 ± 1.6 km 2 ) winter. Movements and home range size were similar for radio-marked birds located during day and night. The high degree of regional and local site fidelity demonstrated that the mixture of natural mud fiats and artificial salt ponds in southern San Francisco Bay provided sufficient resources for large wintering populations of Western Sandpipers.

Ibis↗
USGS2008

Distribution of Xantus' Murrelet Synthliboramphus hypoleucus at sea in the Southern California Bight, 1995-97

We radiomarked 153 Xantus' Murrelets Synthliboramphus hypoleucus captured at sea near Santa Barbara Island (SBI), the largest murrelet colony in the California Channel Islands, USA. We tracked these radiomarked murrelets in the Southern California Bight (SCB) off coastal southern California during the 1995-97 breeding seasons. In 1995 during mild El Niño conditions, the murrelets were distributed in non-upwelling areas. In 1996-97, they were distributed in dense patches, aggregating in cool upwelled waters near the northern Channel Islands or south of San Nicolas Island. Murrelets flew longer distances from SBI to foraging areas in 1997 (x̄= 111 ± 44 km) than in 1996 (x̄= 62 ± 25 km), but the distances they travelled did not differ between months (Apr and May) within years. Mean foraging distances from SBI were similar for ‘incubating’ murrelets (determined on the basis of repeated visits to SBI) and ‘non-incubating’ murrelets during the colony attendance period. We attributed the low return rate of radiomarked murrelets to SBI to the capture and marking of a large proportion of birds that were not actively incubating rather than to any adverse effects of radio attachment. We believe changes in murrelet foraging patterns between the 1970s and 1990s are associated with changes in prey resources in the SCB. Flexibility in the foraging strategies of these murrelets may be related to the highly variable marine environment at the southern end of the California Current Up welling System.

California↗
USGS2004

Sex differences in Little Auk Alle alle parental care: Transition from biparental to paternal-only care

Understanding differences in male and female care in biparental care systems can help interpret the selective pressures that shape parental strategies. We examined Little Auk Alle alle parental care at a breeding colony during the chick-rearing and fledging periods by conducting observations on marked, known-sex pairs, and by examining the sex ratio of birds carrying food to the colony. Little Auks transitioned from biparental to mostly paternal-only care during late chick-rearing. Males delivered more meals and spent more time at the colony than females during late chick-rearing. Very few females were present at the colony by the end of chick-rearing and through the fledging period, and all marked parents observed accompanying their chick to sea were male. Chick mass loss prior to fledging was associated with the lack of provisioning by the female parent, rather than a reduction in feeding frequency by both parents. The occurrence of paternal-only care during and after fledging is discussed in relation to physiological, ecological and phylogenetic constraints.

Ibis↗
USGS2004

Selection of arboreal termitaria for nesting by cooperatively breeding Micronesian Kingfishers Todiramphus cinnamominus reichenbachii

Limited nest-site availability appears to be an important factor in the evolution of delayed dispersal and cooperative breeding in some cavity-nesting species. The cooperatively breeding Pohnpei subspecies of Micronesian Kingfisher Todiramphus cinnamominus reichenbachii excavates nest cavities from the nests of arboreal termites Nasutitermes spp., or termitaria. In this first published description of nest-sites for this subspecies, we used surveys, remote sensing and radiotelemetry to evaluate the relationship between nest-site availability and co-operation. Results illustrate that nest termitaria are higher in the forest canopy, larger in volume and occur in areas with more contiguous canopy cover than unused termitaria. Nest termitaria were selected independently of the proximity to forest edges and territory boundaries, and we found no difference in characteristics of termitaria used by cooperative groups and breeding pairs. Logistic regression modelling indicated that termitaria with nest-like characteristics were not limited in abundance, suggesting that neither the prospects of inheriting nesting resources nor limited nest-site abundance are probable explanations for delayed dispersal in the Pohnpei subspecies of Micronesian Kingfisher.

Pohnpei↗
USGS2005

Relationship between demographics and diet specificity of Imperial Eagles Aquila heliaca in Kazakhstan

The demographic consequences of within-population variability in predator foraging are not well understood. We assessed the relationship between the degree of diet specialization and two demographic parameters, population density and reproductive output, within a single population of Imperial Eagles Aquila heliaca at a nature reserve in north-central Kazakhstan. Nearest-neighbour distances between eagle nests throughout the reserve, and thus population density, were correlated with the degree to which diets were specialized. Diet diversity showed an extensive regional variability that was linked to prey distributions, but within-year analyses of reproductive output did not show similar linkages. However, multi-year analyses of breeding performance showed inter-regional differences in nesting success that were paralleled, and probably driven by, similar trends in diet diversity. In contrast, brood size at fledging was not linked to diet diversity and was more probably driven by reserve-wide influences such as weather. Finally, the decision to initiate breeding was associated neither with diet diversity nor with environmental variability. Our results indicate that the degree of dietary specialization is linked to the demographics of Imperial Eagle populations. For these and other raptor populations, it is possible that management could be used separately to increase or decrease nesting success, brood size at fledging, and the likelihood that a pair will initiate breeding.

Ibis↗
USGS2008

Body mass of prefledging Emperor Geese Chen canagica: Large-scale effects of interspecific densities and food availability

We studied body mass of prefledging Emperor Geese Chen canagica at three locations across the Yukon–Kuskokwim Delta, Alaska, during 1990–2004 to investigate whether large‐scale variation in body mass was related to interspecific competition for food. From 1990 to 2004, densities of Cackling Geese Branta hutchinsii minima more than doubled and were c . 2–5× greater than densities of Emperor Geese, which were relatively constant over time. Body mass of prefledging Emperor Geese was strongly related (negatively) to interspecific densities of geese (combined density of Cackling and Emperor Geese) and positively related to measures of food availability (grazing lawn extent and net above‐ground primary productivity (NAPP)). Grazing by geese resulted in consumption of ≥ 90% of the NAPP that occurred in grazing lawns during the brood‐rearing period, suggesting that density‐dependent interspecific competition was from exploitation of common food resources. Efforts to increase the population size of Emperor Geese would benefit from considering competitive interactions among goose species and with forage plants.

Ibis↗
USGS2009

Satellite-marked waterfowl reveal migratory connection between H5N1 outbreak areas in China and Mongolia

The role of wild birds in the spread of highly pathogenic avian influenza H5N1 has been greatly debated and remains an unresolved question. However, analyses to determine involvement of wild birds have been hindered by the lack of basic information on their movements in central Asia. Thus, we initiated a programme to document migrations of waterfowl in Asian flyways to inform hypotheses of H5N1 transmission. As part of this work, we studied migration of waterfowl from Qinghai Lake, China, site of the 2005 H5N1 outbreak in wild birds. We examined the null hypothesis that no direct migratory connection existed between Qinghai Lake and H5N1 outbreak areas in central Mongolia, as suggested by some H5N1 phylogeny studies. We captured individuals in 2007 from two of the species that died in the Qinghai Lake outbreaks and marked them with GPS satellite transmitters: Bar-headed Geese Anser indicus (n = 14) and Ruddy Shelduck Tadorna ferruginea (n = 11). Three of 25 marked birds (one Goose and two Shelducks) migrated to breeding grounds near H5N1 outbreak areas in Mongolia. Our results describe a previously unknown migratory link between the two regions and offer new critical information on migratory movements in the region. ?? 2009 British Ornithologists' Union.

Ibis↗
USGS2009

Ecological factors regulating brood attendance patterns of the western sandpiper calidris mauri

Parental brood attendance patterns vary greatly among shorebird species. For monogamous calidridine species, biparental care with female-first brood departure is most common. It is believed that adult sandpipers balance potential individual survival costs associated with extended parental care against the benefit gained by their brood of prolonged parental care. These costs and benefits are difficult to quantify and factors affecting the termination of parental brood attendance are unclear. We compared clutch size, nesting phenology, and parental attendance patterns of Western Sandpipers Calidris mauri at Nome and Kanaryarmiut, Alaska, sites separated by three degrees of latitude. The sites differed in breeding density and duration of breeding season, but the distribution of clutch sizes did not differ between sites or between nesting attempts. Parental attendance patterns were similar between sites, suggesting that parental attendance is a highly conserved life-history trait in Western Sandpipers. Male Western Sandpipers attended broods longer than females, and the duration of parental attendance decreased at a similar rate for both sexes as the season progressed. Male and female Western Sandpipers undertake differential migrations to their non-breeding grounds, with males typically settling at more northerly locations and females at more southerly sites, a migration pattern shared by certain other monogamous calidridine species. These same species exhibit similar parental brood attendance patterns, suggesting the strong role of overall migration distance in shaping the expression of parental attendance behaviours. A contrast of more geographically disjunct sites coupled with a better understanding of the migratory connectivity between Western Sandpiper breeding and non-breeding populations would elucidate the role of cross-seasonal effects on parental brood attendance decisions. ?? 2009 British Ornithologists' Union.

Ibis↗
USGS2010

Satellite‐tracking of Northern Pintail Anas acuta during outbreaks of the H5N1 virus in Japan: Implications for virus spread

We fitted Northern Pintail Anas acuta in Japan with satellite transmitters and monitored their spring migration movements relative to locations where the highly pathogenic H5N1 avian influenza virus was detected in Whooper Swans Cygnus cygnus in 2008. Pintails were assumed not to be infected with the H5N1 virus at the time they were marked because capture occurred between 2 and 5 months before reported outbreaks of the virus in Japan. We assessed spatial and temporal overlap between marked birds and occurrence of the virus and tracked Pintails after they departed outbreak locations. Eight of 66 (12.1%) Northern Pintails marked with satellite transmitters used wetlands in Japan where the H5N1 virus was detected in Whooper Swans. Apparent survival did not differ between Pintails that used H5N1 sites and those that did not. However, the proportion of Pintails that migrated from Japan was significantly lower among birds that used H5N1 sites compared with those that did not (0.50 vs. 0.79). Northern Pintails were present at the H5N1 sites from 1 to 88 days, with five birds present at the sites from 0 to 7 days prior to detection of the virus in Swans. The six Pintails observed to depart H5N1 sites did so within 2–77 days of the reported outbreaks and moved between 6 and 1200 km within 4 days of departure. Four Pintails migrated to eastern Russia. After their departure from outbreak sites, Northern Pintails made long‐distance migrations within the period when newly infected ducks would shed the H5N1 virus. This supports a hypothesized mechanism by which a highly pathogenic avian influenza virus could be spread by migratory birds.

Ibis↗
USGS2010

Pre‐moult patterns of habitat use and moult site selection by Brent Geese Branta bernicla nigricans: Individuals prospect for moult sites

In environments where habitat quality varies, the mechanism by which individuals assess and select habitats has significant consequences on their spatial distribution and ability to respond to environmental change. Each year, thousands of Black Brent Geese Branta bernicla nigricans migrate to the Teshekpuk Lake Special Area (TLSA), Alaska, to undergo a flightless wing‐moult. Over the last three decades, moulting Brent Geese have changed their distribution within the TLSA, redistributing from inland, freshwater wetlands towards coastal, brackish wetlands. To understand better the mechanism by which Brent Geese select a moult site, as well as reasons behind the long‐term shift of moulting distributions, we examined movements and habitat use of birds marked with GPS‐transmitters during the pre‐moult period. Brent Geese did not generally migrate directly to their moulting site during the pre‐moult period, defined as the time from arrival at the moulting grounds to the onset of flightlessness. Rather, individuals used an average of 3.7 ± 0.6 (se) wetland complexes and travelled a minimum of 95.14 ± 15.84 km during the pre‐moult period. Moreover, 69% of Brent Geese visited their final moult site only to leave and visit other sites before returning for the flightless moult. Brent Geese spent significant time in both inland freshwater and coastal estuarine habitats during the pre‐moult, irrespective of the habitat in which they ultimately moulted. Whereas previous research suggested that Brent Geese choose moult sites based largely upon the experience of previous years, our observations suggest a mechanism of moult site selection whereby Brent Geese ‘prospect’ for moult sites, visiting multiple potential moult sites across varied habitat types, presumably gathering information from each site and correspondingly using this information to choose an appropriate moult site. By allowing individuals to adjust their distributions in response to habitat quality cues that may change annually, such as forage type and availability, prospecting may have influenced the long‐term shift in moulting distributions of Brent Geese in the TLSA .

Alaska↗
USGS2011

Migratory movements of waterfowl in Central Asia and avian influenza emergence: Sporadic transmission of H5N1 from east to west

Waterfowl in the genera Anas and Tadorna are suspected as vectors in the long‐distance transmission of highly pathogenic avian influenza H5N1. The former Soviet Republics of Central Asia are situated at an important migratory crossroads for these and other species of birds that bridges regions where the disease is prevalent. However, waterfowl movements through Central Asia are poorly quantified. In this study, historical data derived from over 80 years of bird ringing are combined with recent satellite tracking data to delineate migration routes, movement chronology and habitat use patterns of waterfowl in relation to H5N1 outbreak locations. Results confirm migratory linkage between breeding and moulting areas in northern Kazakhstan and southern Siberia, with non‐breeding areas in the Caspian, Black and eastern Mediterranean Sea basins, as well as with South Asia. However, unlike the situation in neighbouring regions, most notably western China, H5N1 outbreaks have not been recurrent in Central Asia after they were first reported during summer 2005 and spring 2006. These findings have implications in relation to potential sampling biases, species‐specific variation in migratory behaviour and continuing regional H5N1 transmission risks.

Siberia↗
USGS2012

The effect of changes in habitat conditions on the movement of juvenile Snail Kites Rostrhamus sociabilis

The degradation of habitats due to human activities is a major topic of interest for the conservation and management of wild populations. There is growing evidence that the Florida Everglades ecosystem continues to suffer from habitat degradation. After a period of recovery in the 1990s, the Snail Kite Rostrhamus sociabilis population suffered a substantial decline in 2001 and has not recovered since. Habitat degradation has been suggested as one of the primary reasons for this lack of recovery. As a consequence of the continued degradation of the Everglades, we hypothesized that this would have led to increased movement of juvenile Kites over time, as a consequence of the need to find more favourable habitat. We used multistate mark-recapture models to compare between-site movement probabilities of juvenile Snail Kites in the 1990s (1992&ndash;95; which corresponds to the period before the decline) and 2000s (2003&ndash;06; after the decline). Our analyses were based on an extensive radiotelemetry study (266 birds tracked monthly over the entire state of Florida for a total period of 6 years) and considered factors such as sex and age of marked individuals. There was evidence of increased movement of juvenile Snail Kites during the post-decline period from most of the wetland regions used historically by Kites. Higher movement rates may contribute to an increase in the probability of mortality of young individuals and could contribute to the observed declines.

Florida↗