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At least 523 records · Page 29Linked to original sources
USGS2002

Feeding habitat selection by Great Blue Herons and Great Egrets nesting in east central Minnesota

Great Blue Herons ( Ardea herodias ) and Great Egrets ( Casmerodius albus ) partitioned feeding habitat based on wetland size at Peltier Lake rookery in east central Minnesota. Great Blue Herons preferred large waterbodies (350 ha), whereas Great Egrets fed most often at small ponds (<25 ha). Forty-nine percent of Great Blue Herons used wetlands 301-400 hectares in size and 83% of Great Egrets fed in wetlands <100 ha in size. Great Blue Herons selected large wetlands more often than expected both at the regional (30-km radius) and local (4-km radius) scales. Habitat use by Great Egrets was in proportion to availability at the regional scale, but they selected smaller wetlands for feeding more often than expected at a local scale. The median flight distance of Great Blue Herons was 2.7 km, similar to distances reported elsewhere. Great Egrets flew farther to feeding sites than Great Blue Herons, and flew farther (median = 13.5 km) than reported in other geographic areas.

Minnesota↗
USGS2002

Stable isotope analysis of temporal variation in the diets of pre-fledged Laughing Gulls

The δ 13 C, δ 15 N, and δ 34 S stable isotopic values of feathers from pre-fledged Laughing Gulls ( Larus atricilla ) in coastal Virginia and Jamaica Bay, New York were used to examine dietary variation during the nestling period. The tip portions of the feathers were used to indicate diet during the initiation of primary feather growth, whereas the base portions indicated diet during the period immediately prior to fledging. The results indicate that diets of the nestlings in Virginia moved to a higher trophic level during the period prior to fledging, however the New York nestlings did not appear to undergo any appreciable dietary change during this period. Overall, nestlings from both colonies consumed proportionately more foods of marine origin than freshwater or terrestrial. Therefore, the results do not support those of earlier studies that suggested that partially developed salt glands in young gulls might restrict the diet to more terrestrial or freshwater prey in the early stages of nestling growth.

Waterbirds↗
USGS2002

Activity patterns and monitoring numbers of Horned Puffins and Parakeet Auklets

Nearshore counts of birds on the water and time-lapse photography were used to monitor seasonal activity patterns and interannual variation in numbers of Horned Puffins ( Fratercula corniculata ) and Parakeet Auklets ( Aethia psittacula ) at the Semidi Islands, Alaska. The best period for over-water counts was mid egg-laying through hatching in auklets and late prelaying through early hatching in puffins. Daily counts (07.00 h-09.30 h) varied widely, with peak numbers and days with few or no birds present occurring throughout the census period. Variation among annual means in four years amounted to 26% and 72% of total count variation in puffins and auklets, respectively. Time-lapse photography of nesting habitat in early incubation revealed a morning (08.00 h-12.00 h) peak in the number of puffins loitering on study plots. Birds recorded in time-lapse images never comprised more than a third of the estimated breeding population on a plot. Components of variance in the time-lapse study were 29% within hours, 9% among hours (08.00 h-12.00 h), and 62% among days (8-29 June). Variability of over-water and land-based counts is reduced by standardizing the time of day when counts are made, but weather conditions had little influence on either type of count. High interannual variation of population indices implies low power to detect numerical trends in crevice-nesting auklets and puffins.

Alaska↗
USGS2002

Distribution, abundance and habitat use of American White Pelicans in the Delta Region of Mississippi and along the Western Gulf of Mexico Coast

Aerial surveys of American White Pelicans ( Pelecanus erythrorhynchos ) were conducted over coastal Louisiana and the delta region of Mississippi on 1-2 days during December, February, and April each year from 1997 to 1999. Additional surveys were conducted in coastal Texas and Mexico during January 1998 and 1999. The numbers, location, and habitat of all pelicans observed were recorded. The coastal zone of Louisiana consistently had higher numbers of pelicans (18,000 to 35,000 birds) than other areas surveyed (3,000 to 8,000 birds), indicating that Louisiana may be the most important wintering area for American White Pelicans east of the Rocky Mountains. Among the four regions surveyed, the average size of pelican flocks was largest in Mississippi during January-February, particularly in 1999 (x̄ = 245 birds/flock). Pelican numbers in Mississippi peaked in February but in Louisiana they were more variable. Pelicans in the delta region of Mississippi were found most often in fresh water and sand bar habitats during December, flooded field habitats during February, and catfish ponds in April. In Louisiana, pelicans used fresh, intermediate, and brackish marshes during December, but showed a preference for brackish and saline marshes in February and April.

Louisiana, Mississippi, Tamaulipas, Texas, Veracru↗
USGS2002

Individual foraging strategies of kleptoparasitic Roseate Terns

We describe the kleptoparasitic behavior of ten adult Roseate Terns ( Sterna dougallii ) breeding at a colony at Falkner Island, Connecticut, USA between 1995 and 1998. These birds were considered habitual kleptoparasites because they stole fish repeatedly from other terns in every year they were observed at the site. No other breeding individuals were observed attempting to steal fish during our study. Kleptoparasitic techniques included aerial piracy, ground-based attacks, and deceptive behavior, but with one exception, each individual used one method exclusively. Success varied among individuals, but overall, kleptoparasites obtained prey at a significantly higher rate than did 'honest' foragers. Eight of the ten kleptoparasites were females, suggesting a sex-biased tendency in Roseate Terns to engage in this behavior. Our observations indicate that kleptoparasitism by Roseate Terns is a specialized behavior, used regularly by only a few individuals at this breeding colony. This conclusion is consistent with a recent theoretical prediction regarding kleptoparasitism in birds.

Connecticut↗
USGS2002

Use of satellite telemetry to identify common loon migration routes, staging areas and wintering range

We developed a satellite transmitter attachment technique for adult Common Loons ( Gavia immer ) that would help in identifying important migration routes, staging areas, and the location of wintering grounds of birds that breed in the north central United States. During the autumn and winter of 1998, the migration of six adult loons that were radio marked in northern Wisconsin and Minnesota was monitored. The results of this work offer insight into autumn movement patterns of Common Loons. Timing of autumn staging and migration to wintering grounds appeared to be related to low pressure systems that delivered winter weather to the Upper Midwest. Most of the radiomarked birds staged on the Great Lakes and then followed one of two distinct migration routes to the Gulf of Mexico and Atlantic coasts. Several of the birds used lakes and reservoirs in the southeastern United States during migration. This study provides a basis for more extensive studies of Common Loon migration.

Waterbirds↗
USGS2002

Responses of dabbling ducks to wetland conditions in the Prairie Pothole Region

The relationships between wetland water conditions and breeding numbers of Mallard ( Anas platyrhynchos ), Northern Pintail ( A. acuta ), Blue-winged Teal ( A. discors ), and Northern Shoveler ( A. clypeata ) during May of 1992-1995, were examined on twelve study areas in the eastern Prairie Pothole Region. Data were collected on water levels (by wetland class [temporary, seasonal, semipermanent]), pond density (density of wet basins), and numbers of indicated pairs for each species from weekly roadside transect surveys. Comparison of models relating duck numbers to wetlands using Akaike’s Information Criterion indicated that measures of water condition generally were of similar value for explaining duck numbers. The model containing effects of semipermanent wetland water levels was among the best in explaining duck numbers for all species. Inclusion of temporary and seasonal wetland water levels in models for Mallard and Northern Pintail was not strongly supported by the data. Variation in duck numbers was much higher among areas than among years. Water conditions accounted for nearly all among-year variation for individual sites, but a large proportion of residual variation remained unexplained. Water condition measures (excluding spatial and temporal factors) explained 9-49% of variation in duck numbers, leaving 51-91% unexplained. Comparisons of these results to those of studies conducted at local or regional scale indicated that the relationship between duck numbers and pond numbers varied with scale, and suggested that other area-related factors should be considered at smaller landscape scales.

Iowa, MInnesota, Nebraska, North Dakota, South Dak↗
USGS2003

A voluntary program to curtail boat disturbance to waterfowl during migration

A voluntary waterfowl avoidance area (VWAA) was established on Lake Onalaska in Navigation Pool 7 of the Upper Mississippi River, Wisconsin, USA, in 1986, to reduce boating disturbance to migratory waterfowl. We monitored boater compliance with the VWAA program in 1993 and 1997. Of 1,664 "boating events" observed on Lake Onalaska, boats intruded into the VWAA on 127 occasions. Boating events have increased from 1.82 boating events/h in 1986-88 to 1.97 in 1993 and 2.58 in 1997. Despite a 60% increase in boating traffic, the lake-wide disturbance rates in 1997 were comparable to that in 1981. We attribute this to a significant reduction in the proportion of lake-wide boating events that resulted in disturbance, a direct consequence of the VWAA program. Rate of intrusion into the VWAA was 0.11 per boating event in 1997 compared to 0.18 per boating event in 1986-88. Boating disturbances to waterfowl within the VWAA occurred at about half the rate (0.24 to 0.28 disturbances∙hr -1 ) observed prior to establishment of the program (0.48 disturbances∙hr -1 ). We also identified access points used by boaters and boating activities that were most likely to result in intrusion into the VWAA and associated disturbance to waterfowl. Results of these analyses have provided useful information to resource managers for targeting public education efforts. The VWAA program has contributed to the value of Lake Onalaska as a waterfowl refuge and demonstrates an effective collaboration among government agencies and non-governmental organizations.

Wisconsin↗
USGS2003

Predator exclusion methods for managing endangered shorebirds: Are two barriers better than one?

Reproductive success of shorebirds can be improved by placement of predator exclosure fences along beaches or wire-mesh exclosure “cages” over nests. We predicted that these two types of exclosures used simultaneously might further improve reproductive success over that when cages alone are used. Field experiments were carried out on Piping Plovers ( Charadrius melodus ) on prairie alkali lakes in North Dakota and Montana. During 1996 and 1997, we compared success of nesting plover pairs provided with: (1) no protection, (2) cages that protected eggs in individual nests from both mammalian and avian predators, and (3) a combination of cages plus a temporary electric fence that excluded mammalian predators from the entire nesting beach where chicks were being reared. In 20 replicated trials, fledgling production rates were: no protection, 0.72 chicks/pair (95% CI: 0.29-1.15, N = 43 pairs); cage only, 1.73 (1.30-2.16, N = 46); fence plus cage, 2.06 (1.63-2.49, N = 50). Production by protected pairs was significantly greater than for unprotected pairs. However, no significant difference in production was detected between the two protection types. Temporary electric fences were relatively expensive to apply and added little to the effectiveness of cages, but may be appropriate in situations where cages cannot be used or where mammalian predation on chicks is a greater threat.

Montana, North Dakota↗
USGS2003

Radio-telemetry evidence of re-nesting in the same season by the Marbled Murrelet

Unlike other alcids, laying of replacement eggs has not been well documented in Brachyramphus murrelets. Observations of two radio-marked Marbled Murrelets ( Brachyramphus marmoratus ) in northern California during 2001 and 2002 suggested that they can re-lay in the same breeding season. In 2001, aircraft telemetry first detected a male Marbled Murrelet at a forested inland location on 17 May. This bird alternated 24h incubation bouts with 24h at sea periods until 29 May, when data logger recordings indicated that the bird arrived at the nest at 05.17 h (PDT), but left at 05.32 h. This nesting effort had apparently failed. Sixteen days later, on 14 June this murrelet arrived in the vicinity of the first nest site at 05.19 h and remained there until 18.57 h that same evening and then left. We suspected that this event represented a second breeding effort that also failed, either near or at the site of the first effort. In 2002 a female Marbled Murrelet, first detected inland on 13 June by aircraft telemetry, alternated on the nest one day and at sea the next until 23 June when the breeding effort is presumed to have failed. This bird was again detected inland on 21 July, and alternated on the nest one day and at sea the following day until 3 August, when the radio-transmitter fell off the bird. Video recordings at the nest site indicated this second nesting attempt continued until 1 September, when the chick died of unknown causes. As in other alcids, re-laying apparently occurred 2-4 weeks after failure of the first eggs, either near or at the site of first eggs. Re-nesting may be frequent in murrelets, given the high rates of breeding failure reported.

California↗
USGS2003

Deciphering the social structure of Marbled Murrelets from behavioral observations at sea

We surveyed Marbled Murrelets ( Brachyramphus marmoratus ) daily from small boats in Auke Bay and Fritz Cove, Alaska, from May through August 1992 and 1993. Differences in numbers of juveniles and in the timing of their presence in the study area between the two years indicated that breeding phenology was late and productivity was low in 1992 compared to 1993. This difference was consistent with variability in the physical environment. Of 99 fish identified in the bills of fish-holding adult murrelets, 81 (82%) were Pacific Sand Lance ( Ammodytes hexapterus ). Counts of fish-holding adult murrelets were significantly higher in the evening than at any other time of day. Time of day had no significant effects on counts of fledglings, indicating that juveniles were moving into and out of the study area during the day. Murrelets were predominantly found in groups of two or more, even during incubation, suggesting that murrelets incur an appreciable benefit, such as increased foraging efficiency, from foraging in groups. For both summers, there was no correlation between counts of murrelets on the water and numbers of murrelet detections in the adjacent forest. We suggest that many behavior patterns of the Marbled Murrelet (displaying, choosing of mates, and pair-bonding, finding of nest sites and successful foraging of juveniles) may be socially facilitated.

Waterbirds↗
USGS2003

Body size and condition of male mallard during mid-winter in North Dakota, USA

Mallard ( Anas platyrhynchos ) may winter in northern areas if they have access to adequate food and open water. We compared individual body size (indexed by first principal component scores from three morphometric measurements) and body condition (body mass adjusted for body size) of male Mallard wintering in North Dakota, USA during 1996-99 with a baseline reference group of Mallard from Ontario, Canada measured during late summer. Size and condition of Mallard wintering in North Dakota was also compared, using a sample from a traditional wintering area in Arkansas, USA. Male Mallard body size and condition in North Dakota relative to weather severity during mid-winter was assessed. Body size of adult males in North Dakota was significantly greater than that of birds from Ontario, but similar to those from Arkansas. Adult males remaining in North Dakota during the coldest winter were not larger than those remaining in North Dakota during milder winters. Immature males in North Dakota were significantly smaller than those from Arkansas, and the former were not larger during the coldest winter. Body condition of adult males in North Dakota was greater than that of those from Ontario and Arkansas and mean body mass of adult males in North Dakota during winter was greater than that of those wintering elsewhere. Further, adult males in North Dakota were in the best condition during the coldest winter. Mean body condition of immature males in North Dakota was similar to that of those from Arkansas. Body mass of immatures in North Dakota was similar to that of immatures wintering elsewhere. These findings indicate that maintenance of high fat reserves, not large body size, is the primary factor allowing adult males to winter in the extremely cold conditions of North Dakota. The small size of immature males in North Dakota, combined with the lack of evidence of their superior condition as compared to those wintering elsewhere, suggests that immatures wintering in North Dakota are mainly late-hatched individuals that may not have been able to store sufficient fat reserves to migrate before freeze-up.

North Dakota↗
USGS2004

Movements of flightless long-tailed ducks during wing molt

We examined the movements of flightless Long-tailed Ducks ( Clangula hyemalis ) during the wing molt in the near-shore lagoons of the Beaufort Sea in Alaska. Estimates of site fidelity during the 21-day flightless period ranged from 1-100%, with considerable variation among locations and within locations among years. There was no effect of low-level experimental disturbance or an underwater seismic survey on site fidelity of molting Long-tailed Ducks. Birds molting along a relatively consistent habitat gradient were more likely to move than those molting in a fragmented habitat. While flocks of birds are consistently observed in the same locations, these data suggest considerable turnover within these aggregations. These results, in conjunction with other studies, suggest that forage is relatively uniformly distributed within lagoons. We conclude that habitat selection by molting Long-tailed Ducks is likely influenced by protection from wind and associated waves.

Waterbirds↗
USGS2004

Response of predators to Western Sandpiper nest exclosures

In 2001, predator exclosures were used to protect nests of the Western Sandpiper ( Calidris mauri ) in western Alaska. During the exclosure experiment, nest contents in exclosures had significantly higher daily survival rates than control nests, however, late in the study predators began to cue in on exclosures and predate the nest contents. An Arctic Fox ( Alopex lagopus ) dug under one exclosure and took the newly hatched chicks, and Long-tailed Jaegers ( Stercorarius longicaudus ) learned to associate exclosures with active nests and repeatedly visited them. The jaegers attempted to gain access to exclosed nests and pursued adult sandpipers as they emerged from the exclosures. The exclosures were removed to reduce potential mortality to adult and young sandpipers, but subsequently, post-exclosure nests had lower daily survival rates than controls during the same time period. Predation of post-exclosure eggs and chicks highlighted the lasting influence of the exclosure treatment on offspring survival because predators probably remembered nest locations. Researchers are urged to use caution when considering use of predator exclosures in areas where jaegers occur.

Alaska↗
USGS2004

Reproductive success of the Black-crowned Night Heron at Alcatraz Island, San Francisco Bay, California, 1990-2002

Nesting chronology, habitat use, subcolony use, and hatchability were documented for the Black-crowned Night Heron ( Nycticorax nycticorax ) nesting at Alcatraz Island, San Francisco Bay, California during 1990-2002. Reproductive success was estimated using the Mayfield method and compared among years. Totals of monitored nests per year ranged from 68 in 2001 to 341 in 1996, with a trend of declining numbers since 1996. An increase in numbers of the Western Gull ( Larus occidentalis ), the Black-crowned Night Heron’s primary competitor, occurred during the same period. Overall reproductive success of the Black-crowned Night Heron at Alcatraz Island was below the 13-year average of 56.4% since 1996. During the study, the average number of chicks fledged per nest each year ranged from 0.46 to 1.27, which is less than the two chicks per nest suggested as a requirement for a sustained population. Embryos in five of 187 failed Black-crowned Night Heron eggs were deformed. In 1990 and 1991, eggs were analyzed for a wide range of contaminants, but none appeared to be sufficiently elevated to have caused the observed deformities. Based on these relatively low levels of contaminants, a high hatchability rate (94.5%), and relatively low levels of embryotoxicity, contaminants did not appear to significantly affect Black-crowned Night Heron reproduction at Alcatraz Island. However, predation by the Common Raven (Corvus corax) and Western Gull, interspecific competition with the Western Gull, habitat deterioration, and possible human disturbance are likely factors contributing to the decline in Black-crowned Night Heron reproductive success on Alcatraz Island in recent years.

Waterbirds↗
USGS2004

Habitat use and home range of the Laysan Teal on Laysan Island, Hawaii

The 24-hour habitat use and home range of the Laysan Teal ( Anas laysanensis ), an endemic dabbling duck in Hawaii, was studied using radio telemetry during 1998-2000. Radios were retained for a mean of 40 days (0-123 d; 73 adult birds radio-tagged). Comparisons of daily habitat use were made for birds in the morning, day, evening, and night. Most birds showed strong evidence of selective habitat use. Adults preferred the terrestrial vegetation (88%), and avoided the lake and wetlands during the day. At night, 63% of the birds selected the lake and wetlands. Nocturnal habitat use differed significantly between the non-breeding and breeding seasons, while the lake and wetland habitats were used more frequently during the non-breeding season. Most individuals showed strong site fidelity during the study, but habitat selection varied between individuals. Mean home range size was 9.78 ha ( SE ± 2.6 ) using the fixed kernel estimator (95% kernel; 15 birds, each with >25 locations). The average minimum convex polygon size was 24 ha ( SE ± 5.6 ). The mean distance traveled between tracking locations was 178 m ( SE ± 30.5 ), with travel distances between points ranging up to 1,649 m. Tracking duration varied from 31-121 days per bird (mean tracking duration 75 days).

Hawaii↗
USGS2004

Habitat selection by tundra swans on Northern Alaska breeding grounds

Habitat selection by the Tundra Swan ( Cygnus columbianus columbianus ) was evaluated on the Colville River Delta prior to oil field development (1982-1989). Tundra Swan territories comprised a lake, used for refuge and foraging, and terrestrial habitats and ponds near the lake's perimeter used for foraging and nesting. Tundra swan sightings from early and late summer aerial surveys were used to investigate habitat selection at the territory and within-territory scale. At the territory or lake scale, swan sightings/lake increased with lake size, and increased from discrete to tapped (i.e., connected to a river channel) to drained lakes within size categories. Overall, 49% of the variation in swan sightings/lake was explained by lake size and type, a size-x-type interaction term, and the proportion of lake perimeter comprised of Halophytic Ponds and Halophytic Wet Meadows. At the within-territory or within-lake scale, foraging swans significantly selected Halophytic Ponds, Halophytic Wet Meadows, and Fresh Ponds relative to Uplands; nesting swans significantly selected Halophytic Ponds and significantly avoided Fresh Wet Meadows relative to Uplands. Vegetation sampling indicated that sites used by Tundra Swans on river channels and tapped lakes were significantly more likely to have Sheathed Pondweed ( Potamogeton vaginatus ) than control sites. The three major components of Tundra Swan diet were Carex sedges, Sheathed Pondweed, and algae, together comprising 85% of identifiable plant fragments in feces.

Alaska↗
USGS2004

Distribution and abundance of the Mariana subspecies of the Common Moorhen

Island-wide surveys for the endangered Mariana subspecies of the Common Moorhen ( Gallinula chloropus guami ) were conducted on Guam and the Commonwealth of the Northern Mariana Islands from May through September 2001. Based on these counts, the total adult moorhen population is estimated to be 287, with 154, 41, 2, and 90 adult moorhens on Saipan, Tinian, Rota, and Guam, respectively. Results suggest an overall increase in birds on Saipan and Tinian, although moorhen numbers on Guam may be declining. High counts of moorhens on Lake Hagoi, Tinian, during the wet season suggested movement from Saipan to Tinian occurs at the onset of the wet season each year. Conservation efforts need to consider Saipan and Tinian moorhens as a single demographic unit. Further, monitoring of moorhens, invasive vegetation management, and predator and ungulate control on wetlands are critical for this small population.

Waterbirds↗