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At least 487 records · Page 27Linked to original sources
USGS2025

Effects of nest exclosure on nest and adult survival of piping plover (Charadrius melodus) in the lower Platte River System, Nebraska

Conservation of imperiled species often includes management strategies intended to improve specific vital rates. However, some management practices can have unforeseen consequences that negate the intended benefit. For example, nest exclosures are often used for ground-nesting avian species to reduce nest predation but may increase depredation of adults. Tradeoffs between nest survival and adult mortality of nest exclosures likely depend on local predator community dynamics. Therefore, investigations are most informative when assessed in specific settings. Piping Plovers ( Charadrius melodus , hereafter plovers) in the lower Platte River system, Nebraska, nest at off-river sandpit sites, which provide an additional study system and habitat to assess the context-dependent effects of nest exclosures. The Tern and Plover Conservation Partnership monitors plovers at off-river sites by monitoring nests, installing nest exclosures, and banding and resighting. Effects of nest exclosures were tested on both nest survival, from 340 plover nests from 2008–2024, and weekly within-season apparent survival, from 71 breeding adults from 2011–2024. There was weak evidence that nest exclosures marginally improved nest survival but no evidence of an effect for within-season survival of breeding adults. Daily nest survival was slightly higher for exclosed nests (0.99, [85% CI = 0.98–0.99]) than unexclosed nests (0.98, [0.98–0.99]). Within-season apparent weekly survival for breeding plovers was 0.90 (95% CI = 0.83–0.93); cumulative survival over the breeding period was 0.51 (0.33–0.69). Nest exclosures may be used to increase nest survival at off-river sites with minimal threat to adult survival unless considerable concerns arise.

Nebraska↗
USGS2025

Variation in detection distance of Eastern Black Rail (Laterallus jamaicensis jamaicensis) vocalizations by autonomous recording units

Autonomous recording units (ARUs) are an emerging technology that allows for passive monitoring of soniferous animals and soundscapes. Over the past decade, ARUs have become a popular tool for monitoring birds for their potential to reduce the labor and costs of traditional in-person sampling procedures. However, uncertainty surrounding factors affecting detection of avian taxa using ARUs can inhibit their monitoring efficacy. Eastern Black Rails ( Laterallus jamaicensis jamaicensis ) are a secretive marsh bird listed as a federally threatened species in the U.S.A. Eastern Black Rail vocalizations are difficult to detect by field personnel, and numerous in-person surveys can be required to confirm their presence at a site. While ARUs are an alternative for detecting Eastern Black Rails, it is unknown at what maximum distance an ARU can detect their vocalizations. We evaluated factors affecting the detection distance of simulated vocalizations for ARUs in four marsh vegetation types under a range of environmental conditions. Detection distances varied across models, vocalization and vegetation types, and call volume. Kickeedo vocalizations were detected at greater distances, and detection distances increased for all vocalization types in open vegetation. High relative humidity increased detection distances, while louder background noise decreased detection distances. High wind speeds in cordgrass ( Spartina spp .) decreased detection probability disproportionately relative to other vegetation types. Based on these results, considerations of survey area, vegetation type, and site condition can allow land managers and researchers to optimize Eastern Black Rail monitoring using ARUs. Given the substantial staff time needed to monitor this species, ARUs may increase the likelihood of detection and provide an efficient alternative to in-person monitoring.

Waterbirds↗
USGS2002

Regional fidelity and movement patterns of wintering killdeer in an agricultural landscape

Killdeer ( Charadrius vociferus ) is a common and widespread North American species for which there are few studies of residency patterns and movements. We quantified fidelity and movement patterns of 24 radio-tagged Killdeer in the Willamette Valley of Oregon during the winter of 1999-2000. Results from telemetry surveys and census efforts revealed that the group monitored was composed of winter residents (63%), winter transients (26%), and year-round residents (11%). Movements were localized with birds detected at an average distance of 5.15 ± 0.91 (SE) km from the site of capture. Mean home range size (95% kernel) was 7.73 ± 3.19 km 2 . However, results also indicated periodic exploratory movements, with some birds detected up to 30 km from marking sites. Overall, individuals exhibited a low degree of fidelity to specific sites and were detected at an average of 11.9 ± 1.1 sites. No differences were found in monthly movement patterns. In almost all cases, year-round residents were more sedentary than winter residents and winter transients. Results indicate a complex regional population structure and highlight the need to consider both migrant and resident birds, as well as seasonal differences in habitat needs and space use requirements, in future conservation planning efforts.

Oregon↗
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

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↗
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

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

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

Comparison of detection rates of breeding marsh birds in passive and playback surveys at Lacreek National Wildlife Refuge, South Dakota

We compared detection rates of passive and playback breeding bird survey techniques on elusive marsh birds - Pied-billed Grebe (Podilymbus podiceps), American Bittern (Botaurus lentiginosus), Least Bittern (Ixobrychus exilis), Virginia Rail (Rallus limicola), and Sora (Porzana carolina) - during a two-year study at Lacreek National Wildlife Refuge, in southwestern South Dakota. We conducted 151 passive point counts followed by playback-response surveys at the same points in marsh-bird habitat on the refuge. Playback surveys detected secretive water birds more frequently than our passive surveys, increasing rates for each species by factors of 2.4 to 7.0. The distance a bird was detected from a point varied with the species and the survey technique.

South Dakota↗
USGS2004

Do adult Little Egrets respond to disturbance at their nest by increased breeding dispersal?

When studying breeding dispersal with marked individuals, manipulation-induced disturbance should not affect movement patterns. As part of a study on the Little Egret ( Egretta garzetta ), we tested whether the capture of breeding adults at their nest and handling (i.e., disturbance) increased their probability to move to a new colony in the subsequent breeding season (i.e., breeding dispersal). The proportion of adults disturbed in a given year that had changed colony in the subsequent breeding season was compared with the dispersal of adults observed during at least two consecutive years at colonies and not disturbed on the previous year: (1) birds marked as chicks and (2) birds marked as adults and observed ≥ two years after capture at the nest . Disturbed birds were not found to have an increased propensity to disperse. We conclude that, for this species, capture did not increase the subsequent breeding dispersal.

Camargue↗
USGS2005

Habitat use, movements and home range of wintering Lesser Scaup in Florida

Radio telemetry and diurnal time activity budgets were used to show that wintering Lesser Scaup ( Aythya affinis ) used different habitats for comfort and feeding activities at Merritt Island National Wildlife Refuge (Merritt Island), Florida and adjacent estuarine areas. Management should take this spatial consideration into account. The same data were used to determine if habitat use differed between sexes. Data on movements and home range were used to evaluate habitat quality and potential effects of human disturbance. Scaup foraged more in impounded wetlands and rested more in open estuarine regions. Mean distance between diurnal and nocturnal sites was 2.7 km (SE ± 0.3), and was similar between sexes and from mid to late winter. Male and female fixed kernel home ranges and core use areas did not differ. Mean fixed kernel 95% home range and 50% core use areas were 15.1 km 2 (SE ± 2.0) and 2.7 km 2 (SE ± 0.5) respectively, representing 3% and 0.5% of surveyed habitats. Males and females used habitats similarly and short distances traveled between diurnal and nocturnal sites suggested that habitat conditions were similar across the impounded wetlands and shallow portions of both the Indian River and Banana River. Sedentary or short movements suggested that disturbance was probably negligible at the principal areas used by Lesser Scaup. Habitat management strategies for scaup should not be restricted to Merritt Island. Adjustments should be made to take into account that maintenance activities occur in adjacent estuarine areas as well.

Florida↗
USGS2005

Factors affecting chick provisioning by Caspian Terns nesting in the Columbia River estuary

We investigated factors affecting chick provisioning by radio-tagged Caspian Terns (Sterna caspia) nesting in a large colony on East Sand Island in the Columbia River estuary during 2001. Caspian Tern predation on juvenile salmonids (Oncorhynchus spp.) in the estuary prompted resource managers to relocate ca. 9,000 pairs of terns nesting on Rice Island (river km 34) to East Sand Island (river km 8), where terns were expected to consume fewer salmonids in favor of marine forage fishes. This study investigated factors influencing foraging success, diet composition, and overall reproductive success at the managed Caspian Tern colony. Our results indicated that daytime colony attendance by nesting terns averaged 64% and decreased throughout the chick-rearing period, while duration of foraging trips averaged 47 min and increased during the same period; these seasonal changes were more strongly related to date than chick age. Average meal delivery rates to 2-chick broods (0.88 meals h-1) were 2.6 times greater than to 1-chick broods (0.33 meals h-1). Parents delivered more juvenile salmonids to chicks during ebb tides than flood tides, but meal delivery rates to the nest remained constant, suggesting diet composition tracks relative availability of prey species. Foraging trips resulting in delivery of juvenile salmonids averaged 68% longer than foraging trips for schooling marine forage fishes, indicating higher availability of marine prey near the colony. High availability of marine forage fish in the Columbia River estuary during 2001 was apparently responsible for high colony attendance, short foraging trips, high chick meal delivery rates, and high nesting success of Caspian Terns on East Sand Island.

Waterbirds↗