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Results for “Journal of Field Ornithology”

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At least 127 records · Page 7Linked to original sources
USGS1984

Reproductive success of black skimmers in Texas relative to environmental pollutants

We studied the nesting ecology of Black Skimmers along the lower Texas coast during 1978-1981 to learn more of their reproductive status and to evaluate the effects of organochlorine pollutants, such as DDE, on productivity. For 542 nests, the average clutch size was 3.3 eggs. Flooding was the major cause of colony destruction and abandonment. Clutch size in renest attempts decreased significantly from that in first attempts. Overall fledging success (fledglings/total pairs) averaged 1 0 fledgling per pair. There was a significant negative correlation between number of nest attempts and fledging success on a colony basis. Also, clutch size and fledging success were significantly correlated. DDE residues in some skimmer eggs were high (up to 51 ppm, wet weight), with 35% of all eggs sampled containing- >1 0 ppm DDE. However, eggshell thinning of only 4-12% was demonstrated on a colony basis and log DDE residues in individual eggs were not significantly correlated with shell thickness. DDE residues in Texas eggs were 5-fold higher than in South Carolina eggs where no shell thinning was detected.

Journal of Field Ornithology↗
USGS1985

Breeding chronology, molt, and measurements of accipiter hawks in northeastern Oregon

Most northern goshawks completed laying eggs in April, while most Cooper's hawks completed their clutches in May with essentially no overlap. The sharp-shinned hawks laid in late May and June. Juvenile females represented 4% of the northern goshawk breeding population; 22% of the Cooper's hawk breeding population (highest reported for the species) and 60% of the sharp-shinned hawk breeding population, northern goshawks and Cooper's hawks in juvenal plumage generally nested later in the season, but not sharp-shinned hawks. Females of each species began molting first. Primaries were molted from the innermost outward in all species, but rectrix molt sequence was variable. Usually R1 was molted first. Primary molt of the 2 wings was usually synchronous; however, the rectrix molt was not as orderly. Arrested molt was observed in some individuals of all species; it probably has an energy-saving function. Wing chords of adult northern goshawks from Oregon were not different from Wisconsin fall migrants or birds from Alaska; however, rectrices were significantly shorter in Oregon than Wisconsin. Cooper's hawks nesting in Oregon were much smaller than those trapped in Wisconsin. Wing chords and rectrices were significantly shorter for both sexes, and, although weights were not directly comparable, Oregon Cooper's hawks also weighed much less. The limited number of sharp-shinned hawks measured precluded statistical analyses.

Journal of Field Ornithology↗
USGS1986

Dieldrin and endrin residues in fulvous whistling-ducks in Texas in 1983

Fulvous Whistling-Ducks were collected near nesting areas in the rice fields of Texas in 1983 to determine if these birds continue to carry residue levels of organochlorine contaminants, and if the contaminants were acquired in Texas or Mexico. Adults were collected immediately after they arrived from wintering grounds and juveniles were collected in late summer before their departure to wintering grounds. Carcasses of 7 of 15 adults, some of which had been feeding in rice fields, contained residues of dieldrin in low to moderately high levels and 4 contained low levels of endrin. None of 16 flightless juveniles contained organochlorine residues. The contaminated adults were most likely exposed to aldrin or dieldrin via illegal treatment of rice seed with aldrin in some nesting areas of Texas.

Journal of Field Ornithology↗
USGS1986

Winter distribution and oiling of common terns in Trinidad: A further look

Common Terns were studied during January and March 1985 in Trinidad as part of wintering terns in Latin America. Eighty-nine birds were captured, 33 in January, 56 in March. Terns averaged 102 .+-. 0.9 g, with March birds weighing more than those caught in January. This weight is similar to that reported earlier by Blokpoel et al. (1982, 1984) and is considerably less than weights of either premigratory immature or adult Common Terns. Terns in Trinidad appear to be opportunistic, using human fishing for their food source and roosting on boats, oil platforms and other man-made structures. One-half of the captured sample of birds had at least detectable amounts of oil on the plumage. This represents the highest frequency of oiling reported yet for any seabird living under 'baseline' (non-spill) conditions in North or Central America. Oiling had no apparent major effect on the condition of birds since oiled birds had similar weights and blood parameters when compared to unoiled birds.

Journal of Field Ornithology↗
USGS1987

Some aspects of the breeding biology of the snail kite in Florida

The breeding biology of the Snail Kite was studied in Florida from 1968-1977 and intermittently from 1978-1980. Breeding occurred every month, but not in the same year. Peak egg-laying occurred from February through April or generally about 8 1 d before the onset of the rainy season in mid- or late May. Courtship displays, copulation and duration of copulation are described. Mean egg-laying interval was 2.2 d, and clutch size ranged from 1-6 eggs (x = 2.92). The frequency of large clutches (4-6 eggs) was significantly greater before 1940 than after. Incubation, which was shared by both sexes, lasted 24-30 d (x = 27.4). Egg length and breadth, eggshell thickness and weight, and whole egg volume and weight are presented. Hatching success was 57.5%. Mean hatching success for all clutches was 1.7 young or 2.3 per successful clutch. Hatching success of 2- and 3-egg clutches did not differ significantly. The nestlin period averaged 28.7 d (range 23-34). The interval between fledging of the first and last nestling in 1 brood was up to 5 d. An average of 2.0 young were raised per successful nest, and 50.5% of the nests were successful. The mean percent of successful nests per year for the 11-yr period (excluding the drought year 1971 in which there was no nesting) was 56.5 (range 17.1-84.6/yr). Nestling mortality was 37% overall, but was less during favorable high water conditions. Twenty-two factors are identified as causing nesting failure in kites, principal among these was predation (44%).

Journal of Field Ornithology↗
USGS1987

A quick-catch corral trap for wintering canvasbacks

We designed a bait trap for wintering Canvasbacks (Aythya valisineria) that has proven more effective than conventional funnel or slot entrance traps for diving ducks. The unique feature of this trap is the corral entrance that presents unimpaired access to the bait and thus ease of entrance to the trap. Catches of 50-75 ducks have been made in a matter of minutes at prebaited sites.

Journal of Field Ornithology↗
USGS1989

Nesting phenology and success of ring-necked ducks in east-central Maine

Selected aspects of the nesting biology of Ring-necked Ducks in east-central Maine were studied during 1983-1985 and compared to previous studies. Nesting chronology, clutch size, and hatching success were similar to results reported from previous studies, but nest success was 32-42% lower. Thirty-eight percent of the nests were successful; % of the eggs in successful nests hatched. Among unsuccessful nests, predation and flooding caused most failures.

Journal of Field Ornithology↗
USGS1989

An improved method to monitor nest attentiveness using radio-telemetry

An improved method of automatically monitoring nest attentiveness was designed and tested using radio-equipped American Woodcock (Scolopax minor). Shielded coaxial cable (RG-58) was extended from a receiver and placed 30 cm above the nest, with a 3.8 cm section of the inner wire exposed. Presence, absence, and activity of birds within 10.1 ? 5.2 m (SD) of the nest were clearly indicated on a Rustrak recorder while extraneous signal interference was minimized.

Journal of Field Ornithology↗
USGS1989

Solar radio-transmitters on snail kites in Florida

The effectiveness and safety of one- and two-stage solar radio-transmitters in tracking the movements and survival of adult and fledgling Snail Kites (Rostrhamus sociabilis) were evaluated between 1979 and 1983 in southern Florida. Transmitters were attached to birds with back-pack arrangements using teflon ribbon straps. Accessory plastic shields minimized feather coverage of the solar cells. Intact transmitters were seen on birds up to 47 mo after installation. Operating lives ranged from 8 to 21 mo for one-stage, and 10 to 14 mo for two-stage transmitters. Because survival of adult and nestling radio-marked kites was high, we conclude that our transmitter-attachment method had little effect on the birds.

Journal of Field Ornithology↗
USGS1992

Feeding flights of breeding double-crested cormorants at two Wisconsin colonies

Unmarked Double-crested Cormorants (Phalacrocorax auritus) (n = 523) were followed by airplane from Cat Island and Spider Island, two nesting colonies in Wisconsin, to their first landing site. Cormorants flew an average of 2.0 km from Cat Island (maximum 40 km) and 2.4 km from Spider Island (maximum12 km). The mean direction of landing sites differed seasonally for fights from Spider Island, but not from Cat Island. Cormorants generally landed in Green Bay or Lake Michigan (>99%) and rarely landed in inland lakes or ponds. The most frequent (> 80%) water depth at landing sites for each colony was < 9,1 m. Water depths >9.l m were used less frequently than available within the maximum observed flight distance for each colony. The average flight speed for cormorants was 61 km/h.

Wisconsin↗
USGS1990

Wintering localities of Cooper's hawks nesting in northeastern Oregon

The life span of the Cooper's Hawks banded between 1974 and 1979 is now believed completed. The band recoveries provide the first information on the migratory characteristics of the species in the Pacific Northwest. Cooper's Hawks nesting in northeastern Oregon winter in western Mexico. The second-year female shot near Zihuatanejo, Guerrero, Mexico on November, 12, 1977, is one of the southernmost records for the species.

Journal of Field Ornithology↗