Black Skimmer (Rynchops niger)
Black Skimmer

Black Skimmer (Rynchops niger)

Black SkimmerThe breeding adult black skimmer has brown-black upperparts, contrasting with a white forehead and underparts. The upperwing shows a white trailing edge from the secondaries to the inner primaries. The tail is white, with dark central feathers. The bill is black with a reddish-orange base. The legs and feet are also reddish-orange. Male black skimmers are slightly larger than females. Nonbreeding adult plumage is similar, but duller, to that of breeding adults. In winter, the bill and upperparts are somewhat paler. In addition, white feathers on the nape form a light collar around the neck. Juvenile skimmers appear similar to adults, but have duller brown upperparts with light feather edges and streaked crowns. The legs, feet, and base of the bill are dusky-red. Juveniles acquire adult-like plumage the following summer.



I examined colony-site tenacity and reproductive success in 19 colonies of Black Skimmers (Rynchops niger)f or 5 yr in New Jersey . Frequent colony-site shifts occurred, and only two sites were occupied in all 5 yr. Although in one year fledging success was nearly zero due to flood tides, in most years tides destroyed less than 25% of the colonies, while predators destroyed up to 50% of the colonies. Skimmers usually abandoned unsuccessful sites and continued to nest in successful sites. Colony abandonment was greater in colonies subjected to predation pressures than in those subjected to flooding. I suggest that this difference related to the high predictability of future low reproductive success when a colony was destroyed by predators (high probability of future loss) as compared to floods (low predictability)

Source: The Auk 99: 109-115

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Diurnal and Nocturnal Visual Function in two Tactile Foraging Waterbirds: The American White Ibis and the Black Skimmer

Author(s): Luz Marina Rojas, Raymond Mcneil, Therese Cabana, and Pierre Lachappelle

We compared the diurnal and nocturnal visual function in two tactile foragingwaterbird species, the red subspecies of the American White Ibis (Eudocimus ruberruber, formerly the Scarlet Ibis), which is known to feed exclusively during daytime, andthe Black Skimmer (Rynchops niger), which forages primarily during darkness. Live birdswere captured in coastal lagoons of northeastern Venezuela. Electroretinograms (ERGs)were obtained at different light intensities from anesthetized birds, and the retinae weresubsequently processed for histological observations. The ERGs of the skimmer were ofmuch larger amplitude than those of the ibis in scotopic (rod-mediated) conditions, but,in contrast, under photopic (cone-mediated) conditions, the amplitude of the ERGs alwayswas significantly larger for the ibis than for the skimmer. The scotopic:photopicb-wave ratio, calculated with b-waves obtained at the highest flash luminance, was 6.82: 1for the skimmer and 0.89:1 for the ibis. The retina of the ibis contained, on the average,18.8 rods/310 [mu]m and 56.6 cones/310 [mu]m, for a rod:cone ratio of 1:3. The retina of theskimmer contained 90.2 rods/310 [mu]m and 16.8 cones/310 [mu]m, for a ratio of 5:1. Thehigher density of rods in the skimmer is in some way counterbalanced by their thinness.Compared to the nocturnally active skimmer, the ibis has highly inferior rod functionand, consequently, potentially inferior nocturnal visual capabilities. The latter would seemto explain the temporal differences observed in feeding behaviors of the two species.Key words: waterbirds, Rynchops niger, Eudocimus ruber, Black Skimmer, AmericanWhite Ibis, Scarlet Ibis, vision, retina, rod, cone, electroretinogram, nocturnal foraging,nocturnal activity.

Source: Condor: Vol. 99, No. 1, January-February, 1997

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Title Overwintering of Black Skimmers in California:: Site Fidelity and Inter-Site Movements

Author(s): Kathleen T. Gazzaniga
During the last two decades, Black Skimmers (Rynchops niger) have become increasingly common along the southern California coast.They are now found year-round in southwestern California (Collinse t al. in press) and in northwestern Baja California (Palacios and Alfaro 1992). Little detailed information has been published, however, about their winter distribution and abundance in this region. Most previous studies of the Black Skimmer have focused on the breeding season, with little attention paid to survival, behavior, and habitat requirement in the wintering areas. Since the difficulties skimmers face on the breeding grounds (e .g., predation, human disturbance, parasitism, disease, inclement weather, contaminants, entanglements, and food shortage) may affect the mal soon the wintering grounds, Burger and Gochfeld (1990) suggested that further studies of wintering birds are needed. They suggested also that most mortality of adults takes place away from the breeding grounds and that young birds are particularly vulnerable during their first winter.

Source: Western Birds: Vol. 27, No. 3, 1996

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Post-natal development was studied in 40 southern California Black Skimmer (Rynchops niger) chicks in order to develop a reliable method of aging and sexing pre-flying young in this sexually dimorphic species. Ages of chicks were determined from hatching dates and were calculated also from wing chord measurements. At fledging, male and female chicks exhibited the same degree of sexual size dimorphism previously demonstrated in adult birds. Sex of chicks was determined after day 23 when differences in body weight became significant. At day 24 or older, chicks were classified as male if their weight exceeded 320 g, and as female if less than 300 g. This technique should allow a closer examination of sexually related aspects of Black Skimmer demography during the pre-reproductive period.

Source: Journal of Field Ornithology: Vol. 61, No. 2, Spring, 1990

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Author(s): PAM G. KRANNITZ

Nests of Black Skimmers (Rynchops niger) (n = 37), Large-billed Terns (Phaetusa simplex) (n = 121), and Yellow-billed Terns (Sterna superciliaris) (n = 16) on an exposed sandbar in the Trombetas River, Brazil, were monitored during incubation and hatching in 1982. The species were interspersed throughout the colony, though Black Skimmers nested closer to the river than the other two species. Black Skimmers had larger clutches (2.83 eggs/clutch) than Large-billed (2.30 eggs) and Yellow-billed (1.94 eggs) terns. Abandonment and flooding accounted for the majority of nest and egg losses during incubation for Large-billed Terns (22 of 27 nest failures) and Yellow-billed Terns (two failures, one due to flooding). Black Skimmers lost no eggs or nests to flooding, but abandoned three nests (seven eggs) and three clutches disappeared (11 eggs). Black Skimmer clutches hatched on averaged of 5 d earlier than Large-billed Tern clutches, and 2 d earlier than Yellow-billed Tern clutches. Estimated number of young leaving the nest for Black Skimmers was 1.66 young/nest, 1.08 for Large-billed Terns, and 1.04 for Yellow-billed Terns.

Source: Journal of Field Ornithology: Vol. 60, No. 2, Spring, 1989

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Challenges and prospects of population genetic studies in terns (Charadriiformes, Aves)

Author(s): Patrícia J. Faria, Erika Baus, João S. Morgante and Michael W. Bruford

Little information is available about the population structure of communally nesting terns (Sternidae) and skimmers (Rynchopidae) throughout the world. In order to fill this gap, a survey of molecular markers was carried out for six species of terns (Anous stolidus, Sterna hirundinacea, S. fuscata, S. superciliaris, Thalasseus maximus and Phaetusa simplex) and one species of skimmer (Rynchops niger). First, we describe the results of the construction of genomic DNA libraries and document problems encountered during this procedure. Secondly, we tested the cross-amplification of 18 microsatellite loci previously described for related species (the number of polymorphic loci ranged from three to seven). Thirdly, we tested the usefulness of mtDNA (control region, ND2, Cytochrome b and ATPase 6/8) for phylogeographic studies in this group of birds.

Source: Genetics and Molecular Biology, 30, 3, 681-689 (2007)

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Author(s): LESLIE M. TUCK

Sea-birds from the West Indies and nearby subtropical regions occasionally occur in New England and the Maritime Provinces of Canada as a result of hurricanes. Peterson (1947) lists three species, the Sooty Tern (Sterna fuscata) and the Noddy (Anous stolidus) which breed at Dry Tortugas and the Yellow-billed Tropic-bird (Phaethon lepturus) which breeds in Bermuda

Source: Bird Banding vol. 24

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