Density and Total Population Estimates for the Threatened Christmas Island Hawk-Owl Ninox natalis

1998 ◽  
Vol 98 (3) ◽  
pp. 209-220 ◽  
Author(s):  
F.A. Richard Hill ◽  
Alan Lill
Keyword(s):  
Total Population ◽  
Population Estimates ◽  
Christmas Island

scholarly journals Short-term movement patterns, population estimates and breeding biology of an island endemic bird, the Tristan Thrush

2019 ◽  
Vol 27 (4) ◽  
pp. 245-252
Author(s):  
Peter G. Ryan ◽  
Ben J. Dilley ◽  
Delia Davies ◽  
Trevor Glass ◽  
Fitsum Abadi
Keyword(s):  
Total Population ◽  
Data Augmentation ◽  
Local Population ◽  
Population Estimates ◽  
Limited Information ◽  
Short Term ◽  
Main Island ◽  
Island Endemic ◽  
Core Study ◽  
Land Bird

AbstractThe Tristan Thrush Turdus eremita is the only land bird that survived human colonisation of the main island of Tristan da Cunha and is listed as “Near Threatened”. Population estimates are confounded by the thrushes’ inquisitive and gregarious nature as well as limited information on their movements. We report the first measures of nest densities on Nightingale Island: 6 nests·ha-1 in Phylica arborea woodland and 4–5 nests·ha-1 in tussock habitat, which suggests that the population is approximately double the previous estimate. At Inaccessible Island, we individually color ringed 110 thrushes over two months to track their short-term movements and estimate the local population size. Individuals moved up to 950 m along the coast, but 96% of resightings were < 100 m. A Bayesian data augmentation approach estimated that some 260 thrushes visited the core study area, a 200-m stretch of cobble and boulder beach where birds come to drink, bathe and forage. This result suggests that the population on Inaccessible Island also is substantially larger than reported previously. We estimate the total population to be 8000–15,000 Tristan Thrushes. The main need is a population estimate for the nominate subspecies on the main island of Tristan.

scholarly journals Status of grey seals (Halichoerus grypus) in Norway

2007 ◽  
Vol 6 ◽  
pp. 23 ◽  
Author(s):  
Kjell Tormod Nilssen ◽  
Tore Haug
Keyword(s):  
Total Population ◽  
Halichoerus Grypus ◽  
Population Estimates ◽  
Grey Seal ◽  
Breeding Area ◽  
Breeding Sites ◽  
Norwegian Coast ◽  
The North ◽  
Minimum Estimate ◽  
Pup Mortality

During the period September-December in 2001-2003, ship based surveys of grey seal (Halichoerus grypus) pups, including tagging, counting and staging of pups, were conducted along the Norwegian coast. All known and other potential breeding areas were surveyed from Rogaland county in the south to Finnmark county in the north. Most of the breeding sites were surveyed only once, but some sites were surveyed 2-4 times. The investigations resulted in a total minimum estimate of 1,159 grey seal pups born in Norwegian waters. Nordland county was the most important breeding area where about 50% of the pups were born. Total population estimates were derived from the recorded number of pups born using a range of multipliers (4.0-4.7), based on observed annual growth rates of approximately 7-12% in other grey seal populations. This gave a total estimate of about 5,800-6,600 grey seals including pups in Norwegian waters. However, the total pup production was probably underestimated due to only one pup count in most of the breeding sites. Observed mean pup mortality was 1.1% during the breeding season along the Norwegian coast.

The Tasmanian Trout Fishery. IV. The Rivers of the South and South-East

1961 ◽  
Vol 12 (1) ◽  
pp. 17 ◽  
Author(s):  
AG Nicholls
Keyword(s):  
Growth Rate ◽  
Total Population ◽  
River System ◽  
Similar Rate ◽  
Population Estimates ◽  
Sea Trout ◽  
Main River ◽  
Spawning Time ◽  
Trout Fishery ◽  
Annual Mortality

Two main river systems are included in this region, the Derwent and the Huon. Data derived from anglers' returns are analysed for each system separately but those from the Huon are insufficient for a thorough study. There is some doubt as to the representativeness of returns from either system. No significant changes have been found in the fishery over a period of 12 seasons either in the rate of daily catch per angler or in the length of fish taken. A study of the fish taken in an upstream trap at spawning time yields an annual mortality rate of about 60% for the Derwent River System and recaptures of tagged fish show a similar rate. Population estimates based on recaptures of tagged fish and on the spawning potential within the system indicate a total population of between one- half and one million, of which about 20% is of takable size. The contribution made by the release of hatchery-reared fish is shown to be insigniiicant. Evidence is produced which leads to the conclusion that there may be two distinct races of trout in Tasmania, the result of separate introductions of river and sea trout, distinguished by inherent meristic differences as well as by differences in growth rate and habits.

scholarly journals Revisiting the Demography of Disaster: Population Estimates After Hurricane Maria

2019 ◽  
Author(s):  
Alexis R Santos-Lozada
Keyword(s):  
Puerto Rico ◽  
Total Population ◽  
Vital Statistics ◽  
Population Estimates ◽  
Flow Data ◽  
Monthly Basis ◽  
Administrative Records ◽  
Passenger Flow ◽  
Migration Flows ◽  
The U.S

Hurricane María made landfall in Puerto Rico, in September 2017, causing economic damages and affecting the population by increasing temporarily increasing mortality and outgoing passenger flow. Because of the disruption in the migration flows, the volatility of this time series we must approach the production of population estimates, projections and forecasts carefully. Given that population estimates have been difficult to produce for Puerto Rico before Hurricane Maria and even more challenging following this disaster, this paper proposes an application of the demographic balancing equation using administrative records to produce population estimates on a monthly basis for Puerto Rico. A combination of data from: (1) monthly counts for deaths and births obtained from the Puerto Rico Vital Statistics Systems, (2) passenger flow data produced by the U.S. Bureau of Transportation Statistics, and (3) baseline census counts. I employ this approach to produce monthly estimates of the population for Puerto Rico, and use 2010 Census counts to assess the accuracy of the model. According to the 2010 decennial census, the population of Puerto Rico was 3,725,789 people; by employing the demographic balancing equation approach, the population was estimated to be 3,669,676 people in April 1, 2010. Using this model, I find that after Hurricane Maria, the population of Puerto Rico reached less than 3 million persons in December 2017 (2.97 million). The total population went back to over 3.0 million by January 2018 with an estimated population of 3.02 million people on September 2018.

Fish population size estimates from a small intermittently open estuary in South Africa, based on mark-recapture techniques

2001 ◽  
Vol 52 (3) ◽  
pp. 283 ◽  
Author(s):  
P. D. Cowley ◽  
A. K. Whitfield
Keyword(s):  
Population Size ◽  
Total Population ◽  
Fish Population ◽  
Minimum Size ◽  
Population Estimates ◽  
Likelihood Estimator ◽  
Mark Recapture ◽  
Population Size Estimates ◽  
Population Sizes ◽  
Size Estimates

Population sizes of the migratory marine-spawning fishes in the small intermittently open East Kleinemonde Estuary (33&ordm;32′S, 27&ordm;03′E) were estimated during two independent mark–recapture studies between 1994 and 1996. Seines were used to sample fishes during the closed-mouth phase of the estuary. All individuals above a stipulated minimum size were marked by fin-clipping. Population estimates were obtained by use of two mark–recapture models (Schnabel and a maximum-likelihood estimator) and a derived method. The total population size was estimated at ~18 000 and ~133 000 individuals during the two study periods respectively. The large temporal (interannual) variability was ascribed to both abiotic (estuary mouth conditions) and biotic-conditions. The dominant species during both periods was Rhabdosargus holubi, which accounted for ~75% and ~80%of the total population of marine fishes in the estuary. The success of this species is attributed to an extended breeding season and the ability to recruit during mouth overwash events.

scholarly journals Sensitivity analysis identifies high influence sites for estimates of penguin krill consumption on the Antarctic Peninsula

2012 ◽  
Vol 25 (1) ◽  
pp. 19-23 ◽  
Author(s):  
Heather J. Lynch ◽  
Norman Ratcliffe ◽  
Jennifer Passmore ◽  
Emma Foster ◽  
Philip N. Trathan
Keyword(s):  
Total Population ◽  
Antarctic Krill ◽  
Euphausia Superba ◽  
Population Estimates ◽  
High Quality ◽  
Significant Component ◽  
Scotia Sea ◽  
The Antarctic ◽  
Critical Link ◽  
High Influence

AbstractKrill consumption by natural predators represents a critical link between surveys and models of standing krill biomass and the design of a sustainable krill fishery for the Scotia Sea. Antarctic krill (Euphausia superba) is a significant component of diet for penguins breeding in this region and, consequently, uncertainties regarding penguin population abundances contribute to uncertainties in krill predation estimates. We use a comprehensive database of Antarctic penguin abundances to identify 14 breeding colonies that contribute most significantly to uncertainty regarding the total number of pygoscelid penguins breeding in this region. We find that a high quality survey of Zavodovski Island alone would decrease uncertainty in total population by 24.8%, whereas high quality surveys of all 14 “high-influence” locations would decrease uncertainty by almost 72%. Updated population estimates at these sites should be considered top priority for future fieldwork in the region. Our results are based on a robust quantitative method for assessing data priorities in estimating krill consumption that is easily extended to other groups of krill predators.

Population Ecology of the Brook Trout, Salvelinus fontinalis, in Matamek Lake, Quebec

1970 ◽  
Vol 27 (3) ◽  
pp. 413-424 ◽  
Author(s):  
Lloyd H. Saunders ◽  
G. Power
Keyword(s):  
Brook Trout ◽  
Total Population ◽  
Survival Rates ◽  
Standing Stock ◽  
Age Groups ◽  
Population Estimates ◽  
Lake Ecosystem ◽  
High Survival ◽  
Factors Affecting ◽  
Trout Population

Population estimates of an unexploited brook trout population at Matamek Lake, Quebec, indicated that more than 86% of the total population inhabited the tributaries of the lake during the summer of 1968. As opposed to the stream habitat, the combination stream–lake ecosystem moderated the mortality rates of the intermediate age-groups and allowed survival to higher ages in the population. Estimates of standing stock and production in the lake were 3.1 and 2.2 kg/ha respectively during 1968.The population was characterized by a slower growth rate, higher age at maturity, higher survival rate in the intermediate age-groups, and longer life span when compared with an exploited population in Wisconsin. Increased numbers of trout in higher age-groups at Matamek Lake were attributed to high survival rates in the intermediate age-groups in the absence of exploitation. Low estimates of standing stock and production were attributed to environmental factors affecting growth.

Comparison of Ward Population Estimates from FHSA Patient Registers with the 1991 Census

1995 ◽  
Vol 27 (11) ◽  
pp. 1849-1858 ◽  
Author(s):  
R M Haynes ◽  
A A Lovett ◽  
G Bentham ◽  
J S Brainard ◽  
S H Gale
Keyword(s):  
Regression Analysis ◽  
Health Service ◽  
Total Population ◽  
Family Health ◽  
Armed Forces ◽  
Population Estimates ◽  
High Population Density ◽  
Acceptable Alternative ◽  
Patient Register ◽  
Census Figure

Postcode addresses from National Health Service patient registers for Norfolk and Suffolk current on census day 1991 were assigned to census wards, and estimates of populations in wards were produced for the total population and for twelve age—sex groups. These were compared with adjusted counts of usual residents from the 1991 Census. Regression analysis was used to identify the characteristics of wards with consistent differences between register estimates and census counts. Patient register estimates were less than census counts for children aged 0–4 years. Patient register estimates exceeded census counts for residents aged 15–44 years (especially males) and over 74 years. Wards with high rates of in-migration and high proportions of residents employed in the armed forces tended to have lower register estimates than census counts. Areas of high population density had higher register estimates than census counts. Taking these effects into account, about half the patient register estimates of total population were within 5% of the equivalent census figure, and 95% of wards had estimates within 20%. The main differences between patient register population estimates and census counts can be explained by delays in the updating of records in family health service authority (FHSA) registers and by undercounting in the 1991 Census. In Norfolk and Suffolk, FHSA registers are an acceptable alternative to the census for population estimation purposes. This supports recent arguments for wider use of population registers and suggests that they may be particularly valuable as a source of intercensal information.

The decline of a large yellow-footed rock-wallaby (Petrogale xanthopus) colony following a pulse of resource abundance

2010 ◽  
Vol 32 (2) ◽  
pp. 99 ◽  
Author(s):  
Andy Sharp ◽  
Hamish McCallum
Keyword(s):  
Carrying Capacity ◽  
Marked Reduction ◽  
Total Population ◽  
Population Increase ◽  
Population Estimates ◽  
Strong Positive Correlation ◽  
Short Term ◽  
Visual Survey ◽  
Average Rainfall ◽  
Exponential Rates

The dynamics of a yellow-footed rock-wallaby (Petrogale xanthopus) colony in central-western Queensland were monitored between spring 1991 and winter 1994. The two years immediately before the study witnessed well above average rainfall, while average rainfall was recorded during the period of the study. Both trapping and standardised visual survey data were modelled using the Jolly–Seber–Cormack (JSC) mark–recapture estimator and the Minta–Mangel (MM) mark–resight estimator. The JSC population estimates were considerably lower than those derived from the MM estimator, indicating that the trapping program sampled only a portion of the total population. Nevertheless, a strong degree of correlation existed between both estimators, suggesting that the dynamics of the trappable subpopulation mirrored those of the total population. The colony declined markedly in size throughout the study (103 to 48 individuals, winter 1992 to winter 1994, JSC estimates; 175 to 116 individuals, summer 1993 to winter 1994, MM estimates). No significant correlations (P > 0.05) were found between seasonal and/or biannual exponential rates of population increase (r) and environmental variables. Nevertheless, a strong positive correlation was observed between biannual r and short-term rainfall (r = 0.90) and pasture conditions (r = 0.85–0.93), suggesting that the colony was influenced to some extent by fluctuations in available resources. Annual r was calculated at –0.29 (1992–93) and –0.49 (1993–94). The marked reduction in colony size suggested that it was declining towards its average carrying capacity, following a strong pulse of recruitment linked to the above-average rainfalls of 1990.

From the Oort cloud to Halley-type comets

1999 ◽  
Vol 173 ◽  
pp. 327-338 ◽  
Author(s):  
J.A. Fernández ◽  
T. Gallardo
Keyword(s):  
Total Population ◽  
Complex Function ◽  
Dynamical Evolution ◽  
Oort Cloud ◽  
Capture Process ◽  
Influx Rate ◽  
Short Period ◽  
Dynamical Properties ◽  
Orbital Periods ◽  
Probability Of Capture

AbstractThe Oort cloud probably is the source of Halley-type (HT) comets and perhaps of some Jupiter-family (JF) comets. The process of capture of Oort cloud comets into HT comets by planetary perturbations and its efficiency are very important problems in comet ary dynamics. A small fraction of comets coming from the Oort cloud − of about 10−2− are found to become HT comets (orbital periods &lt; 200 yr). The steady-state population of HT comets is a complex function of the influx rate of new comets, the probability of capture and their physical lifetimes. From the discovery rate of active HT comets, their total population can be estimated to be of a few hundreds for perihelion distancesq &lt;2 AU. Randomly-oriented LP comets captured into short-period orbits (orbital periods &lt; 20 yr) show dynamical properties that do not match the observed properties of JF comets, in particular the distribution of their orbital inclinations, so Oort cloud comets can be ruled out as a suitable source for most JF comets. The scope of this presentation is to review the capture process of new comets into HT and short-period orbits, including the possibility that some of them may become sungrazers during their dynamical evolution.

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