Analysis of an Instaneous Census Method for Heathland Birds

1983 ◽  
Vol 10 (3) ◽  
pp. 521 ◽  
Author(s):  
GH Pyke
Keyword(s):  
Frequency Distribution ◽  
Bird Species ◽  
Time Of Day ◽  
Vegetation Height ◽  
Time Of Year

Birds were censused from the top of a 2.5-m ladder positioned at the centre of circles of radius 20 m. Every 1 min the observer visually scanned one half of a circle, recording the identity of and the distance to every bird seen. This procedure was carried out for about eight scans and then repeated for the complementary semicircle. Birds tended to be repulsed from the observer and/or ladder. Consequently the census method cannot be used to estimate absolute densities. However, the frequency distribution of bird-observer distances was found to be independent of time of day, time of year, and bird species. The method can, therefore, be used at a particular location to compare different bird species and different times. Vegetation height affected the frequency distribution of bird-observer distances and so the method cannot provide accurate comparisons of bird densities in different areas. Fewer birds were seen per scan when the census was carried out 4-6 h after sunrise. The two observers in the study saw the same average number of birds per scan.

scholarly journals Prey, management and landscape requirements of an endangered population of the Woodlark Lullula arborea in Southwest Germany

2021 ◽  
Author(s):  
Verena Rösch ◽  
Pascal Aloisio ◽  
Martin H. Entling
Keyword(s):  
Food Resource ◽  
Bird Species ◽  
Ground Cover ◽  
Main Food ◽  
Vegetation Height ◽  
Endangered Population ◽  
Rhine Valley ◽  
Territory Selection ◽  
Main Food Source ◽  
Upper Rhine

AbstractVineyards can be valuable habitats for biodiversity conservation. For example, in Rhineland-Palatinate (Germany) over a third of the state’s critically endangered Woodlark (Lullula arborea) population breeds in vineyards along the western margin of the Upper Rhine Valley. We here aim to elucidate how local ground cover management, food availability and the proximity to settlements affect territory selection by this bird species in the region. As climate, site conditions and management differ greatly from more continental or Mediterranean wine-growing areas, conditions for Woodlark conservation may differ as well.We compared 26 Woodlark territories in vineyards with 26 nearby reference areas from which Woodlarks were absent. We recorded vineyard ground cover in the inter-rows (% cover) as well as vegetation height and composition (forbs vs. grasses). Arthropods were sampled using pitfall traps, since they are the main food resource of Woodlarks during the breeding season. In addition, the distance to built-up areas was measured. The vegetation in Woodlark territories was shorter (mean 14.2 vs. 19.6 cm) and more dominated by forbs (39% vs. 27% cover) than in absence areas. The vegetation cover in the inter-rows had no effect on Woodlark territory presence or absence. Woodlarks also favoured areas with a higher abundance of arthropods (mean abundance 69.1 vs. 57.5) and a greater distance to built-up areas (mean distance 554 vs. 373 m). We conclude that to promote the Woodlark in wine-growing areas, short, forb-rich swards should be created, facilitating arthropod detectability. This is likely to require low levels of nitrogen fertilization since fertilizers favour tall-growing grasses that outcompete forbs. Pesticide applications should be kept at a minimum to enhance arthropods as the main food source for Woodlarks and their chicks. In addition, the expansion of settlements into breeding areas of Woodlarks should be avoided.

Effect of time of day, time of year, and life history strategy on time budgeting in juvenile Atlantic salmon, Salmo salar

1999 ◽  
Vol 56 (12) ◽  
pp. 2397-2403 ◽  
Author(s):  
Sveinn K Valdimarsson ◽  
Neil B Metcalfe
Keyword(s):  
Life History ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Life History Strategy ◽  
Time Of Day ◽  
Life History Strategies ◽  
Foraging Efficiency ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon ◽  
Time Of Year

Traditionally, behavioural studies on juvenile Atlantic salmon, Salmo salar, have been conducted during the day in summer. It is known that Atlantic salmon become nocturnal in winter, but very little is known about their behaviour at that time. Therefore, observations in a seminatural stream were carried out during the day and night, from February to June, comparing diel and seasonal differences in behaviour between fish adopting alternative life history strategies. The results showed a general trend for more activity in spring than in winter, and the fish were found to be foraging at surprisingly low light levels. There were differences in relative feeding rate between the life history strategies; the early migrant fish foraged mostly during the day whereas the delayed migrant fish did more foraging at night. There is some evidence that the early migrant fish made fewer feeding attempts over the winter, which is surprising, since they grow faster over that period. This suggests differences in foraging efficiency, which could contribute to the separation into these two life history strategies.

scholarly journals Urbanization and species occupancy frequency distribution patterns in core zone areas of European towns

2016 ◽  
Vol 2 (2) ◽  
pp. 23-43 ◽  
Author(s):  
Jukka Jokimäki ◽  
Jukka Suhonen ◽  
Marja-Liisa Kaisanlahti-Jokimäki
Keyword(s):  
Frequency Distribution ◽  
Bird Species ◽  
Selection Procedure ◽  
Distribution Patterns ◽  
Habitat Diversity ◽  
Natural Habitats ◽  
Environmental Diversity ◽  
The North ◽  
Core Species ◽  
Species Occupancy

AbstractMore and more of the globe is becoming urbanized. Thus, characterizing the distribution and abundance of species occupying different towns is critically important. The primary aim of this study was to examine the effect of urbanization and latitude on the patterns of species occupancy frequency distribution (SOFD) in urban core zones of European towns (38 towns) along a 3850-km latitudinal gradient. We determined which of the three most common distributional models (unimodal-satellite dominant, bimodal symmetrical, and bimodal asymmetrical) provides the best fit for urban bird communities using the AICc-model selection procedure. Our pooled data exhibited a unimodal-satellite SOFD pattern. This result is inconsistent with the results from previous studies that have been conducted in more natural habitats, where data have mostly exhibited a bimodal SOFD pattern. Large-sized towns exhibited a bimodal symmetric pattern, whereas smaller-sized towns followed a unimodal- -satellite dominated SOFD pattern. The difference in environmental diversity is the most plausible explanation for this observation because habitat diversity of the study plots decreased as urbanization increased. Southern towns exhibited unimodal satellite SOFD patterns, central European towns exhibited bimodal symmetric, and northern towns exhibited bimodal asymmetric SOFD patterns. One explanation for this observation is that urbanization is a more recent phenomenon in the north than in the south. Therefore, more satellite species are found in northern towns than in southern towns. We found that core species in European towns are widely distributed, and their regional population sizes are large. Our results indicated that earlier urbanized species are more common in towns than the species that have urbanized later. We concluded that both the traits of bird species and characteristics of towns modified the SOFD patterns of urban-breeding birds. In the future, it would be interesting to study how the urban history impacts SOFD patterns and if the SOFD patterns of wintering and breeding assemblages are the same.

The Diet of American Robins: An Analysis of U.S. Biological Survey Records

The Auk ◽  
1986 ◽  
Vol 103 (4) ◽  
pp. 710-725 ◽  
Author(s):  
Nathaniel T. Wheelwright
Keyword(s):  
Quantitative Description ◽  
Geographical Location ◽  
Bird Species ◽  
Stomach Contents ◽  
Time Of Day ◽  
Food Items ◽  
Biological Survey ◽  
American Robins ◽  
Differential Digestion ◽  
The U.S

Abstract I present a quantitative description of the diet of American Robins (Turdus migratorius) and consider how food habits (particularly the proportion of fruit eaten and the diversity of individual meals) are influenced by season, habitat, sex, and time of day. The study is based on an analysis of records of stomach contents compiled by the U.S. Biological Survey and the U.S. Fish and Wildlife Service. Across their entire range, robins ate fruits representing over 50 genera and invertebrates representing over 100 families. Diets were diverse even within local regions, and there was no obvious single feeding niche. The major food classes, consumed in every combination, were soft-bodied invertebrates, hard-bodied invertebrates, and fruits. The same taxa (especially fruits of the family Rosaceae and invertebrates of the orders Coleoptera and Lepidoptera) predominated in robins' diets, irrespective of habitat or geographical location, which presumably reflects both selective foraging and the availability of these widespread taxa. The proportion of fruit (by volume) in the diet was much higher in the fall and winter (median values >90%) than in the spring (<10%); summer values were intermediate. The transition from a diet dominated by invertebrates to a diet dominated by fruits occurred over a 1-2-month period. The number of distinct food items in stomachs, a measure of the species diversity of individual meals, was positively correlated with the fraction of invertebrates in the diet. Thus, at the time of year when robins were dependent on fruits for food, the diversity of their meals was also lowest. The degree of fullness of the stomach showed few consistent trends with season or habitat. Despite different sex roles and nutritional requirements, male and female robins did not differ in the proportion of fruit in the diet in any month or in any region. Nor did their stomachs contain different numbers of distinct food items, different amounts of food, or a different range or distribution of prey taxa. Habitat was an important variable explaining dietary differences. The Biological Survey records have unavoidable shortcomings, most notably problems of sampling biases and the inability to correct for differential digestion of food items. Nonetheless, they are a valuable and underused data base for testing hypotheses, generating new questions of ecological interest, and describing in detail the diets of North American bird species.

scholarly journals Winter bird abundance, species richness and functional guild composition at Delhi’s ponds: does time of day and wetland extent matter?

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Prakhar Rawal ◽  
Swati Kittur ◽  
Murali Krishna Chatakonda ◽  
K S Gopi Sundar
Keyword(s):  
Species Richness ◽  
Species Abundance ◽  
Bird Species ◽  
Time Of Day ◽  
Conservation Priorities ◽  
Bird Abundance ◽  
Functional Guilds ◽  
Β Diversity ◽  
Functional Guild ◽  
Guild Composition

Abstract Urbanisation can limit species persistence and bias composition of functional guilds with serious consequences for ecosystem functioning and conservation planning. Standardised biodiversity surveys are missing at most tropical urban cities where biodiversity levels are high alongside rapidly increasing rates of urbanisation. We explored the utility of time-bound surveys to document winter birds at ponds (wetlands ≤ 5 ha) in Delhi, India at two different times of the day (morning and evening) and in areas with varying extents of wetlands. Systematic surveys at 39 ponds during January–March 2020 yielded an estimated 173 ± 22 bird species (∼37% of Delhi’s birds). The total bird species assemblage at ponds did not vary significantly with time of day, but β-diversity increased marginally with increasing extent of wetlands. Total bird abundance and species richness varied substantially with time of day, with differences apparent across several species rich functional feeding and habitat guilds. Abundance and species richness of some guilds, including species-poor guilds, varied in ponds located in areas with differing extent of wetlands. Reliable and comparable measures of species abundance and species richness (both total and across functional guilds)— metrics commonly used to set research and conservation priorities—in urban habitats can be obtained after appropriately standardising field effort. Such standardised efforts can help underscore the importance of maintaining and improving erstwhile-ignored habitats such as unprotected ponds that are providing refugia to hundreds of bird species in mega-cities like Delhi.

Xylem sap analysis for determining nutritional status of trees: Pseudotsugamenziesii

1985 ◽  
Vol 15 (2) ◽  
pp. 429-437 ◽  
Author(s):  
N. Stark ◽  
C. Spitzner ◽  
D. Essig
Keyword(s):  
Xylem Sap ◽  
Time Of Day ◽  
Tree Age ◽  
Poor Growth ◽  
Field Problem ◽  
Soil Extracts ◽  
Growth Site ◽  
Ion Concentrations ◽  
The Poor ◽  
Time Of Year

Xylem sap extraction of branches as a new field problem-solving technique in forestry, environmental pollution, and botany is described. The influence of extraction pressure, crown aspect, height into the crown, tree age, time of year and day, and soil chemistry on the ion concentrations in xylem sap are discussed. Xylem sap extraction with a pressure chamber provides a good indication of the nutrient status of a species if the trees are of similar age, and if they are sampled at the same aspect, crown height, time of day, time of year, and on the same soils. Pseudotsugamenziesii (Mirb.) Franco (Douglas-fir), growing on nutrient-poor acid soils and moderately fertile alkaline soils showed significant differences in growth rate and ion concentrations in the xylem sap and soil. Trees on the faster growth site (< 12 rings/2.54 cm) had significantly more Ca, K, Mn, P, and N in the xylem sap. Trees on the poor growth site had high levels of Mg in the sap. Trees growing on the poor site which was also K deficient transpired more rapidly than those with faster growth. It is hypothesized that insufficient plant K could reduce the ability of the guard cells to control water loss. The stem water potential was slightly, but not significantly, higher on the poor growth site. Although there is no proof that the deficient ions are the cause of poor growth, they are suspect, given the similar water availability on the two sites. The concept of nutrient supplying potential of a tree, or its ability to supply its needles and meristems with water and nutrients is discussed. Distilled water soil extracts and foliar analyses would not have reflected the same ion relationships (deficiencies or excesses) that are evident in the xylem sap. Evidence for the factors controlling growth in these stands is being sought through fertilizer tests.

scholarly journals Should it matter when we record? Time of year and time of day as factors influencing frontal EEG asymmetry

2012 ◽  
Vol 91 (2) ◽  
pp. 283-291 ◽  
Author(s):  
Jamie R. Velo ◽  
Jennifer L. Stewart ◽  
Brant P. Hasler ◽  
David N. Towers ◽  
John J.B. Allen
Keyword(s):  
Time Of Day ◽  
Eeg Asymmetry ◽  
Frontal Eeg Asymmetry ◽  
Record Time ◽  
Factors Influencing ◽  
Time Of Year

scholarly journals Solar Dish Field System Model for Spacing Optimization

2007 ◽  
Author(s):  
John Igo ◽  
Charles E. Andraka
Keyword(s):  
Capital Investment ◽  
Meteorological Data ◽  
Field Performance ◽  
Energy Performance ◽  
Time Of Day ◽  
Plant Production ◽  
Electrical Grid ◽  
Time Of Year ◽  
The Individual ◽  
The Impact

Dish Stirling power generation systems have been identified by DOE, Sandia National Laboratories, and Stirling Energy Systems (SES) as having the capability of delivering utility-scale renewable energy to the nation’s electrical grid. SES has proposed large plants, 20,000 units or more (0.5 GW rated power) in one place, in order to rapidly ramp up production automation. With the large capital investment needed in such a plant it becomes critical to optimize the system at the field level, as well as at the individual unit level. In this new software model, we provide a tool that predicts the annual and monthly energy performance of a field of dishes, in particular taking into account the impact of dish-to-dish shading on the energy and revenue streams. The Excel-based model goes beyond prior models in that it incorporates the true dish shape (flexible to accommodate many dish designs), multiple-row shading, and a revenue stream model that incorporates time-of-day and time-of-year pricing. This last feature is critical to understanding key shading tradeoffs on a financial basis. The model uses TMY or 15-minute meteorological data for the selected location. It can incorporate local ground slope across the plant, as well as stagger between the rows of dish systems. It also incorporates field-edge effects, which can be significant on smaller plants. It also incorporates factors for measured degraded performance due to shading. This tool provides one aspect of the decision process for fielding many systems, and must be combined with land costs, copper layout and costs, and O&M predictions (driving distance issues) in order to optimize the loss of power due to shading against the added expense of a larger spatial array. Considering only the energy and revenue stream, the model indicates that a rectangular, unstaggered field layout maximizes field performance. We also found that recognizing and accounting for true performance degradation due to shading significantly impacts plant production, compared with prior modeling attempts.

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