scholarly journals Aerial Surveys Do Not Reliably Survey Boreal-nesting Shorebirds

2010 ◽  
Vol 124 (2) ◽  
pp. 145
Author(s):  
Kyle H. Elliott ◽  
Paul A. Smith ◽  
Victoria H. Johnston
Keyword(s):  
Aerial Survey ◽  
Breeding Birds ◽  
Detection Rates ◽  
Aerial Surveys ◽  
Closed Forest ◽  
On Line ◽  
Line Transects ◽  
Intensive Observation ◽  
Bodies Of Water ◽  
Nest Searching

Aerial surveys have been used as a method for surveying boreal-nesting shorebirds, which breed in difficult-to-access terrain; however, the fraction of breeding birds observed from the air is unknown. We investigated rates of detection by conducting simultaneous air and ground surveys for shorebirds at three sites in the boreal forest of the Northwest Territories, Canada, in 2007. Helicopter surveys included both pond-based surveys where the helicopter flew around the perimeter of each wetland and transect-based surveys where observers recorded birds seen on line transects. Ground surveys involved intensive observation, territory mapping and nest searching in 5 km2 of plots over a period of 5-6 weeks. Shorebird densities observed from the helicopter were highest near large bodies of water. No shorebirds were observed over closed forest despite breeding densities on ground surveys being highest in closed forest. Detection rates were very low, varied among species and aerial survey types, and were inconsistent over time. Ground-based observations showed that the shorebirds often did not flush in response to the helicopter passing overhead. Owing to poor rates of detection, we conclude that helicopter surveys are not an appropriate method for surveying breeding shorebirds in boreal habitats, but may have some utility for monitoring birds' use of stop-over locations.

scholarly journals Surfacing and vertical behaviour of Atlantic bluefin tuna (Thunnus thynnus) in the Mediterranean Sea: implications for aerial surveys

2020 ◽  
Vol 77 (5) ◽  
pp. 1979-1991
Author(s):  
Robert Klaus Bauer ◽  
Fabien Forget ◽  
Jean-Marc Fromentin ◽  
Manuela Capello
Keyword(s):  
Mediterranean Sea ◽  
Fork Length ◽  
Bluefin Tuna ◽  
Aerial Survey ◽  
Thunnus Thynnus ◽  
Survey Period ◽  
Atlantic Bluefin Tuna ◽  
Aerial Surveys ◽  
Gulf Of Lion ◽  
Nw Mediterranean

Abstract Atlantic bluefin tuna (Thunnus thynnus) (ABFT) frequently engage in surface basking and foraging behaviour that makes them detectable from afar. This behaviour is utilized for the development of fisheries-independent abundance indices based on aerial surveys, although changes in the surface-feeding dynamics of ABFT are not yet accounted for. We investigated the daytime surfacing behaviour of ABFT at different temporal and vertical resolutions based on 24 individuals (117–158 cm fork length), tagged with pop-up archival tags in the Gulf of Lion, NW-Mediterranean Sea between 2015 and 2016. The results suggest that ABFT remain usually <2 min continuously within the visible surface (0–1 m) during daytime. ABFT presence in the 0–1 and 0–20 m layers varied over time and between individuals but showed a seasonal decline towards autumn with the breakdown of thermal stratification. Furthermore, the rate of surfacing events was highly correlated with the time spent in the 0–20 m layer. Geolocation estimates confirm a strong site fidelity of ABFT during the aerial survey period (August–October) in the Gulf of Lion. Our results support the choice of the survey region and period, but related indices should account for the seasonality of ABFT surface behaviour [i.e. the time spent in the 0–20 m layer.

scholarly journals Boreal old-growth forest structural diversity challenges aerial photographic survey accuracy

2020 ◽  
Vol 50 (2) ◽  
pp. 155-169 ◽  
Author(s):  
Maxence Martin ◽  
Nicole J. Fenton ◽  
Hubert Morin
Keyword(s):  
Sustainable Forest Management ◽  
Forest Succession ◽  
Structural Diversity ◽  
Aerial Survey ◽  
Old Growth ◽  
Tree Species Composition ◽  
Forest Inventories ◽  
Old Growth Forest ◽  
Aerial Surveys ◽  
Old Growth Forests

The erosion of old-growth forests in boreal managed landscapes is a major issue currently faced by forest managers; however, resolving this problem requires accurate surveys. The intention of our study was to determine if historic operational aerial forest surveys accurately identified boreal old-growth forests in Quebec, Canada. We first compared stand successional stages (even-aged vs. old-growth) in two aerial surveys performed in 1968 (preindustrial aerial survey) and 2007 (modern aerial survey) on the same 2200 km2 territory. Second, we evaluated the accuracy of the modern aerial survey by comparing its results with those of 74 field plots sampled in the study territory between 2014 and 2016. The two aerial surveys differed significantly; 80.8% of the undisturbed stands that were identified as “old-growth” in the preindustrial survey were classified as “even-aged” in the modern survey, and 60% of the stands identified as “old-growth” by field sampling were also erroneously identified as “even-aged” by the modern aerial survey. The scarcity of obvious old-growth attributes in boreal old-growth forests, as well as poorly adapted modern aerial survey criteria (i.e., criteria requiring high vertical stratification and significant changes in tree species composition along forest succession), were the main factors explaining these errors. It is therefore likely that most of Quebec’s boreal old-growth forests are currently not recognized as such in forest inventories, challenging the efficacy of sustainable forest management policies.

Some human, aircraft and animal factors affecting aerial surveys: how to enumerate animals from the air

2008 ◽  
Vol 35 (4) ◽  
pp. 258 ◽  
Author(s):  
Peter J. S. Fleming ◽  
John P. Tracey
Keyword(s):  
Visual Acuity ◽  
New South ◽  
Human Memory ◽  
Aerial Survey ◽  
Factors Affecting ◽  
Counting Error ◽  
Aerial Surveys ◽  
South Wales ◽  
Survey Estimates ◽  
Aerial Platforms

Aerial surveys of wildlife involve a noisy platform carrying one or more observers moving over animals in order to quantify their abundance. This simple-sounding system encapsulates limits to human visual acuity and human concentration, visual attention, salience of target objects within the viewed scene, characteristics of survey platforms and facets of animal behaviours that affect the detection of animals by the airborne observers. These facets are too often ignored in aerial surveys, yet are inherent sources of counting error. Here we briefly review factors limiting the ability of observers to detect animals from aerial platforms in a range of sites, including characteristics of the aircraft, observers and target animals. Some of the previously uninvestigated limitations identified in the review were studied in central and western New South Wales, showing that inaccuracies of human memory and enumeration processes are sources of bias in aerial survey estimates. Standard protocols that minimise or account for the reviewed factors in aerial surveys of wildlife are recommended.

On bias, precision and accuracy in wildlife aerial surveys

2008 ◽  
Vol 35 (4) ◽  
pp. 253 ◽  
Author(s):  
Jim Hone
Keyword(s):  
Survey Data ◽  
Wildlife Management ◽  
Aerial Survey ◽  
Review Of The Literature ◽  
Density Estimates ◽  
True Value ◽  
Wildlife Population ◽  
Aerial Surveys ◽  
Precision And Accuracy ◽  
Definition Of

Bias, precision and accuracy have been studied extensively in wildlife population estimation including aerial surveys. A review of the literature shows that the concepts of bias and precision are used broadly consistently. Aerial survey data from known populations of feral pig carcases and white-tailed deer show that few density estimates are unbiased and precise. Research is needed, however, to clarify how much bias and how much precision are enough for the various types of wildlife management activities. Accuracy is used in two closely related but different ways. One set of definitions of accuracy relates to deviations from the true value (bias) and the second set relates to squared deviations from the true value (bias and precision). The implications are that authors are encouraged to clearly state which definition of accuracy they use, or focus solely on bias and precision.

Calibrating Aerial Surveys of Kangaroos by Comparison With Drive Counts

1988 ◽  
Vol 15 (3) ◽  
pp. 277 ◽  
Author(s):  
J Short ◽  
J Hone
Keyword(s):  
Aerial Survey ◽  
Survey Area ◽  
Aerial Surveys ◽  
Drive Counts

Densities of red and western grey kangaroos and euros were assessed by aerial survey and compared with densities obtained in the same area by drive counts. The survey area (12.1 km2) was long, narrow and sparsely vegetated. Lakes and a kangaroo-proof fence bounded the area on three sides facilitating the drive count. Densities from aerial surveys ranged between 38 and 54% of the corresponding drive counts for red kangaroos, between 15 and 23% for western grey kangaroos, and between 9 and 10% for euros. The time of morning at which the surveys were conducted altered these percentages. About twice as many red and western grey kangaroos were counted on aerial surveys at sunrise compared to surveys 3.5 h later.

Sightability as a Factor in Aerial Survey of Bird Species and Communities

1985 ◽  
Vol 12 (1) ◽  
pp. 57 ◽  
Author(s):  
LS Broome
Keyword(s):  
New England ◽  
Water Body ◽  
Bird Species ◽  
Abundant Species ◽  
Common Species ◽  
Aerial Survey ◽  
Flying Height ◽  
South Wales ◽  
Population Sizes ◽  
Bodies Of Water

Experimental aerial and ground censuses of waterbirds were conducted on three small, isolated bodies of water on the New England tablelands of New South Wales. The flying height at which sightability was optimized for the most common species was 30 m. Aerial and ground counts were significantly correlated for most species on the three watar bodies. Black swan, swamphen, coots, musk ducks and maned ducks were counted in equivalent or greater numbers from the air than from the ground on at least one water body. Other species were counted in lower numbers from the air than from the ground. A fairly high precision in the aerial-ground relationship for the most abundant species indicates that aerial survey can be a useful procedure for obtaining indices or estimates of the population sizes of these species. However, differences in sightability between species and between types of water body indicate that indices should be used and interpreted with caution. Other bird species from a variety of habitat types which are also amenable to aerial survey are discussed, and some recommendations for aerial surveys of birds are provided.

scholarly journals Opportunistically collected data from aerial surveys reveal spatio-temporal distribution patterns of marine debris in German waters

2020 ◽  
Vol 28 (3) ◽  
pp. 2893-2903
Author(s):  
Bianca Unger ◽  
Helena Herr ◽  
Sacha Viquerat ◽  
Anita Gilles ◽  
Patricia Burkhardt-Holm ◽  
...  
Keyword(s):  
Temporal Distribution ◽  
Distribution Patterns ◽  
Aerial Survey ◽  
Marine Debris ◽  
Encounter Rate ◽  
The North ◽  
Aerial Surveys ◽  
Spatio Temporal ◽  
German Waters ◽  
The Baltic

AbstractMarine debris is known for its ubiquitousness and harmful effects on marine life. This study is the first analysis to provide information on the distribution of floating marine debris in German waters using aerial survey data collected between 2002 and 2016. During regular harbour porpoise monitoring flights, 191,167 km were covered and 26,512 floating debris items recorded (average encounter rate 0.1387 items/km). Debris was encountered more often in the North Sea than in the Baltic Sea (0.16 items/km; 0.08 items/km). The average encounter rate was higher in offshore waters than in coastal areas. Overlaps of marine debris distribution with ‘Special Areas of Conservation’ are a particular reason for concern. Moreover, the spring months (March–May) were identified to be the time of the year with the highest average encounter rates for marine debris. Fishing-related debris was shown to contribute up to 25% of the total number of all observed items. This study shows that opportunistically collected data on marine debris from aerial surveys are valuable for identifying distribution patterns of floating debris without additional survey effort and costs. These data can be used as baseline information to inform management schemes such as the Marine Strategy Framework Directive.

Comparison of Helicopter Line Transects with Walked Line Transects for Estimating Densities of Kangaroos

1997 ◽  
Vol 24 (4) ◽  
pp. 397 ◽  
Author(s):  
T. F. Clancy ◽  
A. R. Pople ◽  
L. A. Gibson
Keyword(s):  
Repeated Measures ◽  
Aerial Survey ◽  
Survey Method ◽  
Line Transect ◽  
Attractive Alternative ◽  
Line Transect Sampling ◽  
Density Estimates ◽  
Transect Sampling ◽  
Grey Kangaroo ◽  
Line Transects

The performance of helicopter surveys for estimating population densities of red kangaroos (Macropus rufus), eastern grey kangaroos (Macropus giganteus) and common wallaroos (Macropus robustus) was investigated by comparing line-transect density estimates obtained from helicopter surveys with those from ground (walked) surveys. Comparisons were made at four sites in central western Queensland (areas with high densities of red kangaroos and common wallaroos) that were surveyed during winter and summer from December 1991 until February 1995, and one site in south-eastern Queensland (an area of high eastern grey kangaroo density) surveyed annually during autumn from March 1991 until March 1994. Helicopter surveys generally recorded lower sample sizes than did ground surveys (means ± s.e = 34 ± 6%, 33 ± 9% and 76 ± 2% lower for red kangaroos, eastern grey kangaroos and wallaroos, respectively). Density estimates obtained from the helicopter surveys were not significantly different from those obtained from ground surveys for both red and eastern grey kangaroos as assessed by repeated-measures ANOVA and regression analysis. However, helicopter surveys of common wallaroos consistently returned density estimates about half those of ground surveys. The relationships between the two methods did not differ between winter and summer for any species. The conventional aerial survey method for kangaroos of strip transects from fixed-wing aircraft has limited ability to adjust for varying sightability conditions. Therefore, helicopter surveys with line-transect sampling are an attractive alternative.

Aerial survey of walrus haul-out sites in west Spitsbergen and Moffen

Polar Record ◽  
1993 ◽  
Vol 29 (168) ◽  
pp. 55-58 ◽  
Author(s):  
E. Cruwys ◽  
Dan Weinstein
Keyword(s):  
Aerial Survey ◽  
Northwest Coast ◽  
Physiological Changes ◽  
Engine Noise ◽  
The Past ◽  
Aerial Surveys ◽  
Odobenus Rosmarus ◽  
West Spitsbergen ◽  
Odobenus Rosmarus Rosmarus

ABSTRACTIn July 1992 two aerial surveys were conducted to assess the size of the walrus (Odobenus rosmarus rosmarus) population at haul-out sites reported on the northwest coast of Spitsbergen and on Moffen. Walrus have been extensively hunted in Svalbard during the past 350 years, and in 1952 concern about decreasing stocks caused the Norwegian government to pass a law protecting the animals from hunting. At the time of the survey, it is likely that the walrus would have been at some stage of the moult, and it is tentatively suggested that the physiological changes reported to take place during moulting can cause lethargy and sluggishness that may make walrus less susceptible to disturbance by engine noise. Thirty-seven walrus were counted on the survey around Moffen, and three walrus on the northwest coast of Spitsbergen three days later.

Diet composition and foraging activity of Pipistrellus pygmaeus in a floodplain forest

Biologia ◽  
2008 ◽  
Vol 63 (2) ◽  
Author(s):  
Tomáš Bartonička ◽  
Zdeněk Řehák ◽  
Michal Andreas
Keyword(s):  
Diet Composition ◽  
Food Item ◽  
Late Pregnancy ◽  
Floodplain Forest ◽  
Foraging Activity ◽  
Forest Sites ◽  
On Line ◽  
Line Transects ◽  
Taxonomic Groups ◽  
Main Food Item

AbstractIn 2000–2002 bat droppings were collected under the emerging crevice of a nursery colony of Pipistrellus pygmaeus. The locality was situated in a floodplain forest at the confluence of the Dyje and Morava rivers (S Moravia, Czech Republic). In total, 27 samples (20 pellets in one sample) of droppings were used to analyze prey remains. In the diet, 40 taxonomic groups of invertebrates were found. As expected, small dipteran insects were the main food item in which Nematocera dominated. Besides Chironomidae and Ceratopogonidae also a high percentage of nematoceran eggs were recorded. Surprisingly, a relatively high percentage of Brachycera was recorded. Further frequent prey items belonged to the orders of Trichoptera, Hymenoptera, Coleoptera and Sternorrhyncha. A heterodyne bat detector was used to follow foraging activity of P. pygmaeus on line transects in forest and water habitats in the vicinity of the colony. A significant decrease in foraging activity over water habitats and in forest sites during the late pregnancy (mid-May — early June) and an increase during the lactation and post-lactation periods (mid-June — early August) were found. Changes in the frequency of occurrence of Chironomidae, Neuroptera, Trichoptera, Aphidinea and Simuliidae were correlated with the bats’ foraging activity.

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