Accuracy and variation in estimates of large numbers of birds by individual observers using an aerial survey simulator

Frederick, Peter C.; Hylton, Becky; Heath, Julie A.; Ruane, Martin

doi:10.1648/0273-8570-74.3.281

Cited by 76 publications

(92 citation statements)

References 13 publications

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“…Bird identification and counts are performed either in real time by airborne observers or using on-board cameras to collect aerial imagery that is reviewed and analyzed later. Several studies have indicated that aerial image counts can be more accurate and consistent than live-observer counts (Boyd 2000, Frederick et al 2003, Buckland et al 2012, but a major drawback of the former is the significant time and effort required to manually analyze large volumes of imagery (Woodworth et al 1997, Béchet et al 2004. With burgeoning use of small low-flying unmanned aircraft, or drones, as a means of collecting very high-resolution aerial imagery of birds (Chabot and Bird 2015), as well as increasing possibilities to census birds in satellite imagery (LaRue et al 2017), the challenge of analyzing large volumes of imagery to detect and count subjects has been receiving increased attention.…”

Section: Introductionmentioning

confidence: 99%

An approach for using off-the-shelf object-based image analysis software to detect and count birds in large volumes of aerial imagery

Chabot¹,

Dillon²,

Francis³

2018

ACE

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ABSTRACT. Computer-automated image analysis techniques can save time and resources for detecting and counting birds in aerial imagery. Sophisticated object-based image analysis (OBIA) software is now widely available and has proven effective for various challenging detection tasks, but there is a need to develop accessible and readily adaptable procedures that can be implemented in an operational context. We developed a systematic, repeatable approach using commercial off-the-shelf OBIA software, and tested its effectiveness and efficiency to detect and count Lesser Snow Geese (Chen caerulescens caerulescens) in large numbers of images of breeding colonies across the Canadian Arctic that present a variety of landscapes, numerous confounding features, and varying illumination conditions and exposure levels. Coarse-scale review of analysis results was necessary to remove conspicuous clusters of commission errors, thus rendering the technique semiautomated. It was effective for imagery with spatial resolutions of 4-5 cm, producing overall accurate estimates of goose numbers compared to manual counts (R2 = 0.998, regression coefficient = 0.974) in 41 test images drawn from several breeding colonies. The total automated count (19,920) across all test images exceeded the manual count (19,836) by just 0.4%. We estimate the typical time required to review images for errors to be only 5-10% of that required to count birds manually. This could reduce the person-time required to analyze aerial photos of the major Arctic colonies of Snow Geese from several months to several days. Our approach could be adapted to many other bird detection tasks in aerial imagery by anyone possessing at least basic skills in image analysis and geographic information systems.

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Section: Introductionmentioning

confidence: 99%

An approach for using off-the-shelf object-based image analysis software to detect and count birds in large volumes of aerial imagery

Chabot¹,

Dillon²,

Francis³

2018

ACE

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“…Both overestimation (Green et al 2008) and underestimation (Rodgers et al 2005) of colony size have been reported for visual counts from fixed-wing aircraft (Erwin 1982;Rodgers et al 2005). The use of digital photography improves the accuracy of aerial counts, and Dolbeer et al (1997) showed that aerial photos of Laughing Gull (L. atricilla) nests differed from the ground nest count by -9% to 1% (see also Frederick et al 2003).…”

Section: Discussionmentioning

confidence: 81%

“…Aerial surveys of colonial waterbirds based on visual counts alone may be inaccurate, and the use of photography provides a more reliable means of estimating adults and nests, although some degree of bias is still expected (Dolbeer et al 1997;Frederick et al 2003). Surveys on Lakes Winnipeg, St. Martin, Dog, Shoal and southern Lake Manitoba (south of 50.9° N) were conducted during 11 hr of flight time on 13 June using a Bell 206 Helicopter.…”

Section: Aerial Surveysmentioning

confidence: 99%

Distribution and abundance of nesting common and Caspian terns on the North American Great Lakes, 1976 to 1999

Morris¹,

Weseloh

Cuthbert

et al. 2010

Journal of Great Lakes Research

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“…Estas diferencias pueden estar relacionadas a dos factores: la temporalidad de los censos, pues los trabajos anteriores se limitaron a temporadas de invierno y como se observó en el presente, las abundancias máximas de algunas especies, como el picopando canelo, no necesariamente se alcanzaron en esta época; y a la metodología llevada a cabo, pues pese a las ventajas de los censos aéreos, entre las que se cuenta poder recorrer áreas amplias en poco tiempo, en general esta metodología incrementa los riesgos de subestimación (Briggs et al 1985, Frederick et al 2003.…”

Section: Discussionunclassified

Distribución espacial y temporal de aves playeras (Orden: Charadriiformes) en Laguna San Ignacio, Baja California Sur, México

Mendoza

Carmona

2013

RBT

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Temporal and spatial distribution of shorebirds (Charadriiformes) at San Ignacio Lagoon, Baja California Sur, Mexico. Baja California Peninsula has several wetlands that represent important ecosystems for shorebirds. San Ignacio Lagoon is one of these sites, and supports 10% of the total abundance of shorebirds reported in this Peninsula. Since there is few information about this group in this area, we studied spatial and temporal changes in abundance and distribution of shorebirds in San Ignacio Lagoon. For this, we conducted twelve monthly censuses (October 2007-September 2008 on the entire internal perimeter of the lagoon, which we divided into four areas: two at the North and two at the South. We observed a seasonal pattern, with the lowest abundance in May (1 585 birds) and the highest in October (47 410). The most abundant species were Marbled Godwits (Limosa fedoa; 55% of the total records), Western Sandpipers (Calidris mauri; 23%), and Willet (Tringa semipalmata; 10%). All three species were more abundant in autumn; for both, the Marbled Godwit and Willet, we observed their highest numbers in winter and spring, while the Western Sandpiper showed noticeable oscillations, reaching a maximum in early winter (December). In summer, Marbled Godwit and Willet were the only birds present but in lower numbers. Here present the first records of the Pacific Red Knot (Calidris canutus roselaari) in the area. Bird abundance and species richness were influenced seasonally by migration and spatially by sites in the lagoon. The greatest shorebird abundance was in the South area of the lagoon, probably because of better accessibility to food. Our results allowed the inclusion of San Ignacio Lagoon in the Western Hemisphere Shorebirds Reserve Network (WHSRN) as a site of international importance. Rev. Biol. Trop. 61 (1): 229-241. Epub 2013 March 01.

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Accuracy and variation in estimates of large numbers of birds by individual observers using an aerial survey simulator

Cited by 76 publications

References 13 publications

An approach for using off-the-shelf object-based image analysis software to detect and count birds in large volumes of aerial imagery

An approach for using off-the-shelf object-based image analysis software to detect and count birds in large volumes of aerial imagery

Distribution and abundance of nesting common and Caspian terns on the North American Great Lakes, 1976 to 1999

Distribución espacial y temporal de aves playeras (Orden: Charadriiformes) en Laguna San Ignacio, Baja California Sur, México

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