Great Egret Research Articles

Validating an Unmanned Aerial Vehicle (UAV) Approach to Survey Colonial Waterbirds

Unmanned aerial vehicles (UAVs) can improve detection and count accuracy of avian species and provide an inexpensive alternative to surveying waterbirds compared to ground counts and other aerial methods. To validate this method for surveying colonial waterbirds in logistically challenging areas, we compared counts from images collected with a fixed-wing UAV to ground counts using a marked-subsample method or direct counts at three study sites: 1) in an open field using decoys that represented three colonial waterbird species; 2) constructed platforms in a swamp with colonial nesting Great Egrets (Ardea alba); and 3) an island with a large nesting colony of Brown Pelicans (Pelecanus occidentalis). Estimates or direct counts from UAV images were not significantly different from a known number of decoys or ground counts for Great Egrets but were almost twice as high compared to ground counts for juvenile Brown Pelicans. UAV flights did not cause either Great Egrets or Brown Pelicans to flush from nesting areas while ground surveys flushed the majority of adult Brown Pelicans from the survey area. UAV surveys captured images of eggs in nests that could not be observed by ground surveyors. Our results indicate that UAVs can provide a cost-effective and efficient method of surveying waterbirds with similar or improved results and little disturbance of colonies compared to ground counts.

Piscivorous Bird Use of Aquaculture and Natural Water Bodies in Mississippi

ABSTRACTDouble‐crested cormorants (Phalacrocorax auritus) and great egrets (Ardea alba) have an extensive history of human‐wildlife conflict with the aquaculture industry of western Mississippi, USA, due to their depredation of cultured catfish (Ictalurus spp.). Although aquaculture is abundant, western Mississippi also contains naturally occurring water bodies that offer alternative forage opportunities to these species. How cormorants or egrets distribute themselves among these 2 foraging options is unknown, but it has been generally assumed each species uses aquaculture disproportionately more because of the high density of available prey. To test this assumption, we surveyed these species on aquaculture and naturally occurring water bodies using aerial surveys from October through April of 2015–2016, 2016–2017, and 2017–2018. We modeled the proportion of each species on aquaculture as a function of year, date, and weather‐related variables using quasi‐binomial generalized linear models. Egrets used aquaculture consistently more than what was proportionally available to them and use was not influenced by any of the variables we measured. Proportional use of aquaculture by cormorants was lowest during October through January but steadily increased through April, indicating a distribution shift toward aquaculture in the months immediately prior to their migration. The highest proportional use of aquaculture by cormorants occurred in 2016, a year when lethal control measures were not allowed against cormorants. Conversely, the least proportion of cormorants on aquaculture was in 2015 when cormorants could be lethally controlled under authority of an Aquaculture Depredation Order. This trend highlights the potential influence of changes in mortality risk, caused by changes in policy regarding lethal take of cormorants, on cormorant distribution between foraging options. © 2020 The Wildlife Society.

Letter from the president.

Letter from the president.

INVENTARISASI JENIS BURUNG PANTAI DI KAWASAN PULAU MARSEGU KABUPATEN SERAM BAGIAN BARAT PROVINSI MALUKU

This research was conducted on the island of Marsegu because this area is included in the area of the natural marine tourism park which should be the concern of the government and the community around the island. The study aimed to determine the species of shorebirds found in the Marsegu island region in the western part Seram. The study was conducted in the morning and evening for 2 days at the location which is a gathering place for shorebirds. In the study location, 8 species of shorebirds were found and then inventoried and identified. The number of shorebirds species found in the Marsegu island area was 8 species, among others; Coral egrets (Egratta sacra), Big Egrets (Egretta alba), Trinil Beach (Actitis hypoleucos), Little sea worms (Sterna albifrons), Black wing sea worms (Sterna fuscata), Big (Fregata minor), Sea-eagle belly white (Haliaetus leucogaster), Bondol Hawk (Indus Haliastur), with the dominant species being the Big Cingkalang (Fregata minor). The most common species are large Cikalang (minor Fregata), small sea virgin (Sterna albifrons), and large egret (Egretta alba). Factors that cause the survival of shorebirds on the Marsegu island region because they store a lot of food supplies. In addition, food availability is affected by a lack of human activity in this region and the establishment of this area as a Marine Nature Tourism Park.

Golden Jackal Canis aureus Linnaeus, 1758 (Mammalia: Carnivora: Canidae) distribution pattern and feeding at Point Calimere Wildlife Sanctuary, India

Golden Jackal Canis aureus, a medium-sized omnivore belonging to the family Canidae, ranges widely from Europe and extends across the middle-east to India. It’s adaptable social system according to the distribution of food resources enabling it to range widely from desert to evergreen forests, mangroves, rural, and semi-urban human-agro-ecosystems. Despite its wide distribution, the species has not received adequate scientific attention in much of its southern India range. This study was carried out to assess its distribution pattern, diet composition, and prey preference at Point Calimere Wildlife Sanctuary, a well-known habitat for the jackal and the only predator of the sanctuary. Data on distribution collected through extensive field surveys revealed that the species distribution is uniform in southern and southeastern parts of the sanctuary, in areas where the habitat is more open with grasslands and mudflats and is patch in the tropical dry-evergreen habitat. Analysis of 155 scat samples revealed that the diet comprised 19 species of food items, including mammals, birds, insects, other invertebrates, and plant matter characterizing omnivorous nature. Temporal variation in diet composition—with significantly higher proportion of birds during winter than in summer—coincides with abundance of prey species in relation to season, which indicate the opportunistic foraging and hunting nature of the species. Data on diet preference showed that jackals in the area preferred Black-naped Hare, Spotted Dove and Lapwing followed by Chital, Grey Francolin, Cattle Egret, and Large Egret, while Blackbuck, Bonnet Macaque, and cattle were not preferred, which is discussed under optimal foraging. The jackal being the only large-sized predator of this natural system, more detailed studies and effective measures to conserve the species are vital not only to understand the prey-predator mechanism, but also to conserve the biodiversity of this unique ecosystem.

Prevalence and potential risk of Salmonella enterica in migratory birds from South Korea

Salmonella is a type of zoonotic bacteria that represents an economic and public health concern worldwide. Difficulties in sample collection from migratory birds mean little is known about their importance as a reservoir of Salmonella. The present study evaluated the prevalence and potential risk of Salmonella enterica in migratory birds. From 2012–2017, 3661 cloacal swabs from migratory birds were collected in South Korea and tested to isolate S. enterica. Strains were tested for antimicrobial resistance and the presence of virulence genes. Thirty-six S. enterica strains, including S. enterica serovar Typhimurium (n = 19), S. Berta (n = 16), and S. Virchow (n = 1), were isolated from 34 birds. Two migratory birds were simultaneously co-infected with two serotypes. S. enterica was isolated from the Mallard duck, Northern pintail, Eurasian wigeon, Spot-billed duck, Eastern great egret, and Intermediate egret. S. Virchow was resistant to ciprofloxacin, with a point mutation (Ser-83-Phe) in the gyrA gene. Ten virulence genes were detected; sixteen strains were positive for all ten virulence genes. Salmonella was isolated from different migratory bird species and geographic locations with up to 100 % similarity of PFGE type. Eight S. Virchow strains taken from migratory birds, poultry farms, and chicken meat showed the same PFGE type. Salmonella was transmitted across species, space, and time in migratory birds. These birds may play a role in the dispersal of pathogenic and antimicrobial-resistant Salmonella and sporadic Salmonella infections in poultry; therefore, they may represent a direct or indirect public health threat.

An investigation of the monitoring and management of the habitat of the family Ardeidae in Muan Yongwol-ri Breeding Sites in Korea

The purpose of this study was to investigate the variation in populations and species of the family Ardeidae through an evaluation of environmental habitat characteristics in the breeding sites of the family Ardeidae in Muan Yongwol, Korea. The study area has been protected as a Natural Monument (No. 211) in Korea and is located in Yongwol, Muan, in Korea. The monitoring of the herons was performed in October 2015 and from February to September 2016. The monitoring of vegetation, fish, benthic macroinvertebrates, and amphibian was performed in April and July of 2016, and the monitoring of land insecta was conducted in July 2016. The populations of the Ardeidae family in the Muan Yongwol-ri habitat of egrets and herons were recorded as 840, 1155, 1211, and 52 for Ardea cinerea, Egretta alba, Egretta garzetta, and Nycticorax nycticorax, respectively. Bubulcus ibis was not found. Terrestrial insects were found in 10 orders, 62 families, and 142 species. Benthic macroinvertebrates were in 11 orders, 15 families, and 18 species, and the predominant species was Chironomidae sp. Fish were found in two orders, three families, and nine species, and Carassius auratus were dominant. The proportions of fish, amphibian, reptilia, insecta, and others for food of Ardeidae were observed at 56.9%, 20.2%, 6.4%, 14.7%, and 1.8%, respectively. The area of the nest trees of Ardeidae family was approximately 8805 m2. The nest tree counts of Pinus thunbergii, Quercus serrata, and Quercus acutissima in the breeding sites were 147, 3, and 3, respectively, and all dead trees were Pinus thunbergii. The levels of salinity and available phosphate were much higher in the breeding site of the Ardeidae family than they were in control area. A management plan should be followed in this breeding area, such as understory vegetation thinning, soil improvement, or transplanting nest trees.

Ultraviolet-assisted oiling assessment improves detection of oiled birds experiencing clinical signs of hemolytic anemia after exposure to the Deepwater Horizon oil spill.

While large-scale oil spills can cause acute mortality events in birds, there is increasing evidence that sublethal oil exposure can trigger physiological changes that have implications for individual performance and survival. Therefore, improved methods for identifying small amounts of oil on birds are needed. Because ultraviolet (UV) light can be used to identify thin crude oil films in water and on substrate that are not visually apparent under normal lighting conditions, we hypothesized that UV light could be useful for detecting small amounts of oil present on the plumage of birds. We evaluated black skimmers (Rynchops niger), brown pelicans (Pelecanus occidentalis), clapper rails (Rallus crepitans), great egrets (Ardea alba), and seaside sparrows (Ammodramus maritimus) exposed to areas affected by the Deepwater Horizon oil spill in the Gulf of Mexico as well as from reference areas from 20 June, 2010 to 23 February, 2011. When visually assessed without UV light, 19.6% of birds evaluated from areas affected by the spill were determined to be oiled (previously published data), whereas when examined under UV light, 56.3% of the same birds were determined to have oil exposure. Of 705 individuals examined in areas potentially impacted by the spill, we found that fluorescence under UV light assessment identified 259 oiled birds that appeared to be oil-free on visual exam, supporting its utility as a simple tool for improving detection of modestly oiled birds in the field. Further, UV assessment revealed an increase in qualitative severity of oiling (approximate % of body surface oiled) in 40% of birds compared to what was determined on visual exam. Additionally, black skimmers, brown pelicans, and great egrets exposed to oil as determined using UV light experienced oxidative injury to erythrocytes, had decreased numbers of circulating erythrocytes, and showed evidence of a regenerative hematological response in the form of increased reticulocytes. This evidence of adverse effects was similar to changes identified in birds with oil exposure as determined by visual examination without UV light, and is consistent with hemolytic anemia likely caused by oil exposure. Thus, UV assessment proved useful for enhancing detection of birds exposed to oil, but did not increase detection of birds experiencing clinical signs of anemia compared to standard visual oiling assessment. We conclude that UV light evaluation can help identify oil exposure in many birds that would otherwise be identified visually as unexposed during oil spill events.

Historic and contemporary use of catfish aquaculture by piscivorous birds in the Mississippi Delta

AbstractPiscivorous birds are the primary source of catfish (Ictalurus spp.) depredation at aquaculture facilities in northwestern Mississippi. Of particular concern is the Double-crested Cormorant (Phalacrocorax auritus), which can cost aquaculture producers millions of dollars annually through the depredation of cultured fish. Historical research conducted in the early 2000s estimated cormorant use of aquaculture ponds in the region, but aquaculture area has decreased by more than 70% since those estimates were made. With less aquaculture available, we predicted cormorant densities on aquaculture would be greater today than historically. Applying a similar methodology as in historical studies, we used aerial surveys to collect data on cormorants at night roosts and using catfish aquaculture ponds during 3 consecutive winter seasons, beginning in 2015. Although the mean annual number of cormorants at roosts in the Delta during our study was 64% less than historically, we found no significant change in densities on aquaculture, suggesting that aquaculture area is likely the factor influencing cormorant occurrence in northwestern Mississippi. During contemporary surveys we also measured the abundance of Great Blue Herons (Ardea herodias) and Great Egrets (A. alba) on the aquaculture clusters, and built predictive models of abundance relative to variables associated with forage at and surrounding the clusters. We found abundance of all 3 species was strongly related to the amount of aquaculture area both within and surrounding a cluster, although patterns varied by species. Cormorant abundance was also greater on clusters with proportionately more food fish (≥20 cm in length) than fingerlings (<20 cm) and was positively related to the proximity and size of night roosts. The relationships described here can be used by producers and wildlife managers to predict the abundance of these piscivorous birds at aquaculture facilities and to design efficient management plans to mitigate potential impacts of depredation and disease.

Great White Egret Casmerodius albus in Novgorod Region in 2016–2018

Ninety-six registrations of great white egret from ten districts of Novgorod Region in 2016–2018 were analyzed. The birds were seen from single individuals up to 170 birds in one flock. The main areas of registrations of this species are the surroundings of the city of Novgorod and Lake Ilmen. The birds were seen on the territory from February 25 to October 31. We did not get any documented evidence of this species breeding, but breeding is possible. At present, the great white egret has to be considered as a summering, possibly breeding, and occasionally wintering species of Novgorod Region.

The Diversity, Distribution and Feeding Guild of Mammals and Birds in Institut Teknologi Sumatera (ITERA) Landscape

ITERA was established in 2014 and caused a landscape conversion from a rubber plantation into a construction area. Changes in a landscape usually affect wildlife biodiversity such as mammals and birds. The objective of this research is to identify and to determine the diversity, distribution, and feeding guilds of mammal and bird species. A survey of mammals and birds in the ITERA landscape has conducted between April and September 2019. This research used line transect and trapping method for mammals. The combination of point count and transect method used for birds observation. ITERA Landscape divided into six transects. This research found three species mammals belonging to three families. C. notatus only found in rubber stands. 67% of terrestrial mammals and all feeding guilds are omnivorous. This research found 814 encounters of birds consisting of 28 species belonging to 18 families. Species with the highest dominance are Lonchura punctulata, and the dominant family is Ardeidae. Elanus caeruleus and Ardea alba are a protected species which stated in Indonesia regulation. The transect that has the highest species richness is transect 6 with 22 species, and transect 1 with 21 species. The highest stratification used for foraging of birds community is terrestrial, and the highest feeding guild is insectivorous.

Ege Denizi’nde kıyı balıkçılığı ve deniz kuşları arasındaki bazı etkileşimler

In this study, it is aimed to determine the some interactions between various fishery types and seabirds, results of this interaction and sea bird species that have been interacting due to secondary attraction factors. A total of 80 fishermen, working in fish farms, small scale fishery (SSF) and lagoons located in Izmir, Aydın and Muğla were face-to-face interviewed between September 2016 and December 2018. The great cormorant (Phalacrocorax carbo), yellow-legged gull (Larus michahellis), great white egret (Ardea alba), some yelkouan shearwater (Puffinus yelkouan) and great white pelican (Pelecanus onocrotalus) are the bird species that have an interaction with coastal fishermen and sea-cage fish farms. 82% of employees in sea-cage fish farms mentioned that they have an interaction with sea birds in winter, besides %50 of SSF have an interaction with sea birds in summer. The difference between interaction rate according to seasons has been found as statistically significant (p<0.05). 33% of employees in fish farms expressed that they see sea birds during the day. This ratio is 21.7% and 15% for SSF and fishermen in lagoon, respectively. Furthermore, 8.3% of fishermen in lagoon, 11% of employees in fish farms and SSF mentioned that they have an interaction with seabirds especially in the morning time.

Migratory behaviour and survival of Great Egrets after range expansion in Central Europe.

Great Egret Ardea alba is one of few Western Palearctic species that underwent a rapid range expansion in the recent decades. Originally breeding in central and eastern Europe, the species has spread in northern (up to the Baltic coast) and western (up to the western France) directions and established viable breeding populations throughout almost entire continent. We monitored one of the first Great Egrets colonies established in Poland to infer migratory patterns and survival rates directly after range expansion. For this purpose, we collected resightings from over 200 Great Egret chicks marked between 2002–2017 in central Poland. Direction of migration was non-random, as birds moved almost exclusively into the western direction. Wintering grounds were located mainly in the western Europe (Germany to France) within 800–950 km from the breeding colony. First-year birds migrated farther than adults. We found some, although relatively weak, support for age-dependent survival of Great Egrets and under the best-fitted capture-recapture model, the estimated annual survival rate of adults was nearly twice higher than for first-year birds (φad = 0.85 ± 0.05 vs. φfy = 0.48 ± 0.15). Annual survival rate under the constant model (no age-related variation) was estimated at φ = 0.81 ± 0.05. Our results suggest that Great Egrets rapidly adapted to novel ecological and environmental conditions during range expansion. We suggest that high survival rate of birds from central Poland and their western direction of migration may facilitate further colonization processes in western Europe.

Hazards of wind turbines on avifauna - a preliminary appraisal within the Indian context

Wind farms are substantial sources of renewable energy in India; however, their spread across the country potentially present new hazards to local and migratory birds. This study explored the risk of electrocution and collision of birds with wind turbines close to eco-sensitive zones in India, including Bakkhali, a UNESCO World Heritage site. Geographic information system and remote sensing technology were used. The results indicate vulnerability of local bird species such as barn owl, Indian Scops Owl, Blue Rock Pigeon, Asian Koel, House Crow, Common Sandpiper, Common Snipe, Ruddy Shelduck, Lesser Whistling Duck, Cattle Egret, Great Egret, and Pond Herons, as well as migratory species such as Bar-headed Goose, Red-crested Pochard, and American Black Duck. Modification of wind turbine design and location were considered determinant factors to reduce risk of bird collisions.

생태하천으로 조성된 반석천의 물새류 출현특성

This study was conducted as a basic research to create a sound and vital ecological environment in the city compared to the appearance characteristics of Gap stream(G-stream), which are the main stream of Banseok stream(B-stream), by analyzing the characteristics of waterbirds, including Wild Spot-billed Duck (S-Duck), that live in B-stream built as ecological stream. The waterbird survey was conducted by the line census for 3.2km, Jukdong-bridge to Jamiseon-bridge, from January to August 2018. The analysis of the survey was conducted with Relative species density(RD) of the emerging waterbird species, the Species diversity and Density Per Unit area for 100m²(DPU). The waterbird survey results of B-stream was conducted 65 times. The five types of water birds that appeared during the survey were Spot-billed Duck(Anas poecilorhyncha), Teal(Anas crecca), Little Egret(Egretta garzetta), Great Egret(Egretta alba), and Grey Heron(Ardea cinerea). As a result, for S-Duck at B-stream, RD was 89.9%, monthly species diversity was simple as 0.3801 in January, 0.5943 in February and 0.3501 in August. The DPU of the S-Duck was 0.165/100m² in the B-Stream survey section which was 4.9 times higher than the main stream section, G-stream. The non-freezing zone of the city’s small stream is expected to play an important role as a winter stop for wild birds such as S-Duck during the freezing period of the huge stream. For this reason, considering the ecological characteristics of wild waterbirds such as S-Duck when creating ecological stream, a: space and linear selection of waterways which can minimize the impact of natural enemy and increasing the number of walkers, b: management water-friendly plants in the low flow channel, c: arrangement walking-bicycle road will be necessary.

Fine scale characteristics of catfish aquaculture ponds influencing piscivorous avian species foraging use in the Mississippi Delta.

Piscivorous avian species are the main source of catfish depredation at aquaculture facilities in Mississippi, resulting in the economic loss of millions of dollars every year. Most notable of these avian species are the double-crested cormorant (Phalacrocorax auritus), great blue heron (Ardea herodias), and great egret (A. alba). Understanding why these species select specific ponds can increase management efficiency directed at avian dispersal and provide insight into their decision making with respect to foraging behavior. We collected species presence data on catfish ponds by flying 35 surveys from October through April of 2015–2017, during which an average of 973 catfish ponds were observed each year. We collected data associated with each pond’s physical surroundings and contents and used occupancy modeling to determine their influence on avian occupancy probability. We also collected data associated with stocking practices and catfish health on a subset of ponds, and constructed resource selection functions to model their influence on avian presence. Pond area was positively related to occupancy probability of each species. Cormorant occupancy increased as pond distance from forest cover and activity centers, such as workshops and offices, increased. Distance to nearest activity center was positively related to egret occupancy, while distance to nearest forested area was negative. Ponds containing diseased catfish had an increased probability of use by both herons and egrets. In general, cormorants and egrets showed greater probability of use on the periphery of pond clusters. The abundance of catfish was positively related to cormorant and heron presence. Specific pond contents and characteristics influenced presence of each avian species in different ways, including fish species cultured, production methods, pond systems, and fish types. Many pond selection relationships were species-specific, illustrating inherent differences in their foraging ecology. Consequently, specific management actions aimed to reduce avian presence will depend on the targeted species.

Refinement of an index of ecological condition for marsh bird communities in lower Great Lakes coastal wetlands

Abstract The Laurentian Great Lakes coastal wetlands are highly productive and biologically diverse ecosystems. Ongoing environmental degradation and wetland loss have resulted in a number of restoration and conservation programs. To facilitate reporting on the health and recovery of these wetlands, various indices of ecological integrity have been developed to distill complex biotic community data into results that are easy to interpret and understand. The Index of Ecological Condition (IEC) approach uses a probabilistic framework to derive an index by fitting the observed assemblage of species based on species occurrence along an a priori environmental gradient. This study refines the original IEC by Howe et al. (2007a) using updated methodologies and focusing on marsh bird communities in lower Great Lakes coastal wetlands. The a priori environmental gradient was redeveloped using finer-scale (minimum mapping unit = 50 m2) landscape data than Howe et al. (2007a), including Phragmites australis as an invasive stressor, and incorporating measures of water quality and submerged aquatic vegetation as watershed-level disturbances. The environmental gradient showed a good relationship with known anthropogenic disturbances. Marsh bird communities were surveyed in lakes Erie and Ontario and wetland species with clear responses to the environmental gradient were selected for inclusion in the IEC. Where detection was low, species were grouped into multispecies guilds. The resulting IEC was comprised of 15 biotic response functions: 12 individual species and 3 species guilds, and was highly correlated with the a priori environmental gradient (R2 = 0.54). Species with strong positive responses included Canada Goose (Branta canadensis), Marsh Wren (Cistothorus palustris), Swamp Sparrow (Melospiza georgiana), and American Bittern (Botaurus lentiginosus). Pied-billed Grebe (Podilymbus podiceps) had a particularly strong response and was highly influential in the IEC. Great Egret (Ardea alba) was the only species with a negative relationship to the environmental gradient. The refined IEC performed well and provides easily understood output for coastal wetland practitioners in the lower Great Lakes, tasked with reporting on the ecological integrity of marsh bird communities.

Inside Cover

The inside cover picture shows a dehydrative glycosylation mediated by 2‐aryl‐1,3‐dithiane 1‐oxides. Upon activation of the sulfoxide of the reagent with Tf2O, a temporary leaving group is installed on 1‐OH sugar, which undergoes a comproportionation reaction to deliver the oxocarbenium ion, thus facilitates the glycosylation reaction. In the picture, the ring formed by two great egrets represents the important cyclic 1,3‐dithiane 1‐oxides dehydrative reagent. This picture was captured in Xiangshan town, Nanchang, Jiangxi Province of China by Mr. Yuguo Chen. More details are discussed in the article by Wan et al. on page 43—49. image

Jenis-jenis Burung di Daerah Pasui Kecamatan Buntu Batu Kabupaten Enrekang

<p><em>Bi</em><em>r</em><em>d</em><em>s are living organisms classified into the Kingdom Animalia, phylum Aves and including organisms that possess similar characteristics </em><em>wi</em><em>t</em><em>h body cover </em><em>i</em><em>n the form of feathers and can fly. The aim of this study was to determine the diversity of bird species found in Pasui Village, Buntu Batu District, Enrekang Regency. This research was conducted at Pasui watershed. Birdwatching is done by cruising method at three different stations. The results of this study found 14 bird species classified into 5 orders, 11 families and 13 genera. The bird species obtained are </em><em>Ha</em><em>liastur indus, Collocalia esculenta, Egretta alba, Chalcophaps indica longirostris, Streptopelia chinensin, Corvus enca, Dicaeum aureolimbatum, Eruthrura hyperythra, Lonchura Malacca, Lonchura punctulata, Passer montanus, Pycnonotus aurigaster, Acridontheres javanicus, Zosterops pelpepbrosus.</em></p>

Using flight initiation distance to evaluate responses of colonial‐nesting Great Egrets to the approach of an unmanned aerial vehicle

Using flight initiation distance to evaluate responses of colonial‐nesting Great Egrets to the approach of an unmanned aerial vehicle