Great Blue Heron (Ardea herodias)

Vennesland, Ross G.; Butler, Robert W.

doi:10.2173/bna.25

Cited by 9 publications

(11 citation statements)

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“…Like most wading birds, the Little Blue Heron is constrained by its total leg length (22.52 ± 0.95 cm [mean ± SD]; N = 8; measurements provided from specimens at the Louisiana State University Museum of Natural Science) to feed in a narrow range of water depths (Rodgers and Smith ). The Great White Heron feeds on a variety of prey from small birds to frogs and fish, but it mostly feeds in shallow water when it is available (Vennesland and Butler ). It feeds in a range of water depths with a total average leg‐length of 39 ± 2.1 cm (based on study skins at the University of Miami [Powell ]).…”

Section: Methodsmentioning

confidence: 99%

Time‐integrated habitat availability is a resource attribute that informs patterns of use in intertidal areas

Calle

Green

Strong

et al. 2018

Ecological Monographs

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In dynamic environments, resource availability may change by several orders of magnitude, over hours to months, but the duration of resource availability is not often included as a characteristic attribute of resources even though temporal resource dynamics might limit patterns of use. In our study of wading birds foraging in intertidal areas, tides cause large changes in the areal extent of shallow‐water foraging habitat (i.e., the resource), but tides also constrain the duration of availability, which is often overlooked. We hypothesized that temporal constraints on habitat availability from tides would be reflected in patterns of habitat use by foraging birds. We estimated the time‐integrated habitat availability and compared it to traditional habitat attributes (seagrass cover, substrate type, instantaneous water depth, and proximity to mangrove islands or deep water) that have strong evidential support for influencing patterns of use. To evaluate our hypotheses, we quantified habitat attributes at intertidal areas in the Florida Keys, USA, where wading birds were observed foraging (Little Blue Heron, Egretta caerulea: N = 183; Great White Heron, Ardea herodias occidentalis: N = 162). We tested for nonrandom use by sampling habitat attributes at two spatial scales around the observed feeding locations and we analyzed the data using a conditional logistic regression model. There was no evidence that seagrass cover or substrate explained patterns of use. The proximity of foraging locations relative to mangroves and to deep water were important at both spatial scales but had lower effect sizes (odds ratios) than time‐integrated habitat availability and water depth, and the latter may only serve as a physical constraint on access. We found support that time‐integrated habitat availability was a distinct resource attribute, had the greatest effect size (four‐ to eightfold change in relative probability of use), and best explained patterns of habitat use at the largest spatial scale. In studies of resource use where changes in resource availability are nonlinear or when strong constraints on access are imposed by behavior, incorporating time‐integrated estimates of resource availability into analyses can improve insights into spatiotemporal patterns of resource use.

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Section: Methodsmentioning

confidence: 99%

Time‐integrated habitat availability is a resource attribute that informs patterns of use in intertidal areas

Calle

Green

Strong

et al. 2018

Ecological Monographs

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Section: Methodsmentioning

confidence: 99%

“…We estimated concentrations of Hg in blood and associated risk to adults of 4 species of piscivorous wading birds that are found throughout the south central United States: little blue herons (Egretta caerulea; Rodgers and Smith 2012), green herons (Butorides virescens; Davis and Kushlan 1994), great egrets (Ardea albus; McCrimmon et al 2011), and great blue herons (Vennesland and Butler 2011). We selected these 4 species of wading birds because as adults they consume different sizes of fish prey (Davis and Kushlan 1994;McCrimmon et al 2011;Vennesland and Butler 2011;Rodgers and Smith 2012; Supplemental Data, Table S1), potentially placing them at different levels of risk from Hg exposure. Although piscivorous wading birds can feed primarily on fish, they exhibit opportunistic foraging behavior and consume other aquatic and terrestrial biota, which can comprise a significant proportion of the diet (Davis and Kushlan 1994;McCrimmon et al 2011;Vennesland and Butler 2011;Rodgers and Smith 2012).…”

Section: Methodsmentioning

confidence: 99%

“…We selected these 4 species of wading birds because as adults they consume different sizes of fish prey (Davis and Kushlan 1994;McCrimmon et al 2011;Vennesland and Butler 2011;Rodgers and Smith 2012; Supplemental Data, Table S1), potentially placing them at different levels of risk from Hg exposure. Although piscivorous wading birds can feed primarily on fish, they exhibit opportunistic foraging behavior and consume other aquatic and terrestrial biota, which can comprise a significant proportion of the diet (Davis and Kushlan 1994;McCrimmon et al 2011;Vennesland and Butler 2011;Rodgers and Smith 2012). To estimate risk to birds from Hg exposure, we assumed their diets were composed of 100% fish.…”

Section: Methodsmentioning

confidence: 99%

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Spatial patterns of mercury contamination and associated risk to piscivorous wading birds of the south central United States

Gerstle

Drenner

Chumchal

2018

Enviro Toxic and Chemistry

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Piscivorous birds are top predators in aquatic ecosystems and are vulnerable to mercury (Hg) exposure and associated adverse health effects. In some areas of North America, the health risk posed to piscivorous birds by Hg contamination has not been characterized because concentrations of Hg in bird tissues have not been extensively monitored. When data on Hg in tissues of piscivorous birds are not available, the concentration of Hg in the blood of piscivorous birds can be estimated from the concentration of Hg in prey fish. We used concentrations of Hg in different lengths of a proxy prey fish, bluegill (Lepomis macrochirus), to estimate the concentration of Hg in the blood of 4 species of adult piscivorous wading birds (little blue herons [Egretta caerulea], green herons [Butorides virescens], great egrets [Ardea albus], and great blue herons [Ardea herodias]) in 14 ecoregions of the south central United States. The 4 species of birds consume different sizes of fish with different concentrations of Hg and were predicted to have different concentrations of Hg in their blood, with little blue herons < green herons < great egrets < great blue herons. For each species of bird, there were significant differences in average estimated concentrations of Hg in blood between ecoregions, with estimated concentrations of Hg in blood increasing with Hg deposition. The level of predicted risk varied with ecoregion and bird species and was highest for great blue herons. We recommend that future studies of Hg contamination of piscivorous wading birds of the southern United States focus on great blue herons in water bodies within ecoregions that have high Hg deposition. Environ Toxicol Chem 2019;38:160–166. © 2018 SETAC

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“…Population size and reproductive success of A. h. fannini have shown an apparent decline over the last 30 years (Vennesland 2000;Vennesland and Butler 2004), and it has been designated a species of special concern by the Committee On The Status of Endangered Wildlife in Canada (COSEWIC). Ardea herodias fannini may nest alone or in colonies containing several hundred pairs (Butler 1992;Vennesland 2000;Kenyon et al 2007). The largest colonies historically have been located adjacent to large intertidal foraging sites.…”

Section: Introductionmentioning

confidence: 99%

Recent switch by the Great Blue Heron Ardea herodias fannini in the Pacific northwest to associative nesting with Bald Eagles (Haliaeetus leucocephalus) to gain predator protection

2013

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The Great Blue Heron Ardea herodias fannini Chapman, 1901 in the Pacific northwest appears to have modified nesting behaviour in response to the strong recent recovery of the Bald Eagle (Haliaeetus leucocephalus (L., 1766)) population. Previously undescribed, herons now often nest in close association with some breeding eagles, even though eagles depredate heron nestlings, are implicated in the recent reproductive decline of herons, and may induce abandonment of heron breeding colonies. We tested the hypothesis that breeding herons gain protection from the territorial behaviour of eagles. Natural observations and simulated incursions showed that nesting eagles actively repel other eagles within at least 250 m around the nest site, thereby establishing a relatively safe place for herons to nest. Surveys showed that 70% of heron nests and 19% of heron colonies were located within 200 m of eagle nests with high reproductive success. These herons had greater reproductive success than those nesting far from eagle nests.

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Great Blue Heron (Ardea herodias)

Cited by 9 publications

References 0 publications

Time‐integrated habitat availability is a resource attribute that informs patterns of use in intertidal areas

Time‐integrated habitat availability is a resource attribute that informs patterns of use in intertidal areas

Spatial patterns of mercury contamination and associated risk to piscivorous wading birds of the south central United States

Recent switch by the Great Blue Heron Ardea herodias fannini in the Pacific northwest to associative nesting with Bald Eagles (Haliaeetus leucocephalus) to gain predator protection

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