Great Egret (Ardea alba)

Piscivorous Bird Use of Aquaculture and Natural Water Bodies in Mississippi

“…Therefore, it is likely that less effort goes into the direct harassment of egrets at aquaculture facilities and why the estimated proportions on aquaculture were consistently greater than expected given its availability. Given their high proportional use of aquaculture and their limited consumption of catfish compared to cormorants, egrets may be using aquaculture ponds more as loafing areas or to consume other items such as invertebrates, amphibians, or reptiles (McCrimmon et al 2011).…”

“…Cormorants forage in open water, and therefore have access to the entire area of either aquaculture ponds or naturally occurring water bodies. Egrets, however, are restricted to shallower waters, typically <0.5 m deep (McCrimmon et al 2011). We therefore compared modeled proportion of egrets on aquaculture by perimeter.…”

“…Given this information, we predicted cormorants preparing to migrate north during the latter survey months would seek out foraging habitat with higher food densities to build energy reserves for migration, and therefore show higher use of aquaculture compared to naturally occurring water bodies as opposed to earlier in the fall. Although considered year‐round residents, individual egrets do exhibit migratory behavior typically in February (McCrimmon et al 2011). We therefore predicted to observe similar patterns as cormorants in relation to migration.…”

“…Cormorants inhabit the Delta primarily from October through April as part of their annual migration from the upper midwestern United States, whereas egrets can be found year‐round; although, their numbers are typically higher in spring through fall (McCrimmon et al 2011, King et al 2012, Dorr et al 2014). Because each species has a high affinity for fish, cormorants and egrets regularly use aquaculture facilities throughout the Delta.…”

“…The perceived mortality risk associated with naturally occurring water bodies is likely less than at aquaculture facilities. For instance, aquaculture facilities have full‐time personnel devoted to harassment and lethal take of birds when allowed, whereas there are very few documented natural predators of adult cormorants or egrets, and the few occasional predations reported are mainly attributed to large raptors, such as the bald eagle ( Haliaeetus leucocephalus ; McCrimmon et al 2011, Dorr et al 2014). This increased risk of mortality on aquaculture is supported, at least for cormoants, by long‐term banding data and modeling of breeding cormorant surveys in the Great Lakes in the United States and Canada, indicating increased cormorant mortality due to control efforts on wintering grounds (Seamans et al 2012, Stromborg et al 2012, Guillaumet et al 2014).…”