The contrasting feeding ecology of great egrets and roseate spoonbills in limnetic and estuarine colonies

Abstract

Multispecies colonies of wading birds frequently occur in both freshwater and estuarine environments, in locations with potentially safe places for nesting where the nearby shallow waters provide food for rearing chicks. In 2011/2012, we investigated the feeding ecology of two large-sized waterbirds, the great egret, Ardea alba, and the roseate spoonbill, Platalea ajaja, which breed sympatrically in limnetic and estuarine colonies 65 km apart in southern Brazil. Whole blood from chicks was sampled for d 13 C and d 15 N stable isotopes, and their diets were assessed using direct (conventional) methods. The diet of spoonbills consisted of fish, insects, crustaceans, mollusks, and seeds, whereas great egrets fed mainly on fish, insects, and crustaceans. Bayesian stable isotope mixing models indicated that spoonbills fed exclusively in limnetic habitats, regardless of where they bred, whereas egrets breeding in the estuarine colony fed on both estuarine and limnetic prey, expanding their isotopic niche considerably. Dietary data confirmed this result, with the diets of egrets in the freshwater colony showing high similarity to the diets of spoonbills in both freshwater and estuarine colonies. The isotopic niche overlap was the lowest between species in the estuarine colony, suggesting that the feeding plasticity of egrets reduces interspecific competition during breeding.

Artificial Lighting at Night in Estuaries—Implications from Individuals to Ecosystems

“…The constriction or expansion of diel niches can largely depend on shifts in predator communities (McCauley et al 2012) and may contribute to the avoidance of competitive exclusion and mediate coexistence among predators, prey, and competitor species (Kronfeld-Schor and Dayan 2003). Diel-niche partitioning based on differences in photopic vision capabilities has been suggested as a mechanism that reduces competition among diurnal (e.g., great egret, Ardea alba), cathemeral (e.g., roseate spoonbill, Platalea ajaja), and nocturnal (e.g., black-crowned night heron, Nycticorax nycticorax) wading birds (Britto and Bugoni 2015). Under ALAN conditions, we may then expect a reorganization or a breakdown of temporal niche partitioning with implications across the estuarine community.…”

The combined use of paleolimnological and long-term limnological information to identify natural and anthropogenic environmental changes

“…The role of cormorants and other waterbirds in eutrophication at Lake Biguás seems limited to certain periods, only when cormorants are roosting on its islands. Because cormorants feed on estuarine fish from Patos Lagoon (Barquete et al, 2008a) and piscivorous herons feeding on the Patos Lagoon estuary have higher δ 13 C values than limnetic birds (Britto & Bugoni, 2015;Faria et al, 2016), the decrease in δ 13 C values could be more parsimoniously attributed to cultural eutrophication than to guanotrophication. Likewise, the increase in δ 15 N is also in agreement with this inference (Britto & Bugoni, 2015;Faria et al, 2016).…”

“…Because cormorants feed on estuarine fish from Patos Lagoon (Barquete et al, 2008a) and piscivorous herons feeding on the Patos Lagoon estuary have higher δ 13 C values than limnetic birds (Britto & Bugoni, 2015;Faria et al, 2016), the decrease in δ 13 C values could be more parsimoniously attributed to cultural eutrophication than to guanotrophication. Likewise, the increase in δ 15 N is also in agreement with this inference (Britto & Bugoni, 2015;Faria et al, 2016). The limited influence of birds in freshwater environments seems The combined use of paleolimnological and long-term limnological… Acta Limnologica Brasiliensia, 2022, vol.…”

Crane flies (Diptera, Tipuloidea) from southern Neotropical salt marshes: survey with DNA barcoding

“…Mackenzie et al, 2015) and birds (e.g. Britto & Bugoni, 2015), but there are rare studies on insect groups conducted at these environments (see Giberson et al, 2001;Mackenzie, 2005;Dummel et al, 2011;Bolico et al, 2012;Gantes et al, 2013;Rodrigues et al, 2017). In order to support studies on the classification, biogeography, and ecology of these groups, it is necessary to identify the insect species that inhabit these environments, preferably with high taxonomic resolution, as suggested by Lenat & Resh (2001).…”