Foraging Patterns of Breeding Egrets at Coastal and Interior Locations

Maccarone, Alan D.; Brzorad, John N.

doi:10.1675/1524-4695(2002)025[0001:fpobea]2.0.co;2

Cited by 13 publications

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“…In previous studies, we showed that egret foraging patterns at coastal estuaries differed from those at interior rivers (Maccarone and Brzorad 2002), documented interspecific differences in foraging energetics (Brzorad et al 2004), and demonstrated that foraging habitat selection at a coastal estuary was based on microhabitat characteristics (Maccarone and Brzorad 2005). Here we examine whether egret foraging strategies, levels of aggression, and foraging energetics differ between naturally flowing rivers and weirs.…”

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“…In such cases, flexible foraging behavior and an adaptive feeding strategy might increase chances of survival or improve reproductive success (Iwasa et al 1981, Kent 1987, Warnock and Takekawa 1995, Wanless et al 1998). Across their ranges, many wading birds use different foraging methods and prey capture techniques (Willard 1977, Rodgers 1983, Maccarone and Brzorad 2002). Kushlan (1976) and Kelly et al (2003) documented 35 and 38 different foraging behaviors, respectively, used by eight species of wading birds.…”

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Foraging behavior and energetics of Great Egrets and Snowy Egrets at interior rivers and weirs

Maccarone¹,

Brzorad²

2007

Journal of Field Ornithology

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Wading birds may use different foraging methods and prey capture techniques in particular habitats or under specific conditions. We measured foraging behavior and its energetic costs for Great Egrets (Ardea alba) and Snowy Egrets (Egretta thula) at two weirs (small overflow dams that raise water levels in a stream or river) and in two naturally flowing rivers in Kansas in May and June 2000 and 2005. We observed 99 randomly selected birds (38 Great Egrets and 61 Snowy Egrets) for 1513 min, and noted strike rate, prey capture rate, capture efficiency, prey size, and social interactions. In addition, 30 of these birds were observed for 504 min to estimate ambulation velocities and foraging energetics. Both species had higher strike rates and prey capture rates in rivers, but caught larger fish at weirs. Capture efficiency was higher for Snowy Egrets at weirs, but did not differ between microhabitats for Great Egrets. Snowy Egrets had higher rates of conspecific aggression at weirs than in rivers, but little aggression was documented for Great Egrets. Established algorithms suggest that, while foraging in rivers, Snowy Egrets had similar costs for changes in velocity. Changes in ambulation velocity for Great Egrets were greater at weirs than rivers. For both species, the percentage of time spent standing was twice as high at weirs as in rivers. Both species also used low-cost foraging strategies at weirs that yielded larger fish, so net energetic gains at weirs were higher than in rivers. Weirs appear to be more important to Snowy Egrets than to Great Egrets. Estimates of energy gains and expenses provide valuable predictive power for understanding egret behavior. SINOPSIS. Conducta de forrajeo y gasto energético de Ardea alba y Egretta thula en ríos del interior y en paraderasMedimos la conducta de forrajeo y el costo energético en individuos de Garza Real (Ardea alba) y Garza Blanca (Egretta thula), en dos paraderas o canales de ríos y dos ríos en Wichita, Kansas. El estudio se llevó a cabo en mayo y junio de 2002 y 2005. Observamos al azar 99 aves seleccionadas (38 de Garza Real y 61 Garza Blanca) por un total de 1513 minutos, y las siguientes variables fueron comparadas entre especies y microhabitats: tasa de acometidas, tasa de captura de presas, eficiencia de captura, tamaño de la presa e interacciones sociales. Un subconjunto de aves fue observada por 450 minutos y utilizadas para estimar la velocidad de desplazamiento y el presupuesto energético de forrajeo. Pusimos a prueba la hipótesis que las garzas adaptan los componentes de su forrajeo a las condiciones locales. Si correcto, los patrones de alimentación para ambas especies debio variar entre microhabitats. Ambas especies, exhibieron una tasa mas altas de acometidas y captura de presas en rios, pero capturaron peces de mayor tamano en canales. El muestreo de presas en ambos microhabitats mostró que los peces en canales eran mas grandes que los de rios. La Garza Blanca mostró una tasa más alta de agresión conespecifica en canales que en ríos. Se documento ...

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Foraging behavior and energetics of Great Egrets and Snowy Egrets at interior rivers and weirs

Maccarone¹,

Brzorad²

2007

Journal of Field Ornithology

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“…This is the second largest wader species in my study area after the GBHE. The GREG is a deliberate predator, and mostly uses the " Sit and Wait" method of foraging (Maccarone and Brzorad 2002). This involves standing still in one place and waiting until a potential prey item comes close enough to catch.…”

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“…The SNEG has extremely varied feeding behavior (Willard 1977) and moves quickly and strikes frequently (Maccarone and Brzorad 2002). It will actively pursue prey through shallow water (Jenni 1969) and is largely restricted by high water levels when foraging, as they prefer shallow areas (Maccarone and Parsons 1994).…”

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Social and Physical Influences on Wading Bird Foraging Patch Selection

Aguiar

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The aim of this study was to clarify social foraging, habitat use and choice of cohabitating Ciconiiformes on Virginia's Eastern Shore. In a 2006 study I used two approaches, a manipulative experiment and an observational study. At Chincoteague (37˚ 56'N, 75˚ 25'W), I manipulated prey density and social cues using plastic decoys to address the relative importance of social features versus prey density. I also recorded feeding durations of birds at the different treatments. The observational portion also occurred at Chincoteague at six sites along a causeway from the mainland marshes east to Assateague Island. A second area was Hog Island (37˚ 27'N, 75˚ 40'W), a barrier island about 50 km south of Chincoteague. At both areas, I observed wading bird foraging in different habitats and recorded feeding efficiency, flock size and species use, and attempted to answer the following questions: how were species distributed across habitat types, how did feeding efficiency vary among species and habitat types, and how did tide and season affect habitat use, flocking and feeding efficiency? Multi-way ANOVAs were performed to analyze feeding efficiency data and 2 analyses of goodness-of-fit and association were performed on the flock and species use data. Species' use of habitats differed significantly at both locations, with generalists being more widespread than specialists. Ponds and impoundments were selected for foraging most often by most species. Generalist species tended to have lower feeding efficiencies while species specialized for particular habitats had higher average efficiencies at those locations. Overall, generalists tended to be more widespread but have low efficiency, but specialists had high efficiencies in fewer habitat types. Tidal and seasonal effects were less than habitat and species differences, presumably because of the high caloric demands on birds

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Factors influencing expanded use of urban marine habitats by foraging wading birds

McKinney

Raposa

2012

Urban Ecosyst

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Foraging Patterns of Breeding Egrets at Coastal and Interior Locations

Cited by 13 publications

References 12 publications

Foraging behavior and energetics of Great Egrets and Snowy Egrets at interior rivers and weirs

Foraging behavior and energetics of Great Egrets and Snowy Egrets at interior rivers and weirs

Social and Physical Influences on Wading Bird Foraging Patch Selection

Factors influencing expanded use of urban marine habitats by foraging wading birds

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