Nestling Diet of Three Sympatrically Nesting Wading Bird Species in the Florida Everglades (original) (raw)

The Role of Predation in Determining Reproductive Success of Colonially Nesting Wading Birds in the Florida Everglades

The Condor, 1989

In a sample of 1,609 marked nests of five species of Ciconiiformes in 2 1 colonial nesting aggregations in the Everglades, evidence of abandonment without destruction of nest contents accounted for 31.3% of failures. In 66.9% of the failures, evidence at the nest suggested either predation resulting in nest failure or postabandonment scavenging of nest contents. In a sample of 106 nests isolated by a nonrepelling tracking medium, we found predation by snakes to account for 23% ofnest failures; mammals accounted for an additional 20%. Failures due to these two categories accounted for 12% of the treated nests; abandonments may have been considerably underrepresented in this sample of nests. Mammalian predators rarely visited widely distributed baited tracking stations in the marsh, and we hypothesize that even 5-10 cm of water can substantially restrict travel by raccoons, foxes, and rats. Visitation by mammals to colonies occurred only when the water surrounding them receded, and was not related to the presence of alligators or distance from permanently dry land. We found little evidence of avian predation on wading bird nests, though birds readily scavenged abandoned nest contents. We discuss several attributes of the Everglades marshes which may limit access of predators to nesting colonies.

Variation in size and location of wading bird colonies in the upper St. Johns River basin, Florida, USA

2003

aerial survey methods. A total of 62 colony locations were found over six years, with a maximum of 35 sites active in each of two years. Borrow pits and managed impoundments were the most important nesting locations based on size and persistence. Most of these sites were in or adjacent to the Upper St. Johns River Basin Project, a wetland restoration project. Higher numbers of nests were counted during nesting seasons preceded by above average rainfall than during seasons characterized by drought. Cattle Egrets (Bubulcus ibis) were the most common nesting species in all years, however, the proportion of the total nests that were Cattle Egrets decreased over the study period. Wood Storks (Mycteria americana), a federally endangered species, nested in increasing numbers within three borrow pits adjacent to the Upper St. Johns River Basin Project. This study reveals the importance of borrow pits, most of which are on private land where sites are unprotected, to wading bird nesting in east central Florida.

Nestling diet in five species of herons and egrets in Birama Swamp, Cuba

The Journal of Caribbean Ornithology, 2009

We used 78 boluses regurgitated by disturbed nestlings of five species of egrets and herons in a colony at Birama Swamp, western Cuba, to briefly describe dietary composition and prey sizes. The species included Cattle Egret (Bubulcus ibis), Snowy Egret (Egretta thula), Tricolored Heron (Egretta tricolor), Little Blue Heron (Egretta caerulea), and Green Heron (Butorides virescens). Overall we counted 1,887 items of 16 types of preys. Differences in dietary composition between nestlings and adults should reflect the structure of local prey populations. Cattle Egrets tend to consume more but smaller prey than the other species. A noteworthy find was small catfishes (Claria spp.), a recently introduced exotic species, among the prey consumed by three of the waders, which demonstrate an increase in the fish's population and disruption of the food web of this natural wetland.

Factors affecting breeding status of wading birds in the Everglades

2000

Within the Everglades ecosystem, the vast majority ofnesting was concentrated in the Water Conservation Areas (92%), and the vast majority ofthe remainder in Everglades National Park was in freshwater areas and not in the coastal zone. Within the Water Conservation Areas, the vast majority ofnesting was concentrated in WCAs 2 and 3 (92%), and the vast majority ofthat (96%) was in WCA 3. In LNWR, nesting was about halfthe 8-year average. Although we did not measure reproductive success through documentation of individual nest histories, nesting was largely successful throughout WCA 3. However, in Loxahatchee NWR, the strong pulse ofrains in mid-April resulted in widespread abandonment, including up to two thirds ofthe nests destroyed in some closely monitored colonies. The Systematic Reconaissance Survey team reported that numbers ofbirds in the Everglades ecosystem were normal to well above normal during the winter and spring of 1999/2000, depending on species and month. Thus there were not exceptionally large numbers ofbirds in the Everglades during the winter months, and many more than normal during May. The proportion ofthis total count ofbirds that actually bred in 2000 was calculated to be 100% or above, suggesting that there were few birds that remained in the system, that also chose not to breed this year. This is in stark contrast to many ofthe previous years, when only 30% of adults have bred on average. The reasons for the large nesting event in 2000 are not completely understood, but several contributory factors were evident. The hydrological conditions were generally very favorable, with a long, continuous, and exceptionally rapid surface water recession throughout the winter and spring, beginning from extremely high levels. These hydrological factors apparently created drying and depth conditions that were conducive to making prey animals available to foraging wading birds. In addition, the initially high water conditions also allowed fast drying conditions while maintaining above-average water conditions in most compartments, resulting in a vast acreage ofthe marsh being in very shallow depths, yet relatively little ofit going entirely dry. Drying conditions have not, however, always explained nesting patterns in the past, and we suspect that the 2000 nesting season may have had several contributory sources.

Sensitivity of Nesting Great Egrets ( Ardea Alba ) and White Ibises ( Eudocimus Albus ) to Reduced Prey Availability

Auk, 2010

Resumen.-La teoría sobre historias de vida sugiere que las especies de aves longevas ajustarán su esfuerzo de anidación de acuerdo a las condiciones actuales para balancear los costos y beneficios de la reproducción actual con sus necesidades de largo plazo en relación con la supervivencia y la reproducción futura. Sin embargo, las respuestas a las mismas condiciones del hábitat pueden diferir entre especies, aún en el mismo ecosistema, para producir diferentes patrones de anidación y poblacionales. Examinamos las diferencias en la ecología de anidación de dos especies simpátricas de aves vadeadoras (Ardea alba y Eudocimus albus) entre años con disponibilidad de presas alta (2006) e inferior al promedio (2007) en los Everglades de Florida. El tamaño de la nidada de E. albus disminuyó en cerca del 19% entre 2006 y 2007, mientras que el de A. alba se mantuvo constante. La selección de modelos identificó a la lluvia, la profundidad del agua, la fecha juliana, el año y la biomasa de presas como los parámetros que más influenciaron las tasas de supervivencia diaria (TSD) de los nidos de E. albus, mientras que el estadío del nido, la región, la fecha juliana, la profundidad del agua y la forma cuadrática de la tasa de recesión del agua fueron los factores que más influenciaron las TSD de los nidos de A. alba. La supervivencia diaria de los nidos de A. alba y de E. albus fue mayor en 2006 (TSD = 0.992 y 0.999, respectivamente) que en 2007 (TSD = 0.981 y 0.979). Nuestros resultados apoyan la hipótesis de que la disponibilidad de presas y factores hidrológicos desempeñan papeles cruciales regulando las poblaciones de aves vadeadoras en los Everglades de Florida. Los resultados también demostraron que la reproducción de E. albus fue más sensible a los cambios en condiciones hidrológicas y en la disponibilidad de presas que la de A. alba.

Irruptive White Ibis breeding is associated with use of freshwater crayfish in the coastal Everglades

Ornithological Applications, 2021

As avian reproductive success is generally prey limited, identifying important prey types or sizes and understanding mechanisms governing prey availability are important objectives for avian conservation ecology. Irruptive White Ibis (Eudocimus albus) nesting at coastal colonies in the southern Everglades numbered over 100,000 nests in the 1930s. A century of drainage and altered hydrologic patterns reduced aquatic prey availability and eliminated large nesting events; nesting activity in recent decades has been typically less than 5% of historical peaks. Hydrologic restoration is expected to increase ibis nesting activity, but which prey types will support high nesting effort is less clear. In 2017 and 2018, we collected food boluses from White Ibis chicks at coastal colonies in Everglades National Park. We also monitored regional nesting activity from 1999 to 2018. In 2017, the region had 1,075 nests, typical of the past several decades; but in 2018, there were 30,420 nests, repre...

Population Trends in Some Florida Bay Wading Birds

The Wilson Journal of Ornithology, 1989

Etude des populations de trois especes (Ajaia apaja, Egretta rufescens et Ardea nerodras occidentalis) d'echassier dans la region de la Baie de Floride. Les caracteristiques des populations concernant les adultes sont examinees et les interpretations ecologiques concernant les tendances populationnelles sont recherchees

A comparison between aquatic birds of lakes and coastal rivers in Florida

Hydrobiologia, 2006

Aquatic birds were counted on five Gulf coast Florida rivers to determine if these river systems supported densities, biomass and species richness similar to those found on Florida lakes. Forty-two species were identified and for the species that were found on both Florida streams and lakes similar densities and biomass were encountered. As with Florida lakes, stream bird abundance and species richness were higher in winter months than in summer months, a consequence of migratory bird populations. Total bird abundance, biomass per unit of phosphorus, and species richness per unit of area were similar to data collected on Florida lakes. Thus, Florida rivers are capable of supplying sufficient resources to maintain bird densities, biomass and species richness values similar to lakes of equal size and nutrient concentrations and are therefore important habitats for aquatic bird populations. An examination of individual habitat characteristics indicates that water depth was inversely correlated and submersed aquatic vegetation was positively correlated with bird density, biomass and species richness within the river systems. While both habitat characteristics are important they are also inversely related making it difficult to separate the individual significance of each characteristic.

Feeding ecology of the waterbirds in a tropical mangrove in the southeast Gulf of Mexico

Studies on Neotropical Fauna and Environment, 2019

Species that exploit the same type of environmental resources are defined as a guild, which have similar needs in the use of food or habitat. It was analyzed the diet of five waterbirds' offsprings species (Neotropic Cormorant (Nannopterum brasilianus), Reddish Egret (Egretta rufescens), Boat-billed Heron (Cochlearius cochlearius), Snowy Egret (Egretta thula) and Great Egret (Ardea alba)), by prey identification and calculated the relative importance, overlap and breadth diet. The general diet of the piscivorous guild consisted of 17 fish species from 13 genera and eight families. The highest overlap was between the Reddish Egret and Boat-billed Heron. Fish species dominated the diets of all studied waterbirds, Poecilia velifera was the most abundant prey species in each of the birds, suggesting that they are abundant in the wetlands system of northern Yucatan. Diet overlap in waterbirds species depends on the use of resources and feeding habitat. Since reproductive success largely depends on the availability of food resources, mainly of resident or estuarine fishes. The information about diet is important for the conservation of waterbirds.