Sensitivity of Nesting Great Egrets (<i>Ardea alba</i>) and White Ibises (<i>Eudocimus albus</i>) to Reduced Prey Availability

Herring, Garth; Gawlik, Dale E.; Cook, Mark I.; Beerens, James M.

doi:10.1525/auk.2010.09144

Cited by 40 publications

(41 citation statements)

References 48 publications

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“…This idea is afforded support by a recent 4‐year study of the diets of nestling white ibises in the northern Everglades, which were dominated by P. fallax over a wide range of foraging depths, while fish were consumed disproportionately only rarely during relatively very dry conditions (Dorn et al ., ; Boyle et al ., ). Further, this reliance on P. fallax occurred during two of the most successful ibis nesting seasons (2006 and 2009) in recent decades (Herring et al ., , ), suggesting that crayfish concentration events at the depth reported in this study can be of sufficient magnitude, both spatially and temporally, to fuel large and successful colonies of nesting wading birds. Note, however, that although the average minimum slough depths in this study were within the range exploited by invertivorous wading birds such as the white ibis, they were deeper than is considered optimal for its foraging ( c .…”

Section: Discussionmentioning

confidence: 67%

Seasonal movements of crayfish in a fluctuating wetland: implications for restoring wading bird populations

et al. 2014

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1. Among aquatic fauna of fluctuating wetlands, seasonal interhabitat movement is a widespread phenomenon that can strongly influence predator-prey interactions and population dynamics of vertebrate predators. For example, movements increase the availability of small fishes during seasonal drying, which is critical to the reproductive success of many wading bird (Ciconiiformes) species. However, few studies have examined movements of aquatic fauna in relation to changes in water depth, especially for those taxa that can physiologically tolerate periods of drying and whose responses to hydrology are difficult to predict (e.g. crayfish). 2. Here, we experimentally explore the movement responses of a key prey species in the Florida Everglades -the slough crayfish Procambarus fallax -to a seasonal decline in water depth. The study was conducted in four replicate wetland impoundments (wetlands) which comprise habitats characteristic of the Florida Everglades. In two wetlands, we induced a 60-cm drop in water level and examined crayfish movements between higher-elevation ridge habitats and lower-elevation slough habitats when water levels were (i) relatively deep on ridges; (ii) relatively shallow on ridges; and (iii) below ground on ridges but above ground in sloughs. In two control wetlands, we followed the identical sampling protocol but maintained the deep stage on the ridges. Crayfish movements were quantified by changes in abundance and mark-release-recapture (MRR). 3. Crayfish abundance changed little within habitats while water remained on the ridges, but it decreased on the ridges and considerably increased in the sloughs after the ridges dried. These changes were clearly due to loss of water on the ridges as abundances in control wetlands remained constant throughout sampling. Elevated slough abundances were not explained by differences in trapping efficiency or episodic releases of recently hatched crayfish, suggesting they were due largely to movements from ridges to sloughs. This was supported by the MRR data. 4. Our results show that seasonal water-level recessions can induce crayfish to move from higher to lower-elevation habitats where they become concentrated and potentially available to foraging birds. We discuss the potential implications of these movements for restoring hydrologic conditions for wading birds in large fluctuating wetlands.

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Section: Discussionmentioning

confidence: 67%

Seasonal movements of crayfish in a fluctuating wetland: implications for restoring wading bird populations

et al. 2014

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“…In the Everglades of Florida, varying resource selection strategies across temporal scales are exemplified by several species of long-legged wading birds (White Ibis [Eudocimus albus], Great Egret [Ardea alba]; Beerens et al 2011), whose breeding populations are limited by food availability (Frederick and Spalding 1994, Ogden 2005, Herring et al 2010, and availability of prey is driven by water depth and density of prey (Gawlik 2002). In this shallow, subtropical wetland system, length of inundation over periods of months and years increases the production of the aquatic prey base (Trexler 2010), whereas dry season drying and ponding of water over periods of weeks concentrates prey and is linked to wading bird foraging density (Russell et al 2002;Fig.…”

Section: Introductionmentioning

confidence: 99%

Determining habitat quality for species that demonstrate dynamic habitat selection

Beerens

Frederick

Noonburg

et al. 2015

Ecology and Evolution

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Determining habitat quality for wildlife populations requires relating a species' habitat to its survival and reproduction. Within a season, species occurrence and density can be disconnected from measures of habitat quality when resources are highly seasonal, unpredictable over time, and patchy. Here we establish an explicit link among dynamic selection of changing resources, spatio‐temporal species distributions, and fitness for predictive abundance and occurrence models that are used for short‐term water management and long‐term restoration planning. We used the wading bird distribution and evaluation models (WADEM) that estimate (1) daily changes in selection across resource gradients, (2) landscape abundance of flocks and individuals, (3) conspecific foraging aggregation, and (4) resource unit occurrence (at fixed 400 m cells) to quantify habitat quality and its consequences on reproduction for wetland indicator species. We linked maximum annual numbers of nests detected across the study area and nesting success of Great Egrets (Ardea alba), White Ibises (Eudocimus albus), and Wood Storks (Mycteria americana) over a 20‐year period to estimated daily dynamics of food resources produced by WADEM over a 7490 km2 area. For all species, increases in predicted species abundance in March and high abundance in April were strongly linked to breeding responses. Great Egret nesting effort and success were higher when birds also showed greater conspecific foraging aggregation. Synthesis and applications: This study provides the first empirical evidence that dynamic habitat selection processes and distributions of wading birds over environmental gradients are linked with reproductive measures over periods of decades. Further, predictor variables at a variety of temporal (daily‐multiannual) resolutions and spatial (400 m to regional) scales effectively explained variation in ecological processes that change habitat quality. The process used here allows managers to develop short‐ and long‐term conservation strategies that (1) consider flexible behavioral patterns and (2) are robust to environmental variation over time.

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“…3) Obstructing and supplanting nestmates. Nestlings, particularly larger ones, could potentially prevent their nestmates from eating food by supplanting or pushing them aside, as in ibises (Skead , Herring et al ) and jabiru storks Jabiru mycteria (J. Villarreal‐Orias pers. comm.…”

Section: Methodsmentioning

confidence: 99%

Kind to kin: weak interference competition among white stork Ciconia ciconia broodmates

Romero

Redondo

2016

Journal of Avian Biology

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Altricial nestlings in structured families show a diverse array of behavioural mechanisms to compete for food, ranging from signalling scrambles to aggressive interference. Rates of filial infanticide are moderately high in white storks. It has been hypothesized that this unusual behaviour is an adaptive parental response to the absence of efficient mechanisms of brood reduction (aggression or direct physical interference) by nestlings. To test this latter assumption, we analyzed video recordings of 41 complete feeding episodes at 32 broods during the first half of the nestling period, when nestlings complete 90% of growth and chick mortality and size asymmetries are highest. Parents delivered food to all nestlings simultaneously by regurgitating on the nest floor. No direct (bill to bill) feeding was recorded. Senior nestlings were never observed to limit their junior nestlings from eating food, either by aggression or physical interference. Experimental feeding tests revealed that heavier nestlings handled prey items more efficiently and ate food at a higher speed. The high degree of tolerance shown by senior nestlings is unusual among birds with similar ecological and phylogenetic affinities, such as herons. Tolerance by seniors cannot be easily explained by absence of parental favouritism or proximate factors known to affect the occurrence of sibling aggression in other species (rate of food transfer, brood size, hatching asynchrony or length of nestling period).

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

Cited by 40 publications

References 48 publications

Seasonal movements of crayfish in a fluctuating wetland: implications for restoring wading bird populations

Seasonal movements of crayfish in a fluctuating wetland: implications for restoring wading bird populations

Determining habitat quality for species that demonstrate dynamic habitat selection

Kind to kin: weak interference competition among white stork Ciconia ciconia broodmates

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