Aquatic prey switching and urban foraging by the White Ibis <i>Eudocimus albus</i> are determined by wetland hydrological conditions

Dorn, Nathan J.; Cook, Mark I.; Herring, Garth; Boyle, Robin A.; Nelson, Jennifer; Gawlik, Dale E.

doi:10.1111/j.1474-919x.2011.01101.x

Cited by 37 publications

(42 citation statements)

References 32 publications

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“…Historical data suggest that years of high nesting activity of the white ibis (Eudocimus albus) came 1-2 years after relatively strong regional droughts (Frederick and Ogden 2001). These droughts presumably reduced Wsh populations Parkos et al 2011) and, as the diets of white ibis chicks are frequently dominated by crayWsh (Dorn et al 2011), these relationships may indicate that the secondary production of the Everglades temporarily shifts to high crayWsh productivity following droughts. Similar suggestions of drought-induced prey release in wetlands have been made by others (Chase and Knight 2003) and should be considered further here and in other shallow aquatic ecosystems.…”

Section: Discussionmentioning

confidence: 96%

Consumptive effects of fish reduce wetland crayfish recruitment and drive species turnover

Kellogg

Dorn

2011

Oecologia

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Predators and dry-disturbances have pronounced effects on invertebrate communities and can deterministically affect compositional turnover between discrete aquatic habitats. We examined the effect of sunfish (Lepomis spp.) predators on two native crayfish, Procambarus alleni and P. fallax, that regionally coexist in an expansive connected wetland in order to test the hypotheses that sunfish predation limits crayfish recruitment (both species) and that it disproportionately affects P. alleni, the species inhabiting temporary wetlands. In replicate vegetated wetlands (18.6 m(2)), we quantified summertime crayfish recruitment and species composition across an experimental gradient of sunfish density. Separately, we quantified effects of sunfish on crayfish growth, conducted a complimentary predation assay in mesocosms, and compared behavior of the two crayfish. Sunfish reduced P. alleni summertime recruitment by >99% over the full sunfish gradient, and most of the effect was caused by low densities of sunfish (0.22-0.43 m(-2)). P. alleni dominated wetlands with few or no sunfish, but the composition shifted towards P. fallax dominance in wetlands with abundant sunfish. P. fallax survived better than P. alleni over 40 h in smaller mesocosms stocked with warmouth. Sunfish reduced P. fallax recruitment 62% in a second wetland experiment, but growth rates of caged crayfish (both species) were unaffected by sunfish presence, suggesting predatory effects were primarily consumptive. Consistent with life histories of relatively fish-sensitive invertebrates, P. alleni engaged in more risky behaviors in the laboratory. Our results indicate that sunfish predators limit recruitment of both species, but disproportionately remove the more active and competitively dominant P. alleni. Spatially and temporally variable dry-disturbances negatively co-varying with sunfish populations allow for regional coexistence of these two crayfish and may release populations of either species from control by predatory fishes.

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Section: Discussionmentioning

confidence: 96%

Consumptive effects of fish reduce wetland crayfish recruitment and drive species turnover

Kellogg

Dorn

2011

Oecologia

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“…Gawlik, ) may not be appropriate for birds exploiting crayfish. 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.…”

Section: Discussionmentioning

confidence: 99%

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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“…Fish are typically not a large component of ibis diets during the nesting season unless water depths reach extremely low levels in the Everglades (Dorn et al. , Boyle et al. ), so we suspect that crayfish were the primary prey of ibis in the wetlands we studied.…”

Section: Discussionmentioning

confidence: 96%

“…The total biomass of crayfish was calculated for each throw trap using crayfish carapace lengths and length‐dry mass regressions (Dorn et al. ).…”

Section: Methodsmentioning

confidence: 99%

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Feeding on the edge: foraging White Ibis target inter‐habitat prey fluxes

2019

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Avian population dynamics are influenced by the availability of spatiotemporally variable prey resources, but the conditions producing abundant and accessible prey are not always clear. In the Florida Everglades, wading birds nest in the dry season when receding water levels concentrate prey and facilitate improved foraging efficiency. White Ibis (Eudocimus albus) feed extensively on crayfish in sloughs, and previous studies have demonstrated that crayfish move downgradient from higher elevation, heavily vegetated ridge habitats into adjacent less-vegetated sloughs when ridges are almost dry. Most White Ibis foraging is thought to occur in sloughs with relatively shallow water (< 19 cm), but crayfish move and their densities peak when water in sloughs is deeper (~21-32 cm). We conducted an observational study of White Ibis foraging in drying wetlands to determine if White Ibis restricted their foraging to shallow water or if they foraged in relatively deep water when crayfish were migrating. In a series of large drying wetlands, we used time-lapse imagery to quantify White Ibis foraging activity over 61 d from February to April 2017 and we also quantified crayfish biomass density in sloughs. Crayfish biomass density peaked when ridges were almost dry. Most White Ibis foraging occurred over 2-3 d when ridges were almost dry and water in sloughs averaged ≥ 29 cm deep. White Ibis selected slough edges for foraging, suggesting that they were capturing crayfish migrating between habitats. Our results point to a new mechanism of prey exploitation driven by inter-habitat prey flux when ridge habitat dries. Although the results of previous studies suggest that White Ibis will not forage on fish in deeper water (> 25 cm), we found that White Ibis will forage on crayfish in water at those depths. Maintenance of habitat elevational differences and hydro-patterns that promote crayfish production will be necessary to promote this predator-prey interaction in the ridge-slough landscape of the Everglades.

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Aquatic prey switching and urban foraging by the White Ibis Eudocimus albus are determined by wetland hydrological conditions

Cited by 37 publications

References 32 publications

Consumptive effects of fish reduce wetland crayfish recruitment and drive species turnover

Consumptive effects of fish reduce wetland crayfish recruitment and drive species turnover

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

Feeding on the edge: foraging White Ibis target inter‐habitat prey fluxes

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