Fallen Nestlings and Regurgitant as Mechanisms of Nutrient Transfer from Nesting Wading Birds to Crocodilians

Nell, Lucas A.; Frederick, Peter C.

doi:10.1007/s13157-015-0664-0

Cited by 10 publications

(14 citation statements)

References 73 publications

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“…The survival of the majority of cottonmouth snakes on SHK seems directly tied to the presence of the nesting waterbirds, particularly on the west end of the island. Our results are similar to those from a recent study of alligators that found elevated BCI values for individuals living below nesting waterbirds (Nell & Frederick, ).…”

Section: Discussionsupporting

confidence: 91%

Collapse of a unique insular bird–snake relationship

2017

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Seahorse Key (SHK) supports a population of Florida cottonmouth snakes, Agkistrodon conanti, which have a unique trophic association with colonially nesting waterbirds. Each spring >10 000 birds have nested on SHK and provided an influx of food in the form of fish carrion that snakes scavenge on the ground. Because of this allochthonous input of trophic resources, the cottonmouth population on SHK historically was dense, with snakes of large body size. Suddenly and unexpectedly, the entire waterbird colony abandoned its nests during April, 2015 and did not return. We examined data collected from 1999 to 2016 on the abundance and body size of SHK cottonmouths to quantify how the bird abandonment has affected the snake population. Our results show that abundance and body condition index (BCI) have decreased significantly, particularly on the west end of SHK where the bird rookery historically concentrated. Abundance of snakes (counts per survey) along a west beach transect was higher during the pre-abandonment period (10.99 AE 8.11 SD) than during the post-abandonment period (7.52 AE 4.64). Similarly, we observed a significant decrease in the BCI of snakes from the west end of SHK between the pre-(0.04 AE 0.10) and post-abandonment periods (À0.12 AE 0.14). Loss of the bird rookery as a source of energy has negatively affected the SHK cottonmouth population. In contrast, numbers and body condition of cottonmouths appear to have increased on an adjacent island where~3000 to 5000 waterbirds began nesting in 2015 and 2016.

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Section: Discussionsupporting

confidence: 91%

Collapse of a unique insular bird–snake relationship

2017

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“…This has two important effects which could serve to reinforce this relationship: First, a comparatively large portion of nutrition from breeding birds should directly or indirectly reach alligators, as the latter could take advantage of an increase in small aquatic prey that may be fuelled by bird-guano deposition yet are large enough to consume chicks of all sizes. Brood reduction is common in all wading birds [ 36 , 102 , 103 ], and the resulting chick carcasses from wading bird nesting colonies represent the most substantive food source for associate alligators [ 37 ]. Because alligators can utilize this food source, brood reduction by wading birds is likely another vital component of this relationship, providing a steady flow of nutrients from protectee to protector.…”

Section: Discussionmentioning

confidence: 99%

“…Further, many colonially nesting birds lay more eggs than they can raise, and adjust brood size to fit available food resources through several processes of brood reduction (reviewed in [ 36 ]). This often amounts to 1–2 chicks being ejected alive or dead from each nest, providing a potentially substantial source of food for protectors, especially in concentrated nesting associations [ 37 ]. Thus colonies of breeding birds offer multiple avenues through which they could nutritionally benefit protectors that do not necessitate exploitation by either partner.…”

Section: Introductionmentioning

confidence: 99%

“…Wading bird nesting aggregations can substantially increase nearby nutrient deposition [ 45 – 47 ] and may enhance primary and secondary productivity as a result. Moreover, the quantity of food potentially available to scavengers from wading bird colonies via dead chicks is substantial, enough to theoretically support large populations of alligators [ 37 ]. Given the potential for significant energetic benefits to alligators in wading bird nesting colonies, we predicted that alligators associated with wading bird colonies will have higher body condition indices than alligators in similar habitat without colonies.…”

Section: Introductionmentioning

confidence: 99%

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Presence of Breeding Birds Improves Body Condition for a Crocodilian Nest Protector

et al. 2016

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Ecological associations where one species enhances habitat for another nearby species (facilitations) shape fundamental community dynamics and can promote niche expansion, thereby influencing how and where species persist and coexist. For the many breeding birds facing high nest-predation pressure, enemy-free space can be gained by nesting near more formidable animals for physical protection. While the benefits to protected species seem well documented, very few studies have explored whether and how protector species are affected by nest protection associations. Long-legged wading birds (Pelecaniformes and Ciconiiformes) actively choose nesting sites above resident American alligators (Alligator mississippiensis), apparently to take advantage of the protection from mammalian nest predators that alligator presence offers. Previous research has shown that wading bird nesting colonies could provide substantial food for alligators in the form of dropped chicks. We compared alligator body condition in similar habitat with and without wading bird nesting colonies present. Alligator morphometric body condition indices were significantly higher in colony than in non-colony locations, an effect that was statistically independent of a range of environmental variables. Since colonially nesting birds and crocodilians co-occur in many tropical and subtropical wetlands, our results highlight a potentially widespread keystone process between two ecologically important species-groups. These findings suggest the interaction is highly beneficial for both groups of actors, and illustrate how selective pressures may have acted to form and reinforce a strongly positive ecological interaction.

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“…This, combined with density compensation, niche expansion, and low predation pressure, has resulted in lizards being important pollinators on many island FIGURE 2 | Examples of reptiles' roles imperiled by human activities: (A) By-catch events drown up to 9,000 olive ridley turtles per year in Odisha, India (Behera et al, 2016)-sea turtles provide important surfaces for encrusting epibionts (Bjorndal and Jackson, 2003;Photo: Supraja Dharini). Crocodilians are important nutrient linkers (Nell and Frederick, 2015), and (B) shows a broad-snouted caiman (Caiman latirostris) with tail amputed while it was alive (Photo: Andrei Jara). Ecosystem engineers such as spiny tailed lizards (Uromastyx aegyptia) create burrows that offer refuge to other species in their native desert landscapes (Williams et al, 1999); they are, however, are hunted in their hundreds for meat, as seen in (C) (Anonymous photo).…”

Section: Reptiles As Gene Transportersmentioning

confidence: 99%

The Plight of Reptiles as Ecological Actors in the Tropics

Miranda

Everton²

2017

Front. Ecol. Evol.

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Earth's tropical ecosystems have witnessed several extinctions and a dramatic reduction of the range and abundance of large reptile species, which is directly related to the rise of early and modern humans. The occurrence of such extinctions, range reduction, species loss, and the consequences for several paramount ecosystem processes are poorly documented compared to other large vertebrate species. Here, I reviewed the literature on the ecological processes performed by large tropical reptile species and their human-induced widespread demise in order to determine knowledge gaps and encourage a paradigm shift in understanding on the interactiveness of such species. The interactions and species involved indicate that large abundant reptiles in the tropics are important in ecological processes, and can consequently have an important role in ecosystem function through gene dispersal, nutrient cycling, trophic action, and ecosystem engineering. These important interactions performed by reptiles are not solely performed by few species, or geographically restricted to islands, but instead present a pattern that repeatedly occurs in large reptiles distributed over tropical ecosystems. The observed tendency of reptiles to be tightly involved in these ecological interactions has important implications for the ecology of tropical ecosystems. Lost and current ecological processes performed by large reptiles may be orders of magnitude higher than what is currently perceived, and the misleading baseline of those processes must be addressed otherwise we risk losing species and services that are dependent of such interactions. To fix this bias I suggest: (a) Increase information spreading about Pleistocene-Holocene reptile extinctions using popular media; (b) Improved exchange between the research field of megafauna effects in ecosystems and herpetologists working with large reptiles; (c) Increase research effort on anthropogenic reptile extinctions and their potential to predict future losses; (d) Address the knowledge gaps, as human-reptile conflict, chelonian seed dispersal and nutrient movement; (e) Increase quantitative research on large reptile population ecology, density, and abundance. (f) address the potentially present or lost ecosystem effects of extant and extinct reptile species. Although the importance of reptiles in most tropical ecosystems has been perceived as negligible, this study shows that this may be a misleading paradigm.

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Fallen Nestlings and Regurgitant as Mechanisms of Nutrient Transfer from Nesting Wading Birds to Crocodilians

Cited by 10 publications

References 73 publications

Collapse of a unique insular bird–snake relationship

Collapse of a unique insular bird–snake relationship

Presence of Breeding Birds Improves Body Condition for a Crocodilian Nest Protector

The Plight of Reptiles as Ecological Actors in the Tropics

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