Nutrient Utilization and Diet Preference of American White Pelicans Consuming Either a Mono- or Multi-Species Diet

Ferguson, Treena L.; Rude, Brian J.; King, D. Tommy

doi:10.1675/063.034.0211

Cited by 4 publications

(8 citation statements)

References 21 publications

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“…Although we were not able to assign a predator species to a large proportion of our recovered tags, it is not unreasonable to infer a parsing of predation from cormorants and pelicans similar to those observed from nest recoveries. While it is well known that energetic demands differ between these avian predators (Hall 1925;Ferguson et al 2011;Seefelt and Gillingham 2008), prey selection or vulnerability may also differ (DeBruyne et al 2013). In our study, the number of PIT tags that were found specifically in cormorants nests at the Minidoka colony exceeded the numbers that were found in pelican 150).…”

Section: Watercontrasting

confidence: 50%

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Colonial Waterbird Predation and Angler Catch of Hatchery Rainbow Trout Stocked in Southern Idaho Fisheries

2019

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The abundance of piscivorous colonial waterbirds such as double‐crested cormorants Phalacrocorax auritus and American white pelicans Pelecanus erythrorhynchos has increased dramatically in recent decades in North America, resulting in increased conflict between these birds and fisheries resources, which raises the need to quantify the effects of waterbird predation on fisheries. We estimated avian predation and angler use of two sizes of hatchery‐reared Rainbow Trout Oncorhynchus mykiss (250 mm and 300 mm on average; termed standard catchables and magnum catchables) at 15 Idaho waters with known cormorant and pelican presence. Fish were tagged with passive integrated transponder (PIT), radio, and T‐bar anchor tags prior to release; the tags were subsequently recovered from bird nesting, roosting, and loafing sites. Estimated angler use, which included fish harvested as well as those that were catch‐and‐release, averaged 17%, while avian predation averaged 35%. Angler catch at study waters declined exponentially as avian predation increased. Predation specifically attributed to double‐crested cormorants and American white pelicans was related to their relative abundance at the waterbodies where the fish were stocked. Avian predation rates were similar for standard and magnum catchables, suggesting that larger fish were not able to escape predation any better than smaller ones. Our results add to existing evidence indicating that in some southern Idaho fisheries, piscivorous birds, rather than anglers, are the dominant consumers of hatchery trout. This study further contributes to the larger issue of competition between humans, wildlife, and fisheries populations.

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Section: Watercontrasting

confidence: 50%

“…While it is well known that energetic demands differ between these avian predators (Hall ; Ferguson et al. ; Seefelt and Gillingham ), prey selection or vulnerability may also differ (DeBruyne et al. ).…”

Section: Discussionmentioning

confidence: 99%

Colonial Waterbird Predation and Angler Catch of Hatchery Rainbow Trout Stocked in Southern Idaho Fisheries

2019

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“…For example, for 4 of our 19 pelican predation estimates, we assumed that pelicans and cormorants were equally successful at foraging on hatchery catchable trout, and that their energetic demands were equivalent. While the relative foraging success of pelicans and cormorants on hatchery catchable trout is unknown, energetic demands are four to eight times higher for pelicans (Hall 1925;Ferguson et al 2011) than for cormorants (Hatch and Weseloh 1999;Seefelt and Gillingham 2008). By apportioning tags based solely on bird abundance without adjusting for differing energy requirements, we likely underestimated pelican predation (and consequently overestimated cormorant predation) unless cormorants were four to eight times more successful foragers on our stocked fish.…”

Section: Discussionmentioning

confidence: 99%

“…Adult double-crested cormorants require approximately 320 g of fish per day (Hatch and Weseloh 1999) compared with 1,500 g for American white pelicans (Ferguson et al 2011), and cormorant chicks require an estimated 8-9 kg of food from hatching to fledging (Seefelt and Gillingham 2008) compared with 68 kg for American white pelican chicks (Hall 1925). Tag assignment based solely on bird abundance was thus modified to account for these energetic differences (Table 2).…”

Section: Methodsmentioning

confidence: 99%

Predation by American White Pelicans and Double‐Crested Cormorants on Catchable‐Sized Hatchery Rainbow Trout in Select Idaho Lentic Waters

Meyer

Sullivan

Kennedy

et al. 2016

N American J Fish Manag

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In southern Idaho, population growth of American white pelicans Pelecanus erythorhynchos at the Blackfoot Reservoir and Lake Walcott colonies since the early 1990s has generated concerns about whether pelican predation is impacting angler catch of hatchery trout stocked in Idaho waters. To evaluate this concern, we estimated rates of pelican predation (i.e., the proportion of fish consumed by pelicans) and angler catch (i.e., the proportion of fish caught by anglers) for 19 unique springtime fish stocking events over 3 years across 12 study waters; where feasible we also estimated double‐crested cormorant Phalacrocorax auritus predation. Stocked Rainbow Trout Oncorhynchus mykiss averaged 247 mm in length and were internally PIT‐tagged (to monitor bird predation) and externally anchor‐tagged (to monitor angler catch) before stocking. Additional hatchery trout were PIT‐tagged, euthanized, and fed directly to pelicans to estimate PIT tag deposition rates at the colonies; feeding was unsuccessful for cormorants. After the juvenile pelicans and cormorants fledged in the fall, we recovered PIT tags from stocked and fed fish that were deposited at the two colonies. Deposition rates for pelican‐consumed tags averaged 21% and declined exponentially as distance increased from the colonies. Pelican predation on hatchery trout averaged 18% and ranged from 0 to 48%, whereas angler catch averaged 21% and ranged from 0 to 82%. Mean angler catch was nearly four times higher when pelican predation was low (i.e., <25%) than when pelican predation was high (≥25%). Cormorant predation estimates (available for seven stocking events) were minimum estimates only (i.e., they assumed 100% of tags consumed by cormorants were recovered) and averaged 14% (range, 2–38%). Our results suggest that predation by American white pelicans and double‐crested cormorants on catchable‐sized hatchery Rainbow Trout stocked in southern Idaho waters often exceeds the total catch of those fish by anglers who compete directly with avian predators for use of stocked trout.Received June 23, 2015; accepted November 8, 2015 Published online March 30, 2016

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“…Regurgitate samples collected from parent pelicans in South Dakota sub-colonies had a narrow range of variation, perhaps indicating that birds in this region are sharing a common food resource or have dietary preferences (Ferguson et al 2011). It is notable that regurgitate from South Dakota pelicans contained a large proportion of tiger salamanders (Ambystoma tigrinum; 50-90%), whereas regurgitate from North Dakota pelicans contained a much wider variety of fish species.…”

Section: Discussionmentioning

confidence: 99%

American White Pelican (Pelecanus erythrorhynchos) Growth, Nutrition and Immunology

2019

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Limited information about nutrition exists on American White Pelicans (Pelecanus erythrorhynchos) from hatching to fledging. To detail immunity, metabolism and nutrition of juvenile American White Pelicans, during 22-23 July 2011, 103 samples of regurgitate matter were collected at five Chase Lake, North Dakota, USA, and three Bitter Lake, South Dakota, USA, sub-colonies. Regurgitate sample nutrient content was significantly different for organic matter (P = 0.012), crude protein (P = 0.001), neutral detergent fiber (P = 0.014), acid detergent fiber (P = 0.005) and energy (P = 0.034) between North (n = 5) and South (n = 3) Dakota American White Pelican colonies. Average concentrations of immunoglobulins Y (2.74 ± 1.85 ng/mL) and A (9.04 ± 9.41 ng/mL) demonstrated passive transfer of immunity in regurgitate. To enhance information on growth and morphology in hand-reared American White Pelicans (n = 8), a 9-week captive trial was also conducted raising chicks from hatching to fledging. Predictive models were created to describe chick growth for intake, body weight, culmen length and tarsus length. Data collected during this study enhances both American White Pelican general ecology and conservation with implications for both captive and wild bird management.

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Nutrient Utilization and Diet Preference of American White Pelicans Consuming Either a Mono- or Multi-Species Diet

Cited by 4 publications

References 21 publications

Colonial Waterbird Predation and Angler Catch of Hatchery Rainbow Trout Stocked in Southern Idaho Fisheries

Colonial Waterbird Predation and Angler Catch of Hatchery Rainbow Trout Stocked in Southern Idaho Fisheries

Predation by American White Pelicans and Double‐Crested Cormorants on Catchable‐Sized Hatchery Rainbow Trout in Select Idaho Lentic Waters

American White Pelican (Pelecanus erythrorhynchos) Growth, Nutrition and Immunology

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