Aggression in Flocks of Foraging Shorebirds During Spring Stopover at Delaware Bay, USA

Novčić, Ivana

doi:10.1675/063.041.0110

Cited by 9 publications

(12 citation statements)

References 13 publications

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“…17,19,20 During spring migration through Delaware Bay, some pairs of species differ in time of passage and such temporal separation is the most important variable for ecological segregation of species. 21 Nevertheless, in Fortescue, although several species also differed by arrival time, 49 all species started arriving there following the rise of Horseshoe Crabs and congregated in large numbers, when birds exhibited high degree of overlap both in use of microhabitats and feeding techniques.…”

Section: Discussionmentioning

confidence: 99%

“…During the reproductive season, female Horseshoe Crabs lay clusters of eggs on intertidal beaches of Delaware Bay, in the sand near the tide line, at depths ranging 5–30 cm. 50,51 At low tides, shorebirds are distributed around crab nests 23,52 but also, numerous birds are spread over the beach to prey upon eggs that are scattered over the intertidal zone by the receding water. 53 In this study, over 50% of foraging shorebirds were observed on sand and gravel away from the tide line, particularly turnstones, Sanderlings, and knots, which used this habitat significantly more compared to other habitats.…”

Section: Discussionmentioning

confidence: 99%

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Weak niche partitioning by migrating shorebirds in a single-food-type environment

Novčić

2019

Avian Biology Research

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This study examined foraging niche partitioning among coexisting species of shorebirds on a sandy beach dominated by a single food type, Horseshoe Crab ( Limulus polyphemus) eggs, where use of foraging microhabitats of limited variety is temporarily restricted due to tidal cycle. The major goal of the study was to examine whether co-occurring species differed in selection of foraging microhabitats and use of feeding techniques. Ruddy Turnstone ( Arenaria interpres), Red Knot ( Calidris canutus), and Sanderling ( Calidris alba) foraged significantly more on sand and gravel compared to pools and swash zone, Semipalmated Sandpiper ( Calidris pusilla) foraged significantly more on sand and gravel compared to swash zone, but not significantly more compared to pools, while differences in use of microhabitats by Dunlin ( Calidris alpina), and Short-billed Dowitcher ( Limnodromus griseus) were non-significant. Turnstones used digging and turning stones, and pecking significantly more than probing, Semipalmated Sandpipers used pecking significantly more than probing, while all other species used probing significantly more than pecking. Knots and Sanderlings had the highest level of overlap both in use of microhabitats and foraging techniques, while turnstones and dowitchers had the lowest. Ruddy Turnstones were the only birds that used digging and turning stones to obtain food and these two foraging methods seemed to be the most important variables discriminating turnstones from other co-occurring shorebirds. However, despite the slight differences in use of foraging methods and microhabitats by different species, this study documented weak partitioning among shorebirds, particularly between sandpipers and dowitchers. These results indicate that the short-term absence of clear niche partitioning on a local scale may occur in shorebird communities.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Weak niche partitioning by migrating shorebirds in a single-food-type environment

Novčić

2019

Avian Biology Research

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“…While competition has been well‐studied in ecology broadly, information on such interspecific interactions during migration remains rare (Moore and Yong 1991, Novcic 2018). Our results were consistent with this, uncovering only three studies on avian species that discussed co‐migrant competition.…”

Section: Resultsmentioning

confidence: 99%

“…Simultaneously, migrant bird species compete for these valuable foods. Some birds, like sanderlings C. alba , display aggressive behaviors towards other bird species as they race to eat the nutrient‐packed eggs (Novcic 2018). During co‐migrations across taxonomic groups, migrants could affect other migrant species through a range of interactions, including relationships characterized by: commensalism (when one species benefits and the other is not harmed); mutualism (when both species benefit); antagonism (when one species benefits at the expense of the other, such as through parasitism or predation); amensalism (when one species suffers a cost and the other is not affected); and competition (when both species experience negative effects while competing for resources).…”

Section: Introductionmentioning

confidence: 99%

‘Chancing on a spectacle:’ co‐occurring animal migrations and interspecific interactions

Cohen

Satterfield

2020

Ecography

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Migrations of diverse wildlife species often converge in space and time, with their journeys shaped by similar forces (i.e. geographic barriers and seasonal resources and conditions); we term this ‘co‐migration’. Recent studies have illuminated multi‐speciesmigrations by land and sea including the simultaneous movements of numerous insects, birds, bats and of fish invertebrates marine predators. Beyond their significance as natural wonders, species with overlapping migrations may interact ecologically, with potential effects on population and community dynamics. Direct and indirect ecological interactions (including predation and competition) between migrant species remain poorly understood, in part because migration is the least‐studied phase of animals’ annual cycles. To address this gap, we conducted a literature review to examine whether animal migration studies incorporate multiple species and to what extent they investigate interspecific interactions between co‐migrants. Following a key word search, we read all migration research papers in 23 relevant peer‐reviewed journals during 2008–2017. Thirty percent of animal migration papers reported two or more species with coinciding migrations, suggesting that co‐migrations are common, although few studies investigated or discussed these mixed‐species migrations further. Synthesizing these, we present examples and describe five types of ecological interactions between migrating species, including predator–prey, host–parasite and commensal relationships. Considering migratory animals as interacting with migrant communities will enhance understanding of the drivers of migration and could improve predictions about wildlife responses to global change. Further research focused on multi‐species migrations could also inform conservation efforts for migratory animal populations, many of which are declining or shifting, with unexplored consequences for other co‐migratory species.

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“…Despite the potential of wintering shorebirds to aggregate in recreational beaches, flocks with a high density of conspecifics are very competitive, and there may be reduced food availability per foraging area (Stinson 1980, Metcalfe and Furness 1986, Newton 2006, Novcic 2018. Greater monospecific flocks may also have lower feeding rates because of their disruption effect on prey (e.g.…”

Section: Introductionmentioning

confidence: 99%

Keeping safe and fed: large heterospecific shorebird flocks to decrease intraspecific competition

Cestári

Gonçalves

Melo

2020

Journal of Avian Biology

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Journal of Avian Biology 2020: e02316Shorebirds join cohesive flocks for safety. The joining of individuals of several species in large heterospecific flocks can optimise individual vigilance and foraging. However, a large number of conspecific individuals in flocks may deplete food resources and increase intraspecific competition. In the present study, we argue that Nearctic-Neotropical migratory shorebird species join large heterospecific flocks in a balanced number as a way of controlling intraspecific competition. We recorded monospecific and heterospecific flocks in urban beaches from southeastern Brazil and annotated the species richness and the number of individuals per bird species per flock. Besides, we recorded the number of people around shorebird flocks to examine any relationship with flock size. We also recorded the foraging rate of the semipalmated plover Charadrius semipalmatus, a common migrant species in the region, as a species model to test competition and vigilance. We hypothesised that this species would exhibit a low foraging rate in scenarios with high intraspecific competition (i.e. large flocks with a high number of conspecifics) and high density of people, which may disturb birds. In the initial results, the density of people did not influence size of monospecific and heterospecific flocks; heterospecific flocks were larger than monospecific flocks, and heterospecific flocks increased in size by the addition of more species rather than more individuals of the same species. These data reflect a decrease in the relative abundance of individuals per species. Additionally, the semipalmated plover foraging rate was reduced in monospecific flocks, flocks with a high relative abundance (and total number) of the specific individuals and flocks surrounded by a high density of people. All these results indicate that shorebirds may adjust flock composition and size according to preferred foraging conditions, i.e. large and balanced heterospecific flocks with less intraspecific competition and less vigilance to potential predators in wintering areas.

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Aggression in Flocks of Foraging Shorebirds During Spring Stopover at Delaware Bay, USA

Abstract: BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

Cited by 9 publications

References 13 publications

Weak niche partitioning by migrating shorebirds in a single-food-type environment

Weak niche partitioning by migrating shorebirds in a single-food-type environment

‘Chancing on a spectacle:’ co‐occurring animal migrations and interspecific interactions

Keeping safe and fed: large heterospecific shorebird flocks to decrease intraspecific competition

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