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Shen Y, Holyoak M, Goodale E, Mammides C, Zou F, Chen Y, Zhang C, Quan Q, Zhang Q. Mixed-species bird flocks re-assemble interspecific associations across an elevational gradient. Proc Biol Sci 2022; 289:20221840. [PMID: 36541168 PMCID: PMC9768660 DOI: 10.1098/rspb.2022.1840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 11/24/2022] [Indexed: 12/24/2022] Open
Abstract
Understanding how non-trophic social systems respond to environmental gradients is still a challenge in animal ecology, particularly in comparing changes in species composition to changes in interspecific interactions. Here, we combined long-term monitoring of mixed-species bird flocks, data on participating species' evolutionary history and traits, to test how elevation affected community assemblages and interspecific interactions in flock social networks. Elevation primarily affected flocks through reassembling interspecific associations rather than modifying community assemblages. Specifically, flock networks at higher elevations (compared to low elevations) had stronger interspecific associations (larger average weighted degree), network connectivity (enhanced network density) and fewer subnetworks. A phylogenetic and functional perspective revealed that associations between similar species weakened, whereas connections between dissimilar and/or random species were unchanged or strengthened with elevation. Likewise, network assortativity for the traits of vertical stratum and breeding period declined with elevation. The overall pattern is a change from modular networks in the lowlands, where species join flocks with other species that have matching traits, to a more open, random system at high elevations. Collectively, this rewiring of interspecific networks across elevational gradients imparts network stability and resiliency and makes mixed-species flocks less sensitive to local extinctions caused by harsh environments.
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Affiliation(s)
- Yong Shen
- Guangdong Key Laboratory of Animal Conservation and Resource Utilization, Guangdong Public Laboratory of Wild Animal Conservation and Utilization, Institute of Zoology, Guangdong Academy of Sciences, Guangzhou 510260, People's Republic of China
| | - Marcel Holyoak
- Department of Environmental Science and Policy, University of California, Davis, CA 95616, USA
| | - Eben Goodale
- Department of Health and Environmental Science, Xi'an Jiaotong-Liverpool University, Suzhou 215123, People's Republic of China
| | - Christos Mammides
- Nature Conservation Unit, Frederick University, Nicosia 1036, Cyprus
| | - Fasheng Zou
- Guangdong Key Laboratory of Animal Conservation and Resource Utilization, Guangdong Public Laboratory of Wild Animal Conservation and Utilization, Institute of Zoology, Guangdong Academy of Sciences, Guangzhou 510260, People's Republic of China
| | - Yuxin Chen
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, College of the Environment and Ecology, Xiamen University, Xiamen 361102, People's Republic of China
| | - Chaoming Zhang
- Guangdong Nanling National Nature Reserve, Shaoguan 512727, People's Republic of China
| | - Qing Quan
- Guangdong Key Laboratory of Animal Conservation and Resource Utilization, Guangdong Public Laboratory of Wild Animal Conservation and Utilization, Institute of Zoology, Guangdong Academy of Sciences, Guangzhou 510260, People's Republic of China
| | - Qiang Zhang
- Guangdong Key Laboratory of Animal Conservation and Resource Utilization, Guangdong Public Laboratory of Wild Animal Conservation and Utilization, Institute of Zoology, Guangdong Academy of Sciences, Guangzhou 510260, People's Republic of China
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Hariharan P, Bangal P, Sridhar H, Shanker K. Habitat use by mixed-species bird flocks in tropical forests of the Western Ghats, India. J Trop Ecol . [DOI: 10.1017/s026646742200030x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Abstract
While mixed-species flocks of birds (hereafter ‘flocks’) have been widely studied, few studies have looked at the effect of habitat structure on flock presence and flocking propensity within a site. Here, we employ a use-availability approach in locations with flocks and random locations to ask whether habitat characteristics influence the presence of flocks, and whether structurally similar microhabitats support compositionally similar flocks. We also examine the effect of habitat on flock size and species richness, and the effect of intraspecifically gregarious flock participants on habitat selection. We find that flocks use a narrow subset of available tree density and canopy cover variation and prefer relatively less-dense areas with large trees and a complex foliage structure. Similar microhabitats do not result in compositionally similar flocks, and while foliage complexity was associated with flock size, no habitat characteristics influenced species richness. Flocks led by the intraspecifically gregarious western crowned warbler (Phylloscopus occipitalis), a potential nuclear species, showed preference for high foliage complexity and tree density. Thus, habitat preferences of intraspecifically gregarious species, which are followed by other species, could play a strong role in habitat selection in flocks. This suggests that degraded forests that cannot provide a suitable range of tree density, canopy cover, and/or complex vegetation structure may not support some core flock species around which flocks form, which may lead to decreased flocking in those patches.
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Bangal P, Sridhar H, Shizuka D, Vander Meiden LN, Shanker K. Flock-species richness influences node importance and modularity in mixed-species flock networks. Oecologia 2021. [PMID: 34709417 DOI: 10.1007/s00442-021-05053-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Accepted: 09/28/2021] [Indexed: 10/20/2022]
Abstract
Interdependencies in social groups of animals are a combination of multiple pairwise interactions. Heterospecific groups are often characterized by important species that contribute more to group initiation, maintenance or function than other species. However, in large heterospecific groups, many pairwise interactions are not realised, while others may not be biologically significant, confounding inferences about species importance. Hence, in this study, we examine context dependent changes in species importance and assortment in mixed-species bird flocks from a tropical field site in Southern India using social network analysis. Specifically, we ask how the structural importance of a species and the clustering patterns of species relationships depends on species richness in mixed-species flocks. We constructed both raw and filtered networks; while our results are largely correlated, we believe that filtered networks can provide insights into community-level importance of species in mixed-flocks while raw networks depict flock-level patterns. We find significant differences in flocks of different richness in that different species emerge as structurally important across flocks of varying richness. We also find that assortment is higher in two-species flocks and decreases with an increase in the number of species in the flock ('flock richness' hereafter). We argue that the link between structural importance of species in mixed-species flock networks and their functional significance in the community critically depends on the social context: namely, the species richness of the mixed-species flock. We propose that examining species structural importance at different flock-richness values provides insights into biologically meaningful functional roles of species. More generally, we suggest that it is important to consider context when interpreting species centrality and importance in network structure.
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Abstract
Abstract
Mixed-species flocks are a key facilitative interaction for tropical birds. Forest fragmentation leads to species loss and spatial turnover in these flocks, yet it is unknown how these changes to composition influence within-flock species interactions. We used network analysis to characterize flocking interactions along a fragment-size gradient in the Colombian Western Andes. We asked 1) how patch size, edge density, and vegetation structure explained network measures indicative of flock cohesion, 2) whether changes were driven by flocking species turnover or changes to the frequency of species co-occurrence, and 3) whether nuclear species, those that maintain flock stability and cohesion, changed in importance across the gradient. We constructed weighted social networks from flock compositions observed on 500-m transects, and then calculated global network measures and the centrality of six nuclear species. Patch size and edge density did not correlate with interspecific co-occurrence patterns, but interaction strength increased with canopy height. Flocks contained numerous, weak interactions, and there were no flock subtypes, suggesting flock composition was dynamic and unstructured. Several redundant nuclear species were present and varied in importance based on ecological conditions. A chlorospingus (Passerellidae) was most central in old-growth forest, whereas several tanager (Thraupidae) species became more central in smaller fragments and disturbed forest. When partitioning network dissimilarity, we found that 66% of dissimilarity resulted from species turnover, whereas only 34% resulted from changes to species co-occurrence. This finding suggests that coherence of flocking behavior itself is maintained even as extensive species turnover occurs from continuous forest to small fragments.
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Affiliation(s)
- Harrison H Jones
- Department of Biology, University of Florida, Gainesville, FL, USA
- Florida Museum of Natural History, University of Florida, Gainesville, FL, USA
| | - Scott K Robinson
- Department of Biology, University of Florida, Gainesville, FL, USA
- Florida Museum of Natural History, University of Florida, Gainesville, FL, USA
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Goodale E, Sridhar H, Sieving KE, Bangal P, Colorado Z GJ, Farine DR, Heymann EW, Jones HH, Krams I, Martínez AE, Montaño-Centellas F, Muñoz J, Srinivasan U, Theo A, Shanker K. Mixed company: a framework for understanding the composition and organization of mixed-species animal groups. Biol Rev Camb Philos Soc 2020; 95:889-910. [PMID: 32097520 PMCID: PMC7383667 DOI: 10.1111/brv.12591] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 02/02/2020] [Accepted: 02/06/2020] [Indexed: 12/19/2022]
Abstract
Mixed-species animal groups (MSGs) are widely acknowledged to increase predator avoidance and foraging efficiency, among other benefits, and thereby increase participants' fitness. Diversity in MSG composition ranges from two to 70 species of very similar or completely different phenotypes. Yet consistency in organization is also observable in that one or a few species usually have disproportionate importance for MSG formation and/or maintenance. We propose a two-dimensional framework for understanding this diversity and consistency, concentrating on the types of interactions possible between two individuals, usually of different species. One axis represents the similarity of benefit types traded between the individuals, while the second axis expresses asymmetry in the relative amount of benefits/costs accrued. Considering benefit types, one extreme represents the case of single-species groups wherein all individuals obtain the same supplementary, group-size-related benefits, and the other extreme comprises associations of very different, but complementary species (e.g. one partner creates access to food while the other provides vigilance). The relevance of social information and the matching of activities (e.g. speed of movement) are highest for relationships on the supplementary side of this axis, but so is competition; relationships between species will occur at points along this gradient where the benefits outweigh the costs. Considering benefit amounts given or received, extreme asymmetry occurs when one species is exclusively a benefit provider and the other a benefit user. Within this parameter space, some MSG systems are constrained to one kind of interaction, such as shoals of fish of similar species or leader-follower interactions in fish and other taxa. Other MSGs, such as terrestrial bird flocks, can simultaneously include a variety of supplementary and complementary interactions. We review the benefits that species obtain across the diversity of MSG types, and argue that the degree and nature of asymmetry between benefit providers and users should be measured and not just assumed. We then discuss evolutionary shifts in MSG types, focusing on drivers towards similarity in group composition, and selection on benefit providers to enhance the benefits they can receive from other species. Finally, we conclude by considering how individual and collective behaviour in MSGs may influence both the structure and processes of communities.
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Affiliation(s)
- Eben Goodale
- Guangxi Key Laboratory for Forest Ecology and Conservation, College of Forestry, Guangxi University, Nanning, Guangxi, 530004, China
| | - Hari Sridhar
- Centre for Ecological Sciences, Indian Institute of Science, Bengaluru, Karnataka, 560012, India.,National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, Karnataka, 560012, India
| | - Kathryn E Sieving
- Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, FL, 32611, U.S.A
| | - Priti Bangal
- Centre for Ecological Sciences, Indian Institute of Science, Bengaluru, Karnataka, 560012, India
| | - Gabriel J Colorado Z
- Departamento de Ciencias Forestales, Universidad Nacional de Colombia, Medellín, 050034, Colombia
| | - Damien R Farine
- Department of Collective Behavior, Max Planck Institute of Animal Behavior, Universitätsstrasse 10, D-78464, Konstanz, Germany.,Centre for the Advanced Study of Collective Behaviour, University of Konstanz, D-78464, Konstanz, Germany.,Department of Biology, University of Konstanz, D-78464, Konstanz, Germany
| | - Eckhard W Heymann
- Deutsches Primatenzentrum, Leibniz-Institut für Primatenforschung, D-37077, Göttingen, Germany
| | - Harrison H Jones
- Department of Biology, University of Florida, Gainesville, FL, 32611, U.S.A.,Florida Museum of Natural History, Gainesville, FL, 32611, U.S.A
| | - Indrikis Krams
- Institute of Ecology and Earth Sciences, University of Tartu, Tartu, 51410, Estonia.,Department of Zoology and Animal Ecology, Faculty of Biology, University of Latvia, Rīga, 1004, Latvia
| | - Ari E Martínez
- Department of Biological Sciences, California State University, Long Beach, CA, 90840, U.S.A
| | - Flavia Montaño-Centellas
- Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, FL, 32611, U.S.A.,Instituto de Ecologia, Universidad Mayor de San Andres, La Paz, 10077, Bolivia
| | - Jenny Muñoz
- Zoology Department and Biodiversity Research Center, University of British Columbia, Vancouver, BC, V6T 1ZA, Canada
| | - Umesh Srinivasan
- Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ, 08540, U.S.A
| | - Anne Theo
- Centre for Ecological Sciences, Indian Institute of Science, Bengaluru, Karnataka, 560012, India
| | - Kartik Shanker
- Centre for Ecological Sciences, Indian Institute of Science, Bengaluru, Karnataka, 560012, India.,Dakshin Foundation, Bengaluru, 560092, India
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Abstract
Animal populations often decline due to habitat disturbance, but the initial response of organisms to human-induced environmental change is usually behavioral. Intra- and inter-specific interactions can restrict or facilitate access to resources, resulting in changes to individual fitness, and resource depletion may affect the frequency and strength of interactions. In birds, it is often assumed that feeding in groups increases foraging efficiency. We assessed how the reduction of seed resources provoked by cattle grazing affected different properties of seed-eating bird flocks in woodlands having the same structural characteristics but differing in seed abundance. Under lower availability of grass seeds (i.e., under grazing), flocks were smaller and less rich and birds showed a lower flocking propensity. This pattern could be explained by three non-exclusive hypotheses. Food reduction caused by grazing (i) decreases the number of seed-eating birds and concomitantly generates smaller flocks; (ii) reduces the density of nuclear species, decreasing the group cohesion in large flocks; (iii) makes large flocks less attractive by increasing individual competence for food. Our results provide evidence that cattle grazing affect the interactions of seed-eating birds and suggest the importance of understanding flocking behavior to bring about management actions.
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Affiliation(s)
- A. Zarco
- Ecodes, Instituto Argentino de Investigaciones de las Zonas Áridas (IADIZA), CONICET, and Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo, Mendoza, 5500, Mendoza, Argentina
| | - V.R. Cueto
- Ecodes, Centro de Investigación Esquel de Montaña y Estepa Patagónica (CIEMEP), CONICET, and Universidad Nacional de la Patagonia San Juan Bosco, Esquel, 9200, Chubut, Argentina
| | - M.C. Sagario
- Ecodes, Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA), CONICET and Universidad Nacional del Comahue. Centro de Ecología Aplicada del Neuquén (CEAN), Junín de los Andes, 8371, Neuquén, Argentina
| | - L. Marone
- Ecodes, Instituto Argentino de Investigaciones de las Zonas Áridas (IADIZA), CONICET, and Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo, Mendoza, 5500, Mendoza, Argentina
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