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Baliga VB, Dakin R, Wylie DR, Altshuler DL. Hummingbirds use distinct control strategies for forward and hovering flight. Proc Biol Sci 2024; 291:20232155. [PMID: 38196357 PMCID: PMC10777153 DOI: 10.1098/rspb.2023.2155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Accepted: 12/08/2023] [Indexed: 01/11/2024] Open
Abstract
The detection of optic flow is important for generating optomotor responses to mediate retinal image stabilization, and it can also be used during ongoing locomotion for centring and velocity control. Previous work in hummingbirds has separately examined the roles of optic flow during hovering and when centring through a narrow passage during forward flight. To develop a hypothesis for the visual control of forward flight velocity, we examined the behaviour of hummingbirds in a flight tunnel where optic flow could be systematically manipulated. In all treatments, the animals exhibited periods of forward flight interspersed with bouts of spontaneous hovering. Hummingbirds flew fastest when they had a reliable signal of optic flow. All optic flow manipulations caused slower flight, suggesting that hummingbirds had an expected optic flow magnitude that was disrupted. In addition, upward and downward optic flow drove optomotor responses for maintaining altitude during forward flight. When hummingbirds made voluntary transitions to hovering, optomotor responses were observed to all directions. Collectively, these results are consistent with hummingbirds controlling flight speed via mechanisms that use an internal forward model to predict expected optic flow whereas flight altitude and hovering position are controlled more directly by sensory feedback from the environment.
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Affiliation(s)
- Vikram B. Baliga
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
| | - Roslyn Dakin
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
- Department of Biology, Carleton University, Ottawa, Ontario, Canada K1S 5B6
| | - Douglas R. Wylie
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2R3
| | - Douglas L. Altshuler
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
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McGuire LP, Leys R, Webber QMR, Clerc J. Heterothermic Migration Strategies in Flying Vertebrates. Integr Comp Biol 2023; 63:1060-1074. [PMID: 37279461 DOI: 10.1093/icb/icad053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 05/25/2023] [Accepted: 05/29/2023] [Indexed: 06/08/2023] Open
Abstract
Migration is a widespread and highly variable trait among animals. Population-level patterns arise from individual-level decisions, including physiological and energetic constraints. Many aspects of migration are influenced by behaviors and strategies employed during periods of stopover, where migrants may encounter variable or unpredictable conditions. Thermoregulation can be a major cost for homeotherms which largely encounter ambient temperatures below the lower critical temperature during migration, especially during the rest phase of the daily cycle. In this review we describe the empirical evidence, theoretical models, and potential implications of bats and birds that use heterothermy to reduce thermoregulatory costs during migration. Torpor-assisted migration is a strategy described for migrating temperate insectivorous bats, whereby torpor can be used during periods of inactivity to drastically reduce thermoregulatory costs and increase net refueling rate, leading to shorter stopover duration, reduced fuel load requirement, and potential consequences for broad-scale movement patterns and survival. Hummingbirds can adopt a similar strategy, but most birds are not capable of torpor. However, there is an increasing recognition of the use of more shallow heterothermic strategies by diverse bird species during migration, with similarly important implications for migration energetics. A growing body of published literature and preliminary data from ongoing research indicate that heterothermic migration strategies in birds may be more common than traditionally appreciated. We further take a broad evolutionary perspective to consider heterothermy as an alternative to migration in some species, or as a conceptual link to consider alternatives to seasonal resource limitations. There is a growing body of evidence related to heterothermic migration strategies in bats and birds, but many important questions related to the broader implications of this strategy remain.
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Affiliation(s)
- Liam P McGuire
- Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Ryan Leys
- Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Quinn M R Webber
- Department of Integrative Biology, University of Guelph,Guelph, ON N1G 2W1, Canada
| | - Jeff Clerc
- National Renewable Energy Laboratory, Golden, CO 80401, USA
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Paxton KL, Baker KM, Crytser ZB, Guinto RMP, Brinck KW, Rogers HS, Paxton EH. Optimizing trilateration estimates for tracking fine‐scale movement of wildlife using automated radio telemetry networks. Ecol Evol 2022; 12:e8561. [PMID: 35169450 PMCID: PMC8831095 DOI: 10.1002/ece3.8561] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 12/13/2021] [Accepted: 12/22/2021] [Indexed: 11/11/2022] Open
Abstract
A major advancement in the use of radio telemetry has been the development of automated radio tracking systems (ARTS), which allow animal movements to be tracked continuously. A new ARTS approach is the use of a network of simple radio receivers (nodes) that collect radio signal strength (RSS) values from animal‐borne radio transmitters. However, the use of RSS‐based localization methods in wildlife tracking research is new, and analytical approaches critical for determining high‐quality location data have lagged behind technological developments. We present an analytical approach to optimize RSS‐based localization estimates for a node network designed to track fine‐scale animal movements in a localized area. Specifically, we test the application of analytical filters (signal strength, distance among nodes) to data from real and simulated node networks that differ in the density and configuration of nodes. We evaluate how different filters and network configurations (density and regularity of node spacing) may influence the accuracy of RSS‐based localization estimates. Overall, the use of signal strength and distance‐based filters resulted in a 3‐ to 9‐fold increase in median accuracy of location estimates over unfiltered estimates, with the most stringent filters providing location estimates with a median accuracy ranging from 28 to 73 m depending on the configuration and spacing of the node network. We found that distance filters performed significantly better than RSS filters for networks with evenly spaced nodes, but the advantage diminished when nodes were less uniformly spaced within a network. Our results not only provide analytical approaches to greatly increase the accuracy of RSS‐based localization estimates, as well as the computer code to do so, but also provide guidance on how to best configure node networks to maximize the accuracy and capabilities of such systems for wildlife tracking studies.
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Affiliation(s)
- Kristina L. Paxton
- Hawaiʻi Cooperative Studies Unit University of Hawaiʻi Hilo Hawaiʻi National Park Hawaii USA
| | - Kayla M. Baker
- Department of Ecology, Evolution, and Organismal Biology Iowa State University Ames Iowa USA
| | - Zia B. Crytser
- Department of Ecology, Evolution, and Organismal Biology Iowa State University Ames Iowa USA
| | - Ray Mark P. Guinto
- U.S. Geological Survey Pacific Island Ecosystems Research Center Hawaiʻi National Park Hawaii USA
| | - Kevin W. Brinck
- Hawaiʻi Cooperative Studies Unit University of Hawaiʻi Hilo Hawaiʻi National Park Hawaii USA
| | - Haldre S. Rogers
- Department of Ecology, Evolution, and Organismal Biology Iowa State University Ames Iowa USA
| | - Eben H. Paxton
- U.S. Geological Survey Pacific Island Ecosystems Research Center Hawaiʻi National Park Hawaii USA
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Schmaljohann H, Eikenaar C, Sapir N. Understanding the ecological and evolutionary function of stopover in migrating birds. Biol Rev Camb Philos Soc 2022; 97:1231-1252. [PMID: 35137518 DOI: 10.1111/brv.12839] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 01/31/2022] [Accepted: 02/01/2022] [Indexed: 12/14/2022]
Abstract
Global movement patterns of migratory birds illustrate their fascinating physical and physiological abilities to cross continents and oceans. During their voyages, most birds land multiple times to make so-called 'stopovers'. Our current knowledge on the functions of stopover is mainly based on the proximate study of departure decisions. However, such studies are insufficient to gauge fully the ecological and evolutionary functions of stopover. If we study how a focal trait, e.g. changes in energy stores, affects the decision to depart from a stopover without considering the trait(s) that actually caused the bird to land, e.g. unfavourable environmental conditions for flight, we misinterpret the function of the stopover. It is thus important to realise and acknowledge that stopovers have many different functions, and that not every migrant has the same (set of) reasons to stop-over. Additionally, we may obtain contradictory results because the significance of different traits to a migrant is context dependent. For instance, late spring migrants may be more prone to risk-taking and depart from a stopover with lower energy stores than early spring migrants. Thus, we neglect that departure decisions are subject to selection to minimise immediate (mortality risk) and/or delayed (low future reproductive output) fitness costs. To alleviate these issues, we first define stopover as an interruption of migratory endurance flight to minimise immediate and/or delayed fitness costs. Second, we review all probable functions of stopover, which include accumulating energy, various forms of physiological recovery and avoiding adverse environmental conditions for flight, and list potential other functions that are less well studied, such as minimising predation, recovery from physical exhaustion and spatiotemporal adjustments to migration. Third, derived from these aspects, we argue for a paradigm shift in stopover ecology research. This includes focusing on why an individual interrupts its migratory flight, which is more likely to identify the individual-specific function(s) of the stopover correctly than departure-decision studies. Moreover, we highlight that the selective forces acting on stopover decisions are context dependent and are expected to differ between, e.g. K-/r-selected species, the sexes and migration strategies. For example, all else being equal, r-selected species (low survival rate, high reproductive rate) should have a stronger urge to continue the migratory endurance flight or resume migration from a stopover because the potential increase in immediate fitness costs suffered from a flight is offset by the expected higher reproductive success in the subsequent breeding season. Finally, we propose to focus less on proximate mechanisms controlling landing and departure decisions, and more on ultimate mechanisms to identify the selective forces shaping stopover decisions. Our ideas are not limited to birds but can be applied to any migratory species. Our revised definition of stopover and the proposed paradigm shift has the potential to stimulate a fruitful discussion towards a better evolutionary ecological understanding of the functions of stopover. Furthermore, identifying the functions of stopover will support targeted measures to conserve and restore the functionality of stopover sites threatened by anthropogenic environmental changes. This is especially important for long-distance migrants, which currently are in alarming decline.
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Affiliation(s)
- Heiko Schmaljohann
- Institute for Biology and Environmental Sciences (IBU), Carl von Ossietzky University of Oldenburg, Carl-von-Ossietzky-Straße 9-11, Oldenburg, 26129, Germany.,Institute of Avian Research, An der Vogelwarte 21, Wilhelmshaven, 26386, Germany
| | - Cas Eikenaar
- Institute of Avian Research, An der Vogelwarte 21, Wilhelmshaven, 26386, Germany
| | - Nir Sapir
- Department of Evolutionary and Environmental Biology and the Institute of Evolution, University of Haifa, 199 Aba Khoushy Ave, Haifa, 3498838, Israel
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Zenzal TJ, Ward MP, Diehl RH, Buler JJ, Smolinsky J, Deppe JL, Bolus RT, Celis‐Murillo A, Moore FR. Retreat, detour or advance? Understanding the movements of birds confronting the Gulf of Mexico. OIKOS 2021. [DOI: 10.1111/oik.07834] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Theodore J. Zenzal
- U.S. Geological Survey, Wetland and Aquatic Research Center Lafayette LA USA
- School of Biological, Environmental, and Earth Sciences, Univ. of Southern Mississippi Hattiesburg MS USA
| | - Michael P. Ward
- Dept of Natural Resources and Environmental Sciences, Univ. of Illinois Urbana IL USA
| | - Robert H. Diehl
- U.S. Geological Survey, Northern Rocky Mountain Science Center Bozeman MT USA
| | - Jeffrey J. Buler
- Dept of Entomology and Wildlife Ecology, Univ. of Delaware Newark DE USA
| | - Jaclyn Smolinsky
- Dept of Entomology and Wildlife Ecology, Univ. of Delaware Newark DE USA
- Cherokee Nation System Solutions, contracted to the US Geol. Surv., Wetland and Aguatic Res. Center Lafayette LA USA
| | | | | | | | - Frank R. Moore
- School of Biological, Environmental, and Earth Sciences, Univ. of Southern Mississippi Hattiesburg MS USA
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Abstract
Abstract
Many migrants must forage en route when fuel reserves are depleted and access to resources can be influenced by a variety of factors, including the sex, age, and current fuel stores of individuals, as well as resource availability. The objective of this study is to determine the factors that influence the use and defence of resources by migrating ruby-throated hummingbirds (Archilochus colubris). Our results illustrate that resource use: (1) is dependent on sex and resource defence, (2) decreases with fuel load and (3) increases with stopover duration as well as the number of unique feeders visited. Resource defence is closely tied to (1) competition, with the greatest conspecific density resulting in focal individuals being chased from feeders and (2) the interplay between resource quality and fuel load. Our research enhances our understanding of strategies migratory birds use to acquire and defend resources during stopover.
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Affiliation(s)
- Theodore J. Zenzal
- School of Biological, Environmental, and Earth Sciences, The University of Southern Mississippi, Hattiesburg, MS 39406, USA
| | - Frank R. Moore
- School of Biological, Environmental, and Earth Sciences, The University of Southern Mississippi, Hattiesburg, MS 39406, USA
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