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Brown HKM, Rubega M, Dierssen HM. The light's in my eyes: optical modeling demonstrates wind is more important than sea surface-reflected sunlight for foraging herons. PeerJ 2021; 9:e12006. [PMID: 34692240 PMCID: PMC8485832 DOI: 10.7717/peerj.12006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 07/27/2021] [Indexed: 11/20/2022] Open
Abstract
Multiple lineages of birds have independently evolved foraging strategies that involve catching aquatic prey by striking at them through the water’s surface. Diurnal, visual predators that hunt across the air-water interface encounter several visual challenges, including sun glint, or reflection of sunlight by the water surface. Intense sun glint is common at the air-water interface, and it obscures visual cues from submerged prey. Visually-hunting, cross-media predators must therefore solve the problem of glint to hunt effectively. One obvious solution is to turn away from the sun, which would result in reduction of glint effects. However, turning too far will cast shadows over prey, causing them to flee. Therefore, we hypothesized that foraging herons would orient away from, but not directly opposite to the sun. Our ability to understand how predators achieve a solution to glint is limited by our ability to quantify the amount of glint that free-living predators are actually exposed to under different light conditions. Herons (Ardea spp.) are a good model system for answering questions about cross-media hunting because they are conspicuous, widely distributed, and forage throughout a variety of aquatic habitats, on a variety of submerged prey. To test our hypothesis, we employed radiative transfer modeling of water surface reflectance, drawn from optical oceanography, in a novel context to estimate the visual exposure to glint of free-living, actively foraging herons. We found evidence that Ardea spp. do not use body orientation to compensate for sun glint while foraging and therefore they must have some other, not yet understood, means of compensation, either anatomical or behavioral. Instead of facing away from the sun, herons tended to adjust their position to face into the wind at higher wind speeds. We suggest that radiative transfer modeling is a promising tool for elucidating the ecology and evolution of air-to-water foraging systems.
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Affiliation(s)
- Holly K M Brown
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, United States of America
| | - Margaret Rubega
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, United States of America
| | - Heidi M Dierssen
- Department of Marine Sciences, University of Connecticut at Avery Point, Groton, CT, United States of America
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Vrettos M, Reynolds C, Amar A. Malar stripe size and prominence in peregrine falcons vary positively with solar radiation: support for the solar glare hypothesis. Biol Lett 2021; 17:20210116. [PMID: 34062086 DOI: 10.1098/rsbl.2021.0116] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Many falcons (Falco spp.) exhibit a distinct dark plumage patch below the eye, termed the malar stripe. This stripe is hypothesized to reduce the amount of solar glare reflected into the eyes while foraging, thereby increasing hunting efficiency in bright conditions. Here, we use a novel, global-scale correlative approach to test this 'solar glare hypothesis' in peregrine falcons (Falco peregrinus), the most widespread falcon species, using web-sourced photographs from across the species' global range. We found that the size and prominence of the malar stripe were positively associated with average annual solar radiation, but not with other environmental variables, such as temperature and rainfall. Our results provide the first published evidence for the hypothesis that this plumage feature functions to reduce the amount of solar glare reflected into the falcon's eyes, thereby improving the ability to pinpoint and target agile prey in bright conditions.
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Affiliation(s)
- Michelle Vrettos
- FitzPatrick Institute of African Ornithology, DSI-NRF Centre of Excellence, Department of Biological Sciences, University of Cape Town, South Africa
| | - Chevonne Reynolds
- FitzPatrick Institute of African Ornithology, DSI-NRF Centre of Excellence, Department of Biological Sciences, University of Cape Town, South Africa.,School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Arjun Amar
- FitzPatrick Institute of African Ornithology, DSI-NRF Centre of Excellence, Department of Biological Sciences, University of Cape Town, South Africa
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Golawski A, Kasprzykowski Z, Al Sariri TS. Foraging behaviour and diet in two sympatric shrike species during autumn migration across the Arabian Peninsula. Saudi J Biol Sci 2020; 27:1462-1466. [PMID: 32489281 PMCID: PMC7254029 DOI: 10.1016/j.sjbs.2020.04.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 04/07/2020] [Accepted: 04/09/2020] [Indexed: 11/29/2022] Open
Abstract
In situations of restricted food supply, the trophic niches of closely-related species of animals should be separate. For sit-and-wait hunters, such as shrikes, this is associated with competition for food and hunting sites. In the present study, the foraging behaviour of two shrike species - Red-tailed Shrike Lanius phoenicuroides and Red-backed Shrike Lanius collurio - was studied in a desert habitat in Oman. The fieldwork was carried out in September 2019, during the peak migration of these birds. Their behaviour was recorded in detail during 30-minute observation bouts. A General Linear Mixed Model with logit link function and binomial error variance was used to compare their behaviour. The type of perch and its height did not differ between them, but there were significant differences in their use of look-out posts only in the mean duration of a single perching event, which was more than twice as long in Red-backed Shrike. No differences in prey size were found between the species and hunting success (the ratio of successful attacks to all attacks) was similar in both (RtS-RbS: 46 vs. 61%). Dietary diversity was twice as great in Red-tailed Shrike as in Red-backed Shrike, but in general, their diets did not differ very much. Dietary overlap between the species at this level of prey identification was 92%. This absence of differences in some aspects of behaviour and diet may be due to the similarity of the two species, above all their same body size, and even the possibility of hybridization. If the species compared are so similar due to body size, behaviour and evolutionary relationship their food niches may overlap.
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Affiliation(s)
- Artur Golawski
- Siedlce University of Natural Sciences and Humanities, Faculty of Exact and Natural Sciences, Prusa 14, 08-110 Siedlce, Poland
| | - Zbigniew Kasprzykowski
- Siedlce University of Natural Sciences and Humanities, Faculty of Exact and Natural Sciences, Prusa 14, 08-110 Siedlce, Poland
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Minias P, Janiszewski T. Evolution of a conspicuous melanin-based ornament in gulls Laridae. J Evol Biol 2020; 33:682-693. [PMID: 32050039 DOI: 10.1111/jeb.13604] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 11/29/2019] [Accepted: 02/05/2020] [Indexed: 11/28/2022]
Abstract
Melanin- and carotenoid-based ornaments often signal different aspects of individual quality or similar components of quality under different environmental conditions and, thus, they may become evolutionarily integrated into a composite sexual trait. On the other hand, functionally and developmentally different characters (e.g. coloration characters of different developmental origin) are more likely to evolve independently from each other than more similar traits. Here, we examined evolutionary correlations between the occurrence of a conspicuous melanin-based ornament (hood) and carotenoid-based bare-part ornaments within gull family. We also aimed to identify major ecological, life-history and biogeographical predictors of hood occurrence and reconstruct evolutionary history of this ornament. We found that hood occurrence was associated with red or dark coloration of unfeathered traits (bill and legs), whereas combinations of hood with yellow carotenoid-based coloration of integument were evolutionarily avoided. Also, hood occurrence correlated negatively with the occurrence of other melanin-based plumage character (mantle). Breeding latitude and habitat were identified as major predictors of hood occurrence in gulls, as hoods were recorded more frequently in low-latitude and inland (rather than marine) species. Finally, our analysis provided support for evolutionary lability in hood occurrence, with a dominance of transitions towards hood loss in the evolutionary history of gulls. The results of our study provide one of the first evidence for a correlated evolution of melanin- and carotenoid-based ornaments in an avian lineage, which supports evolutionary modularity of developmentally and functionally different coloration traits.
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Affiliation(s)
- Piotr Minias
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Łódź, Poland
| | - Tomasz Janiszewski
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Łódź, Poland
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Papageorgiou D, Barboutis C, Kassara C, Giokas S. Habitat selection of woodchat shrikes Lanius senator during spring stopover is related to foraging strategy. Curr Zool 2018; 63:139-149. [PMID: 29491971 PMCID: PMC5804170 DOI: 10.1093/cz/zow079] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 06/10/2016] [Indexed: 11/14/2022] Open
Abstract
Every spring a huge number of passerines cross the Sahara Desert and the Mediterranean Sea on their way to their breeding grounds. Stopover sites after such extended barriers where birds can rest, refuel, and find shelter from adverse weather, are of crucial importance for the outcome of their migration. Stopover habitat selection used by migrating birds depends on landscape context, habitat patch characteristics, as well as on the particular energetic conditions and needs of individual birds, but it is still poorly investigated. We focused on a long-distance migrating passerine, the woodchat shrike, in order to investigate for the first time the species’ habitat selection at a spring stopover site (island of Antikythira, Greece) after the crossing of the Sahara Desert and Mediterranean Sea. We implemented radio-tracking, color-ringing, and visual behavioral observations to collect data on microhabitat use. Generalized Linear Mixed Models were developed to identify the species’ most preferred microhabitat during its stopover on this low human disturbed island. We found that high maquis vegetation surrounded by low vegetation was chosen as perches for hunting. Moreover, high maquis vegetation appeared to facilitate hunting attempts toward the ground, the most frequently observed foraging strategy. Finally, we discuss our findings in the context of conservation practices for the woodchat shrike and their stopover sites on Mediterranean islands.
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Affiliation(s)
- Danai Papageorgiou
- Department of Biology, University of Patras, Panepistimioupoli, Patras, GR -26500, GreeceAntikythira Bird Observatory, Hellenic Ornithological Society, Themistokleous 80, Athens, GR-10681, Greece
| | - Christos Barboutis
- Department of Biology, University of Patras, Panepistimioupoli, Patras, GR -26500, GreeceAntikythira Bird Observatory, Hellenic Ornithological Society, Themistokleous 80, Athens, GR-10681, Greece
| | - Christina Kassara
- Department of Biology, University of Patras, Panepistimioupoli, Patras, GR -26500, GreeceAntikythira Bird Observatory, Hellenic Ornithological Society, Themistokleous 80, Athens, GR-10681, Greece
| | - Sinos Giokas
- Department of Biology, University of Patras, Panepistimioupoli, Patras, GR -26500, GreeceAntikythira Bird Observatory, Hellenic Ornithological Society, Themistokleous 80, Athens, GR-10681, Greece
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Sustaita D, Rubega MA. The anatomy of a shrike bite: bill shape and bite performance in Loggerhead Shrikes. Biol J Linn Soc Lond 2014. [DOI: 10.1111/bij.12298] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Diego Sustaita
- Department of Ecology & Evolutionary Biology; University of Connecticut; 75 N. Eagleville Rd. Unit 3043 Storrs CT 06269-3043 USA
| | - Margaret A. Rubega
- Department of Ecology & Evolutionary Biology; University of Connecticut; 75 N. Eagleville Rd. Unit 3043 Storrs CT 06269-3043 USA
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