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Alothyqi N, Thornton A, Stevens M. Ground-nesting birds learn egg appearance to guide background choice for camouflage. Curr Biol 2024; 34:R722-R723. [PMID: 39106826 DOI: 10.1016/j.cub.2024.06.039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 06/13/2024] [Accepted: 06/18/2024] [Indexed: 08/09/2024]
Abstract
Camouflage is vital for the survival of many prey species1,2, including ground-nesting birds3,4,5,6. Egg camouflage via background matching and disruptive coloration (high contrast markings that break up the body outline) is often behaviourally mediated by selecting substrates that enhance egg camouflage1,2,3,4,5,6. However, the mechanisms controlling this behaviour in birds have remained unknown. Several, not mutually exclusive, mechanisms have been suggested to control background choice for egg camouflage7. These include where individual background preferences are genetically linked to egg coloration, enabled through learning egg appearances from previous breeding attempts, or modified by imprinting on visual backgrounds during early life7, Here, using predator vision models, we compared the camouflage of Japanese quail (Coturnix japonica) eggs among females who were allowed to choose one of four coloured substrates on which to lay3. Birds were divided into experienced females who had been given the opportunity to observe the appearance of their eggs, versus naïve females breeding for the first time. Our experiment revealed that breeding experience leads to improved background choices made for egg background matching. However, substrate choice for disruptive coloration appeared genetically determined, as both bird groups chose backgrounds that enhanced egg disruptiveness regardless of experience. These mechanisms underpin behaviours that are likely essential for birds and other animals to optimise camouflage and avoid predation6.
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Affiliation(s)
- Nafee Alothyqi
- Centre for Ecology and Conservation, University of Exeter (Penryn Campus), Penryn, Cornwall TR10 9FE, UK; Department of Biology, Umm Al-Qura University, Makkah, Saudi Arabia.
| | - Alex Thornton
- Centre for Ecology and Conservation, University of Exeter (Penryn Campus), Penryn, Cornwall TR10 9FE, UK
| | - Martin Stevens
- Centre for Ecology and Conservation, University of Exeter (Penryn Campus), Penryn, Cornwall TR10 9FE, UK
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2
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de Alcantara Viana JV, Campos Duarte R, Vieira C, Augusto Poleto Antiqueira P, Bach A, de Mello G, Silva L, Rabelo Oliveira Leal C, Quevedo Romero G. Crypsis by background matching and disruptive coloration as drivers of substrate occupation in sympatric Amazonian bark praying mantises. Sci Rep 2023; 13:19985. [PMID: 37968331 PMCID: PMC10652001 DOI: 10.1038/s41598-023-46204-x] [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: 08/02/2023] [Accepted: 10/29/2023] [Indexed: 11/17/2023] Open
Abstract
Background matching and disruptive coloration are common camouflage strategies in nature, but few studies have accurately measured their protective value in living organisms. Amazon's Bark praying mantises exhibit colour patterns matching whitish and greenish-brown tree trunks. We tested the functional significance of background matching and disruptive coloration of different praying mantis morphospecies (white, grey and green) detected by DNA barcoding. Through image analysis, avian visual models and field experiments using humans as potential predators, we explored whether the background occupation of mantises provides camouflage against predation. Data were obtained for individuals against their occupied tree trunks (whitish or greenish-brown) and microhabitats (lichen or bryophyte patches), compared to non-occupied trunks. White and grey mantises showed lower colour contrasts against occupied trunks at the scale of tree trunk, with no differences in luminance contrasts. Conversely, green mantises showed lower colour and luminance contrasts against microhabitats and also exhibited high edge disruption against greenish-brown trunks. The camouflage of white and green mantis models against colour-matching trunks increased search time and reduced encounter distance of human predators. We highlight the importance of camouflage strategies at different spatial scales to enhance individual survival against predators. Specifically, we present a stunning study system to investigate the relationship of phylogenetically related species that use camouflage in sympatry.
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Affiliation(s)
- João Vitor de Alcantara Viana
- Programa de Pós-Graduação em Ecologia, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil.
- Laboratório de Interações Multitróficas e Biodiversidade, Departamento de Biologia Animal, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6109, Campinas, São Paulo, CEP 13083-970, Brazil.
| | - Rafael Campos Duarte
- Universidade Federal Do ABC, São Bernardo Do Campo, São Paulo, CEP 09606-045, Brazil
- Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn, TR10 9FE, UK
| | - Camila Vieira
- Departamento de Ciências Básicas, Universidade de São Paulo (USP), Campus de Pirassununga, Pirassununga, São Paulo, CEP 13635-900, Brazil
| | - Pablo Augusto Poleto Antiqueira
- Laboratório de Interações Multitróficas e Biodiversidade, Departamento de Biologia Animal, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6109, Campinas, São Paulo, CEP 13083-970, Brazil
| | - Andressa Bach
- Programa de Pós-Graduação Em Ecologia E Conservação da Biodiversidade, Instituto de Biociências, Universidade Federal de Mato Grosso, Avenida Fernando Corrêa da Costa, N° 2367, Boa Esperança, Cuiabá, 78060900, Brazil
| | - Gabriel de Mello
- Programa de Pós-Graduação Em Ecologia E Conservação da Biodiversidade, Instituto de Biociências, Universidade Federal de Mato Grosso, Avenida Fernando Corrêa da Costa, N° 2367, Boa Esperança, Cuiabá, 78060900, Brazil
| | - Lorhaine Silva
- Programa de Pós-Graduação Em Ecologia E Conservação da Biodiversidade, Instituto de Biociências, Universidade Federal de Mato Grosso, Avenida Fernando Corrêa da Costa, N° 2367, Boa Esperança, Cuiabá, 78060900, Brazil
| | - Camila Rabelo Oliveira Leal
- Laboratório de Interações Multitróficas e Biodiversidade, Departamento de Biologia Animal, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6109, Campinas, São Paulo, CEP 13083-970, Brazil
| | - Gustavo Quevedo Romero
- Laboratório de Interações Multitróficas e Biodiversidade, Departamento de Biologia Animal, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6109, Campinas, São Paulo, CEP 13083-970, Brazil
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3
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Malinowska K, Szala K, Podkowa P, Surmacki A. Effect of light intensity in the nest site on eggshell pigmentation in a hole-nesting passerine. Sci Rep 2023; 13:9764. [PMID: 37328505 PMCID: PMC10276044 DOI: 10.1038/s41598-023-36658-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Accepted: 06/07/2023] [Indexed: 06/18/2023] Open
Abstract
Daylight is an important factor necessary for the proper embryonic development of birds, which raises the question, what happens when birds nest in relatively dim sites? The study experimentally tested whether there is a relationship between light conditions at the nesting site and the protoporphyrin-based pigmentation in the eggshell of the Great Tit (Parus major). We hypothesised that at lower light levels, eggs are less pigmented to increase the amount of light reaching the embryo. Our study system consisted of two types of nest boxes: "dark", in which the only source of light was the entrance hole, and "bright", which had two additional side windows. Photographs of clutches taken during the incubation period were used to quantify eggshell pigmentation. Multispectral image analyses were performed to measure variables correlating with protoporphyrin content, such as spot brightness, average spot size, spotting coverage, and spot red chroma. Repeatability analysis indicated that eggshell colouration characteristics were significantly and moderately repeatable between eggs from a single clutch, which suggests that they are under genetic and environmental control. However, none of the pigmentation traits differed significantly between the two types of nest boxes. We speculate about other ecological aspects that might have influenced the observed variability in eggshell pigmentation.
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Affiliation(s)
- Katarzyna Malinowska
- Population Ecology Lab, Faculty of Biology, Adam Mickiewicz University, Uniwersytetu Poznańskiego 6, 61-614, Poznań, Poland.
- Department of Avian Biology and Ecology, Faculty of Biology, Adam Mickiewicz University, Uniwersytetu Poznańskiego 6, 61-614, Poznań, Poland.
| | - Klaudia Szala
- Department of Avian Biology and Ecology, Faculty of Biology, Adam Mickiewicz University, Uniwersytetu Poznańskiego 6, 61-614, Poznań, Poland
| | - Paweł Podkowa
- Department of Avian Biology and Ecology, Faculty of Biology, Adam Mickiewicz University, Uniwersytetu Poznańskiego 6, 61-614, Poznań, Poland
- Institute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, 30-387, Kraków, Poland
| | - Adrian Surmacki
- Department of Avian Biology and Ecology, Faculty of Biology, Adam Mickiewicz University, Uniwersytetu Poznańskiego 6, 61-614, Poznań, Poland
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4
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Yang C, Ye P, Wu N, Yao X, Liang W. Revealing the roles of egg darkness and nest similarity for a cryptic parasite egg versus host's cognition: an alternate coevolutionary trajectory. Proc Biol Sci 2023; 290:20230103. [PMID: 37132235 PMCID: PMC10154918 DOI: 10.1098/rspb.2023.0103] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Accepted: 03/27/2023] [Indexed: 05/04/2023] Open
Abstract
As a text-book example of coevolution, the escalating interactions between egg mimicry by parasitic cuckoos and egg recognition by their hosts constitute a key battlefield for parasitism and anti-parasitism strategies. However, some parasite-host systems have deviated from this coevolutionary trajectory because some cuckoos do not lay mimetic eggs, while the hosts do not recognize them, even under the high costs of parasitism. The cryptic egg hypothesis was proposed to explain this puzzle, but the evidence to date is mixed and the relationship between the two components of egg crypticity, egg darkness (dim egg coloration) and nest similarity (similarity to host nest appearance), remains unknown. Here, we developed a 'field psychophysics' experimental design to dissect these components while controlling for undesired confounding factors. Our results clearly show that both egg darkness and nest similarity of cryptic eggs affect recognition by hosts, and egg darkness plays a more influential role than nest similarity. This study provides unambiguous evidence to resolve the puzzle of absent mimicry and recognition in cuckoo-host systems and explains why some cuckoo eggs were more likely to evolve dim coloration rather than similarity to host eggs or host nests.
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Affiliation(s)
- Canchao Yang
- Ministry of Education Key Laboratory for Ecology of Tropical Islands, College of Life Sciences, Hainan Normal University, Haikou 571158, People's Republic of China
| | - Ping Ye
- Ministry of Education Key Laboratory for Ecology of Tropical Islands, College of Life Sciences, Hainan Normal University, Haikou 571158, People's Republic of China
| | - Neng Wu
- Ministry of Education Key Laboratory for Ecology of Tropical Islands, College of Life Sciences, Hainan Normal University, Haikou 571158, People's Republic of China
| | - Xiaogang Yao
- Ministry of Education Key Laboratory for Ecology of Tropical Islands, College of Life Sciences, Hainan Normal University, Haikou 571158, People's Republic of China
- Kuankuoshui National Nature Reserve, Suiyang 563300, People's Republic of China
| | - Wei Liang
- Ministry of Education Key Laboratory for Ecology of Tropical Islands, College of Life Sciences, Hainan Normal University, Haikou 571158, People's Republic of China
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5
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Miller AE, Hogan BG, Stoddard MC. Color in motion: Generating 3-dimensional multispectral models to study dynamic visual signals in animals. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.983369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Analyzing color and pattern in the context of motion is a central and ongoing challenge in the quantification of animal coloration. Many animal signals are spatially and temporally variable, but traditional methods fail to capture this dynamism because they use stationary animals in fixed positions. To investigate dynamic visual displays and to understand the evolutionary forces that shape dynamic colorful signals, we require cross-disciplinary methods that combine measurements of color, pattern, 3-dimensional (3D) shape, and motion. Here, we outline a workflow for producing digital 3D models with objective color information from museum specimens with diffuse colors. The workflow combines multispectral imaging with photogrammetry to produce digital 3D models that contain calibrated ultraviolet (UV) and human-visible (VIS) color information and incorporate pattern and 3D shape. These “3D multispectral models” can subsequently be animated to incorporate both signaler and receiver movement and analyzed in silico using a variety of receiver-specific visual models. This approach—which can be flexibly integrated with other tools and methods—represents a key first step toward analyzing visual signals in motion. We describe several timely applications of this workflow and next steps for multispectral 3D photogrammetry and animation techniques.
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6
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Zheng J, Zuidema E, Zhang Z, Guo M, Székely T, Komdeur J. A novel function of egg burial: burying material prevents eggs rolling out of wind-swayed nests. Anim Behav 2022. [DOI: 10.1016/j.anbehav.2022.04.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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7
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Rohr VA, Volkmer T, Metzler D, Küpper C. Neoptile feathers contribute to outline concealment of precocial chicks. Sci Rep 2021; 11:5483. [PMID: 33750790 PMCID: PMC7943783 DOI: 10.1038/s41598-021-84227-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 02/12/2021] [Indexed: 11/22/2022] Open
Abstract
Camouflage is a widespread strategy to increase survival. The cryptic plumage colouration of precocial chicks improves camouflage often through disruptive colouration. Here, we examine whether and how fringed neoptile feathers conceal the outline of chicks. We first conducted a digital experiment to test two potential mechanisms for outline concealment through appendages: (1) reduction of edge intensity and (2) luminance transition. Local Edge Intensity Analysis showed that appendages decreased edge intensity whereas a mean luminance comparison revealed that the appendages created an intermediate transition zone to conceal the object's outline. For edge intensity, the outline diffusion was strongest for a vision system with low spatial acuity, which is characteristic of many mammalian chick predators. We then analysed photographs of young snowy plover (Charadrius nivosus) chicks to examine whether feathers increase outline concealment in a natural setting. Consistent with better camouflage, the outline of digitally cropped chicks with protruding feathers showed lower edge intensities than the outline of chicks without those feathers. However, the observed mean luminance changes did not indicate better concealment. Taken together, our results suggest that thin skin appendages such as neoptile feathers improve camouflage. As skin appendages are widespread, this mechanism may apply to many organisms.
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Affiliation(s)
- Veronika A Rohr
- Research Group for Behavioural Genetics and Evolutionary Ecology, Max Planck Institute for Ornithology, Seewiesen, Germany.
- Division of Evolutionary Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Planegg-Martinsried, Germany.
| | - Tamara Volkmer
- Department of Migration, Max Planck Institute of Animal Behavior, Radolfzell, Germany
| | - Dirk Metzler
- Division of Evolutionary Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Planegg-Martinsried, Germany
| | - Clemens Küpper
- Research Group for Behavioural Genetics and Evolutionary Ecology, Max Planck Institute for Ornithology, Seewiesen, Germany.
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8
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Gómez J, Gordo O, Minias P. Egg recognition: The importance of quantifying multiple repeatable features as visual identity signals. PLoS One 2021; 16:e0248021. [PMID: 33661988 PMCID: PMC7932075 DOI: 10.1371/journal.pone.0248021] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 02/17/2021] [Indexed: 11/18/2022] Open
Abstract
Brood parasitized and/or colonial birds use egg features as visual identity signals, which allow parents to recognize their own eggs and avoid paying fitness costs of misdirecting their care to others’ offspring. However, the mechanisms of egg recognition and discrimination are poorly understood. Most studies have put their focus on individual abilities to carry out these behavioural tasks, while less attention has been paid to the egg and how its signals may evolve to enhance its identification. We used 92 clutches (460 eggs) of the Eurasian coot Fulica atra to test whether eggs could be correctly classified into their corresponding clutches based only on their external appearance. Using SpotEgg, we characterized the eggs in 27 variables of colour, spottiness, shape and size from calibrated digital images. Then, we used these variables in a supervised machine learning algorithm for multi-class egg classification, where each egg was classified to the best matched clutch out of 92 studied clutches. The best model with all 27 explanatory variables assigned correctly 53.3% (CI = 42.6–63.7%) of eggs of the test-set, greatly exceeding the probability to classify the eggs by chance (1/92, 1.1%). This finding supports the hypothesis that eggs have visual identity signals in their phenotypes. Simplified models with fewer explanatory variables (10 or 15) showed lesser classification ability than full models, suggesting that birds may use multiple traits for egg recognition. Therefore, egg phenotypes should be assessed in their full complexity, including colour, patterning, shape and size. Most important variables for classification were those with the highest intraclutch correlation, demonstrating that individual recognition traits are repeatable. Algorithm classification performance improved by each extra training egg added to the model. Thus, repetition of egg design within a clutch would reinforce signals and would help females to create an internal template for true recognition of their own eggs. In conclusion, our novel approach based on machine learning provided important insights on how signallers broadcast their specific signature cues to enhance their recognisability.
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Affiliation(s)
| | - Oscar Gordo
- Catalan Ornithological Institute, Barcelona, Spain
| | - Piotr Minias
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Łódź, Poland
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9
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Biagolini-Jr C, Perrella DF. Bright coloration of male blue manakin is not connected to higher rates of nest predation. Acta Ethol 2020. [DOI: 10.1007/s10211-020-00352-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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10
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Pérez de Vargas A, Cuadrado M, Camarero PR, Mateo R. An assessment of eggshell pigments as non-invasive biomarkers of organochlorine pollutants in gull-billed tern. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 732:139210. [PMID: 32438180 DOI: 10.1016/j.scitotenv.2020.139210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 05/01/2020] [Accepted: 05/02/2020] [Indexed: 06/11/2023]
Abstract
Eggshell pigmentation has been assessed as an indicator of exposure to environmental pollutants in birds, but these studies have only used reflectance spectrophotometry to measure such pigmentation. The present study is the first one that measures eggshell pigments and pollutants in the same eggs to explore their use as biomarkers in birds. We have studied the concentration of organochlorine pesticides and polychlorinated biphenyls (PCBs) in the content of 97 deserted eggs of gull-billed terns (Gelochelidon nilotica) after the abandonment of the colony in Mesas de Asta (Cádiz, S Spain) in 2012. Eggshell thickness and stage of embryo development were studied together along with the concentrations of protoporphyrin IX and biliverdin in eggshells. p,p'-DDE concentrations were high when compared with other studies done with terns in the Mediterranean basin in the past. p,p'-DDE and PCB levels associated with reduced reproductive success were found in 5.1% and 2.1% of the eggs respectively. Eggshell index was largely affected by the embryo development stage, which highlights the need of knowing this information to avoid potential biases in the interpretation of results. The concentrations of protoporphyrin IX and biliverdin in the eggs of gull-billed terns were negatively associated with DDTs levels, which seems to confirm previous observations with phylogenetically related species.
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Affiliation(s)
- Ana Pérez de Vargas
- Instituto de Investigación en Recursos Cinegéticos (IREC), CSIC-UCLM-JCCM, Ronda de Toledo 12, 13005 Ciudad Real, Spain; Veterinary Diagnostic and Research Unit, Veterinary Section, Al Ain Zoo, PO Box 1204, United Arab Emirates
| | - Mariano Cuadrado
- ZooBotánico Jerez - Ayuntamiento de Jerez, Madreselva s/n, 11408 Jerez de la Frontera, Cádiz, Spain
| | - Pablo R Camarero
- Instituto de Investigación en Recursos Cinegéticos (IREC), CSIC-UCLM-JCCM, Ronda de Toledo 12, 13005 Ciudad Real, Spain
| | - Rafael Mateo
- Instituto de Investigación en Recursos Cinegéticos (IREC), CSIC-UCLM-JCCM, Ronda de Toledo 12, 13005 Ciudad Real, Spain.
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11
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Nokelainen O, Sreelatha LB, Brito JC, Campos JC, Scott-Samuel NE, Valkonen JK, Boratyński Z. Camouflage in arid environments: the case of Sahara-Sahel desert rodents. JOURNAL OF VERTEBRATE BIOLOGY 2020. [DOI: 10.25225/jvb.20007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Ossi Nokelainen
- Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland; e-mail:
| | - Lekshmi B. Sreelatha
- CIBIO-InBIO Associate Laboratory, Research Center in Biodiversity and Genetic Resources, University of Porto, Vairão, Portugal; e-mail:
| | - José Carlos Brito
- CIBIO-InBIO Associate Laboratory, Research Center in Biodiversity and Genetic Resources, University of Porto, Vairão, Portugal; e-mail:
| | - João C. Campos
- CIBIO-InBIO Associate Laboratory, Research Center in Biodiversity and Genetic Resources, University of Porto, Vairão, Portugal; e-mail:
| | | | - Janne K. Valkonen
- Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland; e-mail:
| | - Zbyszek Boratyński
- CIBIO-InBIO Associate Laboratory, Research Center in Biodiversity and Genetic Resources, University of Porto, Vairão, Portugal; e-mail:
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12
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Abstract
Currently R is the most popular software for data analyses among biologists. Here, we present bwimage, a package designed to describe patterns from black and white images. The package can be used for a wide range of applications. We implemented functions previously described in the literature to calculate parameters designed originally, but not exclusively, for vegetation structures. Additionally, we propose a new parameter: the aggregation index. We demonstrate applications for field work, providing examples that range from calculation of canopy openness, description of patterns in vertical vegetation structure, to patterns in bird nest structure. We provide advice and illustrated examples of how to produce high quality images for analyses.
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Affiliation(s)
- Carlos Biagolini-Jr.
- Programa de Pós-Graduação em Ecologia, Universidade de Brasília, Brasília, DF, 70910-900, Brazil
| | - Regina H. Macedo
- Departamento de Zoologia, Universidade de Brasília, Brasília, DF, 70910-900, Brazil
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13
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Veldsman LM, Kylin H, Bronkhorst P, Engelbrecht I, Bouwman H. A method to determine the combined effects of climate change (temperature and humidity) and eggshell thickness on water loss from bird eggs. ENVIRONMENTAL GEOCHEMISTRY AND HEALTH 2020; 42:781-793. [PMID: 30864071 DOI: 10.1007/s10653-019-00274-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Accepted: 02/27/2019] [Indexed: 06/09/2023]
Abstract
Differences in bird eggshell thicknesses occur due to numerous factors, including thinning due to persistent organic pollutants. Not only does thinning weaken the shell; weaker shells combined with elevated ambient temperature and changes in humidities may result in changes in water loss rates from the egg contents. Therefore, thinner eggshells raise concern of water being lost faster than normal at lower relative humidities, which may affect hatching. To investigate the combined effects, we developed and tested an effective method that measures water loss through different thickness eggshells at controlled temperatures and relative humidities to assist in ascertaining the combined effects of climate change (temperature and humidity) and changes in eggshell thickness on bird reproduction. The fastest rate of loss was at 40% RH at 40 °C (0.1 mL/cm2/day), and the slowest was at 22 °C at 80% RH (0.02 mL/cm2/day). Eggshell thickness had a significant effect on water loss at all humidity treatments, except at the highest temperature and humidity treatment (80% RH and 40 °C). Temperature explained 40% of the variance, RH explained 20%, and interactions between temperature and humidity explained 15% of the variance (repeated-measures, two-way ANOVA). Generalized linear analyses revealed that both factors temperature and humidity contributed significantly in any two-way combinations. We have laid the ground for a system to test the combined effects of temperature and humidity changes associated with climate change and eggshell thinning associated with pollutants, on water loss across eggshells.
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Affiliation(s)
- L-M Veldsman
- Research Unit: Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
| | - H Kylin
- Research Unit: Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
- Department of Thematic Studies - Environmental Change, Linköping University, Linköping, Sweden
| | - P Bronkhorst
- Research Unit: Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
| | - I Engelbrecht
- Research Unit: Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
| | - H Bouwman
- Research Unit: Environmental Sciences and Management, North-West University, Potchefstroom, South Africa.
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14
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Gómez J, Liñán-Cembrano G, Ramo C, Castro M, Pérez-Hurtado A, Amat JA. Does the use of nest materials in a ground-nesting bird result from a compromise between the risk of egg overheating and camouflage? Biol Open 2019; 8:bio042648. [PMID: 31757805 PMCID: PMC6918762 DOI: 10.1242/bio.042648] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Accepted: 11/14/2019] [Indexed: 11/22/2022] Open
Abstract
Many studies addressing the use of nest materials by animals have focused on only one factor to explain its function. However, the consideration of more than one factor could explain the apparently maladaptive choice of nest materials that make nests conspicuous to predators. We experimentally tested whether there is a trade-off in the use of nest materials between the risks of egg predation versus protection from overheating. We studied the ground-nesting Kentish plover, Charadrius alexandrinus, in southern Spain. We added materials differing in thermal properties and coloration to the nests, thus affecting rates of egg heating, nest temperature and camouflage. Before these manipulations, adults selected materials that were lighter than the microhabitat, probably to buffer the risk of egg overheating. However, the adults did not keep the lightest experimental materials, probably because they reduced camouflage, and this could make the nests even more easily detectable to predators. In all nests, adults removed most of the experimental materials independently of their properties, so that egg camouflage returned to the original situation within a week of the experimental treatments. Although the thermal environment may affect the choice of nest materials by plovers, ambient temperatures were not so high at our study site as to determine the acceptance of the lightest experimental materials.
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Affiliation(s)
- Jesús Gómez
- Departamento de Ecología de Humedales, Estación Biológica de Doñana (EBD-CSIC), Calle Américo Vespucio 26, 41092 Sevilla, Spain
| | - Gustavo Liñán-Cembrano
- Instituto de Microelectrónica de Sevilla (IMSE-CNM), Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Sevilla, Calle Américo Vespucio 28, 41092 Sevilla, Spain
| | - Cristina Ramo
- Departamento de Ecología de Humedales, Estación Biológica de Doñana (EBD-CSIC), Calle Américo Vespucio 26, 41092 Sevilla, Spain
| | - Macarena Castro
- Instituto Universitario de Investigación Marina (INMAR), Universidad de Cádiz, Campus de Excelencia Internacional del Mar (CEIMAR). Campus Universitario de Puerto Real, 11510 Puerto Real (Cádiz), Spain
| | - Alejandro Pérez-Hurtado
- Instituto Universitario de Investigación Marina (INMAR), Universidad de Cádiz, Campus de Excelencia Internacional del Mar (CEIMAR). Campus Universitario de Puerto Real, 11510 Puerto Real (Cádiz), Spain
| | - Juan A Amat
- Departamento de Ecología de Humedales, Estación Biológica de Doñana (EBD-CSIC), Calle Américo Vespucio 26, 41092 Sevilla, Spain
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