Unscrambling variation in avian eggshell colour and patterning in a continent-wide study

L'Herpiniere, Kiara L.; Russell, Andrew F.; Duursma, Daisy Englert; Griffith, Simon C.

doi:10.1098/rsos.181269

Cited by 4 publications

(1 citation statement)

References 66 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Each species has phenotypic traits more prone to evolve towards identity signals than others, as egg phenotypic traits may be also constrained by other important functions [ 79 , 84 , 85 ], such as camouflage [ 80 , 86 ], protection against radiation [ 87 ], or flight biomechanics [ 88 ]. This fact may explain why in some species most variation among eggs arises in colour [ 42 , 43 , 46 , 81 ], while in others the eggs primarily vary in shell marks [ 28 , 55 , 80 ], shape and size [ 82 , 83 ], or a combination of different traits [ 21 , 30 , 60 , 89 ]. Theory predicts that individual recognition traits must be independent [ 63 ], so they can maximize the diversity of combinations among individuals and contain the greatest amount of information [ 32 , 34 , 81 ].…”

Section: Discussionmentioning

confidence: 99%

Egg recognition: The importance of quantifying multiple repeatable features as visual identity signals

Gómez¹,

Gordo

Minias

2021

PLoS ONE

View full text Add to dashboard Cite

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.

show abstract

Section: Discussionmentioning

confidence: 99%

Egg recognition: The importance of quantifying multiple repeatable features as visual identity signals

Gómez¹,

Gordo

Minias

2021

PLoS ONE

View full text Add to dashboard Cite

show abstract

Rectifying I: three point and continuous fit of the spatial autocorrelation metric, Moran’s I, to ideal form

et al. 2021

View full text Add to dashboard Cite

The global distribution of avian eggshell colours suggest a thermoregulatory benefit of darker pigmentation

et al. 2019

View full text Add to dashboard Cite

The survival of a bird's egg depends upon its ability to stay within strict thermal limits.Avian eggshell colours have long been considered a phenotype that can help them stay within these thermal limits 1,2 , with dark eggs absorbing heat more rapidly than bright eggs.Although disputed 3,4 , evidence suggests that darker eggs do increase in temperature more rapidly than lighter eggs, explaining why dark eggs are often considered as a cost to tradeoff against crypsis [5][6][7] . Although studies have considered whether eggshell colours can confer an adaptive benefit 4,6 , no study has demonstrated evidence that eggshell colours have actually adapted for this function. This would require data spanning a wide phylogenetic diversity of birds and a global spatial scale. Here we show evidence that darker and browner eggs have indeed evolved in cold climes, and that the thermoregulatory advantage for avian eggs is a stronger selective pressure in cold climates. Temperature alone predicted more than 80% of the global variation in eggshell colour and luminance. These patterns were directly related to avian nesting strategy, such that all relationships were stronger when eggs were exposed to incident solar radiation. Our data provide strong evidence that sunlight and nesting strategies are important selection pressures driving egg pigment evolution through their role in thermoregulation. Moreover, our study advances understanding of how traits have adapted to local temperatures, which is essential if we are to understand how organisms will be impacted by global climate change.The impact of global climate patterns on the evolution and distribution of traits is an area of increasing importance as global temperatures continue to rise. Birds' eggs are an ideal system for certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.

show abstract

Unscrambling variation in avian eggshell colour and patterning in a continent-wide study

Cited by 4 publications

References 66 publications

Egg recognition: The importance of quantifying multiple repeatable features as visual identity signals

Egg recognition: The importance of quantifying multiple repeatable features as visual identity signals

Rectifying I: three point and continuous fit of the spatial autocorrelation metric, Moran’s I, to ideal form

The global distribution of avian eggshell colours suggest a thermoregulatory benefit of darker pigmentation

Contact Info

Product

Resources

About