The bare head of the Northern bald ibis (Geronticus eremita) fulfills a thermoregulatory function

Tracing the Fate of the Northern Bald Ibis over Five Millennia: An Interdisciplinary Approach to the Extinction and Recovery of an Iconic Bird Species

Simple Summary

Once widespread around the Mediterranean region, the Northern Bald Ibis (Geronticus eremita) became one of the rarest birds in the world. In this paper, we trace the history of the species through different epochs up to the present. A particular focus is placed both on its life in and disappearance from ancient Egypt, where the bird attained significant cultural importance, and on the modern endeavour to re-wild and restore the species. The Northern Bald Ibis is an outstanding example of how an interdisciplinary cultural-historical and natural-scientific approach significantly promotes the interpretation of historical evidence as well as helps implement current rewilding and restoration efforts.

Abstract

We trace the history of the endangered Northern Bald Ibis through different epochs to the present. A particular focus is placed on its life in and disappearance from ancient Egypt, where the bird attained great cultural and religious significance, and on the modern endeavour to re-wild the species. Due to the characteristic appearance, behaviour and habitat of the species as well as its need for open foraging areas, a close mutualistic relationship between humans and the birds was formed in ancient Egypt, as in other cultures. A clear benefit for the Northern Bald Ibis was the availability of feeding habitats, which were cleared by humans for farming or grazing. The benefit to people was rather cultural because the bird attracted religious veneration or symbolic meanings from ancient Egypt to medieval Europe. The proximity to humans, however, carried a high risk as well. We discuss various types of impact (including human impacts as well as climate change) as triggers for the extinction of the species. The evidence for a triple disappearance of the Northern Bald Ibis (around 2000 BCE, around 1600 CE and in modern time) represents a unique basis for studying both the bird’s habitat preferences and its vulnerability. This is because different, mainly anthropogenic, causes stood behind these three historical disappearances, although the disappearances in all three epochs occurred during a period of climate change.

Rethinking Gloger's Rule: Climate, Light Environments, and Color in a Large Family of Tropical Birds (Furnariidae)

AbstractEcogeographic rules provide a framework within which to test evolutionary hypotheses of adaptation. Gloger's rule predicts that endothermic animals should have darker colors in warm/rainy climates. This rule also predicts that animals should be more rufous in warm/dry climates, the so-called complex Gloger's rule. Empirical studies frequently demonstrate that animals are darker in cool/wet climates rather than in warm/wet climates. Furthermore, sensory ecology predicts that, to enhance crypsis, animals should be darker in darker light environments. We aimed to disentangle the effects of climate and light environments on plumage color in the large Neotropical passerine family Furnariidae. We found that birds in cooler and rainier climates had darker plumage even after controlling for habitat type. Birds in darker habitats had darker plumage even after controlling for climate. The effects of temperature and precipitation interact so that the negative effect of precipitation on brightness is strongest in cool temperatures. Finally, birds tended to be more rufous in warm/dry habitats but also, surprisingly, in cool/wet locales. We suggest that Gloger's rule results from complementary selective pressures arising from myriad ecological factors, including crypsis, thermoregulation, parasite deterrence, and resistance to feather abrasion.

Ecotypic changes of alpine birds to climate change

In endotherm animals, several traits are related to climate. For example, Bergmann’s rule predicts a decrease in body size within species and across closely related species with increasing temperature, whereas Gloger’s rule states that birds and mammals should be darker in humid and warm environments compared to colder and drier areas. However, it is still not clear whether ecotypic responses to variation in the local environment can also apply to morphological and colouration changes through time in response to climate change. We present a 100-year-long time series on morphological and melanin-based colours of snowfinch (325 Montifringilla, 92 Pyrgilauda and 30 Onychostruthus) museum specimens. Here we show that the tarsus length of the species has decreased and the saturation of the melanin-based colour has increased, which was correlated with the increase of temperature and precipitations. As ecotypic variations are tightly linked to individual behavioural and physiological responses to environmental variations, differently sized and coloured individuals are expected to be differently penalized by global changes. This study opens the pertinent question about whether ecotypic responses can enhance population persistence in the context of global change.

Avian predation intensity as a driver of clinal variation in colour morph frequency

Phenotypic variation provides the framework for natural selection to work upon, enabling adaptive evolution. One of the most discernible manifestations of phenotypic variability is colour variation. When this variation is discrete, genetically based colour pattern morphs occur simultaneously within a population. Why and how colour polymorphisms are maintained is an evolutionary puzzle. Several evolutionary drivers have been hypothesized as influencing clinal patterns of morph frequency, with spatial variation in climate and predation being considered especially important. Despite this, no study has examined both of their roles simultaneously. The aims of this study were to: (a) examine the covariation of physiology, environmental variables and colouration at a local scale; and (b) determine if these factors and their interplay explain broad clinal variation in morph frequency. We used the lizard Liopholis whitii as a model system, as this species displays a discrete, heritable polymorphism for colour pattern (plain-backed, patterned morphs) whose morph frequency varies latitudinally. We measured reflectance, field activity temperatures and microhabitat structure to test for differences in crypsis, thermal biology and microhabitat selection of patterned and plain-backed morphs within a single population where colour morphs occur sympatrically. We then used data from the literature to perform a broad-scale analysis to identify whether these factors also explained the latitudinal variation of morph frequency in this species. At the local scale, plain-backed morphs were found to be less cryptic than patterned morphs while no other differences were detected in terms of thermal biology, dorsal reflectance and microhabitat use. At a broader scale, predation was the most influential factor mediating morph frequency across latitudes. However, the observed pattern of morph frequency is opposite to what the modelling results suggest in that the incidence of the least cryptic morph is highest where predation pressure is most severe. Clinal variation in the level of background matching between morphs or the potential reproductive advantage by the plain-backed morph may, instead, be driving the observed morph frequency. Together, these results provide key insights into the evolution of local adaptation as well as the ecological forces involved in driving the dynamics of colour polymorphism.