Unintelligent Design News - Another Arms Race - Between Birds

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The common cuckoo lays its eggs in the nests of other bird species, burdening these hosts with the task of raising its young.

Photo by Olda Mikulica

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Yellow warblers sometimes abandon their nests when a cowbird lays an egg in them. Another strategy involves building a new nest on top of the old one, sealing off the parasitic egg.

Photo by Pookie Fugglestein

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Researchers report that brood parasites, like this common cuckoo, top, have larger eyes than the birds they target – beyond the difference expected as a result of their larger body size. Common cuckoos will parasitize the nests of European robins, bottom left, but not those of European bee-eaters, bottom right.

Photos by Tomas Grim

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The great reed warbler
sometimes has its nest parasitized by cuckoos.

Photo by Olda Mikulica

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An adult common redstart feeds a parasitic cuckoo chick in its nest.

Photo by Tomas Grim

Birds' eye size offers clues to coevolutionary arms race between brood parasites, hosts | Illinois

The existence of arms races is about as good evidence as you can get that there is no intelligence behind life on Earth. After all, what single intelligent entity would indulge in an ultimately futile competition with itself where a solution to a problem is then turned around into another problem to be solved and so ad infinitum, in a futile, never-ending cycle of redesign for no ultimate purpose save possibly to make more parasites?

And this example of one such arms races is a good example. As so often with these arms races, it starts off with one species becoming an obligate parasite on another - and obligate parasites are themselves more evidence of the lack of intelligence since it will inevitably lead to yet another arms race as the parasitised species develops ways to resist or mitigate the parasite and the parasite has to counter those measures or become extinct. Any half-decent biologist will understand this, so it shouldn't be beyond the comprehension of an intelligent designer god.

And let's remind ourselves that Creationism's putative designer god is also normally the supposedly omniscient Abrahamic god of Christianity, Islam and Judaism who should therefore have foreseen that a pointless and ultimately futile arms race would ensue when it allegedly designed an obligate parasite.

The parasitism in question is that of the obligate bird brood parasites - species of bird that have lost the ability to make nests and incubate eggs and rear their own young, but instead lay their eggs in the nests of other birds which then do the incubating and rearing. Readers of my popular, illustrated book The Malevolent Designer: Why Nature's God is not Good will be familiar with several examples of these brood parasites and the ensuing arms races, which get a chapter all of their own.

This phenomenon was the subject of a fascinating piece of research by two scientists: Ian J. Ausprey, of Florida Museum of Natural History and Department of Biology, University of Florida, Gainesville, FL, USA and Mark E. Hauber, of Department of Evolution, Ecology, and Behavior, School of Integrative Biology, University of Illinois at Urbana-Champaign, Champaign, IL, USA. Their findings are published open access in the Royal Society's online journal, Biology Letters. The article by Diana Yates in Illinois News Bureau, which accompanies this publication, explains:

Birds have much better vision overall than we do as humans. They have four color receptors instead of our three. They also can see into the ultraviolet range. What we did not know before this study was whether their eyes are adapted to egg rejection.

Non-host birds tend to have larger eyes than hosts. One interpretation of that is that the parasites go for birds with poorer eyesight.

Professor Mark Hauber
Professor of evolution, ecology and behavior
University of Illinois Urbana-Champaign
Champaign, IL, USA

Some bird species targeted by brood parasites can recognize a foreign egg. These birds will pierce or grasp the egg and eject it, abandon the parasitized nest or – in some cases – enshrine the parasite’s egg by building a new nest on top of the old one. This allows them to devote their parenting efforts solely to their own offspring.

The failure of some host birds to recognize foreign eggs in their own nests is somewhat perplexing, said Mark Hauber, a professor of evolution, ecology and behavior at the University of Illinois Urbana-Champaign, who co-led the new research with Ian Ausprey, a recent doctoral graduate at the University of Florida department of biology and the Florida Museum of Natural History.

Having larger eyes is similar to having a bigger camera lens. By collecting more light, large eyes improve a bird’s visual acuity, its ability to resolve an image in dim conditions and at long distances.

Nest parasitism exerts enormous selective pressure on host populations, with major implications for population demography and local species persistence. It’s incredible that such a simple trait as eye size can provide a powerful window into the sensory systems that mediate the coevolutionary arms race between nest parasites and their hosts.

Dr. Ian Ausprey
Department of Biology
University of Florida
Gainesville, FL, USA
And Florida Museum of Natural History.

To study the relationship between eye size and brood parasitism, the researchers turned to data collected in the 1970s by Stanley Ritland, a student at the University of Chicago who measured the eyeballs of more than 4,000 species of birds in museum collections. Ausprey and his colleagues digitized Ritland’s data and explored the implications of eye size on a variety of traits. In a recently published study, for example, he found that birds with larger eyes were more likely to forage on insects or other prey that would require farsightedness, while those with smaller eyes tended to eat nectar or seeds that could be detected up close.

When analyzing eye size in different bird species in relation to their lifestyle as brood parasites, hosts or non-host birds, Ausprey found that brood parasites had larger eyes than host birds – beyond the difference expected as a result of their larger body size – and that birds with larger eyes relative to their overall body mass were less likely to have their nests parasitized. Eye size in host birds also was positively associated with their likelihood of recognizing foreign eggs – unless the eggs looked a lot like the hosts’ own eggs, the researchers found.

Hauber collaborated on a recent study that identified specific brain structures that play a role in interactions between a parasitic insect and its host. But the new research in birds is the first to show how a sensory system like the eyes contributes to the interplay between parasite and host, Hauber said.

In the abstract to their published paper, the authors say:

Abstract
In coevolutionary arms-races, reciprocal ecological interactions and their fitness impacts shape the course of phenotypic evolution. The classic example of avian host–brood parasite interactions selects for host recognition and rejection of increasingly mimetic foreign eggs. An essential component of perceptual mimicry is that parasitic eggs escape detection by host sensory systems, yet there is no direct evidence that the avian visual system covaries with parasitic egg recognition or mimicry. Here, we used eye size measurements collected from preserved museum specimens as a metric of the avian visual system for species involved in host–brood parasite interactions. We discovered that (i) hosts had smaller eyes compared with non-hosts, (ii) parasites had larger eyes compared with hosts before but not after phylogenetic corrections, perhaps owing to the limited number of independent evolutionary origins of obligate brood parasitism, (iii) egg rejection in hosts with non-mimetic parasitic eggs positively correlated with eye size, and (iv) eye size was positively associated with increased avian-perceived host–parasite eggshell similarity. These results imply that both host-use by parasites and anti-parasitic responses by hosts covary with a metric of the visual system across relevant bird species, providing comparative evidence for coevolutionary patterns of host and brood parasite sensory systems.

Ausprey Ian J. & Hauber Mark E.
Host and brood parasite coevolutionary interactions covary with comparative patterns of the avian visual system
Biology Letters 17(9), 2021; DOI: 10.1098/rsbl.2021.0309

Copyright: © 2021 The authors. Published by the Royal Society
Open access
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

To anyone who understands evolutionary biology, fascinating though this is, the mechanism by which this relationship arose is easy to understand in terms of evolution by natural selection because while the hosts are more successful if they can detect the eggs of brood parasites, the brood parasites are more successful if they can target potential hosts who are less able to detect their eggs.

In terms of intelligent [sic] design, however, this is impossible to present as the deliberate design of an intelligent designer. Any designer who came up with parasitism, not realising the wasteful and futile arms race that would inevitably ensue, does not deserve to be called a designer, let alone and intelligent one.

As the result of perfectly natural and understandable natural processes, though, these sorts of findings add to the wonder of nature to be had from an understanding of how it works, rather than dismissing it all as magic and reserving admiration for some supposedly brilliant magic designer, whose stunning incompetence can only be ignored by ignoring most of what it allegedly designed.

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