![\"Apteribis.](\"https:\/\/cdn.sci.news\/images\/enlarge13\/image_14549e-Apteribis.jpg\")
<\/a><\/p>\nApteribis. Image credit: Sarah Citron, University of Lethbridge.<\/p>\n
Evolution on islands often generates specialized lifestyles that are rarely seen in continental species.<\/p>\n
The biota on oceanic islands are, however, prone to extinctions following human colonization, resulting in an incomplete understanding of the lifestyles of species that evolved prior to colonization.<\/p>\n
For example, the Hawaiian Islands hosted a unique and diverse assemblage of endemic species, most of which became extinct following human colonization.<\/p>\n
\u201cApteribis was a relative of the Australian white ibis, commonly known as \u2018bin chicken\u2019 for their habit of rifling through rubbish bins with their beak,\u201d said Sara Citron, a Ph.D. candidate from the University of Lethbridge.<\/p>\n
\u201cBut really, ibises are beautiful and distinct birds: they have exceptionally long, elegant beaks and striking colors that set them apart from other shorebirds.\u201d<\/p>\n
\u201cTheir elongated beaks are key to how they feed. By inserting the beak into mud, shallow water, or soft ground, they probe for subtle vibrations that reveal the presence of hidden prey, such as small invertebrates.\u201d<\/p>\n
In the study, Citron and her colleagues examined skulls from 25 of the 28 living ibis species from museum collections.<\/p>\n
They used advanced imaging technology to create 3D reconstructions of the birds\u2019 brains and compared them with the fossil species.<\/p>\n
\u201cWhat we found was astonishing. All imprints of the visual system on the skull \u2014 like the eyes, the optic nerve, and the optic tectum area where light is processed by the brain \u2014 were dramatically reduced in Apteribis compared to its living relatives,\u201d Citron said.<\/p>\n
Apteribis\u2019 reduced visual system suggests a nocturnal lifestyle, which is an unprecedented trait among ibises.<\/p>\n
The bird likely roamed the Hawaiian landscape under cover of darkness to feed and possibly breed, while resting during the heat of the day.<\/p>\n
\u201cSuch extreme reductions are known only in a few birds, including the elusive Australian night parrot or New Zealand\u2019s kiwi and kakapo,\u201d said Aubrey Keirnan, a Ph.D. student at Flinders University.<\/p>\n
\u201cAll of these species rely very little on sight and are active mainly at night.<\/p>\n
\u201cThe Hawaiian species were targeted because island evolution often produces bizarre anatomies,\u201d said University of Lethbridge\u2019s Dr. Andrew Iwaniuk.<\/p>\n
\u201cFrom the moment we looked at the skull, we could see that the orbits, the spaces where the eyes sit, were far smaller than they should have been.\u201d<\/p>\n
\u201cHawaii is the most isolated archipelago on Earth and originally had no mammalian predators,\u201d said Flinders University\u2019s Dr. Vera Weisbecker.<\/p>\n
\u201cSimilar to the situation in New Zealand, large birds like ibises were safe on the ground and eventually lost the ability to fly.\u201d<\/p>\n
\u201cAccurate sight would not have been a particular advantage.\u201d<\/p>\n
The other factor pushing Apteribis into the dark was probably their prey.<\/p>\n
\u201cThe Hawaiian islands were once home to an extraordinary diversity of snails and flightless crickets,\u201d said Dr. Helen James, curator of birds at the Smithsonian National Museum of Natural History.<\/p>\n
\u201cFlightless crickets and snails are nocturnal and would have been more abundant then, exactly the kind of prey that could drive a bird like Apteribis to adopt night\u2011time foraging.\u201d<\/p>\n
\u201cPossible causes of extinction are changes to the climate and vegetation on the Hawaiian islands, and the first arrival of humans.\u201d<\/p>\n
\u201cThe New Zealand kiwi is often seen as an one\u2011of\u2011a\u2011kind oddity among modern birds,\u201d Dr. Iwaniuk said.<\/p>\n
\u201cBut this extinct ibis shows that similar forms evolved elsewhere.\u201d<\/p>\n
\u201cIt reminds us how much diversity has been lost, and how many ecological roles disappeared, before we ever had the chance to study them.\u201d<\/p>\n