{"id":141969,"date":"2023-08-29T05:23:26","date_gmt":"2023-08-29T11:23:26","guid":{"rendered":"https:\/\/www.featheredphotography.com\/blog\/?p=141969"},"modified":"2023-08-29T05:23:26","modified_gmt":"2023-08-29T11:23:26","slug":"swainsons-hawks-sleeping-unihemispherically","status":"publish","type":"post","link":"https:\/\/featheredphotography.com\/blog\/2023\/08\/29\/swainsons-hawks-sleeping-unihemispherically\/","title":{"rendered":"Swainson’s Hawks – Sleeping Unihemispherically?"},"content":{"rendered":"

Yesterday morning I found nine Swainson’s Hawks perched on utility poles. Eight of them were in pairs, with both birds of the pair perched together on the pole. Normally I don’t photograph raptors on poles, but I often scope them out through my lens in case there’s something interesting or unusual about them.<\/p>\n

This pair got my attention so I did take some photos.<\/p>\n

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This is the first photo I took of them. I was curious as to why the bird on the left had its true eyelid closed. And kept it closed. At first I was concerned that it might be because of an eye injury or illness but soon…<\/p>\n

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both birds were doing it. And they kept them closed for some time. I have lots of photos like this one.<\/p>\n

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A closer look.<\/p>\n

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An even closer look at the bird on the left.<\/p>\n

It was at that point that I suspected, despite the fact that I never did see the right eye of either bird, that they were sleeping unihemispherically.<\/p>\n

“Unihemispheric slow-wave sleep<\/a><\/span><\/span>\u00a0(USWS) is sleep where one half of the brain rests while the other half remains alert. This is in contrast to normal sleep where both eyes are shut and both halves of the brain show unconsciousness. In USWS, also known as\u00a0asymmetric slow-wave sleep, one half of the brain is in deep sleep, a form of non-rapid eye movement sleep and the eye corresponding to this half is closed while the other eye remains open. The phenomenon has been observed in a number of terrestrial, aquatic and avian species.”<\/em><\/p>\n

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Occasionally both birds would open their eye that had been closed, probably to check me out. I’m including this photo so you can see that the bird on the left could open its eye normally, strongly implying that it wasn’t injured. The same thing can be seen with the hawk on the right in photo #1.<\/p>\n

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I’m including this last photo to document how different the transparent nictitating membrane looks when compared to the completely opaque true eyelid. Here the nictitating membrane of the hawk on the right is closed, which diffuses the catch light across a much larger area of the eye than is normal for a catch light.<\/p>\n

Again, I never did see the right eye of either bird so I can’t prove that they were sleeping hemispherically but I strongly suspect that they were. Either way, it was highly unusual for me to photograph two raptors that were keeping their true eyelid closed at the same time so I think that’s interesting in and of itself.<\/p>\n

If you have thoughts on this I welcome your input in the comments. I’m certainly no expert on unihemispheric sleep.<\/p>\n

Ron<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

A pretty nifty trick that even allows birds to sleep while they’re migrating over water. (6 photos)<\/p>\n

Continue reading<\/span><\/i><\/a> <\/p>\n","protected":false},"author":2,"featured_media":141973,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[5,334,395,645],"tags":[647,7105,646,7106,7104,311],"class_list":["post-141969","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-bird-oddities","category-birds","category-miscellaneous","category-swainsons-hawks","tag-buteo-swainsoni","tag-keeping-one-eye-closed","tag-swainsons-hawk","tag-true-eyelid-versus-nictitating-membrane","tag-unihemispheric-sleep","tag-utah-2"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/featheredphotography.com\/blog\/wp-content\/uploads\/2023\/08\/swainsons-hawk-0662-big-crop-ron-dudley.jpg","jetpack_shortlink":"https:\/\/wp.me\/p1zzJh-AVP","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/featheredphotography.com\/blog\/wp-json\/wp\/v2\/posts\/141969","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/featheredphotography.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/featheredphotography.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/featheredphotography.com\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/featheredphotography.com\/blog\/wp-json\/wp\/v2\/comments?post=141969"}],"version-history":[{"count":5,"href":"https:\/\/featheredphotography.com\/blog\/wp-json\/wp\/v2\/posts\/141969\/revisions"}],"predecessor-version":[{"id":142017,"href":"https:\/\/featheredphotography.com\/blog\/wp-json\/wp\/v2\/posts\/141969\/revisions\/142017"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/featheredphotography.com\/blog\/wp-json\/wp\/v2\/media\/141973"}],"wp:attachment":[{"href":"https:\/\/featheredphotography.com\/blog\/wp-json\/wp\/v2\/media?parent=141969"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/featheredphotography.com\/blog\/wp-json\/wp\/v2\/categories?post=141969"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/featheredphotography.com\/blog\/wp-json\/wp\/v2\/tags?post=141969"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}