A studio for bird study

Tag: owl

Barred Owl (Strix varia) Hunting at Mid-day

by Bryce W. Robinson

 

While out for a day of birding Maryland natural areas, Caitlin and I saw a Barred Owl perched on a power line along a two lane highway. I was shocked to see the bird on the line in the open, but more shocked at its alert behavior. The bird was hunting the road edge and it was mid-day.

I’m relatively uneducated about the Barred Owl. I thought these birds were strictly nocturnal and rarely active during the day. After doing some research, I’ve learned they occasionally hunt in daylight, however mostly in the first hour following sunset (Mazur and James 2000) . Despite some tendency towards daytime activity, it stills seems shocking this bird would actively hunt a road edge in the daylight. Either way, I thought I’d share.

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Referenced literature:

Mazur, Kurt M. and Paul C. James. (2000). Barred Owl (Strix varia), The Birds of North America (P. G. Rodewald, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America: https://birdsna.org/Species-Account/bna/species/brdowl

Great Gray Owl Fledglings

by Bryce W. Robinson

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Another highlight from my recent time spent on the Innoko National Wildlife Refuge was happening upon three Great Gray Owl (Strix nebulosa) owlets that had “branched”.

In fact, these birds had hatched in a nest that was nothing more than the top of a birch snag, so far as I could tell. There were no nest structures in the area, only a plenty of broken tree snags about 5 meters tall. I believe that once they were too big to fit, the owlets fledged. Each bird was on a partly fallen truck leaning diagonally, a ramp for them to climb from the ground to relative safety from ground predators.

The first bird my friend Nick and I found sat staring at us, but with only one eye open. It appears from the photo that a Moose Fly (Tabanidae sp.) was biting its eyelid. I became very familiar with these flies during my time in the area, and felt for the poor young owlet.   The flies have pinchers on their mouth that they use to break skin, and from my experience with them it seems they do this to draw the blood and then feed. At least mosquitoes are mostly painless during their blood draws…

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We first heard the owlets begging calls while conducting a point count a few hundred meters away, but by the time we found them they had quieted down and stood extremely still, staring at us. Without a doubt we were the first humans these birds had seen. The Innoko is a very remote place, as we never saw a single person during our five-day stay in the area despite covering a distance of over 200 river miles round trip.

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I was enamored. I’ve seen very few Great Gray Owls in my life, and seeing birds at this age was a first. It has always been something I’ve wanted to see, so it was a dream realized. After getting our fill of the owlets, we began searching for an adult. We soon found a large ghost-like owl, the adult Strix nebulosa, 50 meters from the owlets. In my experience with Great Gray Owls, they’ve been extremely tame birds that tolerate your intrusion and lend themselves to photography. This birds was not tame, and unfortunately flew into the forest as we drew near. I wasn’t able to get any photos, but I managed to watch through my binoculars for a bit.

I captured a short clip of one of the nestlings (below). It’s a rather uneventful short clip, but it adequately describes the experience and the owlets tactful poise as it remained motionless as it kept eyes on Nick while I took video.

 

Here it is in full, the media from my first encounter of a Great Gray Owl family in the remote Alaskan wilderness.

Short-eared Owl Wing-clap Flight Display

by Bryce W. Robinson

Breeding flight displays in birds are a blend of the bizarre and the fantastic, a show of a birds talent and specialty in communicating it’s unique ability to portray fitness. The Short-eared Owl is no exception, as a low consistent hoot softly settles on the sky, while the bird flies with deep, moth-like wingbeats. Then, as if in suspense, the bird begins to clap its primaries in rapid motion, falling from the sky. After multiple claps and an appreciable loss of altitude the bird spreads its wings and continues its deep wing beats as before. The wing-clap is displayed in seeming desperation, as if the bird is throwing all caution to the wind to produce the most excellent round of claps for onlooking (or listening) females, and intruding males.

I rarely post videos back to back, but I’m making an exception this time because in the same evening I was privy to both Long-billed Curlew and Short-eared Owl flight displays. Both were “on my list” of behaviors to capture on video, and my excitement for capturing both in one evening is too difficult to quell. So I share…

This bird flew tirelessly. For near an hour, the owl flew in the sky performing wing clap after wing clap, all the while letting out a low consistent hooting barely audible to my ears. What a scene, and such a scene that I encourage anyone in the area of breeding Short-eared Owls to search out the chance to observe this behavior in real time. It’s bizarre, but it is at the top of the list for must see in behavior birding, and for good reason.

In the future I’ll be refining my camera skills and upgrading my lens, all in hopes of getting a more clear documentation of this behavior. For better video quality, click through the video link and watch on Vimeo in HD.

Female Barn Owl “Spottiness” Signals Genetic Quality

by Bryce W. Robinson

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To begin, I should have illustrated the frontside of this Barn Owl to illustrate the concept I’m about to present. I did not, however, have “spottiness” in mind when I began the illustration, so I decided to illustrate the backside. I find the back patterning mesmerizing.

So, for the concept you’ll just have to imagine the frontside of this bird, being spotted throughout.

Ornamentation in birds is generally considered a male’s way to communicate their quality to females. A more ornamented, vibrant, decorated, etc. male is generally considered higher quality, thus driving selection for particular traits (Peacock is an easy example, but think about birds like the Greater Sage-grouse as well).

Studies supporting this theory have generally focused on males, and for good reason. Males tend to be the showier sex. But, what about species where females exhibit unique markings?

Barn Owls are one species where the female shows more markings (spots) than males. Additionally, studies support that female Barn Owls are not the choosers in breeding, as per usual. Because of these reasons, Roulin et al. (2000) decided to test the theory that heavier spotted females were of higher quality (tease out the mechanisms of spottiness). They hypothesized that females with more spots also had higher levels of specific antibodies important for parasite resistance.

Their study looked into immunocompetence of offspring. They found support for the idea that heavier spottiness communicates immunocompetence, but also may be a “heritable signal of parasite resistance”. This is important for Barn Owls, as they nest in cavities and tight spaces. I remember a few weeks ago I went with a peer, Tempe, to check on a Barn Owl nest for her Master’s Project. The box held four owls (lower than normal), and was full of feces and dead animal remains. In such situations, parasites and all sorts of things may run rampant. Having higher resistance then becomes advantageous, and ways of communicating such resistance will then be selected for and prevail. Makes sense (eureka?).

Literature Referenced:

Roulin, A, T. W. Jungi, H. Pfister, and C. Dijkstra. 2000. Female Barn Owls (Tyto alba) Advertise Good Genes. Proceedings of the Royal Society B-Biological Sciences 267 pp. 937-941