Sunday, January 31, 2010

Sarah Is Nesting! Part II (Lots of Videos!)

January 31, 2010

To recap, I first found Sarah in the The Possible Nest Tree on December 31, the night she and Charles mated twice; the first time I had ever seen them do that. After seeing her in this tree again on January 2 and 3, I made the call that she was nesting. The Possible Nest Tree was now The Nest Tree or to give it a more chronologically accurate name to account for past and future nest trees, The 2009-2010 Nest Tree.

While I made the call that nesting had begun, I kept my mind and my eyes open for more mating. I'm glad I did. On January 3, Sarah emerged from the nest and continued to duet with Charles. Within moments Charles flew in from fifty yards away, landed on Sarah and they mated, after which he flew off north/northeast. See for yourself:

While I appreciate the owls' biological instincts, I thought that Charles was less of a gentleman for not giving Sarah more than a few moments out of the nest before mating with her. Naturally, my associative brain took the keyword "gentleman" and linked the word with a line from a movie, in this case Caddyshack featuring the late great Rodney Dangerfield. Tender ears beware.

But they were not done just quite yet. On January 6, they had a nice duet going when Sarah flew close to Charles and they mated! This was the last time I saw them mate this season.

Overall, I saw them mate thirteen times between December 10 and January 6. This ties last year's record of the most matings seen in a season but it was the longest mating period yet. I have
now seen the owls mate over forty times over the last four years.

So after mating some more and the nest choice made, now what? First off, the eggs would need to be fertilized within Sarah and then gradually formed and then laid. I'm still learning more about this process so I do not want to give incorrect information about it. However, it is fair to say that this process takes several days. Owls lay their eggs asynchronously i.e. at different times. For Great Horned Owls the period between each egg laying is usually one to two days but can be as many as seven to ten days. As the eggs are laid at a different times, so do they hatch at different times, creating a discernible difference in age and size of the owls. This difference in size and age is understood to be a way to ensure that at least some of the owlets will survive the challenging first few weeks and months of their lives.

Sarah keeps the eggs warm and safe. This is an epic task and Sarah handles it with devotion and aplomb. While few animals would take on an adult Great Horned Owl, there are many animals that would love to get to their eggs; squirrels, crows, raccoons, opossums, snakes and a number of birds such as crows and jays. Great Horned Owl eggs are reasonably hardy and able to survive cold temperatures for brief periods of time without being incubated. That said, it is imperative that the eggs stay incubated for the vast majority of the average of thirty-two days it takes for them to hatch after being laid.

Sarah stays on the eggs or with the new owlets all day and night except for a few short breaks. When I come to watch the owls at dusk, Sarah flies out of the nest to a nearby perch and stays out of the nest, on average, for three-six minutes. In that brief time away from the nest she stretches, grooms, defecates and perhaps expels a pellet and then it is back to the nest for many more hours. On slightly warmer days she will stay out up to ten to fifteen minutes and might fly a little more. She may take another break or two during the full twenty-four hour course of the day. From what I have have observed and read I would wager that she is on the eggs for well over ninety percent of a full day through rain, snow, frigid temperatures and more.

As the snag/hollow is not covered on top, Sarah literally acts as the roof of this area. Females Great Horned Owl in exposed nests have been found buried in snow and ice keeping their eggs or young owlets safe and warm. We recently had many day of stretch of weather well-below freezing including some days with temperatures adjust for wind chill below zero degrees Fahrenheit. Several people assumed that I was not going to the park in such cold weather. I corrected them by stating, if the owls can mate and nest in the depths of winter, then I can observe them! That said, it was jolly cold.

Since the owls are nesting in a new (to me) tree and locale within their territory, observing and documenting them during this time and for the coming weeks is and will continue to be a stimulating challenge. I am learning the best places to watch them, where Sarah goes to groom, stretch and expel waste, and the like. At the beginning of the nesting period, I was watching the nest tree at a safe distance from different position in which I could see the opening of the snag/hollow. This year's nest shares a trait with all but one of the other nest locations that I have seen Sarah use; you cannot see inside the nest thus you cannot see Sarah (or anyone else) until they are at the very opening of the nest. It is a classic game of now you don't see it and then you do.

My early viewing post in which I could see the opening of the snag/hollow did not work too well. I was able to see Sarah emerge from the snag/hollow, look around for a few moments before flying away to attend to her toilet. However, as I was looking east she quickly disappeared in the minimal horizon line. I was hesitant to go look for where she perched temporarily due to the poor visibility as I did not want to intrude on her unwittingly.

After a few days at this viewing post, I decided to watch from the other side of things, looking at the nest tree as I faced south/southwest. This observation post was back lit by the setting sun and provided greater illumination and clarity to Sarah's behavior. Even still, as I could not see her emerge from the inner reaches of the snag/hollow, it was tricky to see and document her flying out of The Nest Tree. Finally, I had some luck on January 16 and several subsequent days documenting Sarah's departure from the nest. As you can see below, each day had its differences but all of them were exemplars of the sublime power and grace of Great Horned Owls.

January 16, 2010

January 18, 2010

January 22, 2010

January 24, 2010

Notice that when Sarah leaves the nest she is in free fall; she has to clear the nest tree before she can flap her massive wings. For an example of the reverse procedure, here's Sarah returning to nest on January 20, 2010

So when will the eggs hatch? My best rough estimate is sometime in/around/after February 10. Given the depths of the snag/hollow, I do not think we will see the owlets until they are a few weeks old; towards the end of February or the beginning of March. With the exception of the very visible nest location in 2007-2008, I have never seen owlets until they were at least a few weeks old. I am terribly excited that Sarah is nesting and at the prospect of owlets. Wish them luck!

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