Sunday, November 29, 2009

Thanksgiving owl suprises

November 30, 2009

Thanks to benevolent bosses, I was able to leave work at 2pm on Wednesday, 11/25. I had debated about where to go before I went to Charles and Sarah's territory. I finally decided to head into Kennedy Forest on the west side of the park and then go see the Dynamic Duo. Just short of the summit of the hillside along the southbound Skinker Boulevard, I turned into the forest. I stopped and looked to see if any Barred Owls had returned to some previous perch/roost sites. They had not so I continued on eastward into the forest.

I took one of the non-paved paths that wanders through the forest. As I walked on a northerly portion of this patch I saw some whitewash (bird droppings) on the ground. I looked around the vicinity and I saw some more whitewash. The volume of whitewash was enough to indicate that this was the perch site of a large bird, possibly a large bird of prey.

I looked up and directly above me was indeed a large bird of prey. I was 99% certain it was a Great Horned Owl but I could not see its head and face. Walking carefully to a better vantage point I saw the tell-tale tufts and massive eyes of a Great Horned Owl. Bloody hell.

While I was thrilled to find this owl, I want to emphasize that I did not stumble upon this owl by a mixture of accident and skill alone. I knew that this area had a recent owlish history. In August, one of my owl friends Christine e-mailed me that she had seen a Great Horned Owl in this area. After receiving her e-mail, I searched in vain for an owl amongst the near jungle-like foiliage that had flourished with the record rainfall we had this summer. I had already had my own observations of a pair of Great Horned Owls for a few weeks in February and March of this year in this very section of Kennedy Forest. As quickly as I found them, this pair disappeared. Given the owl occupancy in this stretch of woods, I always keep my eyes peeled for any all signs of an owl when I'm there.

Thrilled to have found a Great Horned Owl again in Kennedy Forest, I called two of my owl friends to see if they were able to come out and see this gorgeous owl. First on the list alphabetically by last name was Edward Crim, photographer extraordinaire of Forest Park 365 fame. Edward was excited to hear about the owl but was had already made his daily sojourn to the park. I let Edward know where the owl was and that it was located where we saw an owl the first time we met back in March. Next on the call list was the aforementioned Chris Gerli. He too was quite chuffed to hear about the owl. He hoped to come out if the day's work finished early and I gave him directions on where to find this owl.

As I called Edward and Chris the owl began to hoot. The low, long notes the owl made indicated that it was a he; a male! I noticed that the hooting was on the tentative side, not quite fully formed. The male owl of the pair I found in this same area in February and March hooted in a similarly immature fashion as well. I went back to watch the owl hoot and was pleased to see that he had altered his position in the tree and was much more visible.

I was struck by his extra-large white bib under his chin and the edge of immaturity in his plumage. He looked and sounded like a sub-adult still on the cusp of full maturation. He kept up a steady rate of hooting and it struck me that he was hooting quite early in the day. It was well over an hour before sunset and generally Great Horned Owls begin to hoot closer to sunset than this chap was.

Filled with excitement about this new owl I headed off to see Charles and Sarah. Less than a third of the way there, my cell phone rang with Chris Gerli on the line. Work had finished early and he wanted to find this owl. We struck an easy bargain: I would show him this owl for a short and then he would drive us to the territory of Charles and Sarah. Chris was along shortly, I piled into his van and we made our way back to the forest.

The owl was still hooting and we could see him easily. As we made our way to our vantage point we saw two people coming the other direction. Through waves and hand signals it became clear that they knew an owl was in the vicinity. They and their extraordinarily well-behaved dog joined us and we exchanged hellos and names. Sally and Patience had been watching this owl for the past three nights and were glad that we could identify the species for them. Chris and I were glad to have some more information about how long this owl had been there. We told them about Charles and Sarah, several aspects of the natural history of the species and I mentioned that they (and anyone) could contact me via this blog. Just before Sally and Patience departed, the owl flew off west and continued to hoot after he landed.

Chris and I got a good look at where it had landed and we headed off to reacquire him. Then things took another turn. The owl continued to hoot and then we heard a response. It was a Barred Owl calling from a southwesterly direction. The Great Horned Owl hooted again and the Barred Owl replied in kind. What became odd was that out of four hoots by the Barred Owl, one sound like a text book Barred Owl call (often rendered as "Who cooks for you? Who cooks for you all?") while the other three sounded like a melange of a Barred Owl hoot and that of a Great Horned Owl. The cadence was Barred Owl like but the tonality had the smooth woodwind sound of a Great Horned Owl. Chris and I were not surprised though no less thrilled to hear a Barred Owl as we both found them in Kennedy Forest over the years. We reacquired the Great Horned Owl and watched him hoot at close range. My apologies for the lack of video footage but I had a memory card error that day and the footage I took was unusable. D'oh.

Between our great chat with Sally and Patience and reacquiring Charles and then looking for the Barred Owl, Chris and I spent more time in this vicinity than we had expected. After discussing the possible location of the Barred Owl, we jumped in his van and headed for the territory of Charles and Sarah. We only saw Charles for a short while and on the following day, Thanksgiving, I was not able to get back to Kennedy Forest or find Charles or Sarah as I described here.

Chris Gerli and Barb Brownell found the owl on Thanksgiving, 11/26 and they observed it hooting in the bright afternoon sun for at least half an hour. On Friday and Saturday, November 27 and 28, I started my time in the park by looking for the Great Horned Owl in Kennedy Forest. On both days, I was able to find this owl brilliantly camouflaged in the same vine covered fork between two large branches. This owl was so well-hidden that on both days, an Eastern Grey Squirrel jumped right over the owl to get to from one fork of the tree to the other without seeming to notice this parked predator. I heard the owl hoot briefly on Friday but not at all on Saturday. The day time hooting, well before dusk, is puzzling. While I have not been able to do an extensive perusal of the literature, I do not recall previously reading anything wild Great Horned Owls hooting in the afternoon like these owls.

On Saturday, 11/28 a new wrinkle in this story emerged. Taking advantage of the unseasonably warm weather, up to 70 F, Chris Gerli and Barb Brownell headed to Kennedy Forest. Their goal was to watch the owl in depth and to gauge his flying skill and maybe even look for signs that it was Mo or Art; one of the owlets that Charles and Sarah had this past nesting season. They called me as I was watching Charles and Sarah. I listened to their intentions and wished them well.

Their next call came a short while later. Not only had they found the male owl and heard it hoot but they also heard the distinctive reply of a female Great Horned Owl before finding this same female! The two owls began to duet and fly to different singing perches with adult aplomb. This behavior demonstrated to Barb and Chris that these were adult owls that had paired up or were actively in the process of doing so. Chris and I spoke twice more on the phone that night and his breathless excitement was infectious. The owls continued to duet and fly south until Barb and Chris lost them as the owls headed off in southeasterly direction.

I looked for these owl on Sunday 11/29 but did not find them at all. I debated looking for the owl on Monday 11/30 but decided instead to hit some recently unvisited parts of the park such as the prairie-savanna and waterway around Steinberg Ice Rink.

I met Chris Gerli and Barb Brownell looking for this owl on Saturday 12/5. This was the first time we had been back to this area since 11/28 and 11/29, respectively. We again did not find the owls or any very recent evidence of them such as fresh whitewash or pellets. Had the owls left or where they in another part of the park? So far, we do not have further information.

So now the big question is who are these Great Horned Owls in Kennedy Forest? Several scenarios exist:
  • one of them is one of Charles and Sarah's owlets from this year
  • one of them is one of Charles and Sarah's owlets from the year before
  • one of them is an young adult from somewhere else in the wider St. Louis area
  • both of them are young adults from somewhere else in the wider St. Louis area

To look at these possibilities, let us review what owlets of the species do when they leave their parents' territory. Great Horned Owls are remarkable parents, mating, nesting and hatching in the depths of winter. They do this because it takes so long for the owlets to mature and become independent. It is also thought that the owlets' efforts at hunting coincide with the arrival of more prey, especially the more inexperienced and thus vulnerable offspring of the owls' prey. After 5 or more months of careful care by the parents, it is time for the owlets to go out on there own. The parent owls stop feeding the owlets and will even chase them out of the parents territory. In describing the slow maturation of the young and the parents eventual cessation of care to human parents, the human parents side with the owl parents. I found this to be especially true if the human parents have children in their late teens and early twenties!

So what next for the owlets? Fundamentally, they have to survive and then work on finding and defending a territory before finding a mate and reproducing. Owlets are known to remain on the edge of the parents territory, the owlets' former home, while doing their best to eek out an existence without incurring the wrath of their parents. But the owls that are not able to raid the veritable fridge, head out away from their parents' territory.

With the exception of some of the northern subspecies of Great Horned Owls, which are forced to move south when prey populations crash, the species is sedentary. That is, if an individual owl is already established in a territory. For those that are not, they have to travel to find a place where they can survive and then work on progressing to territorial ownership, defense and then pair formation and reproduction. This first year or two is the only time of significant travel for most owls of the species.

So how far do they travel? As it is with many aspects of the natural history of Great Horned Owls, it can be hard to generalize. The species is the most widespread, commonly found owl in North America. Even the subspecies we have in Missouri, Bubo bubo virginianus has an immense range; all of the eastern U.S. and past the Mississippi River and portions of southern Canada. This immense range generates countless variables about the lives of owls in these different parts of the range. Great Horned Owls in Springfield, Missouri and Springfield, Florida and Springfield, New Hampshire will have some similarities but also in many differences in: what they eat, where they nest, when they nest, where they roost, population density, territory size and more.

While some studies focus on owls in a particular region or locale, other studies survey these more localized studies to come to more general conclusions. In his encyclopedic and sometimes slightly confusing book, North American Owls: Biology and Natural History, noted biologist Paul Johnsgard cites such a survey type of study that answers the travel range question nicely, "A study by Stewart (1969) of 434 banded recoveries from Great Horned Owls banded in various parts of their breeding range indicated that 93 percent were recovered within 80 kilometers (almost 50 miles) of the point of banded." So many owlets that have dispersed (left their parents territory) travel significant but not immense distances.

With all this in mind, that's why I spelled out the possible origins of these owls as:
  • one of them is one of Charles and Sarah's owlets from this year
  • one of them is one of Charles and Sarah's owlets from the year before
  • one of them is an young adult from somewhere else in the wider St. Louis area
  • both of them are adult from somewhere else in the wider St. Louis area
Owls that are not paired up are called floaters and are the singles of owl life. Very little is known about the lives of floaters and how they transition to couple-hood. That said, it does have to be a challenging life, especially for young adult owls, to be without an established territory and its cover and supply of food. Like many other predators at the top of the food chain, the biggest limiter on the population of Great Horned Owls is starvation. Large portions of Great Horned Owlets, at rates as much as over fifty percent, will not survive their first year. Of those that survive, significant portions of the survivors will not make to or past their second year. Survival is tough, even when one is at the top of the food chain.

Were these young adults stopping by Kennedy Forest as part of their process of establishing their own territory? Did they hear or otherwise run into Charles and Sarah and get the message that attempting to stay longer never mind establish their own territory in the area was a fool's errand? I hope to return to Kennedy Forest soon and try to find these owls again. My gut tells me that I will not find them again but I will keep my eyes and my mind open. Even if my owl friends and I do not find these owls again, this Thanksgiving owl surprise will be an interesting chapter in the annals of Forest Park Owls.

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