Layers of Wildlife Data: Cooper’s Hawks Update 1

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One of 5 successful fledglings in 2015

The Forest Metrix staff came together over time in part because of shared interests that go beyond making professional software for foresters and arborists. Most of us are intense nature geeks; which means that we spend a lot of time out in the woods observing things, taking pictures, and even constructing data sets from which we can derive interesting (to us, at least) learnings.  This post marks the start of our Nature Series, sharing some of our more interesting pictures and observations.

Last year, co-founder Tig Tillinghast spent six weeks observing a Cooper’s hawk nest near the office, rigging up a camera system that would take pictures at set intervals high up in a neighboring tree, taking inventory of all the hawk activity in that patch of forest. We learned a lot from that, and in the process, this family of Cooper’s hawks started to tolerate our presence.

As with forests or individual trees, the level of insight a professional gains from observation is multiplied when looking at the subject at different slices of time. So in 2016, we spent some effort locating the new nest. This was done by conducting an inventory of all hawks nests in about a square half mile, and using our database software to monitor which ones were experiencing some new activity, such as sticks being added. While we were at it, we entered in some basic tree risk assessment information to see if there might be any correlation to that and a nest that gets re-used.  Prior to the hawks finishing their egg laying, we set up a ladder 75′ up a neighboring big tooth aspen tree. We expect many of our clients will chuckle thinking of a forest inventory software programmer trying to figure out how to rig a tree for daily climbing to that height. Let’s just say we survived the debugging process.

A side note: in the academic literature, studying hundreds of Cooper’s nests, not a single one was observed located higher in a tree than this nest. Normally, they choose a location about a dozen yards off the forest floor. They like to choose white pines around here, as the whorls of branches offer a platform that is more secure. They appear to have good instincts on which trees might be poor risks and do so without the benefit of an ISA TRAQ tree risk assessment form.

With better cameras, a much closer location, larger memory cards and a newly hacked-together power system running off a couple deep cycle batteries, we got some great data, and some pretty pictures. What follows is the first of three posts showing some of what we saw.

June 4

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1rst chick on 3rd day with female adult

We saw the first chick today. One of the parents – I believe the male – was on the eggs at 1:24 p.m. when he popped up and looked quite surprised. He stood on the side of the nest and observed, and eventually went in to help in some ways I couldn’t see (tree in middle occludes the center of the nest). The other parent came a half hour later with food. She tore the meat into slivers that I’m guessing were 1-2 cm long, and quite bloody. (Cooper’s chicks are stimulated by red and for the first dozen days are reluctant to eat things that aren’t red.)

I suspect there’s more than one out of the shell, based on the direction of the parents’ glances at times.

The date when we saw the first chicks last year: June 4. Studies have shown they rarely deviate more than 48 hours from year to year, which is interesting. That’s correlated to the female, not the male. A returning male with a new female most often has a different annual timing. This suggests that we have the same mom here this year, which corroborates my feeling that this is the same mother based on her comfort with me so close to the nest.

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75′ of ladder

Coopers typically lay three eggs, and then skip a day and then lay two more. They start brooding after the third egg, which means that one would expect three to pop out at once, with others following a day at a time. The latter two hatchlings can be quite a bit smaller than the first three. I suspect we’ll have at least three hatched when we observe next.

The ladder this year makes the one last year look short. We’re around 75’ up now. That’s more than twice the expected nesting altitude of Cooper’s, but this couple ran high last year too. In the literature, surveying a few hundred nests, there was no Cooper’s nest as high as this one. For convenience, and due to their proclivity for high altitudes, I’m referring to the female as Hillary and the male as Tenzing.

June 6

Verified three young are present today, seeing them all at once. I’m hoping we might see a couple more eggs hatch after the normal fourth-day hatching holiday.

untitled_16-06-08_8378The female continues to tolerate me well, allowing for some interesting behavior observations. In the picture at left,  she is picking something out of the largest chick’s fuzz. The chicks are doing good preening imitations already, even though their feathers won’t break out of their sheaths for another week and a half. Having watched the first born on its first day, and having the photo record every 3 seconds for that day, I can safely say it did the imitation preening even prior to witnessing that behavior in a parent bird.

Photo Geek Stuff:

The closer distance this year gives us much more detail. We can see insects in the down and small food particles on the bills. These are taken at 560mm (a 400 + 1.4 teleconverter). The trees are moving quite a lot at this altitude. It was windy today, so I had to keep shutter speeds up (3200 ISO often to get about 1/500 second) and I needed a big depth of field (shot at f/9 whole day) because the trees were literally traveling greater distances in the wind than the depth of field was deep. This tree movement made for some funny series, with blank air, then the wrong side of the tree, then the birds whooshing past. It’s not so funny when you’re up there changing batteries. I’ll be glad when the hacked-together power system is lit up and I need not return with batteries so frequently. It kills me to shoot JPEG, rather than RAW, but I probably will to minimize ascents, as I can fit an entire day on the dual cards.

Hawk Geek Stuff:

Last year I developed a theory that the hawks instinctively placed their heads with a twig interposed directly between them and a potential threat or prey item. In reviewing tens of thousands of images, it was just too common to be coincidence. This is, fortunately, statistically provable and even processable by a computer, although we haven’t yet spent the time to modify a version of our tree software for the purpose. That same phenomenon jumped out at me this year, and interestingly, the just-born chicks untitled_16-06-08_9481appear to do it at times. They do so more often than not precisely when they take on a posture of awareness and intent. The favored position is to have the pupil bisected by the edge of something like a stick. I can only imagine that this is because the eyes are the biggest visual key in other animal’s attempts to identify threats and prey. In a situation with a hawk 40’ away from a camera with a loud shutter, it gives plenty of time for the bird to line things up to preference. This might be something to deliberately study.
By way of example, at right is a chick waking from a food nap, acquiring the potential threat location (a shutter click 4 seconds after waking), then darting the head. At this age, it’s hard to argue that it’s not instinct.

untitled_16-06-08_8381More interesting to me is the apparent bonding behavior going on with the new siblings and mother, as at left.

There isn’t much in the literature I’ve found on Cooper’s on these intra-nest relationships. We know that Cooper’s are apt to feed the hungrier birds first and avoid a strict pecking order, aside from some gender status rules. Last year we saw what looked a whole heck of a lot like a pecking order, complete with pecking, and that in a good food year. This might also be an interesting area of study.

And, finally, we leave with a lucky shot of one of the chicks defecating. The young will back themselves up to the edge of the nest and literally shoot their “chalk” out the side. Most of the time. They screw themselves up tightly with their little posteriors in the air and let loose a force that is impressive given their size. This keeps the nest clean of feces, but interestingly, they can be untitled_16-06-08_9587seen to leave much in the way of carcasses through the nesting season, attracting clouds of flies. The parents will remove larger skeletons, but individual pieces of meat can be seen to fall between branches in the nest and fester.

The full Cooper’s series:

First Hatching

The Brood

Winnowing‎

Pre-Flight

Flight!

Epilogue

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