Eagle Nest Cam Installation Question
Saturday, June 22 2013 @ 12:44 PM EDT
Contributed by: davidh
Question from Gretchen Butler, Flagler County, Florida:
Can you tell me the percentage of abandonment by the resident eagles once a camera is installed?
Great question. The answer is not so easily determined or perhaps going to provide the info you wish because of the way you framed the question. I don't think cams are a potential problem -- cam installers can be.
1) I see "no evidence" of the existence of a cam per se in the nest as a detriment to the eagles.
2) I see 100% abandonment of all nests when a human has been seen in the nest by the eagle. In many of these cases the reason for the human in the nest was to place a cam, collect samples, band or rescue the young. To me the problem is that the eagle has seen someone in that "inviolate area" -- the eagle nest. If the human intrusion was before egg laying or during incubation the eagles simply did not return -- ever. The nest was immediately abandoned. Most have been seen re-nesting in the territory but in a different tree and nest. This is not acceptable when I have to guarantee to the property owners that our cams or their placements "won't disturb those particular eagles".
3) The installation of a cam during the adult eagles' migration from the area never seems to have caused any abandonment. Most certainly the eagles have "looked at" the cam on return. From some cams we even have video of them walking up to it, thumping the lens with their beak and then within minutes simply ignoring it for the rest of the season. A slight twist on this is that within ptz (pan/tilt/zoom) cams the lens moves and I have seen a few eagles look at the moving lens. In fact I have particularly undertaken movement of the lens while the eagle was insitu to test this before we allowed our special admins to operate the cam. I wanted to be sure the moving lens was not a disturbance. I would think it logical to not move the cam for the first few days after the eagle returns to insure they did not see initial movement. This I am guessing at as logical. In all tests and simple "moves of the cam" I have not seen any eagle more than casually glance at the cam. In other words, once the eagle has seen and accepted the cam, they don't seem to mind the movement of the lens within the dome.
Now, to address the other option: the eagles seeing someone in their nest or well up in the tree besides the nest. There we have a big difference. In every case the eagles have abandoned the nest when they have seen people in their nest. I have never seen an eagle immediately abandon a nest when it had young and the bander was seen entering the nest. All my records show they simple raised their young that year and then always built another nest for the next season. I have no record of them reusing a nest in which a person was seen entering the nest. Some banders have said they annually band young in the same nest. This is different than I have witnessed here. Other banders have told me the bird simply renested a few trees away. That may be okay for the banders but not acceptable for private landowners who treasure their eagles and I am giving then the assurance that I won't drive their favorite eagles away.
Back in the 1960s when I was working on my eagle thesis I had the Charles Broley diaries and I graphed out all his visits to Florida nests (and his alternatives) and I was pressured at the time, to not release the data. It seemed clear his nest banding visits frequently resulted in changed nests. Part of the argument at the time, other than Charles (my mentor and author of the second book I ever bought!!) was the Audubon icon, was that his eagles seemed to re-nest nearby and therefore all was well. If I remember correctly, my data at the time was that a new nest was about 50% less productive than a reused nest. Therefore, if that applied in Florida, the changing of nests, in spite of the eagles re-nesting in a nearby tree, resulted in fewer young being produced by that territory.
A couple of years ago at the famous Sidney, BC nest I made a chick rescue because the chick was obviously seen on cam being snagged in fishline. The chick was going to die of man-made causes within the nest. I had warned the landowner of the possible repercussions of the rescue and she, in spite of buying the farm earlier because it had the eagles nest, agreed that we should make the rescue. Two days later between trips to feed and finish raising their three young, the parents started to build another nest -- yes two days later!!!!
I don't think our urban and suburban and perhaps even coastal birds give a damn about lights etc. They so regularly use them as perches and if they move into the urban-suburban setting they almost have to sit on lights and artificial posts. Half the posts or masts along the harbor have lights on them -- or even cams. The eagles generally don't seem to give a damn about them. I have seen eagles sleep next to pulsating flashing lights -- possibly even using the light source for heat. The intrusion/invasion of the nest by a human seems totally different -- that they generally don't accept at all in our area.
While our eagles' adaptability is my evaluation of why they are so successful, and they have learned to accept so many different artificial platforms for nesting, the invasion of the actual nest by humans still remains, at least in this area, an unacceptable event.
I had projected that the way to band or capture adults without interfering with the nesting would be to trap both adults away from the nest (300 yards?) and with both adults in hand then you could scurry up the tree, band or place a cam, and get away before the adults were released. The humans would not be seen in the nest by the adults. I hear you asking: What happened if the kids told dad what happened while he and mom were away? That takes another explanation. While this would be a lot of coordinated work I think this could result in a banded family and no real detrimental disturbance to the nesting pair or the young.
4. Your specific question of: Can you tell me the percentage of abandonment by the resident eagles once a camera is installed? My answer here is qualified: I have no records of the cams causing any abandonment -- it was always the presence of a human being seen in the nest by the eagles to which I attributed the abandonment. At a couple of our cam sites we have had nests not functional after three or four years of success. In all of these we see other causes for the problem, most being that one or both of the adult eagles did not return from the migration and the remaining territory bird had to find a new mate or the territory got two new nesters, then for them to get effectively working together. I think many of these new adults have to practice. This latter thought seems to be what happened in White Rock this year. This territory went through four ineffective females and the fifth and her male will hopefully return for more success next year. Some keen followers even think that the Delta2 nest might have experienced the loss of one partner this past winter though the nest is still producing -- just not so successfully.
Finally, I wish you the best of luck with the installation. The cams offer such incredible scientific or educational opportunities that the cost and effort is worth the effort. My recommendation is to invest in two ptz cams to give you some insurance, but please make sure the eagles are out of the area before you enter the nest -- I don't want you disturbing the nesting and becoming the rath of your fellow birders. By the way I was honored to have Charles and Myrtle Broley's daughter, Jeanne, here and autographing my original book last winter. I had bought it as a 14 year old over 60 years ago!!
If you need a speaker on this topic I am always available with some excellent power points -- or please come up and see what we do here. If you come in November or December we will show you 3,000 - 10,000 eagles along the 2 miles of the Harrison River near Vancouver.
Hope this is helpful.