Hancock here – lots of interest in Ground Nesting Bald Eagles.

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davidh
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Hancock here – lots of interest in Ground Nesting Bald Eagles.

Post by davidh » Thu Apr 04, 2019 11:54 pm

Hancock here – lots of interest in Ground Nesting Bald Eagles.

While bald eagles regularly nest on the ground there are some interesting recent ‘different examples.’

The current nestings along the Eastern Barrier Islands certainly speaks to the eagles finding what they think is safe nesting sites. My big concern is will these sites be considered safe if the adults see humans entering the nest? Or how regularly can a human enter such a nest before the site is considered unsafe by the eagles? This re-nesting in visited nests is not something I see among our west coast wilderness or even suburban eagles. If they see a person in the nest or even nearby in the tree they react badly If they have eggs, apparently not such a big investment, they usually abandon the eggs. However, if they have young, they rear the young and then build a new nest in a different location the following year. This does not seem to happen in some areas where eagle banders report banding nestlings year after year in the same nest. I found precisely the opposite here on the west coast. I never had an eagle re-nest, at least for many years, in a nest they saw me or another human enter.

I even had back in the 1960’s the shelf of note books by the first ‘Eagle Man’ Mr. Broley. By the way his book was the very first book I personally bought – I think I was 12. About 5 years back his daughter and grandson visited me here and she kindly signed my original and a second copy of his book. He had inspired me along with Frank Beebe to be a falconer and then a raptor biologist. He was a Canadian who got talked into a winter project of banding eagles in Florida during his winter stays. We know more today about early eagles due to Charles than any other earlier contributor.

The startling thing to me was Audubon loaned me his entire shelf of note books to examine. That was before ‘xeroxing’ and after reading and summarizing the content (when I was in Grad school). I sent the books back to the Florida Audubon Biologist Sandy Sprunt. My startling revelation was that Charles’ records showed the same as mine. His Florida birds seldom nested in the same nest he was seen entering to band the chicks. He thought they just regularly changed nests. He did not link the changed nest to his visit since all the banded chicks were reared by the adults. And of course, in those ‘pre-1960’ days the eagles had a lot more trees to simply move to. He witnessed the adults simple move in the same territory 3 tree over! Not so today or in our urban – suburban areas where I have to guarantee each landowner I would not disturb his treasured nest if I inserted CAMs. So, I ONLY enter a nest when the adults have left on migration and are not in the area. Certainly the eagles instantly see the CAMs on return but almost instantly accept them - just another ‘light standard’ like they have sat on a hundred times. I think this is their reasoning. Every CAM I know others have set into nests when the eagles were watching caused the nest to be abandoned and the eggs lost. Here in British Columbia this is an inexcusable disturbance and violation of the Wildlife Act.

We certainly have witnessed a very famous eagle pair returning to a nest after we had ‘un-snagged’ a juvenile and replaced it back into its Sidney nest – an event witnessed by the world on TV a few years ago. However, that pair, in spite of rearing their 3 young that year, started to build a new nest 2 days – yes two days – later which they then occupied for the next 3 years? Then, and I suspect a new female and perhaps even another male, returned to the original nest I had entered that rescue day. So eventually the territory nest was reoccupied but I suspect not the same eagles. I must mention, both the landowner of that original nest tree and our Fish & Wildlife Branch, the FLNR today, had agreed to allow us to rescue the chick. I had predicted the nest change and when it happened the landowner accepted the loss – and FLNR accepted that the snagged eagle was the victim of an artificial fishing line that caused the snagging and this was an "unnatural caused event" that justified a rescue. All worked out well.

Now I mention the above not to cause concern about the Barrier Island ground nesters nest being accessed and their presence is going to cause abandonment since the area appears to have already returned several adults to visited nests in previous years. (Though I hope someone will keep records about the 're-occupancy’ at these sites!) I suspect we are witnessing another way in which eagles are adapting and being conditioned to urban – suburban living. If the nest is left OK and relatively undisturbed then perhaps this violation of the nest is not to be considered ‘totally disruptive’ by the eagles. Time will tell if this adaptation will permeate a bigger part of the eagle population. Be conscious of this potential disturbance - very good intentions can have disastrous consequences.

So here is the rest of the story: Ground nesting is and has been a regular event along the coastal islands on both northern coasts of the continent for as long as we have records. Of course this happens here on off shore islets all the time. It has also happened in the City of Delta – but probably for a different reason. Our pair originally known as Delta 1 CAM - our first CAM on the mainland and the nest near which the young girl and her grandmother were killed by a drunk driver, had an unusual twist. When the original D1 female disappeared and a new female appeared, that new female would not nest in the existing very low tree - 37 feet above the driveway in which kids played daily - and the new female tried 3 years in a row to nest on the adjacent power pole (the high 150' towers) - and finally laid her eggs in a ground nest nearby. I did not get a call until the farmer found the nest on his farm road. When I got there that night in the pouring rain with an OWL representative one egg was broken and the other, I took to incubate. The embryo was dead but both eggs were fertile and had started development. I took this to be a 'desperation nest' - one constructed in an emergency probably as she felt the egg coming down her oviduct. I suspect she hurriedly went to the ground beside the next hydro pole, a site we had not seen her attempting to nest in and laid the eggs in a hurriedly scraped together nest on the little-used dirt farm track. The nest was very rudimentary, scraped in tiny sticks, feathers and leaves – no branches. This unsuccessful nest was our first ground nest in the urban-suburban area. Many British Columbia and Alaska eagles nest on the ground, sometimes on cliffs, along our treeless islands – but D1 was quite different.

Many years back there was a paper outlining how many (200+???) ospreys nested in a colony on the ground on a small island off Long Island, NY. There was so much food and no visitors in the fast swirling tidal waters that they apparently felt safe. So why not eagles. Our eagles regularly lay eggs in trees only a few meters above several houses. We keep cutting down their trees and they are making every effort to adapt. More and more are nesting in the trees we artificially modify or the pole nests we erect - their next best offering to real tall trees. Perhaps re-nesting on the ground is another way to eek out an existence in our fastly modified world.

Thanks
david

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