A Good Eagle Story
Sunday, October 20 2013 @ 12:01 AM EDT
Contributed by: davidh
Banders, Rehabilitators, Citizen Scientists - Contribute to Bald Eagle Knowledge
On March 5, 2013 an adult bald eagle showed up on the Harrison Mills Bald Eagle nest -- in view of our live streaming cams. On March 10 and thereafter two adult eagles were seen working on the nest. However it wasn't until March 31 that we noticed that the female was banded. A number of our volunteers immediately started to focus in on the band numbers. Nine numbers would be needed to get the records from the central North American band office, the USF&WS in Patuxent, Maryland to track down the history of this bird. Only 4 or 5 numbers could be seen on the facing curve of the band. This could be one of thousands of banded eagles -- but which one? Where did our late arriving female come from before appearing on our cams? This was an interesting challenge to unfold -- or uncurl -- over the next 3 months of the breeding season.
But let me give you the background. This Harrison Mills nest (HM) overlooks the world's largest winter gathering of bald eagles ever witnessed -- I counted 7,362 eagles individually in about 2 square kilometers of the Chehalis Flats, directly to the north and east of this nest on December 18, 2010. Probably well over 10,000 eagles were then present in the 5 kilometer area along the Harrison River that we consider our annual bald eagle winter count area. The eagles were here for one purpose, to gorge on the spawned out carcasses of the 5 species of salmon dominating this river -- Canada's first Salmon Stronghold River. Harrison Mills is the region surrounding the Chehalis Flats, the alluvial fan into the Harrison River which supports Canada's most important complex of spawning salmon which in turn attracts the huge numbers of bald eagles.
The date of this pair of eagles' arrival at Harrison Mills nest in early March was also very unusual. Most southern British Columbia breeding eagles return from their brief northern migration in early October (in 2013 many returned in late September) to claim their breeding territory. Southern BC has been one of the most prolific breeding areas, even during the first half of the 1900s, when Alaska was offering a bounty on eagles, BC was supporting thousands of nesting pairs. The eagles had nearly been exterminated from adjacent Washington due to the Alaskan bounty and the prevailing human attitudes of the time. Only on the lower mainland, the greater Vancouver area adjacent to northern Washington State where many of the Alaskan fisherman wintered, were there catastrophic losses of eagles.
From October through February the eagles defend their nesting territories but occasionally leave these territories for a day or two to attend nearby salmon rivers to feast at the buffet where spawned out carcasses roll up on the gravel bars. Some considerable nest building takes place in October but through much of the winter the eagles only stand guard, calling from the territorial hunting perches to any passing eagle. One can only guess what they say but with most screams many approaching eagles change direction. The result seem emphatic: "Keep going, this territory is occupied!"
Normally starting in January the pair again spends considerable time adding sticks to the nest and by mid February are adding the soft mosses and grasses for the nest cup lining, into which the eggs are to be laid. For our geographic area, it is not until late February or March that they actually lay their 1 to 3 eggs.
The March arrival of our pair into the Harrison Mills nest was over 5 months later than most pairs. Where did they originate? How were they all primed, synchronized and ready to lay eggs in such a short time? Well my guess is that we received the pair from the adjacent territory, 4 miles to the north on the west edge of the Morris Valley Slough. On January 23, 2013 that pair had their huge nest cut down -- by permit -- to allow the extension of the BC Hydro high tension power lines to come through the area. That territory had a number of good alternative trees. I had been called in by the Ministry of Environment to suggest some mitigation for the Hydro nest removal so I got to examine the territory in more detail -- my nest HWF # 275 of nearly 400 active territories in the lower Fraser Valley. I did suggest modification of a few of the tree crowns to allow easier construction of a new nest. I also cautioned that having a climber up the tree during February might jeopardize this year's nesting, but at least some trees would be ready for the next 2013-2014 season. With the nest cut down so close to the egg laying period and the continued presence of tower crews clear-cutting the power line, I assumed that this territory was not likely to succeed this season. That was early February. The adults hung around their old Morris Valley territory for nearly 5 weeks.
However, my opinion is that the continued helicopter logging activity, the ground activities clearing the area and the multitude of environmental consultants trying to protect the rare frogs in the Morris Valley wetlands below the nest were an unfortunate but unavoidable disturbance to the eagles building another nest nearby.
Voila -- I believe -- these eagles saw across the valley and just across the Sts'ailes First Nations Village, that their adjacent eagle pair did not return from the winter migration. The adjacent nest territory was empty, the nest unused. Undoubtedly the Morris Valley pair was well into their reproductive cycle by early March: the nesting urges being driven by the light cycle, by hormones and perhaps to the extent that even the ovaries were heavy with developing eggs. What to do? The answer, I am sure these very adaptable birds surmised, seemed simple -- just fly across the Sts'ailes Reserve to the unoccupied site and get on with it! My guess is that the Morris Valley pair had barely changed territory borders -- they just extended their territory south and could continue to hunt the area along the Harrison River they knew so well. They hit it lucky -- the next territory was empty and available -- and they took advantage. This guess, whether I am right about where the pair came from, has little impact on the observations and facts that follow.
Our new Harrison Mills pair seemed to start out a little different. First, they arrived on territory late, but then the time between the 1st and 2nd egg was 4 days -- not the usual 3 days. Of course hatching was 4 days apart also giving the 1st hatched chick an extra day's growth and strength. The 2nd hatched chick seemed to start life with more than its share of disadvantage. My guess is, that it was this age difference from his aggressive sibling that was responsible for prompting the sibling rivalry. The 2nd eaglet to hatch did not get sufficient food and its growth rate quit. At 24 days of age it died - probably at one fifth the weight of it's sibling. Two days later his body became food.
Ma and Pa Harrison Mills, named Mr. and Mrs. Honeycomb by our live streaming cam sponsor Betty Anne of the Pretty Estates, were good hunters and providers. They brought lots of fish from the adjacent Harrison River and appeared to one observer to be bringing in fish from another lake over a mile away. Since we had two PTZ --Pan-Tilt-Zoom -- cameras in the nest tree and infra-lights giving us 24/7 hours of observation, a lot of notes followed. Other people frequently observed the pair from the ground and river. However, even with lots of food the smaller sibling just did not get the opportunity to effectively feed.
The adults coped with the two pairs of osprey nesting directly in front of their territory and with another pair of eagles nesting directly across the river and a further pair, on the north shore of Harrison Bay, just south around the edge of their mountain. Also occupying the Chehalis Flats in front of their nest all spring were a few late migrating sub-adult bald eagles that fed from the ospreys and scavenged the last salmon carcasses. The Chehalis Flats is an eagle-busy area.
On August 4 the young eaglet fledged on the 86th day after hatching. Most of these precise dates are from our Hancock Wildlife Foundation cam observers. Several of these 'eagleholics" noted that this young eaglet had an unusual ridge down the center of the head. The way the feathers came together in the center, a kind of "Mohawk cut" made him distinctive. Three days after his fledge an eaglet from this year was spotted on the shoreline over a kilometer from the nest -- and that bird wore a "Mohawk". Very likely it was our eaglet on his penultimate day on the home territory. The adults were last seen in the area August 14 before migrating north.
So the history of our Harrison Mills "new pair" takes on more color. When on the previous September 7, 2012 I was lifted 172 feet up the length of one of nature's finest Douglas Firs, I found in this nest a dead eaglet. This chick had probably died mid-June of that year. This presented a likely explanation of why we had not seen a chick fledge from this nest in 2012 that we had seen occupied by adults all winter and through to early June. We later learned that a female bald eagle was electrocuted in early June about 2 kilometers to the south, on the shores of Harrison Bay. At first we thought the dead eagle was the female of the nearby nest on Harrison Bay. Now there was another possible explanation. The Harrison Mills female had been electrocuted and her chick had consequently died. Now we found it in the nest where we were about to install two PTZ cams.
Then through the winter of 2012 when the eagle territory holders normally return and defend their territories, only occasional adults were seen around this nest. No pair seemed to claim the nest. Now I say "occasional" in that several thousand eagles occupied the 3 to 4 kilometer area around the nest all winter, feeding off the spawned out salmon carcasses, but only one very distinct adult ever occupied the actual nest. This occupancy was for 3 single nights spread over about 4 weeks. This adult would arrive just at dusk, "flop down" on the nest and leave at daylight. Our eagle cam watchers had actually caught close-up screen captures of the eagle -- and her feet. Some shots were in black and white from the infra-red lights, others at daylight showed the bright yellow of healthy looking feet.
The distinctiveness of this bird was unique. She had no claws on her left foot and only one partial toe -- she was a very recognizable but huge eagle. She would obviously have great difficulty perching during windy nights with only one foot of grasping claws. Did she seek out, perhaps before storms when holding the branch with one foot would be more challenging, a nest to lay down on for the night? She only landed on our HM nest for 3 nights under our infra-red lights. Where and how did she survive? But our Harrison Mills nest remained an unoccupied territory throughout the breeding season until -- March 5, 2013 when the first eagle of our new pair arrived. The first egg was laid on April 4.
But the uniqueness of a "no toed" female was replaced by a more unique female -- our new lady was banded. What an incredible stroke of luck! This pair was successful in rearing one of their two eggs and hatched chicks. As stated above, one chick died from what appeared to be classic sibling rivalry.
One challenge for our observers was to read all 8 numbers that circled her tarsus. These are small numbers engraved into the aluminum band.
The number sequence was complete on June 3. We had been watching # 629-30899. The USF&WS now searched the records and guess what? This bird had been banded at OWL (Orphaned Wildlife Rehabilitation Society), the largest raptor rehab center in all the northwest located in Delta, BC, which we constantly work with and for which many of our viewers spend many hours of volunteer time. It is OWL that releases a banded eagle at our Fraser Valley Bald Eagle Festival every November at Harrison Mills.
The following are notes from bander Elizabeth Thunstrom:
"The eagle was found lying in a ditch in south Surrey by a passerby in April, 2001. It had apparently been hit by a vehicle. The bird was in shock and was taken to OWL for care. There she was treated for shock, a mild concussion and damage to her beak - a lesion and a broken tip. The bird was in good condition and recovered well. It was flight tested prior to banding and release.
In 2001 I was one of a very few licensed banders of rehabilitated birds in North America, with a Master's permit from the Canadian Wildlife Service. I banded rehabilitated birds, on release, for both Wildlife Rescue Association and OWL in 2001. This amazing return is a great indication that rehabilitation, if properly done, can be very successful.
Note: the rehabilitation of wildlife, both birds and mammals, has been a controversial issue with many biologists as well as conservation personnel over the years. Results such as these are a good confirmation of its value for many creatures that would likely not otherwise have survived. The fact this eagle did survive and produce young over the intervening years is really exciting."
Bander / Rehaber
So now we have more details -- Chapter 2 of hopefully many! Our big lady was banded in June, 2001 as a full adult and released after she had completed about 2 months of rehabilitation following collision with a car. So this bird was now a minimum 17 years old when she came to the Harrison Mills nest. She had survived a battle with a vehicle but been found by people who cared. Then again, if my suspicions are correct, she is the female from the Morris Valley nest, she has had another run-in with humans -- this time with disturbing chain saws, consecutive work crews and helicopters -- and again survived. No wonder our eagles have been increasing. Once we changed our attitude and considered predators good icons, essential indicators of how healthy an ecosystem is, they rebounded with the very virility our Harrison Mills pair was continuing to show.
So in conclusion in 2013 our Harrison Mills bald eagle nest, my study nest # 275, produced 2 eggs, lost 1 young and fledged 1 young. We know the female was given a second chance in life by caring people, rehabilitators and banders. This breeding season she will be at least 18 years old. Both parents and the young left the region about August 14, 2013. We are pleased to see them both back in the nest today, Oct. 18, 2013, working on their nest for the 2014 rearing season.
This story is a tribute to those people who care enough to try and save an injured bird, the rehabilitators who spend hundreds of volunteer hours bringing these birds back to health, the network of volunteer birders who work countless hours trapping, banding and keeping records, and finally our army of Hancock Wildlife Foundation "citizen scientists" who spend thousands more hours watching and recording what these birds reveal from our intimate live streaming cams. I thank you all. To watch our Harrison Mills pair go to:
Nearby you can see the Chehalis Tower cams that are to be installed October 20 to view the spawning salmon and the feasting eagles.