Hancock here: Where have all the eagles gone? Long time coming!!! Nov 1, 2021
That is the extent of my musical talents and be thankful you did not hear me sing this! However, I do keep hearing that during the past 10 days that the eagles have disappeared from the lower mainland – at least the early arrivals at the lower valley nests seem to have disappeared from around their nests or are no longer heard calling.
I think we are seeing just an extreme situation of what is quite normal. I have been reporting for years that the resident bald eagles are returning to the Great Vancouver area earlier and earlier. Since the 1960’s when they generally did not return until the end of October or early November, then over the years breeders were showing up earlier and earlier. This reached an early peak the past couple of years when a few adults were seen at nests from late September thru the end of the first week of October. This year we had eagles at two sites in Delta by the 10th and 14th of September. Quite a difference during my 65 years of following them by aerial and ground counts.
So why am I getting frequent calls that this year most of the adults have left their nesting posts at this time? Or as some keen observers and residents with back-yard nesters are saying, “we no longer hear them - they must have left!” I have taken several runs around the lower mainland the past two weeks and initially thought the same. Now, with more time spent on the details, I have a slightly different interpretation – one that totally reconfirms my earlier observations. The past two days were kind of typical. Yesterday we visited the 21 sites of the White Rock nests. Of the first 6 viewed only one nest had two viewable adults -- and these were securely hidden side by side, under a branch on a favorite perch tree about 200m from the nest.
The next 4 sites along the Crescent Beach Cliffs only produced a single adult at one site and then a pair, again side by side deep in the foliage of a huge conifer – again about 100 m from the normally active alternative nest. The next series of 5 nests was even more revealing. Here we could see 4 nest territories from the Crescent Beach Marina -- and 3 sites had a pair sitting within 5 feet of each other and at the fourth, somewhat farther away I could only see 1 adult. All these were seen from the Marina -- below the nests and looking up. But the key is all 4 had adults on guard. At the other sites previously mentioned, the other adults were doing precisely what I have been defining is their traditional behavior in late October or November -- they have greatly reduced their early October fervent nest building to sit around on the edges of their territory and only proclaim ownership when provoked by a passing adult. The adults are likely mostly there, just sitting quietly only making a statement of ownership if another potential competitor adult passes near.
The general quietness and less attention to the actual nest is very apparent at this stage. They have arrived back from the migration, made many loud statements at the nest, welcomed their partner's arrival back, sometimes within a day of their arrival, and sometimes with considerable mating, followed by them both bringing in considerable branches to repair the nest. But then they seem to take a rest from the frenzy in late October and November. This is normal as I have repeatedly seen over the years. Now it seems to be apparent to more observers. Is that because there are more better informed observers, or is the eagle's behavior changing. I think the former. This does not mean that there are no seasonal differences -- and longer term changes due to climate change. Our warming climate is certainly also complicating or changing how the eagles respond.
So the BIG noticeable changes this season could also simply be extremes of general variances. Two of these come to mind. First, the availability of local fish carcasses is key. Our fisheries predictions are almost always totally wrong. The continuing diminished capacity of the Department of Fisheries to make the needed fish counts is totally due to their reduction of staff. This has resulted this year in unexpectedly good early runs of salmon on some local streams. About 3 weeks ago our little Campbell River had over 1000 springs and coho arrived at the hatchery. Quite a wonderful early record. Will these numbers be repeated for all the runs over the next few months? Probably not and they seem to have already ended.
The same happened at the Weaver Creek spawning channel. The Hatchery, designed in the late 1960’s to hold about 30,000 sockeye spawners last year had only about 100 fish return. This forecasts a disastrous return four years from now when their eggs are expected to return as mature salmon. This year, with little hope after several years of poor returns, there were no great expectations. No fishery or even test fishery off the north end of Vancouver Island had predicted a good run for 2021. Actually this was probably the saving grace. Normally if the test fishery states any good news this encourages so much overfishing at the north end of the Island, down the entire Johnson Straights, and then the final decimation of the returning fish happens as the schools amass at the mouth of the Fraser where the final over-kill takes place. Generally, any prediction of a good run forecasts a lousy spawn due to the greed of the fishery. Don’t we ever learn?
So what happened this year? The Little Campbell, the Weaver and even the Pitt has a good early run. Now it is imperative to stress that a good early run is not predictive that all the runs that cover 3 to 6 months of the spawning season will also be good. Generally that is not the case. Some runs, often fish that will end up in a few hundred meters of a river to spawn, will be totally overfished at sea and disappear as a spawning entity for several years. Hopefully other runs escape the fishery and survive to allow some spawning in that river – as seems to have happened this year.
Well, the Weaver spawning channel had an unexpected early 40,000 sockeye pounding at the fish gate to enter the artificial spawning channel. Incredible. No advance fishery warning, just masses of fish wanting to spawn. Well quickly the hatchery crew jumped into action, got water into the channel, allowed some 25,000 sockeye and about 5000 mixed early coho and chum runs in as well. Today the channel is well stocked with eggs and the carcasses have largely died off and been removed. The year 2025 should be a good early run return year if the stocks don’t suffer overfishing or other natural catastrophes in the next 4 years.
So, my point of the above, and its implication to our eagles is simple. This year, with a few of the rivers along the north side of the Fraser, no more than a 30 to 45 minute flight away even from the White Rock breeding eagles, having reasonable early salmon runs, has produced local carcasses for the floater population of eagles. These are the non-established breeders and immatures and they are concentrated at these early banquets. Even, I suspect, but our tracking program has yet to prove this, many of the local breeders spend some time at this easy food supply so close to their back door. I have often suggested that perhaps only one of a pair at a time goes off to the buffet while the other adult stays to defend the nesting territory. Time will tell if my observations are supported by tracking evidence. To date our only resident breeder that wears a tracker suggests this is so. One eagle makes a poor scientific conclusion. We have work to do.
The second variable that is possibly bearing on our local territorial pair movements is the local weather. Not only does it influence the salmon runs but the weather is the main driving force to move the 50,000 eagles that are presently along the northern BC coast and salmon river drainages all the way to South East Alaska, down to our warmer Fraser River. If – and when –the north gets cold the fish carcasses are placed under ice and no longer available. The eagles come south to the Harrison and our other south coastal streams all the way over to Vancouver Island. Nature’s system works well. This too gets more complicated, but I will leave it here that with the warm weather this fall to the north of us, few of the northern eagles have yet to need to descend upon our unfreezing Fraser River system. The big question for our eagle abundance is: Will the freeze-up happen before all the spawning fish have spawned out and their carcasses washed out in the many still high-water creeks and rivers? The eagles depend on the spawned-out carcasses being exposed as low water leave them hung up on the shallow gravel bars – the exposed buffets.
First, my long-term comments on the migration or dispersal patterns have not changed. The adult breeders have been returning earlier and earlier each year. I may not fully understand all the reasons, but I suspect two major influences. First, the return of adults to their nesting sites is, I believe, to reclaim their nesting territory – to make sure they are present to scream and holler and when necessary, chase away potential nesting intruders to their nest territory. The increased breeding density of the local eagles over the past 6 decades I suspect drives this competitive behavior.
The normal defensive posturing at the local nesting sites stays relatively the same -- regardless of the weather. It is a well-known fact in biology that most resident animals have an advantage of territory ownership over potential intruding newcomers. Our eagles are no exception. I suspect the local birds hold and defend territories and don’t abandon it for even a short period because this might offer a dangerous opportunity for a newcomer to get a few days of increased confidence of ownership. This confidence, based on familiarity with local food and perches, would give an advantage that the regular owners do not wish to offer. This is likely an incentive to stay home and defend the nest homeland. Maybe the males and females trade off as to who goes to a nearby stream for a day of feasting.
So, our local breeding territories holders, singularly or together, may well have been relaxing sitting under cover on a favorite hunting perch – just waiting to chase off a potential intruder with some defiant language or even a chase. Perhaps we eagle viewers need to look closer, in all the surrounding territorial trees to see if the pair is really on guard -- just resting up for the big season.
If we get the usual cold spell soon enough, we could have a big fall eagle season.
PS This may be copied by anyone or rebroadcast with credits -- please watch our Live Streaming Web CAMS -- the season is about to start. We invlite you to the Harrison to see the world's largest annual gathering of bald eagles. The peak of 5,000 to 15,000 on a single day is always a phenomenon to behold.
David Hancock, Biologist Hancock Wildlife Foundation, The home of Streaming Wildlife CAMS: www.hancockwildlife.org firstname.lastname@example.org Any press can utilize any images on our web site.