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Update: Bald Eaglets and Red-tailed Hawklet Share Same Nest in the Wild!

Wildlife News

What an unusual split family. Our Roberts Bay, Sidney, BC pair of bald eagles raises a young red-tailed hawk along with their three much faster growing and much larger eaglets.

The recent photos and videos posted to our www.Hancockwildlife.org forum from Lynda & Ian of three large eaglets about nine weeks old plus one 3 to 4 week old red-tailed hawklet in the same nest, and being very satisfactorily reared by the parent bald eagles, is quite extraordinary. However after spending the day at the site watching the six raptors interact so successfully then re-plotting the potential ages of the young raptors, and contemplating the options of how we got to today, begs some interesting thoughts.

First, this nest on the shores of the Saanich Peninsula historically has been a very successful nest, usually rearing three young, less frequently two and, like most eagles, even occasionally failing. In talking with the incredibly friendly and supportive neighbors who love 'their eagles', this nest tree has been occupied for more than 25 years. The surrounding harbors and huge areas of intertidal zone are incredibly productive. Many of the residents and fishermen that frequent the area speak of the eagles commonly taking ‘course fish’ – the undesirable by-catch thrown away by the fishermen. This pair of eagles not only lives in a subdivision on an incredibly busy fishing harbor, but they totally accept the closeness of residents, beach walkers, dogs and incessant boat traffic on the water and vehicles on the roads below. These are very successful urban eagles! I personally grew up a few miles to the south of this nest and knew of this and about five other nests in the adjacent area going back 60 years. This eagle territory was one of the first urban areas occupied by bald eagles that only 10 miles east on the nearby San Juan Island, Washington State, were not just being shot but were subject to a $2.00 bounty for their pair of legs. Yes, we humans have come a long way, with the eagles trying desperately to lead that way to cooperative sharing of the common habitat.

So this pair of bald eagles, like most eagles in southern BC and now even the re-occupied eagle habitat of Washington State, get the resident eagles returning from their brief northern migration in early October, some as early as late September. This Sidney pair are also early occupiers of their territory, probably doing so to insure no intruders take over this prime habitat. So eagles here occupy their territory by early October, defend that territory until they lay their eggs in late February or early March. The young hatch after 35-37 days of incubation and are fed in the nest usually 83-85 days before making their first flight from the nest tree – their fledge. The parents oversee the fledged offspring about 5-10 days before abandoning them and flying north, where by July the northern salmon rivers of Alaska and Northern BC are already strewn with dead spawned out salmon carcasses. The eaglets follow about a week later. None return to southern BC until the end of September and largely into October, with breeders and non-breeders peaking in our southern regions about mid December.

But what about the other member of this ‘split family’, our tiny red-tailed hawklet? First off, our western red-tails, along with their even tinier secretive short-winged cousin, the coopers hawk, are common breeding raptors of southern British Columbia and nest within site of most urban/suburban bald eagle nests. This common nest distribution results in constant harassment of the larger less agile bald eagles from either of the smaller more maneuverable raptors. Prior to this above ‘shared nest rearing’ I have two other local records of bald eagles rearing a single red-tailed hawk to presumably fledging. Other researchers have reported several similar incidents of bald eagles rearing mixed species broods. So how does nature work that it allows mortal enemies, the giant 7 to 14 pound bald eagle to nurture a few ounce to 3.5 pound tiny red-tailed chick? This little red-tailed chick is sharing the nest with three fast growing, usually aggressive siblings. Sibling rivalry and fratricide is not uncommon in eagles. So here are a couple of possible scenarios.

The red-tailed hawk, as witnessed by many, very frequently dive bombs neighboring bald eagles. The far less maneuverable eagle usually just ducks its head, does a last minute sideslip and gets out of the way. The red-tailed aggression is readily observable, intensifying this aggression to its big neighbor as the nesting season heightens. Egg-laying and chick rearing are of course the peak seasons of aggression. So did our red-tail, with an egg in its oviduct and its hormonal aggression at peak mode, make a bad poorly aimed attack and the annoyed eagle do an extra skillful barrel-roll and snatch the diving red-tail out of the air as it was diving by? Quite possible. This has been witnessed before. I have seen many such attacks but I have only witnessed one coopers hawk actually get caught in this maneuver. On that occasion the eagle simply disappeared over the horizon and was out of site carrying its tormentor. I did on one occasion actually retrieve a dead uneaten coopers hawk from an eagle nest containing two fresh eagle eggs.

If the attacking red-tail, egg in oviduct, did get carried back to the nearby eagle nest it is not unlikely that either in the death throws or upon being torn apart (less likely in my experience!) the egg got deposited into the eagle nest. If the eagle, which nests during the same overlapping time period, already had eggs or was about to have eggs saw another egg it is not unlikely that the eagle would simply incubate this smaller but additional egg along with its own eggs. Eagle eggs may occasionally be eaten by marauding eagles as we have seen on our live streaming cams, but generally there cannot be a lot of positive natural selection favoring eagles eating eggs in their nests! What would happen at hatching? What if the timing was a bit off? What if 7 to 14 day old eaglets weighing nearly a pound sat beside a three ounce hawklet? At the heart of this issue has to be another profound issue. What stops an adult eagle tearing up one of its own chicks and feeding it to its other chick? How is this much different from tearing up a ‘little eaglet, a red-tailed chick, and feeding it to its bigger sibling? Then of course, what constitutes the difference between mommy eagles tearing up a heron chick, or a gosling and feeding it to its young vs tearing up its own chick? Or a red-tailed chick? Wow. I had never pondered this obvious question before. However it is quite profound and fundamental to evolution and survival of such predators.

So here is a second scenario. Bald eagles, while primarily fish feeders, do predate small mammals, catch in season ducklings and goslings and commonly scavenge road kills. In our area many great blue heron nests are predated by eagles. This is so common that smaller heron colonies in this area have largely failed and the very abundant great blue herons have learned to nest in heronries of huge numbers, closely surrounding a bald eagle nest. The theory that makes sense of this to me is that the herons learned that by nesting beside an active bald eagle nest they are invoking the territorial defensive behavior of the eagle to protect their own nest and the heronry in general from predation from every passing eagle. The nesting eagles keep the other eagles away from their nest and the heronry. This has been shown a successful strategy for a great blue heron colony besides one of my favorite bald eagle nests, our earlier Delta 3 nest. So we know bald eagles predate heron chicks. This is well documented. So here is the dilemma. How does the eagle bringing home a heron chick, distinguish tearing up that little grey heron chick and feeding it to its similar sized grey eaglets, as opposed to tearing up its own eaglet and feeding it to a possibly live heron or red-tailed chick? Yes eagles do kill red-tailed chicks. Our Delta 2 Live Streaming Cam Site started out as a red-tailed nest that I witnessed being predated by a nearby pair of nesting bald eagles. They killed and tore apart and ate the large hawklets right in the hawk nest. I saw it. Two years later the eagles, and I believe the same territorial pair, built up this red-tail nest to suit their needs and this site, the following year became our Delta 2 Cam Site. For those of you watching our CAMs you will know I supplemented the tree crotch with some heavier timbers! The new 2016 Delta 2 nest site, about 100 feet from the original Delta 2 site, is also a completely modified tree in which we built the supports to support the eagles when their original nest tree had blown down.

So here we are again trying to decide if the little red-tailed hawklet in the bald eagle nest in Sidney came into existence as an egg that was then incubated, hatched and reared by the eagles. Was it predated as a chick from a nearby red-tailed hawk nest and then accepted as another sibling? Sure wish we had had a live cam on this site!

As stated above I at first favored the first scenario – the egg was exuded by a dead or dying red-tail, then incubated by the eagles and now was being reared by them. Our Hancock Wildlife Foundation Director, Dr. David Bird, actually lives near this Sidney nest with the mixed brood, but he had not heard of this unusual event until we called him to come over and have a look this past Sunday. He came and we started to debate how this chick got into this nest as defined above. He suggested another theory. Perhaps the red-tailed parents had initiated the nest and then it was taken over by the eagles. Dr. Bird did not know the history of this site nor this year’s record of occupancy by the eagles since October. This option, while plausible and accepted in some other ‘take-overs of nests by other species’, was not likely feasible here. A version of this, whereby the female red-tail might have lost her nest while she felt the egg coming down her oviduct, she might have flown over to the nearby eagle nest and dropped the egg. Again not likely the option here as you can see below with the timing.

The timing of reproduction at this site is quite interesting and perhaps telling, well telling something but I am not quite sure what! The present three eaglets are now about nine weeks old at maximum. This meant they hatched about April 1, were laid as eggs about February 25. If the red-tail is now about 25 – 28 days of age then it was laid around April 8 - 10, just after the eaglets hatched! Perhaps our hawklet is a runt, just incubated and reared at the extreme end of normal and another week older, suggesting it was possibly laid about the same time as the first eaglet was about to hatch. Wow. What questions did our eagle parents face? What is this little egg? But perhaps that is not valid! The hatching process must surely be critical moments in a bird's life: the transition from sitting quietly for five weeks, not allowing the incubating eggs to get cold or predated, but then having to shift to keeping the body high to prevent crushing the newborn chick, still keeping it warm and them evaluating when, within usually 12 to 36 hours, when and how to feed this hatchling. Oh lots of decisions. Perhaps another little egg lost in the midst of midwifery was inconsequential.

So back to the other theory! Did this little red-tailed hawklet arrive as food for new eaglets? Was the little red-tailed chick taken by the eagles from a red-tail nest as food for their young? Then, did it’s little buteo presence in the nest shift the eagles ‘tear-up and feed’ motivation to more primal urges of ‘attend and nurture’? After re-looking at the age of both the eaglets and the hawklet I now favor this latter option. Was something about a little hawk, with hooked beak, perhaps generic looks and begging sounds, able to shift the parent eagles from killing to nurturing? Why would a similar little grey heron chick serve as food and a little red-tail chick become a ‘sibling’? Certainly it is easy to speculate that a little gosling is ‘golden’ and not white or grey, a little vole furry not like an eaglet. Even a road kill, perhaps parts of a rabbit, comes in really ‘dead’ and not easily confused! The little heron chick, speckled at least at some stages, could be an eaglet look-a-like, but perhaps there are some keys: the hooked beak, a buteo basic begging call, or something I don’t understand that enables the adult eagles to make the distinction between food and eaglet?

So how satisfying is that? You pick your choice or come up with a new theory. Good luck but particularly good luck to “Hawklet” for he/she will need it. At fledging he will not be given a 4 to 8 week tutorial on how to catch voles, snakes or whatever else the region is offering as opportune feeding strategies. Nature does not normally treat vagaries well. Perhaps we are working towards another evolutionary leap. Could our world be full of rats and mice that take little experience in catching?

David Hancock
Hancock Wildlife Foundation

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